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This chapter comprises the clinical entities of delirium and catatonia. These syndromes, while presenting different and specific pathophysiology and phenomenology, may share a number of characteristics, including subacute alterations in mental status, precipitation by medical comorbidities, need for inpatient level of care, and others. The differential diagnosis and institution of timely and appropriate therapeutic and supportive measures are essential for prognosis.



Delirium, a constellation of symptoms sometimes described in neurologic contexts as encephalopathy, is the most common neuropsychiatric syndrome observed among medically hospitalized patients.1 Rates of delirium vary based upon setting, with elderly and more severely ill patients at highest risk. Among general medical inpatients, the prevalence of delirium per admission is between 11% and 42%, with a prevalence rate of 10–31% at the time of admission.2 Among critically ill, mechanically ventilated patients, the prevalence of delirium is upwards of 54%, with some studies citing rates greater than 80%.3,4 In addition to high rates of delirium among critically ill patients, the syndrome is common among burn patients and nonelective surgical patients, with incidence rates of 39% and greater than 50% respectively.5,6 Delirium affects up to 85% of terminally ill patients during their final few weeks of life.7

Significant risk factors for delirium include age, cognitive impairment including both mild cognitive disorder and dementia, high degree of illness severity, visual impairment, urinary catheterization, nutritional deficiency, and length of hospital stay.8,9 Neither genetic factors nor family history is known to contribute to the risk of developing delirium. The relationship between sociodemographic factors (e.g., race, socioeconomic status [SES], and education) and delirium is unclear.10


As delirium symptoms arise secondary to underlying etiologies and are often multifactorial, the pathophysiology remains complex and variable across patient populations, as it can be for an individual patient over time. Complementary processes of inflammation, oxidative stress, hypoxia, and a variety of toxic-metabolic insults contribute to increased vulnerability of brain circuits and structures to impairment: delirium is the final common neurobehavioral pathway of these systemic disturbances.11

Clinical Presentation


Delirium is an acute confusional state caused by an underlying physiologic disturbance. According to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5),12 delirium is characterized by a disturbance in consciousness (attention and awareness) accompanied by at least one other cognitive deficit, that develops over a short period of time, fluctuates, and cannot be accounted for by a preexisting cognitive disorder. The phenomenology of delirium is varied, as a range of cognitive impairments can be observed, including deficits in memory, language, and visuospatial processing. Psychotic symptoms such as hallucinations, delusions, or paranoia occur in more than 40% of delirious patients.13 In addition to alterations in consciousness and ...

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