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

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

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