Organic Mental Syndromes (Organic Brain Syndrome)

– A constellation of behavioral signs and symptoms associated with transient or permanent dysfunction of the brain and characterized by impaired intellectual functioning, confusion, and agitation. The most common categories and the ones discussed here are delirium and dementia. Delirium is a reversible, self-limiting condition characterized by a reduced ability to maintain attention to or appropriately shift attention among external stimuli. Dementia is a structurally caused, permanent decline in memory, abstract thinking, and judgment.

Causes and Incidence

Delirium most often occurs as a result of withdrawal from intoxication in chronic alcohol and barbiturate abusers and in acute inflammatory disorders such as meningitis and encephalitis. The most common cause of dementia is Alzheimer’s disease; other causes include vascular disease, HIV infection, central nervous system infection, severe head injury, toxic metabolic disturbances, normal pressure hydrocephalus, underlying neurologic disease (parkinsonism, Huntington’s chorea, multiple sclerosis, Pick’s disease), and drug, alcohol, or nutritional abuse. More than 1 million individuals in the United States have dementia, and the elderly are at greatest risk. As the incidence of AIDS increases, the incidence of dementia is expected to increase (an estimated 50% of individuals with end-stage AIDS develop dementia).

Disease Process

The pathophysiology of organic mental syndromes is not yet understood. Pathologic changes vary by causation, and in Alzheimer’s-related dementia include atrophy of brain tissue with wide sulci and dilated ventricles, senile plaque formation, and neurofibrillary tangles. Vascular disease–induced dementia is characterized by multiple cerebral infarcts. In AIDS-related dementia, the neurons are infected with HIV, and in hydrocephalus, cerebrospinal fluid circulation and absorption are impeded.


Rapid onset; disorientation, including loss of self-recognition in some instances; impaired memory; inability to maintain or shift attention; irritability, agitation, restlessness, hyperactivity; perceptual disturbance, hallucinations, delusions; rambling, fragmented speech; impaired sleep-wake cycle; lucid intervals, symptoms worse at night; duration about 1 week on average

Symptoms vary widely, but the overall picture is a slow, insidious disintegration of personality and intellect with impaired insight and judgment and loss of affect; memory impairment is often the most prominent initial symptom, and others include increasing rigidity of thought; restricted interests; easy distractibility; lack of initiation; speech disturbances; loss of impulse control; change of former traits or exaggeration of those traits (e.g., a neat person becomes slovenly or becomes obsessively preoccupied with orderliness); depression

Potential Complications

Delirium may lead to dementia. Dementia (except that caused by trauma) is progressive; the individual eventually becomes totally oblivious to his or her surroundings and ultimately dies. Individuals with dementia are more susceptible to accidents and infection.

Diagnostic Tests

The diagnosis of delirium is based on the clinical presentation, particularly the fluctuation of symptoms with periods of lucidity, and a history of one or more etiologic agents. Electroencephalography shows a generalized slowing of background activity. A diagnosis of dementia is warranted with demonstrable impairment of long- and short-term memory and demonstrable disturbances in abstract thinking, judgment, personality, or other higher cortical functions that interfere with social activities and relationships. Attention and arousal tend to be normal in dementia, and manifestations are relatively stable, worsening over time. A definitive diagnosis is available only on autopsy.



Delirium: withdrawal of toxic agents (alcohol, barbiturates) and IV sedation with antianxiety agents for agitation, seizure activity, and tremors Dementia: treatment of underlying disorders; antianxiety agents as disease progresses to relieve anxiety and frustration.

Delirium: adequate fluid and electrolytes; seizure precautions; safety precautions (e.g., to prevent wandering, climbing over bedrails); long-term treatment for substance abuse when it is the etiologic agent Dementia: kept in familiar surroundings with minimal environmental changes; use of frequent orientation devices (clocks, calendars, schedules, memory books, name tags); encouragement to do familiar, repetitive routines; safety precautions to prevent wandering; use of adult day care, respite care, or home care to relieve caregiver; family support groups and counseling; prevention of disuse syndrome in end-stage disease.