Reversible Cognitive Disorder – Delirium

One of the most common reversible cognitive disorders is delirium, which is a sudden and drastic change in the ability to focus attention. People also become extremely confused about where they are and what time it is. Delirium is caused by an acute (short term) medical condition that either disrupts brain metabolism (i.e., the brain's process of creating and using energy) or alters the level of neurotransmitters (chemical messengers in the brain and nervous system). Both types of disturbance can significantly affect brain functioning.

The diagnosis of delirium is complicated because it often co-occurs with chronic (long-lasting) conditions that often have overlapping symptoms. For instance, memory problems and confusion are characteristic of both dementia and delirium, and the coexistence of delirium and dementia is particularly common in hospital settings. In fact, dementia is actually a risk factor for developing delirium.

Symptoms of Delirium

According to the DSM-IV diagnostic criteria, a person with delirium must exhibit a disturbance of consciousness (e.g., a reduced awareness of the surroundings or severe attention problems). Second, there must be a change in cognitive functioning (e.g., problems with memory, orientation, language, or perception) that isn't caused by dementia. Third, the symptoms must develop over a short period of time - such as hours or days - and fluctuate throughout the day.

Deliriums are identified by their cause. According to the DSM-IV, there are five main causes for delirium:

• Delirium Due to a General Medical Condition - Delirium that is caused by general medical conditions such as urinary tract infections, meningitis (an infection that causes inflammation of the membranes covering the brain and spinal cord), endocrine disorders (e.g., diabetes), hypothermia (body temperature that falls below 95F), electrolyte imbalances (when body chemicals like sodium and potassium are not at optimal levels, such as during dehydration), or heat stroke (when core body temperature rises to a dangerous level).
• Substance Intoxication Delirium - Delirium that is caused by intoxication from a substance (often alcohol, prescription medications, or illegal drugs) or from a medication interaction (when two or more drugs react to each other to produce negative side effects).
• Substance Withdrawal Delirium - Delirium that develops during or shortly after a withdrawal syndrome (problems that occur when the concentration of alcohol, prescription, over-the-counter, or illegal drugs is decreasing in the body's tissues and fluids).
• Delirium Due to Multiple Etiologies - Delirium that has more than one cause; for example, delirium caused by a combination of a urinary tract infection and a medication interaction.
• Delirium Not Otherwise Specified (NOS) - Delirium that does not meet the criteria of any of the above classifications, either because there is insufficient evidence to determine the cause, or because the cause is different from those described above. For example, delirium due to sensory deprivation (a total lack of sensory stimulation, such as a prisoner who is placed in a dark, noiseless solitary confinement room), and following general anesthesia (when a person is asleep during surgery) have been documented.

Prevalence of Delirium

Delirium most frequently occurs in older adults who are hospitalized. Ten percent of people age 65+ who are hospitalized for a general medical condition are delirious at admission; 10-15% go on to develop delirium during their hospital stay. Nursing homes are another common environment where delirium is found. Approximately 6% to 12% of nursing home residents develop delirium every year. Each of these estimates is considered conservative because delirium often goes undetected in all settings.

Diagnosis of Delirium

Although dementia can often be detected using imaging procedures (non-surgical techniques that produce detailed pictures of the brain; click here to return to our previous discussion of these procedures), delirium does not usually affect the brain in a way that is identifiable by CT scans, MRIs, or PET scans. Therefore, delirium is usually diagnosed by conducting a thorough medical history, physical exam, and using laboratory tests (e.g., blood and urine tests) to evaluate the cause of the symptoms.

Treatment of Delirium

The appropriate method of treatment for delirium depends fully upon its cause. Quick and accurate treatment is imperative, because some deliriums - if left untreated - can cause permanent brain damage or even death. For example, untreated meningitis, heat stroke, or electrolyte imbalances due to dehydration can be fatal. People with delirium almost always require hospitalization for treatment.

Prognosis for Delirium

If the cause of delirium is properly identified and treated, delirium often lasts less than one month from the onset of symptoms to the time of recovery. However, an episode of delirium may last anywhere from a few hours to many weeks, depending on the cause and necessary treatment. Delirium in the presence of dementia often lasts longer than other forms of delirium.