Genetic and physiological. Both major and mild NCDs can increase the risk for delir- ium and complicate the course. Older individuals are especially susceptible to delirium compared With younger adults. Susceptibility to delirium in infancy and through child- hood may be greater than in early and middle adulthood. In childhood, delirium may be related to febrile illnesses and certain medications (e.g., anticholinergics).
In addition to laboratory findings characteristic of underlying medical conditions (or in- toxication or withdrawal states), there is often generalized slowing on electroencephalog- raphy, and fast activity is occasionally found (e.g., in some cases of alcohol withdrawal delirium). However, electroencephalography is insufficiently sensitive and specific for di- agnostic use.
Functional Consequences of Deiirium
Delirium itself is associated with increased functional decline and risk of institutional placement. Hospitalized individuals 65 years or older with delirium have three times the risk of nursing home placement and about three times the functional decline as hospital- ized patients without delirium at both discharge and 3 months postdischarge.
Psychotic disorders and bipolar and depressive disorders with psychotic features.
Delirium that is characterized by vivid hallucinations, delusions, language disturbances, and agitation must be distinguished from brief psychotic disorder, schizophrenia, schizo- phreniform disorder, and other psychotic disorders, as well as from bipolar and depres- sive disorders with psychotic features.
Acute stress disorder. Delirium associated with fear, anxiety, and dissociative symptoms, such as depersonalization, must be distinguished from acute stress disorder, which is pre- cipitated by exposure to a severely traumatic event.
Malingering and factitious disorder. Delirium can be distinguished from these disor- ders on the basis of the often atypical presentation in malingering and factitious disorder and the absence of another medical condition or substance that is etiologically related to the apparent cognitive disturbance.
Other neurocognitive disorders. The most common differential diagnostic issue when evaluating confusion in older adults is disentangling symptoms of delirium and dementia.
The clinician must determine whether the individual has delirium; a delirium superim- posed on a preexisting NCD, such as that due to Alzheimer’s disease; or an NCD without delirium. The traditional distinction between delirium and dementia according to acute- ness of onset and temporal course is particularly difficult in those elderly individuals who had a prior NCD that may not have been recognized, or who develop persistent cognitive impairment following an episode of delirium.
780.09 (R41.0)
This category applies to presentations in which symptoms characteristic of delirium that cause clinically significant distress or impairment in social, occupational, or other impor- tant areas of functioning predominate but do not meet the full criteria for delirium or any of the disorders in the neurocognitive disorders diagnostic class. The other specified delirium category is used in situations in which the clinician chooses to communicate the specific reason that the presentation does not meet the criteria for delirium or any specific neuro- cognitive disorder. This is done by recording “other specified delirium" followed by the spe- cific reason (e.g., “attenuated delirium syndrome").
An example of a presentation that can be specified using the “other specified” desig- nation is the following:
Attenuated delirium syndrome: This syndrome applies in cases of delirium in which the severity of cognitive impairment falls short of that required for the diagnosis, or in which some, but not all, diagnostic criteria for delirium are met.
780.09 (R41.0)