Alzheimer's disease (AD), also known as just Alzheimer's, is a chronic ​neurodegenerative disease that usually starts slowly and gets worse over time. It is the cause of 60% to 70% of cases of dementia. The most common early symptom is difficulty in remembering recent events (short-term memory loss). As the disease advances, symptoms can include problems with language, disorientation (including easily getting lost), mood swings, loss of motivation, not managing self-care, and behavioral issues. As a person's condition declines, they often withdraw from family and society. Gradually, bodily functions are lost, ultimately leading to death. Although the speed of progression can vary, the average life expectancy following diagnosis is three to nine years.
The cause of Alzheimer's disease is poorly understood. About 70% of the risk is believed to be genetic with many genes usually involved. Other risk factors include a history of head injuries, depression, or hypertension. The disease process is associated with plaques and tangles in the brain. A probable diagnosis is based on the history of the illness and cognitive testing with medical imaging and blood tests to rule out other possible causes. Initial symptoms are often mistaken for normal aging. Examination of brain tissue is needed for a definite diagnosis. Mental and physical exercise, and avoiding obesity may decrease the risk of AD. There are no medications or supplements that decrease risk.
No treatments stop or reverse its progression, though some may temporarily improve symptoms. Affected people increasingly rely on others for assistance, often placing a burden on the caregiver; the pressures can include social, psychological, physical, and economic elements. Exercise programs are beneficial with respect to activities of daily living and can potentially improve outcomes. Treatment of behavioral problems or psychosis due to dementia with antipsychotics is common but not usually recommended due to there often being a little benefit and an increased risk of early death.
In 2015, there were approximately 48 million people worldwide with AD. It most often begins in people over 65 years of age, although 4% to 5% of cases are early-onset Alzheimer's which begins before this. It affects about 6% of people 65 years and older. In 2010, dementia resulted in about 486,000 deaths. It was first described by, and later named after, German psychiatrist and pathologist Alois Alzheimer in 1906. In developed countries, AD is one of the most financially costly diseases.

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The disease course is divided into four stages, with a progressive pattern of cognitive and functional impairment.
Pre-dementia the first symptoms are often mistakenly attributed to aging or stress. Detailed neuropsychological testing can reveal mild cognitive difficulties up to eight years before a person fulfills the clinical criteria for diagnosis of AD. These early symptoms can affect the most complex activities of daily living. The most noticeable deficit is short-term memory loss, which shows up as difficulty in remembering recently learned facts and an inability to acquire new information.
Subtle problems with the executive functions of attentiveness, planning, flexibility, and abstract thinking, or impairments in semantic memory (memory of meanings, and concept relationships) can also be symptomatic of the early stages of AD. Apathy can be observed at this stage and remains the most persistent neuropsychiatric symptom throughout the course of the disease. Depressive symptoms, irritability, and reduced awareness of subtle memory difficulties are also common. The preclinical stage of the disease has also been termed mild cognitive impairment (MCI). This is often found to be a transitional stage between normal aging and dementia. MCI can present with a variety of symptoms, and when memory loss is the predominant symptom, it is termed "amnestic MCI" and is frequently seen as a prodromal stage of Alzheimer's disease.
Early in people with AD, the increasing impairment of learning and memory eventually leads to a definitive diagnosis. In a small percentage, difficulties with language, executive functions, perception (agnosia), or execution of movements (apraxia) are more prominent than memory problems. AD does not affect all memory capacities equally. Older memories of the person's life (episodic memory), facts learned (semantic memory), and implicit memory (the memory of the body on how to do things, such as using a fork to eat) are affected to a lesser degree than new facts or memories.
Language problems are mainly characterized by a shrinking vocabulary and decreased word fluency, leading to a general impoverishment of oral and written language. In this stage, the person with Alzheimer's is usually capable of communicating basic ideas adequately. While performing fine motor tasks such as writing, drawing, or dressing, certain movement coordination and planning difficulties (apraxia) may be present, but they are commonly unnoticed. As the disease progresses, people with AD can often continue to perform many tasks independently but may need assistance or supervision with the most cognitively demanding activities.
Moderate
A photograph of a patient at West Riding Lunatic Asylum with dementia Progressive deterioration eventually hinders independence, with subjects being unable to perform most common activities of daily living. Speech difficulties become evident due to an inability to recall vocabulary, which leads to frequent incorrect word substitutions (paraphasia's). Reading and writing skills are also progressively lost. Complex motor sequences become less coordinated as time passes and AD progresses, so the risk of falling increases. During this phase, memory problems worsen, and the person may fail to recognize close relatives. Long-term memory, which was previously intact, becomes impaired.
Behavioral and neuropsychiatric changes become more prevalent. Common manifestations are wandering, irritability, and labile affect, leading to crying, outbursts of unpremeditated aggression, or resistance to caregiving. Sundowning can also appear. Approximately 30% of people with AD develop illusionary misidentifications and other delusional symptoms. Subjects also lose insight into their disease process and limitations (anosognosia). Urinary incontinence can develop. These symptoms create stress for relatives and carers, which can be reduced by moving the person from home care to other long-term care facilities.
Advanced During the final stages, the patient is completely dependent upon caregivers. Language is reduced to simple phrases or even single words, eventually leading to a complete loss of speech. Despite the loss of verbal language abilities, people can often understand and return emotional signals. Although aggressiveness can still be present, extreme apathy and exhaustion are much more common symptoms. People with Alzheimer's disease will ultimately not be able to perform even the simplest tasks independently; muscle mass and mobility deteriorate to the point where they are bedridden and unable to feed themselves. The cause of death is usually an external factor, such as infection of pressure ulcers or pneumonia, not the disease itself.

The cause for most Alzheimer's cases is still mostly unknown except for 1% to 5% of cases where genetic differences have been identified.
Several competing hypotheses exist trying to explain the cause of the disease:
The genetic heritability of Alzheimer's disease (and memory components thereof), based on reviews of twin and family studies, range from 49% to 79%. Around 0.1% of the cases are familial forms of autosomal (not sex-linked) dominant inheritance, which have an onset before age 65. This form of the disease is known as early-onset familial Alzheimer's disease. Most autosomal dominant familial AD can be attributed to mutations in one of three genes: those encoding amyloid precursor protein (APP) and presenilin 1 and 2. Most mutations in the APP and presenilin genes increase the production of a small protein called Aβ42, which is the main component of senile plaques. Some of the mutations merely alter the ratio between Aβ42 and the other major forms—particularly Aβ40—without increasing Aβ42 levels. This suggests that presenilin mutations can cause disease even if they lower the total amount of Aβ produced and may point to other roles of presenilin or a role for alterations in the function of APP and/or its fragments other than Aβ. There exist variants of the APP gene which are protective.
Most cases of Alzheimer's disease do not exhibit autosomal-dominant inheritance and are termed sporadic AD, in which environmental and genetic differences may act as risk factors. The best-known genetic risk factor is the inheritance of the ε4 allele of apolipoprotein E (APOE). Between 40 and 80% of people with AD possess at least one APOEε4 allele. The APOEε4 allele increases the risk of the disease by three times in heterozygotes and by 15 times in homozygotes. Like many human diseases, environmental effects, and genetic modifiers result in incomplete penetrance. For example, certain Nigerian populations do not show the relationship between the dose of APOEε4 and the incidence or age-of-onset for Alzheimer's disease seen in other human populations. Early attempts to screen up to 400 candidate genes for association with late-onset sporadic AD (LOAD) resulted in a low yield. More recent genome-wide association studies (GWAS) have found 19 areas in genes that appear to affect the risk. These genes include: CASS4, CELF1, FERMT2, HLA-DRB5, INPP5D, MEF2C, NME8, PTK2B, SORL1, ZCWPW1, SlC24A4, CLU, PICALM, CR1, BIN1, MS4A, ABCA7, EPHA1, and CD2AP.
Mutations in the TREM2 gene have been associated with a 3 to 5 times higher risk of developing Alzheimer's disease. A suggested mechanism of action is that when TREM2 is mutated, white blood cells in the brain are no longer able to control the amount of beta-amyloid present.
Cholinergic hypothesis The oldest, on which most currently available drug therapies are based, is the cholinergic hypothesis, which proposes that AD is caused by reduced synthesis of the neurotransmitter acetylcholine. The cholinergic hypothesis has not maintained widespread support, largely because medications intended to treat acetylcholine deficiency have not been very effective. Other cholinergic effects have also been proposed, for example, the initiation of large-scale aggregation of amyloid, leading to generalized neuroinflammation.
Amyloid hypothesis In 1991, the amyloid hypothesis postulated that extracellular amyloid beta (Aβ) deposits are the fundamental cause of the disease. Support for this postulate comes from the location of the gene for the amyloid precursor protein (APP) on chromosome 21, together with the fact that people with trisomy 21 (Down Syndrome) who have an extra gene copy almost universally exhibit at least the earliest symptoms of AD by 40 years of age. Also, a specific isoform of apolipoprotein, APOE4, is a major genetic risk factor for AD. Whilst apolipoproteins enhance the breakdown of beta-amyloid, some isoforms are not very effective at this task (such as APOE4), leading to excess amyloid buildup in the brain. Further evidence comes from the finding that transgenic mice that express a mutant form of the human APP gene develop fibrillar amyloid plaques and Alzheimer's-like brain pathology with spatial learning deficits.
An experimental vaccine was found to clear the amyloid plaques in early human trials, but it did not have any significant effect on dementia. Researchers have been led to suspect non-plaque Aβ oligomers (aggregates of many monomers) as the primary pathogenic form of Aβ. These toxic oligomers also referred to as amyloid-derived diffusible ligands (ADDLs), bind to a surface receptor on neurons and change the structure of the synapse, thereby disrupting neuronal communication. One receptor for Aβ oligomers may be the prion protein, the same protein that has been linked to mad cow disease and the related human condition, Creutzfeldt–Jakob disease, thus potentially linking the underlying mechanism of these neurodegenerative disorders with that of Alzheimer's disease. One study found possible evidence of human-to-human transmission.
In 2009, this theory was updated, suggesting that a close relative of the beta-amyloid protein, and not necessarily the beta-amyloid itself, maybe a major culprit in the disease. The theory holds that an amyloid-related mechanism that prunes neuronal connections in the brain in the fast-growth phase of early life may be triggered by aging-related processes in later life to cause the neuronal withering of Alzheimer's disease. N-APP, a fragment of APP from the peptide's N-terminus, is adjacent to beta-amyloid and is cleaved from APP by one of the same enzymes. N-APP triggers the self-destruct pathway by binding to a neuronal receptor called death receptor 6 (DR6, also known as TNFRSF21). DR6 is highly expressed in the human brain regions most affected by Alzheimer's, so it is possible that the N-APP/DR6 pathway might be hijacked in the aging brain to cause damage. In this model, beta-amyloid plays a complementary role, by depressing synaptic function.

