Acute brain syndrome

Acute brain syndrome


Delirium is a condition of severe confusion and rapid changes in brain function. It is usually caused by a treatable physical or mental illness.

Alternative Names

Acute confusional state; Acute brain syndrome


Acute confusional states most often result from physical or mental illness and are usually temporary and reversible. Disorders that cause delirium are numerous and varied. They may include conditions that deprive the brain of oxygen or other substances.

Delirium may be caused by diseases of body systems other than the brain, by poisons, by fluid/electrolyte or acid/base disturbances, and by other serious, acute conditions. Infections such as urinary tract infections or pneumonia may trigger delirium in individuals with pre-existing brain damage (prior strokes, dementia).

Patients with more severe pre-existing brain injury are more likely to develop delirium from additional illness.


Delirium involves a rapid alternation between mental states (for example, from lethargy to agitation and back to lethargy), with attention disruption, disorganized thinking, disorientation, changes in sensation and perception, and other symptoms.

  • Attention disturbance (disrupted or wandering attention)
    • Inability to maintain goal directed, purposeful thinking or behavior
    • Concentration problems
  • Disorganized thinking, evidenced by
    • Incoherent speech
    • Inability to stop speech patterns or behaviors
  • Disorientation to time or place
  • Changes in sensation and perception (increases the disorientation)
    • May come before illusions or hallucinations
  • Altered level of consciousness or awareness
  • Altered sleep patterns, drowsiness
  • Alertness may vary, usually more alert in the morning, less alert at night (see drowsiness)
  • Decrease in short-term memory and recall
    • Unable to remember events since onset of delirium (anterograde amnesia)
    • Unable to remember past events (retrograde amnesia)
  • Changes in motor activities, movement (for example, may be lethargic or slow moving)
  • Movements triggered by changes in the nervous system (psychomotor restlessness)
  • Emotional or personality changes
    • Anxiety
    • Anger
    • Apathy
    • Depression
    • Euphoria
    • Irritability

Exams and Tests

Neurologic examination may reveal abnormalities, including abnormal reflexes and abnormal levels of normal reflexes. Psychologic studies and tests of sensation, cognitive function, and motor function may be abnormal.

The following tests may be done:

  • Serum electrolytes
  • Blood chemistry (chem-20)
  • Serum calcium
  • Glucose test
  • Serum magnesium - test
  • CPK
  • Liver function tests
  • Ammonia levels
  • Thyroid stimulating hormone level
  • Thyroid function tests
  • B-12 level
  • Drug, alcohol levels (toxicology screen)
  • Urinalysis
  • Blood gas analysis
  • EEG, electroencephalograph
  • Head CT scan
  • Head MRI scan
  • CSF (cerebrospinal fluid) analysis
  • Chest x-ray


The goal of treatment is to control or reverse the cause of the symptoms. Treatment depends on the specific condition causing delirium. The person should be in a pleasant, comfortable, non-threatening, physically safe environment for diagnosis and initial care. Hospitalization may be required for a short time.

Stopping or changing medications that worsen confusion, or that are not essential to the care of the person, may improve cognitive functioning even before treatment of the underlying disorder. Medications that may worsen confusion include anticholinergics, analgesics, cimetidine, central nervous system depressants, lidocaine, and other medications (including alcohol and illegal drugs).

Disorders that contribute to confusion should be treated. These may include heart failure, decreased oxygen (hypoxia), excessive carbon dioxide levels (hypercapnia), thyroid disorders, anemia, nutritional disorders, infections, kidney failure, liver failure, and psychiatric conditions (such as depression). Correction of co-existing medical and psychiatric disorders often greatly improves mental functioning.

Medications may be required to control aggressive or agitated behaviors or behaviors that are dangerous to the person or to others. These are usually given in very low doses, with adjustment as required.

Medications that may be considered for use include:

  • Thiamine
  • Sedating medications such as clonazepam or diazepam
  • Serotonin-affecting drugs (trazodone, buspirone)
  • Dopamine blockers (such as haloperidol, olanzapine, Risperdal, clozapine)
  • Fluoxetine, imipramine, Celexa (may help stabilize mood)

Sensory functioning should be evaluated and augmented as needed by the use of hearing aids, glasses, or cataract surgery.

Formal psychiatric treatment may be necessary. Behavior modification may be helpful for some people to control unacceptable or dangerous behaviors. This consists of rewarding appropriate or positive behaviors and ignoring inappropriate behaviors (within the bounds of safety). Reality orientation, with repeated reinforcement of environmental and other cues, may help reduce disorientation.

Outlook (Prognosis)

The outcome varies. Acute disorders that cause delirium may co-exist with chronic disorders that cause dementia

Delirium often lasts only about 1 week, although it may take several weeks for cognitive function to return to normal levels. Full recovery is common.

Possible Complications

  • Loss of ability to function or care for self
  • Loss of ability to interact
  • May progress to stupor or coma
  • Side effects of medications used to treat the disorder

When to Contact a Medical Professional

Call your health care provider if a rapid change in mental status occurs.


Treatment of causative disorders and conditions reduces the risk of delirium.

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