Delirium is sudden severe confusion and rapid changes in brain function that occur with physical or mental illness.

Acute confusional state; Acute brain syndrome

Delirium is most often caused by physical or mental illness and is usually temporary and reversible. Many disorders cause delirium, including conditions that deprive the brain of oxygen or other substances.

Causes include:

• Drug abuse
• Infections such as urinary tract infections or pneumonia (in people who already have brain damage from stroke or dementia)
• Poisons
• Fluid/electrolyte or acid/base disturbances

Patients with more severe brain injuries are more likely to get delirium from another illness.

Delirium involves a quick change between mental states (for example, from lethargy to agitation and back to lethargy).

Symptoms include:

• Changes in alertness (usually more alert in the morning, less alert at night)
• Changes in feeling (sensation) and perception
• Changes in level of consciousness or awareness
• Changes in movement (for example, may be inactive or slow moving)
• Changes in sleep patterns, drowsiness
• Confusion (disorientation) about time or place
• Decrease in short-term memory and recall
  • Unable to remember events since delirium began (anterograde amnesia)
  • Unable to remember past events (retrograde amnesia)
• Disrupted or wandering attention
  • Inability to think or behave with purpose
  • Problems concentrating
• Disorganized thinking
  • Speech that doesn't make sense (incoherent)
  • Inability to stop speech patterns or behaviors
• Emotional or personality changes
  • Anger
  • Anxiety
  • Apathy
  • Depression
  • Euphoria
  • Irritability
• Movements triggered by changes in the nervous system (psychomotor restlessness)

The following tests may have abnormal results:

• An exam of the nervous system (neurologic examination)
• Psychologic studies
• Tests of feeling (sensation), thinking (cognitive function), and motor function

The following tests may also be done:

• Ammonia levels
• B12 level
• Blood chemistry (chem-20)
• Blood gas analysis
• Chest x-ray
• Cerebrospinal fluid (CSF) analysis
• CPK
• Drug, alcohol levels (toxicology screen)
• Electroencephalogram (EEG)
• Glucose test
• Head CT scan
• Head MRI scan
• Liver function tests
• Mental status test
• Serum calcium
• Serum electrolytes
• Serum magnesium
• Thyroid function tests
• Thyroid stimulating hormone level
• Urinalysis