In Alzheimer's disease, changes in tau protein lead to the disintegration of microtubules in brain cells. The tau hypothesis proposes that tau protein abnormalities initiate the disease cascade. In this model, hyperphosphorylated tau begins to pair with other threads of tau. Eventually, they form neurofibrillary tangles inside nerve cell bodies. When this occurs, the microtubules disintegrate, destroying the structure of the cell's cytoskeleton which collapses the neuron's transport system. This may result first in malfunctions in biochemical communication between neurons and later in the death of the cells.

A neurovascular hypothesis has been proposed which state that poor functioning of the blood-brain barrier may be involved.
The cellular homeostasis of bimetals such as ionic copper, iron, and zinc is disrupted in AD, though it remains unclear whether this is produced by or causes the changes in proteins. These ions affect and are affected by tau, APP, and APOE, and their dysregulation may cause oxidative stress that may contribute to the pathology. Some studies have shown an increased risk of developing AD with environmental factors such as the intake of metals, particularly aluminum. The quality of some of these studies has been criticized, and the link remains controversial. The majority of researchers do not support a causal connection with aluminum.
Smoking is a significant AD risk factor. Systemic markers of the innate immune system are risk factors for late-onset AD.
There is tentative evidence that exposure to air pollution may be a contributing factor to the development of Alzheimer's disease.
An infection with Spirochetes (a bacterium) in gum disease may cause dementia and may be involved in the pathogenesis of Alzheimer's disease.
Regenesis is a medical hypothesis about the development and progress of Alzheimer's disease proposed by Barry Reisberg in the 1980s. The hypothesis is that just as the fetus goes through a process of neurodevelopment beginning with neurulation and ending with myelination, the brains of people with AD go through a reverse neurodegeneration process starting with demyelination and death of axons (white matter) and ending with the death of gray matter. Likewise,, the hypothesis is, that as infants go through states of cognitive development, people with AD go through the reverse process of progressive cognitive impairment. Reisberg developed the caregiving assessment tool known as "FAST" (Functional Assessment Staging Tool) which he says allows those caring for AD patients to identify the stages of disease progression and that provides advice about the kind of care needed at each stage.

There is cortical atrophy in Alzheimer's Disease, associated with loss of gyri and sulci in the temporal lobe and parietal lobe, and parts of the frontal cortex and cingulate gyrus. Neuropathology Alzheimer's disease is characterized by the loss of neurons and synapses in the cerebral cortex and certain subcortical regions. This loss results in gross atrophy of the affected regions, including degeneration in the temporal lobe and parietal lobe, and parts of the frontal cortex and cingulate gyrus. Degeneration is also present in brainstem nuclei like the locus coeruleus. Studies using MRI and PET have documented reductions in the size of specific brain regions in people with AD as they progressed from mild cognitive impairment to Alzheimer's disease and in comparison, with similar images from healthy older adults.
Both amyloid plaques and neurofibrillary tangles are clearly visible by microscopy in the brains of those afflicted by AD. Plaques are dense, mostly insoluble deposits of beta-amyloid peptide and cellular material outside and around neurons. Tangles (neurofibrillary tangles) are aggregates of the microtubule-associated protein tau which has become hyperphosphorylated and accumulated inside the cells themselves. Although many older individuals develop some plaques and tangles as a consequence of aging, the brains of people with AD have a greater number of them in specific brain regions such as the temporal lobe. Lewy bodies are not rare in the brains of people with AD.

Enzymes act on the APP (amyloid precursor protein) and cut it into fragments. The beta-amyloid fragment is crucial in the formation of senile plaques in AD. Alzheimer's disease has been identified as a protein misfolding disease (protopathic), caused by plaque accumulation of abnormally folded amyloid beta protein, and tau protein in the brain. Plaques are made up of small peptides, 39–43 amino acids in length, called amyloid beta (Aβ). Aβ is a fragment from the larger amyloid precursor protein (APP). APP is a transmembrane protein that penetrates through the neuron's membrane. APP is critical to neuron growth, survival, and post-injury repair. In Alzheimer's disease, gamma secretase and beta secretase act together in a proteolytic process which causes APP to be divided into smaller fragments. One of these fragments gives rise to fibrils of amyloid beta, which then form clumps that deposit outside neurons in dense formations known as senile plaques.
AD is also considered a tauopathy due to abnormal aggregation of the tau protein. Every neuron has a cytoskeleton, an internal support structure partly made up of structures called microtubules. These microtubules act like tracks, guiding nutrients and molecules from the body of the cell to the ends of the axon and back. A protein called tau stabilizes the microtubules when phosphorylated and is therefore called a microtubule-associated protein. In AD, tau undergoes chemical changes, becoming hyperphosphorylated; it then begins to pair with other threads, creating neurofibrillary tangles and disintegrating the neuron's transport system.
Disease mechanism Exactly how disturbances of production and aggregation of the beta-amyloid peptide give rise to the pathology of AD is not known. The amyloid hypothesis traditionally points to the accumulation of beta-amyloid peptides as the central event triggering neuron degeneration. Accumulation of aggregated amyloid fibrils, which are believed to be the toxic form of the protein responsible for disrupting the cell's calcium ion homeostasis, induces programmed cell death (apoptosis). It is also known that Aβ selectively builds up in the mitochondria in the cells of Alzheimer's-affected brains, and it also inhibits certain enzyme functions and the utilization of glucose by neurons.
Various inflammatory processes and cytokines may also have a role in the pathology of Alzheimer's disease. Inflammation is a general marker of tissue damage in any disease and may be either secondary to tissue damage in AD or a marker of an immunological response. There is increasing evidence of a strong interaction between the neurons and the immunological mechanisms in the brain. Obesity and systemic inflammation may interfere with immunological processes which promote disease progression.
Alterations in the distribution of different neurotrophic factors and in the expression of their receptors such as the brain-derived neurotrophic factor (BDNF) have been described in AD.

PET scan of the brain of a person with AD showing a loss of function in the temporal lobe of Alzheimer's disease is usually diagnosed based on the person's medical history, history from relatives, and behavioral observations. The presence of characteristic neurological and neuropsychological features and the absence of alternative conditions is supportive. Advanced medical imaging with computed tomography (CT) or magnetic resonance imaging (MRI), and with single-photon emission computed tomography (SPECT) or positron emission tomography (PET) can be used to help exclude other cerebral pathology or subtypes of dementia. Moreover, it may predict conversion from prodromal stages (mild cognitive impairment) to Alzheimer's disease.
Assessment of intellectual functioning including memory testing can further characterize the state of the disease. Medical organizations have created diagnostic criteria to ease and standardize the diagnostic process for practicing physicians. The diagnosis can be confirmed with very high accuracy post-mortem when brain material is available and can be examined histologically.

The National Institute of Neurological and Communicative Disorders and Stroke (NINCDS) and the Alzheimer's Disease and Related Disorders Association (ADRDA, now known as the Alzheimer's Association) established the most commonly used NINCDS-ADRDA Alzheimer's Criteria for diagnosis in 1984, extensively updated in 2007. These criteria require that the presence of cognitive impairment, and a suspected dementia syndrome, be confirmed by neuropsychological testing for a clinical diagnosis of possible or probable AD. A histopathologic confirmation including a microscopic examination of brain tissue is required for a definitive diagnosis. Good statistical reliability and validity have been shown between the diagnostic criteria and definitive histopathological confirmation. Eight cognitive domains are most commonly impaired in AD--memory, language, perceptual skills, attention, constructive abilities, orientation, problem-solving, and functional abilities. These domains are equivalent to the NINCDS-ADRDA Alzheimer's Criteria as listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) published by the American Psychiatric Association.

Neuropsychological screening tests can help in the diagnosis of AD. In the tests, people are instructed to copy drawings similar to the one shown in the picture, remember words, read, and subtract serial numbers. Neuropsychological tests such as the mini–mental state examination (MMSE) are widely used to evaluate the cognitive impairments needed for diagnosis. More comprehensive test arrays are necessary for high reliability of results, particularly in the earliest stages of the disease. Neurological examination in early AD will usually provide normal results, except for obvious cognitive impairment, which may not differ from that resulting from other disease processes, including other causes of dementia.
Further neurological examinations are crucial in the differential diagnosis of AD and other diseases. Interviews with family members are also utilized in the assessment of the disease. Caregivers can supply important information on the daily living abilities, as well as on the decrease, over time, of the person's mental function. A caregiver's viewpoint is particularly important since a person with AD is commonly unaware of his own deficits. Many times, families also have difficulties in the detection of initial dementia symptoms and may not communicate accurate information to a physician.
Supplemental testing provides extra information on some features of the disease or is used to rule out other diagnoses. Blood tests can identify other causes for dementia than AD—causes which may, in rare cases, be reversible. It is common to perform thyroid function tests, assess B12, rule out syphilis, rule out metabolic problems (including tests for kidney function, electrolyte levels, and for diabetes), and assess levels of heavy metals (e.g. lead, mercury) and anemia. (It is also necessary to rule out delirium).
Psychological tests for depression are employed since depression can either be concurrent with AD (see Depression of Alzheimer's disease), an early sign of cognitive impairment, or even the cause.

Intellectual activities such as playing chess or regular social interaction have been linked to a reduced risk of AD in epidemiological studies, although no causal relationship has been found. At present, there is no definitive evidence to support that any particular measure is effective in preventing AD. Global studies of measures to prevent or delay the onset of AD have often produced inconsistent results. Epidemiological studies have proposed relationships between certain modifiable factors, such as diet, cardiovascular risk, pharmaceutical products, or intellectual activities among others, and a population's likelihood of developing AD. Only further research, including clinical trials, will reveal whether these factors can help to prevent AD.

Although cardiovascular risk factors, such as hypercholesterolemia, hypertension, diabetes, and smoking, are associated with a higher risk of onset and course of AD, statins, which are cholesterol-lowering drugs, have not been effective in preventing or improving the course of the disease.
Long-term usage of non-steroidal anti-inflammatory drugs (NSAIDs) is associated with a reduced likelihood of developing AD. Evidence also supports the notion that NSAIDs can reduce inflammation related to amyloid plaques. No prevention trial has been completed. They do not appear to be useful as a treatment. Hormone replacement therapy, although previously used, may increase the risk of dementia.

