Delirium, Dementia, and Amnesia in Emergency Medicine

Updated: Jul 17, 2018
  • Author: Paul S Gerstein, MD; Chief Editor: Gil Z Shlamovitz, MD, FACEP  more...
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Delirium, dementia, amnesia (and certain other alterations in cognition, judgment, and/or memory) are grouped together in this chapter as organically based disruptions of brain functioning. While psychiatric illnesses can at times mimic some features of these conditions or complicate their presentation in the emergency department, the primary etiologies are physiological rather than psychiatric. Causes of these conditions include metabolic disruptions, endocrine dysfunction, drug toxicity, structural injury (eg, trauma, stroke, chronic dementing process), brain ischemia, severe physiologic/psychological stressors (including prolonged sensory deprivation, "ICU psychosis", sleep deprivation), encephalitis and sepsis.



Altered mental status can be divided into 2 major subgroups: acute (delirium or acute confusional state) and chronic (dementia). A third entity, encephalopathy (subacute organically based brain dysfunction), denotes a gray zone between these extremes; its early course may fluctuate and/or resolve, but it is often persistent and progressive.

The final common pathway of all forms of organically based mental status change is an alteration in cortical brain function, at times in concert with abnormalities of deep brain structures. These conditions result from (1) an exogenous insult or an intrinsic process that affects cerebral neurochemical functioning and/or (2) physical or structural damage to the cortex, subcortex, or to deeper structures involved with memory. Some of the etiologies include trauma, mass lesions, hydrocephalus, strokes (ie, multi-infarct dementia), atrophy, infection, toxins, or dementing processes.

The end result of these disruptions of brain function and/or structure is impairment of cognition that affects some or all of the following: alertness, orientation, emotion, behavior, memory, perception, language, praxis, problem solving, judgment, and psychomotor activity. Knowledge of which areas of this spectrum are affected or spared guides both the workup and the diagnosis.




United States

Delirium accounts for or develops during 10-15% of all admissions to acute-care hospitals but is seen much more frequently in elderly persons (up to 75% of seriously ill and hospitalized), particularly following major surgery, trauma or prolonged ICU care. Delirium is usually transient, but it can be persistent leading to a chronically dementing process in elderly patients.

The prevalence of dementia doubles every 5 years between ages 60 to about 90 years: 1% of persons aged 60-64 years up to 30-50% of those older than 85 years. Approximately 60% of nursing home beds are occupied by patients with dementia. In the ED, patients in nursing homes are more likely to present with delirium than other patients, even after adjusting for delirium risk factors. [1] Alzheimer disease (AD) accounts for most patients with dementia who are older than 55 years (50-90% of all cases). It is estimated that over 4 million people in the United States suffer from AD.

Although slowing of memory and word-finding are normal features of brain aging, approximately 10-15% of patients with mild cognitive impairment, a transitional state between normal functioning and dementia, progress to AD yearly.

For as yet unknown reasons, dementia rates in the United States have been declining over the past several years.


Alzheimer disease is less common and has an older age of onset in Japan, China, and parts of Scandinavia. In these countries, vascular causes of dementia may outnumber Alzheimer disease.


Some causes of delirium (eg, delirium tremens, severe hypoglycemia, CNS infection, heatstroke, thyroid storm) may be fatal or result in severe morbidity if unrecognized and untreated. With some exceptions (such as overdose with tricyclic antidepressants), drug intoxications generally resolve fully with supportive care alone. Failure to provide thiamine when administering glucose may rarely lead to acute Wernicke syndrome (ataxia, confusion, oculomotor palsies in the setting of malnutrition). If unrecognized, Wernicke syndrome may also result in chronic dementia.

Certain withdrawal syndromes can present with delirium (eg, alcohol, benzodiazepines, barbiturates and naloxone-induced acute opiate withdrawal). Some of these withdrawal states can be fatal if if not aggressively treated.

Patients with primary dementia have a significantly reduced life expectancy, depending on the cause of the dementia and its severity and rapidity of progression. [2]


Delirium is seen more commonly in whites than in other races.


Delirium is seen more commonly in females than in males. Alzheimer disease is more prevalent among women because of their longer life expectancy. Lifetime risk in women is estimated to be 32%, whereas the lifetime risk in men is 18%. However, the age-specific risk is equal in both sexes.


Delirium due to physical illness is more frequent among the very young and those older than 60 years. Delirium due to drug and alcohol intoxication or withdrawal is most frequent in persons aged mid teens to the late 30s.

Dementia, particularly Alzheimer disease, is seen predominantly in elderly persons; however, certain types of dementia are seen in younger patients (eg, AIDS-related dementia, certain familial forms of Alzheimer disease), and some cases of variant Creutzfeldt-Jakob disease (ie, bovine spongiform encephalopathy or mad cow disease). AIDS-related dementia is the most common nontraumatic dementia seen in younger persons.


Obesity and a chronically sedentary lifestyle, perhaps in concert with the development of impaired glucose tolerance, are highly significant risk factors for dementia in later life. Smoking and alcohol and drug abuse also can increase dementia risk. The likely unifying factor in lifestyle-induced dementia may be chronic inflammation resulting in small vessel damage in the brain's gray and white matter and hypercortisolemia-induced impairment of healing of critical areas of the brain's memory circuits (especially the hypothalamus). Of all causes of dementia, these are the most modifiable in order to reduce dementia risk.

Genetic Factors

Early-onset familial Alzheimer's Disease, a rare subtype occurring in patients 30-60 years of age, is typically caused by an inhereted mutation in one of three genes: chromosomes 21, 14 and 1. Transmission is autosomal dominant with a high degree of penetration. Other types of early-onset dementia have no known specific causes. Typical late-onset AD, first manifesting around the mid-60s and older, may have some genetically inheritable risk, particularly involving the apolipoprotein E gene on chromosome 19. Researches have now identified many other areas of interest in the Alzheimer's genome that may prove to increase risk of developing the disease to varying degrees.