People who engage in intellectual activities such as reading, playing board games, completing crossword puzzles, playing musical instruments, or having regular social interaction show a reduced risk for Alzheimer's disease. This is compatible with the cognitive reserve theory, which states that some life experiences result in more efficient neural functioning providing the individual a cognitive reserve that delays the onset of dementia manifestations. Education delays the onset of AD syndrome but is not related to earlier death after diagnosis. Learning a second language even later in life seems to delay getting Alzheimer's disease. Physical activity is also associated with a reduced risk of AD.

People who eat a healthy, Japanese, or Mediterranean diet have a lower risk of AD. A Mediterranean diet may improve outcomes in those with the disease. Those who eat a diet high in saturated fats and simple carbohydrates (mono- and disaccharide) have a higher risk. The Mediterranean diet's beneficial cardiovascular effect has been proposed as the mechanism of action.
Conclusions on dietary components have at times been difficult to ascertain as results have differed between population-based studies and randomized controlled trials. There is limited evidence that light to moderate use of alcohol, particularly red wine, is associated with a lower risk of AD. There is tentative evidence that caffeine may be protective. A number of foods high in flavonoids such as cocoa, red wine, and tea may decrease the risk of AD.
Reviews on the use of vitamins and minerals have not found enough consistent evidence to recommend them. This includes vitamins A, C, E, selenium, zinc, and folic acid with or without vitamin B12. Additionally, vitamin E is associated with health risks. Trials examining folic acid (B9) and other B vitamins failed to show any significant association with cognitive decline. In those already affected with AD adding docosahexaenoic acid, an omega-3 fatty acid, to the diet has not been found to slow decline.
Curcumin as of 2010 has not shown benefit in people even though there is tentative evidence in animals. There is inconsistent and unconvincing evidence that ginkgo has any positive effect on cognitive impairment and dementia. As of 2008, there is no concrete evidence that cannabinoids are effective in improving the symptoms of AD or dementia; however, some research looks promising.

There is no cure for Alzheimer's disease; available treatments offer relatively small symptomatic benefits but remain palliative in nature. Current treatments can be divided into pharmaceutical, psychosocial, and caregiving.

Three-dimensional molecular model of donepezil, an acetylcholinesterase inhibitor used in the treatment of AD symptoms.

Molecular structure of memantine, a medication approved for advanced AD symptoms Five medications are currently used to treat the cognitive problems of AD: four are acetylcholinesterase inhibitors (tacrine, rivastigmine, galantamine, and donepezil) and the other (memantine) is an NMDA receptor antagonist. The benefit from their use is small. No medication has been clearly shown to delay or halt the progression of the disease.
Reduction in the activity of the cholinergic neurons is a well-known feature of Alzheimer's disease. Acetylcholinesterase inhibitors are employed to reduce the rate at which acetylcholine (Ach) is broken down, thereby increasing the concentration of Ach in the brain and combating the loss of Ach caused by the death of cholinergic neurons. There is evidence for the efficacy of these medications in mild to moderate Alzheimer's disease, and some evidence for their use in the advanced stage. Only donepezil is approved for the treatment of advanced AD dementia. The use of these drugs for mild cognitive impairment has not shown any effect in a delay of the onset of AD. The most common side effects are nausea and vomiting, both of which are linked to cholinergic excess. These side effects arise in approximately 10–20% of users, are mild to moderate in severity, and can be managed by slowly adjusting medication doses. Less common secondary effects include muscle cramps, decreased heart rate (bradycardia), decreased appetite and weight, and increased gastric acid production.
Glutamate is a useful excitatory neurotransmitter of the nervous system, although excessive amounts in the brain can lead to cell death through a process called excitotoxicity which consists of the overstimulation of glutamate receptors. Excitotoxicity occurs not only in Alzheimer's disease but also in other neurological diseases such as Parkinson's disease and multiple sclerosis. Memantine is a noncompetitive NMDA receptor antagonist first used as an anti-influenza agent. It acts on the glutamatergic system by blocking NMDA receptors and inhibiting their overstimulation by glutamate. Memantine has been shown to have a small benefit in the treatment of Alzheimer's disease. Reported adverse events with memantine are infrequent and mild, including hallucinations, confusion, dizziness, headache, and fatigue. The combination of memantine and donepezil has been shown to be "of statistically significant but clinically marginal effectiveness".
Atypical antipsychotics are modestly useful in reducing aggression and psychosis in people with Alzheimer's disease, but their advantages are offset by serious adverse effects, such as stroke, movement difficulties, or cognitive decline. When used in the long term, they have been shown to associate with increased mortality. Stopping antipsychotic use in this group of people appears to be safe.
Hyperfine A while promising, requires further evidence before its use can be recommended.

A specifically designed room for sensory integration therapy, also called Snoezelen; is an emotion-oriented psycho-social intervention for people with dementia, Psycho-social interventions are used as an adjunct to pharmaceutical treatment and can be classified within behavior-, emotion-, cognition- or stimulation-oriented approaches. Research on efficacy is unavailable and rarely specific to AD, focusing instead on dementia in general.
Behavioral interventions attempt to identify and reduce the antecedents and consequences of problem behaviors. This approach has not shown success in improving overall functioning but can help to reduce some specific problem behaviors, such as incontinence. There is a lack of high-quality data on the effectiveness of these techniques in other behavior problems such as wandering.
Emotion-oriented interventions include reminiscence therapy, validation therapy, supportive psychotherapy, sensory integration, also called Snoezelen, and simulated presence therapy. Supportive psychotherapy has received little or no formal scientific study, but some clinicians find it useful in helping mildly impaired people adjust to their illnesses. Reminiscence therapy (RT) involves the discussion of past experiences individually or in groups, many times with the aid of photographs, household items, music, sound recordings, or other familiar items from the past. Although there are few quality studies on the effectiveness of RT, it may be beneficial for cognition and mood. Simulated presence therapy (SPT) is based on attachment theories and involves playing a recording with the voices of the closest relatives of the person with Alzheimer's disease. There is partial evidence indicating that SPT may reduce challenging behaviors. Finally, validation therapy is based on acceptance of the reality and personal truth of another's experience, while sensory integration is based on exercises aimed to stimulate the senses. There is no evidence to support the usefulness of these therapies.
The aim of cognition-oriented treatments, which include reality orientation and cognitive retraining, is the reduction of cognitive deficits. Reality orientation consists of the presentation of information about time, place, or person to ease the understanding of the person about their surroundings and his or her place in them. On the other hand, cognitive retraining tries to improve impaired capacities by exercitation of mental abilities. Both have shown some efficacy in improving cognitive capacities, although in some studies these effects were transient and negative effects, such as frustration, have also been reported.
Stimulation-oriented treatments include art, music, pet therapies, exercise, and any other kind of recreational activities. Stimulation has modest support for improving behavior, mood, and, to a lesser extent, function. Nevertheless, as important as these effects are, the main support for the use of stimulation therapies is the change in the person's routine.

Caregiving and dementia Since Alzheimer's have no cure and it gradually renders people incapable of tending to their own needs, caregiving essentially is the treatment and must be carefully managed over the course of the disease.
During the early and moderate stages, modifications to the living environment and lifestyle can increase patient safety and reduce the caretaker burden. Examples of such modifications are the adherence to simplified routines, the placing of safety locks, the labeling of household items to cue the person with the disease, or the use of modified daily life objects. If eating becomes problematic, food will need to be prepared in smaller pieces or even pureed. When swallowing difficulties arise, the use of feeding tubes may be required. In such cases, the medical efficacy and ethics of continuing feeding are important considerations of the caregivers and family members. The use of physical restraints is rarely indicated in any stage of the disease, although there are situations when they are necessary to prevent harm to the person with AD or their caregivers.
As the disease progresses, different medical issues can appear, such as oral and dental disease, pressure ulcers, malnutrition, hygiene problems, or respiratory, skin, or eye infections. Careful management can prevent them, while professional treatment is needed when they do arise. During the final stages of the disease, treatment is centered on relieving discomfort until death, often with the help of hospice.
Feeding tubes People with Alzheimer's disease (and other forms of dementia) often develop problems with eating, due to difficulties in swallowing, reduced appetite, or the inability to recognize food. Their careers and families often request they have some form of a feeding tube. However, there is no evidence that this helps people with advanced Alzheimer's to gain weight, regain strength or improve their quality of life. In fact, their use might carry an increased risk of aspiration pneumonia, use of physical restraints, and increased risk of pressure ulcers.

Disability-adjusted life year for Alzheimer's and other dementia per 100,000 inhabitants in 2004.
 
The early stages of Alzheimer's disease are difficult to diagnose. A definitive diagnosis is usually made once cognitive impairment compromises daily living activities, although the person may still be living independently. The symptoms will progress from mild cognitive problems, such as memory loss through increasing stages of cognitive and non-cognitive disturbances, eliminating any possibility of independent living, especially in the late stages of the disease.

​The life expectancy of the population with the disease is reduced. The mean life expectancy following diagnosis is approximately six years. Fewer than 3% of people live more than fourteen years. Disease features significantly associated with reduced survival are an increased severity of cognitive impairment, decreased functional level, history of falls, and disturbances in the neurological examination. Other coincident diseases such as heart problems, diabetes, or a history of alcohol abuse are also related to shortened survival. While the earlier the age at onset the higher the total survival years, life expectancy is particularly reduced when compared to the healthy population among those who are younger. Men have a less favorable survival prognosis than women.
The disease is the underlying cause of death in 68% of all cases. Pneumonia and dehydration are the most frequent immediate causes of death brought by AD, while cancer is a less frequent cause of death than in the general population.
Epidemiology Rates after age 65, Age New affected
per thousand
person-years
65–69 3
70–74 6
75–79 9
80–8423
85–8940
90–    69 Two main measures are used in epidemiological studies: incidence and prevalence. Incidence is the number of new cases per unit of person–time at risk (usually a number of new cases per thousand person–years); while prevalence is the total number of cases of the disease in the population at any given time.
Regarding incidence, cohort longitudinal studies (studies where a disease-free population is followed over the years) provide rates between 10 and 15 per thousand person–years for all dementia and 5–8 for AD, which means that half of new dementia cases each year are AD. Advancing age is a primary risk factor for the disease and incidence rates are not equal for all ages: every five years after the age of 65, the risk of acquiring the disease approximately doubles, increasing from 3 to as much as 69 per thousand person-years. There are also sex differences in the incidence rates, with women having a higher risk of developing AD, particularly in the population older than 85. The risk of dying from Alzheimer's disease is twenty-six percent higher among the non-Hispanic white population than among the non-Hispanic black population, whereas the Hispanic population has a thirty percent lower risk than the non-Hispanic white population.

Deaths per million persons in 2012 due to dementia including Alzheimer's disease.
  0-4
  5-8
  9-10
  11-13
  14-17
  18-24
  25-45
  46-114
  115-375
  376-1266
Prevalence of AD in populations is dependent upon different factors including incidence and survival. Since the incidence of AD increases with age, it is particularly important to include the mean age of the population of interest. In the United States, Alzheimer's prevalence was estimated to be 1.6% in 2000 both overall and in the 65–74 age group, with the rate increasing to 19% in the 75–84 group and to 42% in the greater than 84 group. Prevalence rates in less developed regions are lower. The World Health Organization estimated that in 2005, 0.379% of people worldwide had dementia and that the prevalence would increase to 0.441% in 2015 and to 0.556% in 2030. Other studies have reached similar conclusions. Another study estimated that in 2006, 0.40% of the world population (range 0.17–0.89%; absolute number 26.6 million, range 11.4–59.4 million) were afflicted by AD and that the prevalence rate would triple and the absolute number would quadruple by 2050.
It may contribute to 60% to 70% of cases of dementia.

Alois Alzheimer's patient Auguste Deter in 1902. Hers was the first described case of what became known as Alzheimer's disease. The ancient Greek and Roman philosophers and physicians associated old age with increasing dementia. It was not until 1901 that German psychiatrist Alois Alzheimer identified the first case of what became known as Alzheimer's disease in a fifty-year-old woman he called Auguste D. He followed her case until she died in 1906 when he first reported publicly on it. During the next five years, eleven similar cases were reported in the medical literature, some of them already using the term Alzheimer's disease. The disease was first described as a distinctive disease by Emil Kraepelin after suppressing some of the clinical (delusions and hallucinations) and pathological features (arteriosclerotic changes) contained in the original report of Auguste D. He included Alzheimer's disease, also named presenile dementia by Kraepelin, as a subtype of senile dementia in the eighth edition of his Textbook of Psychiatry, published on 15 July 1910.

For most of the 20th century, the diagnosis of Alzheimer's disease was reserved for individuals between the ages of 45 and 65 who developed symptoms of dementia. The terminology changed after 1977 when a conference on AD concluded that the clinical and pathological manifestations of presenile and senile dementia were almost identical, although the authors also added that this did not rule out the possibility that they had different causes. This eventually led to the diagnosis of Alzheimer's disease independent of age. The term senile dementia of the Alzheimer's type (SDAT) was used for a time to describe the condition in those over 65, with classical Alzheimer's disease being used to describe those who were younger. Eventually, the term Alzheimer's disease was formally adopted in medical nomenclature to describe individuals of all ages with a characteristic common symptom pattern, disease course, and neuropathology.

Alzheimer's disease may be among the costliest diseases for society in Europe and the United States, while their costs in other countries such as Argentina, and South Korea, are also high and rising. These costs will probably increase with the aging of society, becoming an important social problem. AD-associated costs include direct medical costs such as nursing home care, direct nonmedical costs such as in-home daycare, and indirect costs such as lost productivity of both patient and caregiver. Numbers vary between studies, but dementia costs worldwide have been calculated at around $160 billion, while costs of Alzheimer's disease in the United States may be $100 billion each year.

The greatest origin of costs for society is the long-term care by health care professionals and particularly institutionalization, which corresponds to 2/3 of the total costs for society. The cost of living at home is also very high, especially when informal costs for the family, such as caregiving time and the caregiver's lost earnings, are taken into account.
Costs increase with dementia severity and the presence of behavioral disturbances and are related to the increased caregiving time required for the provision of physical care. Therefore, any treatment that slows cognitive decline, delays institutionalization, or reduces caregivers' hours will have economic benefits. Economic evaluations of current treatments have shown positive results.

The role of the main caregiver is often taken by the spouse or a close relative. Alzheimer's disease is known for placing a great burden on caregivers which includes social, psychological, physical or economic aspects. Home care is usually preferred by people with AD and their families. This option also delays or eliminates the need for more professional and costly levels of care. Nevertheless, two-thirds of nursing home residents have dementia.
Dementia caregivers are subject to high rates of physical and mental disorders. Factors associated with greater psycho-social problems of the primary caregivers include having an affected person at home, the carer being a spouse, demanding behaviors of the cared person such as depression, behavioral disturbances, hallucinations, sleep problems or walking disruptions, and social isolation. Regarding economic problems, family caregivers often give up time from work to spend 47 hours per week on average with a person with AD, while the costs of caring for them are high. Direct and indirect costs of caring for an Alzheimer's patient average between $18,000 and $77,500 per year in the United States, depending on the study.
Cognitive behavioral therapy and the teaching of coping strategies either individually or in groups have demonstrated their efficacy in improving caregivers' psychological health.

Charlton Heston and Ronald Reagan at a White House meeting. Both would later be diagnosed with Alzheimer's disease. Because Alzheimer's disease is common, many notable people have developed it. Well-known examples are former United States President Ronald Reagan and Irish writer Iris Murdoch, both of whom were the subjects of scientific articles examining how their cognitive capacities deteriorated with the disease. Other cases include the retired footballer Ferenc Puskás, former Prime Ministers Harold Wilson (United Kingdom) and Adolfo Suárez (Spain), Indian politician George Fernandes, actress Rita Hayworth, actor Charlton Heston, actor-director Robert Loggia, author Harnett Kane, Nobel laureate Charles K. Kao, novelist Terry Pratchett, director Jacques Rivette, and politician and activist Sargent Shriver.

Alzheimer's disease in the media AD has been portrayed in films such as Iris (2001), based on John Bayley's memoir of his wife Iris Murdoch; The Notebook (2004), based on Nicholas Sparks' 1996 novel of the same name; A Moment to Remember (2004); Tharmatha (2005); Memories of Tomorrow (Ashita no Kioku) (2006), based on Hiroshi Ogiwara's novel of the same name; Away from Her (2006), based on Alice Munro's short story "The Bear Came over the Mountain"; Still Alice (2014), about a Harvard professor who has early onset Alzheimer's disease, based on Lisa Genova's 2007 novel of the same name and featuring Julianne Moore in the title role. Documentaries on Alzheimer's disease include Malcolm and Barbara: A Love Story (1999) and Malcolm and Barbara: Love's Farewell (2007), both featuring Malcolm Pointon.

Alzheimer's disease research As of 2014, the safety and efficacy of more than 400 pharmaceutical treatments had been or were being investigated in over 1,500 clinical trials worldwide, and approximately a quarter of these compounds are in Phase III trials, the last step prior to review by regulatory agencies.
One area of clinical research is focused on treating the underlying disease pathology. The reduction of beta-amyloid levels is a common target of compounds[259] (such as apomorphine) under investigation. Immunotherapy or vaccination for the amyloid protein is one treatment modality under study. Unlike preventative vaccination, putative therapy would be used to treat people already diagnosed. It is based upon the concept of training the immune system to recognize, attack, and reverse the deposition of amyloid, thereby altering the course of the disease. An example of such a vaccine under investigation was ACC-001, although the trials were suspended in 2008. Another similar agent is bapineuzumab, an antibody designed as identical to the naturally induced anti-amyloid antibody. Other approaches are neuroprotective agents, such as AL-108, and metal-protein interaction attenuation agents, such as PBT2. A TNF α receptor-blocking fusion protein, etanercept has shown encouraging results.
In 2008, two separate clinical trials showed positive results in modifying the course of disease in mild to moderate AD with methylthioninium chloride, a drug that inhibits tau aggregation, and dimension, an antihistamine. The consecutive phase-III trials of dimebon failed to show positive effects in the primary and secondary endpoints. Work with methylthioninium chloride showed that the bioavailability of methylthioninium from the gut was affected by feeding and by stomach acidity, leading to unexpectedly variable dosing. A new stabilized formulation, the prodrug LMTX, is in phase-III trials (in 2014).

The herpes simplex virus HSV-1 has been found in the same areas as amyloid plaques. This suggested the possibility that AD could be treated or prevented with antiviral medication. Studies of antivirals in cell cultures have shown promising results.

Traumatic brain injury (T.B.I), also known as intracranial injury, occurs when an external force traumatically injures the brain. T.B.I can be classified based on severity, mechanism (closed or penetrating head injury), or other features (e.g., occurring in a specific location or over a widespread area). Head injury usually refers to T.B.I but is a broader category because it can involve damage to structures other than the brain, such as the scalp and skull.
T.B.I is a major cause of death and disability worldwide, especially in children and young adults. Males sustain traumatic brain injuries more frequently than females. Causes include falls, vehicle accidents, and violence. Prevention measures include the use of technology to protect those suffering from automobile accidents, such as seat belts and sports or motorcycle helmets, as well as efforts to reduce the number of automobile accidents, such as safety education programs and enforcement of traffic laws.

Brain trauma can occur as a consequence of a focal impact upon the head, by a sudden acceleration/deceleration within the cranium, or by a complex combination of both movement and sudden impact. In addition to the damage caused at the moment of injury, brain trauma causes secondary injury, a variety of events that take place in the minutes and days following the injury.
These processes, which include alterations in cerebral blood flow and the pressure within the skull, contribute substantially to the damage from the initial injury.
T.B.I can cause a host of physical, cognitive, social, emotional, and behavioral effects, and outcomes can range from complete recovery to permanent disability or death. The 20th century saw critical developments in diagnosis and treatment that decreased death rates and improved outcomes. Some of the current imaging techniques used for diagnosis and treatment include computed tomography and M.R.I  (magnetic resonance imaging). Depending on the injury, treatment required may be minimal or may include interventions such as medications, emergency surgery, or surgery years later. Physical therapy, speech therapy, recreation therapy, occupational therapy, and vision therapy may be employed for rehabilitation. Counseling supported employment, and community support services may also be useful.

TAKE A SCREEN TEST

Traumatic brain injury is defined as damage to the brain resulting from external mechanical force, such as rapid acceleration or deceleration, impact, blast waves, or penetration by a projectile. Brain function is temporarily, or permanently impaired, and structural damage may or may not be detectable with current technology.
TBI is one of two subsets of acquired brain injury (brain damage that occurs after birth); the other subset is a non-traumatic brain injury, which does not involve external mechanical force (examples include stroke and infection). All traumatic brain injuries are head injuries, but the latter term may also refer to injury to other parts of the head. However, the terms head injury and brain injury are often used interchangeably. Similarly, brain injuries fall under the classification of central nervous system injuries and neurotrauma. In the neuropsychology research literature, in general, the term "traumatic brain injury" is used to refer to non-penetrating traumatic brain injuries.
TBI is usually classified based on severity, anatomical features of the injury, and the mechanism (the causative forces). Mechanism-related classification divides TBI into closed and penetrating head injuries. A closed (also called nonpenetrating, or blunt) injury occurs when the brain is not exposed. A penetrating, or open, head injury occurs when an object pierces the skull and breaches the dura mater, the outermost membrane surrounding the brain.

hours Brain injuries can be classified into mild, moderate, and severe categories. The Glasgow Coma Scale (GCS), the most commonly used system for classifying TBI severity, grades a person's level of consciousness on a scale of 3–15 based on verbal, motor, and eye-opening k to stimuli.[14] In general, it is agreed that a TBI with a GCS of 13 or above is mild, 9–12 is moderate, and 8 or below is severe. Similar systems exist for young children. However, the GCS grading system has limited ability to predict outcomes. Because of this, other classification systems such as the one shown in the table are also used to help determine severity. A current model developed by the Department of Defense and Department of Veterans Affairs uses all three criteria of GCS after resuscitation, duration of post-traumatic amnesia (PTA), and loss of consciousness (LOC). It also has been proposed to use changes that are visible in neuroimaging, such as swelling, focal lesions, or diffuse injury as a method of classification. Grading scales also exist to classify the severity of mild TBI, commonly called concussion; these use duration of LOC, PTA, and other concussion symptoms.
Pathological features main article: Focal and diffuse brain injury

CT scan Spread of the subdural hematoma (single arrows), and midline shift (double arrows) Systems also exist to classify TBI by its pathological features. Lesions can be extra-axial, (occurring within the skull but outside of the brain) or intra-axial (occurring within the brain tissue). Damage from TBI can be focal or diffuse, confined to specific areas, or distributed in a more general manner, respectively. However, it is common for both types of injury to exist in a given case.
Diffuse injury manifests with little apparent damage in neuroimaging studies, but lesions can be seen with microscopy techniques post-mortem, and in the early 2000s, researchers discovered that diffusion tensor imaging (DTI), a way of processing MRI images that shows white matter tracts, was an effective tool for displaying the extent of diffuse axonal injury. Types of injuries considered diffuse include edema (swelling) and diffuse axonal injury, which is widespread damage to axons including white matter tracts and projections to the cortex. Types of injuries considered diffuse include concussion and diffuse axonal injury, widespread damage to axons in areas including white matter and the cerebral hemispheres.
Focal injuries often produce symptoms related to the functions of the damaged area. Research shows that the most common areas to have focal lesions in non-penetrating traumatic brain injury are the orbitofrontal cortex (the lower surface of the frontal lobes) and the anterior temporal lobes, areas that are involved in social behavior, emotion regulation, olfaction, and decision-making, hence the common social/emotional and judgment deficits following moderate-severe TBI. Symptoms such as hemiparesis or aphasia can also occur when less commonly affected areas such as motor or language areas are, respectively, damaged.
One type of focal injury, cerebral laceration, occurs when the tissue is cut or torn. Such tearing is common in the orbitofrontal cortex in particular, because of bony protrusions on the interior skull ridge above the eyes. In a similar injury, cerebral contusion (bruising of brain tissue), blood is mixed among the tissue. In contrast, intracranial hemorrhage involves bleeding that is not mixed with tissue.
Hematomas, also focal lesions, are collections of blood in or around the brain that can result from hemorrhage. Intracerebral hemorrhage, with bleeding in the brain tissue itself, is an intra-axial lesion. Extra-axial lesions include epidural hematoma, subdural hematoma, subarachnoid hemorrhage, and intraventricular hemorrhage. Epidural hematoma involves bleeding into the area between the skull and the dura mater, the outermost of the three membranes surrounding the brain. In subdural hematoma, bleeding occurs between the dura and the arachnoid mater. Subarachnoid hemorrhage involves bleeding into the space between the arachnoid membrane and the pia mater. Intraventricular hemorrhage occurs when there is bleeding in the ventricles.
Signs and symptoms
Unequal pupil size is potentially a sign of a serious brain injury. Symptoms are dependent on the type of TBI (diffuse or focal) and the part of the brain that is affected. Unconsciousness tends to last longer for people with injuries on the left side of the brain than for those with injuries on the right. Symptoms are also dependent on the injury's severity. With mild TBI, the patient may remain conscious or may lose consciousness for a few seconds or minutes. Other symptoms of mild TBI include headache, vomiting, nausea, lack of motor coordination, dizziness, difficulty balancing, lightheadedness, blurred vision or tired eyes, ringing in the ears, bad taste in the mouth, fatigue or lethargy, and changes in sleep patterns. Cognitive and emotional symptoms include behavioral or mood changes, confusion, and trouble with memory, concentration, attention, or thinking. Mild TBI symptoms may also be present in moderate and severe injuries.
A person with a moderate or severe TBI may have a headache that does not go away, repeated vomiting or nausea, convulsions, an inability to awaken, dilation of one or both pupils, slurred speech, aphasia (word-finding difficulties), dysarthria (muscle weakness that causes disordered speech), weakness or numbness in the limbs, loss of coordination, confusion, restlessness, or agitation. Common long-term symptoms of moderate to severe TBI are changes in appropriate social behavior, deficits in social judgment, and cognitive changes, especially problems with sustained attention, processing speed, and executive functioning. Alexithymia, a deficiency in identifying, understanding, processing, and describing emotions occurs in 60.9% of individuals with TBI. Cognitive and social deficits have long-term consequences for the daily lives of people with moderate to severe TBI but can be improved with appropriate rehabilitation.
When the pressure within the skull (intracranial pressure, abbreviated ICP) rises too high, it can be deadly. Signs of increased ICP include decreasing level of consciousness, paralysis or weakness on one side of the body, and a blown pupil, one that fails to constrict in response to light or is slow to do so. Cushing's triad, a slow heart rate with high blood pressure and respiratory depression is a classic manifestation of significantly raised ICP. Anisocoria, unequal pupil size, is another sign of serious TBI. Abnormal posturing, a characteristic positioning of the limbs caused by severe diffuse injury or high ICP, is an ominous sign.
Small children with moderate to severe TBI may have some of these symptoms but have difficulty communicating them. Other signs seen in young children include persistent crying, inability to be consoled, listlessness, refusal to nurse or eat, and irritability.
Causes The most common causes of TBI in the U.S. include violence, transportation accidents, construction, and sports. Motorbikes are a major cause, increasing in significance in developing countries as other causes reduce. The estimates that between 1.6 and 3.8 million traumatic brain injuries each year are a result of sports and recreation activities in the US. In children aged two to four, falls are the most common cause of TBI, while in older children traffic accidents compete with falls for this position. TBI is the third most common injury to result from child abuse. Abuse causes 19% of cases of pediatric brain trauma, and the death rate is higher among these cases. Although men are twice as likely to have a TBI. Domestic violence is another cause of TBI, as are work-related and industrial accidents. Firearms and blast injuries from explosions are other causes of TBI, which is the leading cause of death and disability in war zones. According to Representative Bill Pascrell (Democrat, NJ), TBI is "the signature injury of the wars in Iraq and Afghanistan." There is a promising technology called activation database-guided EEG biofeedback, which has been documented to return a TBI's auditory memory ability to above the control group's performance.

Ricochet of the brain within the skull may account for the coup-contrecoup phenomenon. The type, direction, intensity, and duration of forces all contribute to the characteristics and severity of TBI. Forces that may contribute to TBI include angular, rotational, shear, and translational forces.
Even in the absence of an impact, significant acceleration or deceleration of the head can cause TBI; however, in most cases, a combination of impact and acceleration is probably to blame. Forces involving the head striking or being struck by something, termed contact or impact loading, are the cause of most focal injuries, and movement of the brain within the skull, termed noncontact or inertial loading, usually causes diffuse injuries. The violent shaking of an infant that causes shaken baby syndrome commonly manifests as diffuse injury. In impact loading, the force sends shock waves through the skull and brain, resulting in tissue damage. Shock waves caused by penetrating injuries can also destroy tissue along the path of a projectile, compounding the damage caused by the missile itself.
Damage may occur directly under the site of impact, or it may occur on the side opposite the impact (coup and contrecoup injury, respectively). When a moving object impacts the stationary head, coup injuries are typical, while contrecoup injuries are usually produced when the moving head strikes a stationary object.
Primary and secondary injury
MRI scan showing damage due to brain herniation after TBI.
Main article: Primary and secondary brain injury A large percentage of the people killed by brain trauma do not die right away but rather days to weeks after the event; rather than improving after being hospitalized, some 40% of TBI patients deteriorate. Primary brain injury (the damage that occurs at the moment of trauma when tissues and blood vessels are stretched, compressed, and torn) is not adequate to explain this deterioration; rather, it is caused by secondary injury, a complex set of cellular processes and biochemical cascades that occur in the minutes to days following the trauma. These secondary processes can dramatically worsen the damage caused by primary injury and account for the greatest number of TBI deaths occurring in hospitals.
Secondary injury events include damage to the blood–brain barrier, release of factors that cause inflammation, free radical overload, excessive release of the neurotransmitter glutamate (excitotoxicity), influx of calcium and sodium ions into neurons, and dysfunction of mitochondria. Injured axons in the brain's white matter may separate from their cell bodies as a result of secondary injury, potentially killing those neurons. Other factors in secondary injury are changes in the blood flow to the brain; ischemia (insufficient blood flow); cerebral hypoxia (insufficient oxygen in the brain); cerebral edema (swelling of the brain); and raised intracranial pressure (the pressure within the skull). Intracranial pressure may rise due to swelling or a mass effect from a lesion, such as a hemorrhage. As a result, cerebral perfusion pressure (the pressure of blood flow in the brain) is reduced, and ischemia results. When the pressure within the skull rises too high, it can cause brain death or herniation, in which parts of the brain are squeezed by structures in the skull. A particularly weak part of the skull that is vulnerable to damage causing extradural hematoma is the pterion, deep in which lies the middle meningeal artery, which is easily damaged in fractures of the pterion. Since the pterion is so weak, this type of injury can easily occur and can be secondary due to trauma to other parts of the skull where the impact forces spread to the pterion.
Diagnosis
CT scan showing epidural hematoma (arrow)Diagnosis is suspected based on lesion circumstances and clinical evidence, most prominently a neurological examination, for example checking whether the pupils constrict normally in response to light and assigning a Glasgow Coma Score. Neuroimaging helps in determining the diagnosis and prognosis and in deciding what treatments to give.
The preferred radiologic test in the emergency setting is computed tomography (CT): it is quick, accurate, and widely available. Follow-up CT scans may be performed later to determine whether the injury has progressed.
Magnetic resonance imaging (MRI) can show more detail than CT and can add information about expected outcomes in the long term. It is more useful than CT for detecting injury characteristics such as diffuse axonal injury in the longer term. However, MRI is not used in the emergency setting for reasons including its relative inefficacy in detecting bleeds and fractures, its lengthy acquisition of images, the inaccessibility of the patient in the machine, and its incompatibility with metal items used in emergency care. A variant of MRI since 2012 is High-definition fiber tracking (HDFT).
Other techniques may be used to confirm a particular diagnosis. X-rays are still used for head trauma, but evidence suggests they are not useful; head injuries are either so mild that they do not need imaging or severe enough to merit the more accurate CT. Angiography may be used to detect blood vessel pathology when risk factors such as penetrating head trauma are involved. Functional imaging can measure cerebral blood flow or metabolism, inferring neuronal activity in specific regions and potentially helping to predict outcomes. Electroencephalography and transcranial Doppler may also be used. The most sensitive physical measure to date is the quantitative EEG, which has documented an 80% to 100% ability in discriminating between normal and traumatic brain-injured subjects.
Neuropsychological assessment can be performed to evaluate the long-term cognitive sequelae and to aid in the planning of the rehabilitation. Instruments range from short measures of general mental functioning to complete batteries formed of different domain-specific tests.
Prevention
Protective sports equipment such as helmets can help to protect athletes from head injuries. Since a major cause of TBI are vehicle accidents, their prevention or the amelioration of their consequences can both reduce the incidence and gravity of TBI. In accidents, damage can be reduced by the use of seat belts, child safety seats, motorcycle helmets, and the presence of roll bars and airbags. Education programs exist to lower the number of crashes. In addition, changes to public policy and safety laws can be made; these include speed limits, seat belt and helmet laws, and road engineering practices.
Changes to common practices in sports have also been discussed. An increase in the use of helmets could reduce the incidence of TBI. Due to the possibility that repeatedly "heading" a ball while practicing soccer could cause cumulative brain injury, the idea of introducing protective headgear for players has been proposed. Improved equipment design can enhance safety; softer baseballs reduce head injury risk. Rules against dangerous types of contact, such as "spear tackling" in American football, when one player tackles another headfirst, may also reduce head injury rates.
Falls can be avoided by installing grab bars in bathrooms and handrails on stairways; removing tripping hazards such as throw rugs or installing window guards and safety gates at the top and bottom of stairs around young children. Playgrounds with shock-absorbing surfaces such as mulch or sand also prevent head injuries. Child abuse prevention is another tactic; programs exist to prevent shaken baby syndrome by educating about the dangers of shaking children. Gun safety, including keeping guns unloaded and locked, is another preventative measure. Studies on the effect of laws that aim to control access to guns in the United States have been insufficient to determine their effectiveness in preventing a number of deaths or injuries.
Recent clinical and laboratory research by neurosurgeon Julian Bailes, M.D., and his colleagues from West Virginia University, have resulted in papers showing that dietary supplementation with omega-3 DHA offers protection against the biochemical brain damage that occurs after a traumatic injury. Rats given DHA prior to induced brain injuries suffered smaller increases in two key markers for brain damage (APP and caspase-3), as compared with rats given no DHA. “The potential for DHA to provide prophylactic benefit to the brain against traumatic injury appears promising and requires further investigation. The essential concept of daily dietary supplementation with DHA, so that those at significant risk may be preloaded to provide protection against the acute effects of TBI, has tremendous public health implications.”
Furthermore, acetylcysteine has been confirmed, in a recent double-blind placebo-controlled trial conducted by the US military, to reduce the effects of blast-induced mild traumatic brain and neurological injury in soldiers. Multiple animal studies have also demonstrated its efficacy in reducing the damage associated with moderate traumatic brain or spinal injury, and also ischemia-induced brain injury. In particular, it has been demonstrated through multiple studies to significantly reduce neuronal losses and improve cognitive and neurological outcomes associated with these traumatic events. Acetylcysteine has been safely used to treat paracetamol overdose for over forty years and is extensively used in emergency medicine.
TreatmentIt is important to begin emergency treatment within the so-called "golden hour" following the injury. People with moderate to severe injuries are likely to receive treatment in an intensive care unit followed by a neurosurgical ward. Treatment depends on the recovery stage of the patient. In the acute stage, the primary aim of the medical personnel is to stabilize the patient and focus on preventing further injury because little can be done to reverse the initial damage caused by trauma. Rehabilitation is the main treatment for the subacute and chronic stages of recovery. International clinical guidelines have been proposed with the aim of guiding decisions in TBI treatment, as defined by an authoritative examination of current evidence.
Certain facilities are equipped to handle TBI better than others; initial measures include transporting patients to an appropriate treatment center. Both during transport and in the hospital the primary concerns are ensuring proper oxygen supply, maintaining adequate blood flow to the brain, and controlling raised intracranial pressure (ICP), since high ICP deprives the brain of badly needed blood flow and can cause deadly brain herniation. Other methods to prevent damage include the management of other injuries and the prevention of seizures. Some data support the use of hyperbaric oxygen therapy to improve outcomes.
Neuroimaging is helpful but not flawless in detecting raised ICP. A more accurate way to measure ICP is to place a catheter into a ventricle of the brain, which has the added benefit of allowing cerebrospinal fluid to drain, releasing pressure in the skull. Treatment of raised ICP may be as simple as tilting the patient's bed and straightening the head to promote blood flow through the veins of the neck. Sedatives, analgesics and paralytic agents are often used. Hypertonic saline can improve ICP by reducing the amount of cerebral water (swelling), though it is used with caution to avoid electrolyte imbalances or heart failure. Mannitol, an osmotic diuretic, appears to be equally effective at reducing ICP. Some concerns; however, have been raised regarding some of the studies performed. Diuretics, drugs that increase urine output to reduce excessive fluid in the system, may be used to treat high intracranial pressures but may cause hypovolemia (insufficient blood volume). Hyperventilation (larger and/or faster breaths) reduces carbon dioxide levels and causes blood vessels to constrict; this decreases blood flow to the brain and reduces ICP, but it potentially causes ischemia and is, therefore, used only in the short term. Administration of corticosteroids is associated with an increased risk of death, so it is recommended that they not be given routinely.
Endotracheal intubation and mechanical ventilation may be used to ensure proper oxygen supply and provide a secure airway. Hypotension (low blood pressure), which has a devastating outcome in TBI, can be prevented by giving intravenous fluids to maintain normal blood pressure. Failing to maintain blood pressure can result in inadequate blood flow to the brain.[ Blood pressure may be kept at an artificially high level under controlled conditions by infusion of norepinephrine or similar drugs; this helps maintain cerebral perfusion. Body temperature is carefully regulated because increased temperature raises the brain's metabolic needs, potentially depriving it of nutrients. Seizures are common. While they can be treated with benzodiazepines, these drugs are used carefully because they can depress breathing and lower blood pressure. TBI patients are more susceptible to side effects and may react adversely or be inordinately sensitive to some pharmacological agents. During treatment, monitoring continues for signs of deterioration such as a decreasing level of consciousness.
Traumatic brain injury may cause a range of serious coincidental complications that include cardiac arrhythmias and neurogenic pulmonary edema. These conditions must be adequately treated and stabilized as part of the core care for these patients.
Surgery can be performed on mass lesions or to eliminate objects that have penetrated the brain. Mass lesions such as contusions or hematomas causing a significant mass effect (shift of intracranial structures) are considered emergencies and are removed surgically. For intracranial hematomas, the collected blood may be removed using suction or forceps or it may be floated off with water. Surgeons look for hemorrhaging blood vessels and seek to control bleeding. In penetrating brain injury, damaged tissue is surgically debrided, and craniotomy may be needed. Craniotomy, in which part of the skull is removed, may be needed to remove pieces of the fractured skull or objects embedded in the brain. Decompressive craniectomy (DC) is performed routinely in the very short period following TBI during operations to treat hematomas; part of the skull is removed temporarily (primary DC). DC performed hours or days after TBI in order to control high intracranial pressures (secondary DC) has not been shown to improve outcomes in some trials and may be associated with severe side effects.

Physical therapy will commonly include muscle strength exercises. Once medically stable, people may be transferred to a subacute rehabilitation unit of the medical center or to an independent rehabilitation hospital. Rehabilitation aims to improve independent function at home and in society and to help adapt to disabilities and has demonstrated its general effectiveness when conducted by a team of health professionals who specialize in head trauma. As for any person with neurologic deficits, a multidisciplinary approach is key to optimizing outcomes. Physiatrists or neurologists are likely to be the key medical staff involved, but depending on the person, doctors of other medical specialties may also be helpful. Allied health professions such as physiotherapy, speech and language therapy, cognitive rehabilitation therapy, and occupational therapy will be essential to assess function and design rehabilitation activities for each person. Treatment of neuropsychiatric symptoms such as emotional distress and clinical depression may involve mental health professionals such as therapists, psychologists, and psychiatrists, while neuropsychologists can help to evaluate and manage cognitive deficits.
After discharge from the inpatient rehabilitation treatment unit, care may be given on an outpatient basis. Community-based rehabilitation will be required for a high proportion of people, including vocational rehabilitation; this supportive employment matches job demands to the worker's abilities. People with TBI who cannot live independently or with family may require care in supported living facilities such as group homes. Respite care, including day centers and leisure facilities for the disabled, offers time off for caregivers, and activities for people with TBI.
Pharmacological treatment can help to manage psychiatric or behavioral problems. Medication is also used to control post-traumatic epilepsy; however, the preventive use of anti-epileptics is not recommended. In those cases where the person is bedridden due to a reduction of consciousness, has to remain in a wheelchair because of mobility problems, or has any other problem heavily impacting self-caring capacities, caregiving, and nursing are critical. The most effective research-documented intervention approach is the activation database-guided EEG biofeedback approach, which has shown significant improvements in the memory abilities of the TBI subject that are far superior to traditional approaches (strategies, computers, medication intervention). Gains of 2.61 standard deviations have been documented. The TBI's auditory memory ability was superior to the control group after the treatment.
The prognosis worsens with the severity of the injury. Most TBIs are mild and do not cause permanent or long-term disability; however, all severity levels of TBI have the potential to cause significant, long-lasting disability. Permanent disability is thought to occur in 10% of mild injuries, 66% of moderate injuries, and 100% of severe injuries. Most mild TBI is completely resolved within three weeks, and almost all people with mild TBI are able to live independently and return to the jobs they had before the injury, although a portion has mild cognitive and social impairments. Over 90% of people with moderate TBI are able to live independently, although a portion requires assistance in areas such as physical abilities, employment, and financial management. Most people with severe closed head injuries either die or recover enough to live independently; the middle ground is less common. Coma, as it is closely related to severity, is a strong predictor of poor outcomes.
Prognosis differs depending on the severity and location of the lesion, and access to immediate, specialized acute management. Subarachnoid hemorrhage approximately doubles mortality. Subdural hematoma is associated with worse outcomes and increased mortality, while people with epidural hematoma are expected to have a good outcome if they receive surgery quickly. Diffuse axonal injury may be associated with coma when severe, and poor outcome. Following the acute stage, the prognosis is strongly influenced by the patient's involvement in activities that promote recovery, which for most patients requires access to a specialized, intensive rehabilitation service. The Functional Independence Measure is a way to track progress and degree of independence throughout rehabilitation.
Medical complications are associated with a bad prognosis. Examples are hypotension (low blood pressure), hypoxia (low blood oxygen saturation), lower cerebral perfusion pressures, and longer times spent with high intracranial pressures. Patient characteristics also influence prognosis. Factors thought to worsen it include abuse of substances such as illicit drugs and alcohol and age over sixty or under two years (in children, younger age at the time of injury may be associated with a slower recovery of some abilities). Other influences that may affect recovery include pre-injury intellectual ability, coping strategies, personality traits, family environment, social support systems, and financial circumstances.
Life satisfaction has been known to decrease for individuals with TBI immediately following the trauma, but evidence has shown that life roles, age, and depressive symptoms influence the trajectory of life satisfaction as time passes.
ComplicationsMain article: Complications of traumatic brain injury

The relative risk of post-traumatic seizures increases with the severity of traumatic brain injury.

A CT of the head years after a traumatic brain injury shows an empty space where the damage occurred marked by the arrow. Improvement of neurological function usually occurs for two or more years after the trauma. For many years it was believed that recovery was fastest during the first six months, but there is no evidence to support this. It may be related to services commonly being withdrawn after this period, rather than any physiological limitation to further progress. Children recover better in the immediate time frame and improve for longer periods.
Complications are distinct medical problems that may arise as a result of the TBI. The results of traumatic brain injury vary widely in type and duration; they include physical, cognitive, emotional, and behavioral complications. TBI can cause prolonged or permanent effects on consciousness, such as coma, brain death, persistent vegetative state (in which patients are unable to achieve a state of alertness to interact with their surroundings), and minimally conscious state (in which patients show minimal signs of being aware of self or environment). Lying still for long periods can cause complications including pressure sores, pneumonia or other infections, progressive multiple organ failure, and deep venous thrombosis, which can cause pulmonary embolism. Infections that can follow skull fractures and penetrating injuries include meningitis and abscesses. Complications involving the blood vessels include vasospasm, in which vessels constrict and restrict blood flow, the formation of aneurysms, in which the side of a vessel weakens and balloons out, and stroke.
Movement disorders that may develop after TBI include tremors, ataxia (uncoordinated muscle movements), myoclonus (shock-like contractions of muscles), and loss of movement range and control (in particular with a loss of movement repertoire). The risk of post-traumatic seizures increases with the severity of trauma (image at right) and is particularly elevated with certain types of brain trauma such as cerebral contusions or hematomas. People with early seizures, those occurring within a week of injury, have an increased risk of post-traumatic epilepsy (recurrent seizures occurring more than a week after the initial trauma). People may lose or experience altered vision, hearing, or smell.
Hormonal disturbances may occur secondary to hypopituitarism, occurring immediately or years after injury in 10 to 15% of TBI patients. Development of diabetes insipidus or an electrolyte abnormality acutely after injury indicates the need for an endocrinologic workup. Signs and symptoms of hypopituitarism may develop and be screened for in adults with moderate TBI and in mild TBI with imaging abnormalities. Children with moderate to severe head injury may also develop hypopituitarism. Screening should take place 3 to 6 months, and 12 months after injury, but problems may occur more remotely.
Cognitive deficits that can follow TBI include impaired attention; disrupted insight, judgment, and thought, reduced processing speed; distractibility; and deficits in executive functions such as abstract reasoning, planning, problem-solving, and multitasking. Memory loss, the most common cognitive impairment among head-injured people, occurs in 20–79% of people with closed head trauma, depending on severity. People who have suffered from TBI may also have difficulty with understanding or producing spoken or written language, or with more subtle aspects of communication such as body language. Post-concussion syndrome, a set of lasting symptoms experienced after mild TBI, can include physical, cognitive, emotional, and behavioral problems such as headaches, dizziness, difficulty concentrating, and depression. Multiple TBIs may have a cumulative effect. A young person who receives a second concussion before symptoms from another one have healed may be at risk for developing a very rare but deadly condition called second-impact syndrome, in which the brain swells catastrophically after even a mild blow, with debilitating or deadly results. About one in five career boxers are affected by chronic traumatic brain injury (CTBI), which causes cognitive, behavioral, and physical impairments. Dementia pugilistica, the severe form of CTBI, affects primarily career boxers' years after a boxing career. It commonly manifests as dementia, memory problems, and parkinsonism (tremors and lack of coordination).
TBI may cause emotional, social, or behavioral problems and changes in personality. These may include emotional instability, depression, anxiety, hypomania, mania, apathy, irritability, problems with social judgment, and impaired conversational skills. TBI appears to predispose survivors to psychiatric disorders including obsessive-compulsive disorder, substance abuse, dysthymia, clinical depression, bipolar disorder, and anxiety disorders. In patients who have depression after TBI, suicidal ideation is not uncommon; the suicide rate among these persons is increased 2- to 3-fold. Social and behavioral symptoms that can follow TBI include disinhibition, inability to control anger, impulsiveness, lack of initiative, inappropriate sexual activity, sociality, social withdrawal, and changes in personality.
TBI also has a substantial impact on the functioning of family systems Caregiving family members and TBI survivors often significantly alter their familial roles and responsibilities following injury, creating significant change and strain on a family system. Typical challenges identified by families recovering from TBI include frustration and impatience with one another, loss of former lives and relationships, difficulty setting reasonable goals, inability to effectively solve problems as a family, increased level of stress and household tension, changes in emotional dynamics, and an overwhelming desire to return to pre-injury status. In addition, families may exhibit less effective functioning in areas including coping, problem-solving, and communication. Psychoeducation and counseling models have been demonstrated to be effective in minimizing family disruption.

TBI fatalities in the US TBI is a leading cause of death and disability around the globe and presents a major worldwide social, economic, and health problem. It is the number one cause of coma; it plays the leading role in disability due to trauma and is the leading cause of brain damage in children and young adults. In Europe, it is responsible for more years of disability than any other cause. It also plays a significant role in half of trauma deaths.
Findings on the frequency of each level of severity vary based on the definitions and methods used in studies. A World Health Organization study estimated that between 70 and 90% of head injuries that receive treatment are mild, and a US study found that moderate and severe injuries each account for 10% of TBIs, with the rest mild.
The incidence of TBI varies by age, gender, region, and other factors. Findings of incidence and prevalence in epidemiological studies vary based on such factors as which grades of severity are included, whether deaths are included, whether the study is restricted to hospitalized people and the study's location. The annual incidence of mild TBI is difficult to determine but maybe 100–600 people per 100,000.
Mortality In the US, the case fatality rate is estimated to be 21% by 30 days after TBI. A study on Iraq War soldiers found that severe TBI carries a mortality of 30–50%. Deaths have declined due to improved treatments and systems for managing trauma in societies wealthy enough to provide modern emergency and neurosurgical services. The fraction of those who die after being hospitalized with TBI fell from almost half in the 1970s to about a quarter at the beginning of the 21st century. This decline in mortality has led to a concomitant increase in the number of people living with disabilities that result from TBI.
Biological, clinical, and demographic factors contribute to the likelihood that an injury will be fatal. In addition, the outcome depends heavily on the cause of the head injury. In the US, patients with fall-related TBIs have an 89% survival rate, while only 9% of patients with firearm-related TBIs survive. In the US, firearms are the most common cause of fatal TBI, followed by vehicle accidents and then falls. Of deaths from firearms, 75% are considered to be suicides.
The incidence of TBI is increasing globally, due largely to an increase in motor vehicle use in low- and middle-income countries. In developing countries, automobile use has increased faster than safety infrastructure could be introduced. In contrast, vehicle safety laws have decreased rates of TBI in high-income countries, which have seen decreases in traffic-related TBI since the 1970s. Each year in the United States, about two million people suffer a TBI, approximately 675,000 injuries are seen in the emergency department, and about 500,000 patients are hospitalized. The yearly incidence of TBI is estimated at 180–250 per 100,000 people in the US, 281 per 100,000 in France, 361 per 100,000 in South Africa, 322 per 100,000 in Australia, and 430 per 100,000 in England. In the European Union, the yearly aggregate incidence of TBI hospitalizations and fatalities is estimated at 235 per 100,000.
DemographicsTBI is present in 85% of traumatically injured children, either alone or with other injuries. The greatest number of TBIs occur in people aged 15–24. Because TBI is more common among young people, its costs to society are high due to the loss of productive years to death and disability. The age groups most at risk for TBI are children ages five to nine and adults over age 80, and the highest rates of death and hospitalization due to TBI are in people over age 65. The incidence of fall-related TBI in First-World countries is increasing as the population ages; thus the median age of people with head injuries has increased.
Regardless of age, TBI rates are higher in males. Men suffer twice as many TBIs as women do and have a fourfold risk of fatal head injury, and males account for two-thirds of childhood and adolescent head trauma. However, when matched for severity of injury, women appear to fare more poorly than men.
Socioeconomic status also appears to affect TBI rates; people with lower levels of education and employment and lower socioeconomic status are at greater risk.
The Edwin Smith PapyrusHead injury is present in ancient myths that may date back before recorded history. Skulls found in battleground graves with holes drilled over fracture lines suggest that trepanation may have been used to treat TBI in ancient times. Ancient Mesopotamians knew of head injury and some of its effects, including seizures, paralysis, and loss of sight, hearing, or speech. The Edwin Smith Papyrus, written around 1650–1550 BC, describes various head injuries and symptoms and classifies them based on their presentation and tractability. Ancient Greek physicians including Hippocrates understood the brain to be the center of thought, probably due to their experience with head trauma.
Medieval and Renaissance surgeons continued the practice of trepanation for head injuries. In the Middle Ages, physicians further described head injury symptoms and the term concussion became more widespread. Concussion symptoms were first described systematically in the 16th century by Berengario da Carpi.
It was first suggested in the 18th century that intracranial pressure rather than skull damage was the cause of pathology after TBI. This hypothesis was confirmed around the end of the 19th century and opening the skull to relieve pressure was then proposed as a treatment.
In the 19th century, it was noted that TBI is related to the development of psychosis. At that time a debate arose around whether post-concussion syndrome was due to a disturbance of the brain tissue or psychological factors. The debate continues today.

Phineas Gage with the tamping iron that entered his left cheek and emerged at the top of his head perhaps the first reported case of personality change after brain injury is that of Phineas Gage, who survived an accident in which a large iron rod was driven through his head, destroying one or both of his frontal lobes; numerous cases of personality change after brain injury have been reported since.
The 20th century saw the advancement of technologies that improved treatment and diagnosis such as the development of imaging tools including CT and MRI, and, in the 21st century, diffusion tensor imaging (DTI). The introduction of intracranial pressure monitoring in the 1950s has been credited with beginning the "modern era" of head injury. Until the 20th century, the mortality rate of TBI was high and rehabilitation was uncommon; improvements in care made during World War I reduced the death rate and made rehabilitation possible. Facilities dedicated to TBI rehabilitation were probably first established during World War I. Explosives used in World War I caused many blast injuries; the large number of TBIs that resulted allowed researchers to learn about the localization of brain functions. Blast-related injuries are now common problems in returning veterans from Iraq & Afghanistan; research shows that the symptoms of such TBIs are largely the same as those of TBIs involving a physical blow to the head.
In the 1970s, awareness of TBI as a public health problem grew, and a great deal of progress has been made since then in brain trauma research, such as the discovery of primary and secondary brain injury. The 1990s saw the development and dissemination of standardized guidelines for the treatment of TBI, with protocols for a range of issues such as drugs and management of intracranial pressure. Research since the early 1990s has improved TBI survival; that decade was known as the "Decade of the Brain" for advances made in brain research.
Research Medications Topics of research for improving outcomes after TBI have included investigations into mannitol, dexamethasone, progesterone, xenon, barbiturates, magnesium, calcium channel blockers, PPAR-γ agonists, curcuminoids, ethanol, NMDA antagonists, caffeine, hypothermia, and hyperbaric oxygen.
Despite this volume of research, no medication is approved to halt the progression of the initial injury to secondary injury, but the variety of pathological events presents opportunities to find treatments that interfere with the damage processes. Neuroprotection, methods to halt or mitigate secondary injury, have been the subject of great interest for their ability to limit the damage that follows TBI. However, clinical trials to test agents that could halt these cellular mechanisms have met largely with failure. For example, interest existed in hypothermia, cooling the injured brain to limit TBI damage, but it has not been sufficiently studied as of 2014 to see if it is useful or not. In addition, drugs such as NMDA receptor antagonists to halt neurochemical cascades such as excitotoxicity showed promise in animal trials but failed in clinical trials. These failures could be due to factors including faults in the trials' design or in the insufficiency of a single agent to prevent the array of injury processes involved in secondary injury.
Procedures In addition to traditional imaging modalities, there are several devices that help to monitor brain injury and facilitate research. Micro dialysis allows ongoing sampling of extracellular fluid for analysis of metabolites that might indicate ischemia or brain metabolisms, such as glucose, glycerol, and glutamate. Intraparenchymal brain tissue oxygen monitoring systems (either Lico or Neurogen-PTO) are used routinely in normotensive care in the US. A noninvasive model called Cer Ox is in development.
Research is also planned to clarify factors correlated to outcomes in TBI and to determine in which cases it is best to perform CT scans and surgical procedures.
Hyperbaric oxygen therapy (HBO) has been evaluated as an adjunctive treatment following TBI, concluding a Cochrane review stating that its use could not be justified. HBO for TBI has remained controversial as studies have looked for improvement mechanisms, and further evidence shows that it may have potential as a treatment.
As of 2010, the use of predictive visual tracking measurement to identify mild traumatic brain injury was being studied. In visual tracking tests, a head-mounted display unit with eye-tracking capability shows an object moving in a regular pattern. People without brain injury are able to track the moving object with smooth pursuit eye movements and correct trajectory. The test requires both attention and working memory which are difficult functions for people with mild traumatic brain injury. The question being studied is whether results for people with brain injury will show visual-tracking gaze errors relative to the moving target.

​Most patients with severe TBI who recover consciousness suffer from cognitive disabilities, including the loss of many higher-level mental skills. Cognitive deficits that can follow TBI include impaired attention; disrupted insight, judgment, and thought, reduced processing speed; distractibility; and deficits in executive functions such as abstract reasoning, planning, problem-solving, and multitasking. Memory loss, the most common cognitive impairment among head-injured people, occurs in 20–79% of people with closed head trauma, depending on severity. Post-traumatic amnesia (PTA), a confessional state with impaired memory, is characterized by the loss of specific memories or the partial inability to form or store new ones.
Alzheimer's disease (AD) is a progressive, neurodegenerative disease characterized by dementia, memory loss, and deteriorating cognitive abilities. Research suggests an association between head injury in early adulthood and the development of AD later in life; the more severe the head injury, the greater the risk of developing AD. Some evidence indicates that a head injury may interact with other factors to trigger the disease and may hasten the onset of the disease in individuals already at risk. For example, head-injured people who have a particular form of the protein apolipoprotein E (apoE4, a naturally occurring protein that helps transport cholesterol through the bloodstream) fall into this increased risk category.
Patients with moderate to severe TBI have more problems with cognitive deficits than do those with mild TBI, but several mild TBIs may have an additive effect. About one in five career boxers are affected by chronic traumatic brain injury (CTBI), which causes cognitive, behavioral, and physical impairments. Dementia pugilistica, also called chronic traumatic encephalopathy, is a severe form of CTBI. Caused by repetitive blows to the head over a long period, the condition primarily affects career boxers and has recently been linked to other contact sports including American football and ice hockey as well as military service (see Ann McKee). It commonly manifests as dementia, or declining mental ability, memory problems, and parkinsonism (tremors and lack of coordination). Symptoms begin anywhere between 6 and 40 years after the start of a boxing career, with an average onset of about 16 years.

Language and communication problems are common disabilities in TBI patients. Some may experience aphasia, difficulty with understanding and producing spoken and written language; or they may have difficulty with the more subtle aspects of communication, such as body language and emotional, and non-verbal signals. Some may have problems with intonation or inflection, called prosodic dysfunction. Problems with spoken language may occur if the part of the brain that controls speech muscles is damaged. In this disorder, called dysarthria, the patient can think of the appropriate language, but cannot easily speak the words because they are unable to use the muscles needed to form the words and produce the sounds. Speech is often slow, slurred, and garbled.

Preliminary research on the effects of meditation on retrieving memory and cognitive functions have been encouraging.
A 2015 review suggests that mindfulness-based interventions may prevent or delay the onset of mild cognitive impairment and Alzheimer's disease.
Rare cases of possible transmission between people are being studied, e.g. to growth hormone patients.
Imaging Of the many medical imaging techniques available, single photon emission computed tomography (SPECT) appears to be superior in differentiating Alzheimer's disease from other types of dementia, and this has been shown to give a greater level of accuracy compared with mental testing and medical history analysis. Advances have led to the proposal of new diagnostic criteria.
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PiB PET remains investigational, but a similar PET scanning radiopharmaceutical called florbetapir, containing the longer-lasting radionuclide fluorine-18, has recently been tested as a diagnostic tool in Alzheimer's disease, and given FDA approval for this use.
Amyloid imaging is likely to be used in conjunction with other markers rather than as an alternative. Volumetric MRI can detect changes in the size of brain regions. Measuring those regions that atrophy during the progress of Alzheimer's disease is showing promise as a diagnostic indicator. It may prove less expensive than other imaging methods currently under study.
In 2011 An FDA panel voted unanimously to recommend approval of florbetapir, which is currently used in an investigational study. The imaging agent can help to detect Alzheimer's brain plaques, but will require additional clinical research before it can be made available commercially.
Early diagnosis Emphasis in Alzheimer's research has been placed on diagnosing the condition before symptoms begin. A number of biochemical tests have been developed to attempt earlier detection. One such test involves the analysis of cerebrospinal fluid for beta-amyloid or tau proteins, both total tau protein and phosphorylated tau181P protein concentrations.

Sensory deficits TBI patients may have sensory problems, especially problems with vision; they may not be able to register what they are seeing or may be slow to recognize objects. Also, TBI patients often have difficulty with hand–eye coordination, causing them to seem clumsy or unsteady. Other sensory deficits include problems with hearing, smell, taste, or touch. Tinnitus, a ringing or roaring in the ears, may occur. A person with damage to the part of the brain that processes taste or smell may perceive a persistent bitter taste or noxious smell. Damage to the part of the brain that controls the sense of touch may cause a TBI patient to develop persistent skin tingling, itching, or pain. These conditions are rare and difficult to treat.
Emotional and behavioral problems TBI may cause emotional or behavioral problems and changes in personality. Emotional symptoms that can follow TBI include emotional instability, depression, anxiety, hypomania, mania, apathy, irritability, and anger. TBI appears to predispose a person to psychiatric disorders including obsessive-compulsive disorder, alcohol or substance abuse or substance dependence, dysthymia, clinical depression, bipolar disorder, phobias, panic disorder, and schizophrenia. About one-quarter of people with TBI suffer from clinical depression, and about 9% suffer from mania. The prevalence of all psychiatric illnesses is 49% in moderate to severe TBI and 34% in mild TBI within a year of injury, compared with 18% of controls. People with TBI continue to be at greater risk for psychiatric problems than others even years after an injury. Problems that may persist for up to two years after the injury include irritability, suicidal ideation, insomnia, and loss of the ability to experience pleasure from previously enjoyable experiences.
​Behavioral symptoms that can follow TBI include disinhibition, inability to control anger, impulsiveness, lack of initiative, inappropriate sexual activity, and changes in personality. Different behavioral problems are characteristic of the location of injury; for instance, frontal lobe injuries often result in disinhibition and inappropriate or childish behavior, and temporal lobe injuries often cause irritability and aggression.