Delirium

Delirium is the most common brain-behavior disorder and the most frequent behavioral manifestation of medical disorders or physiological disruptions. It is an acute change in mental status with prominent changes in attention. There is a disturbance in level of awareness and a fluctuating ability to focus, sustain, and shift attention. These difficult additionally impair instrumental cognitive abilities. There is a spectrum of delirium from mild inattention and distraction to a lethargic and poorly responsive state.

Clinicians may fail to diagnose delirium because they fail to recognize and test for this syndrome. The elderly can have a “quiet” or subtle presentation of delirium that may go undetected. Yet, delirium occurs in 10% to 30% of medically ill patients, a clear majority of hospitalized elderly patients, and 80% or more of patients in the intensive care unit. The consequences of delirium include prolonged hospitalizations, increased mortality, high rates of discharge to institutions, severe impact on caregivers and spouses, and more than $4 billion of annual Medicare expenditures in the United States. Of particular importance is distinguishing delirium from dementia, the other common disorder of cognitive functioning. Delirium is acute in onset (usually hours to a few days), whereas dementia is insidious in onset and progressive. Delirium is an acute neurobehavioral decompensation with fluctuating attention, regardless of whether the patient has underlying cognitive deficits or dementia. In fact, the presence of underlying dementia is a major risk factor for delirium.

There are 10 essential characteristics of delirium ( Box 3.1 ):

• 1.
  

  Acute Onset with Fluctuating Course. Delirium develops over hours or days but sometimes over a week or more. The course progresses to daily fluctuations of attention, arousal, and other symptoms, sometimes interposed with lucid or near normal intervals. Clinicians need to examine these patients at several points in time to get an understanding of the extent and depth of fluctuations.

  
  
• 2.
  

  Attentional Deficits. A disturbance of attention is the defining symptom of delirium. Attention is the ability to focus mental activity on a targeted external or internal stimulus to the exclusion of others. Patients with delirium cannot consistently focus, sustain, or shift their attention to relevant aspects or events, and environmental or internal stimuli, no matter how minor, can easily distract them from the topic at hand.

  
  
• 3.
  

  Confusion or Disorganized Thinking. Patients with delirium cannot maintain a clear and coherent stream of thought. They are unable to perform organized, goal-directed behavior, and their speech reflects this disorganization. Their verbal output is poorly connected, often going from topic to topic in a tangential, circumlocutory, or totally unrelated manner.

  
  
• 4.
  

  Disturbed Arousal. Most patients have alterations in their arousal, or their readiness to react or “alert” to stimuli. This is distinct from attention and the ability to focus mental activity. Arousal refers to the ability to respond or alert; disturbances or arousal range from lethargy to stupor and coma. Most patients with delirium tend to have lethargy and decreased arousal, but some patients with delirium have increased arousal, such as those with delirium tremens. Some patients may have fluctuations that range from hypoarousal to hyperarousal.

  
  
• 5.
  

  Disturbed Perception. A dramatic feature of delirium, when present, are altered perceptions, particularly hallucinations in the visual sphere. These hallucinations are frequently animate, variable, and in color, and they may or may not be frightening to the patient. Other perceptual disturbances include illusions (distorted perceptions or sensations) and misperceptions or misinterpretations. Ultimately, the most common perceptual disturbances are missed perceptions, or failure to appreciate things that are going on around them.

  
  
• 6.
  

  Disturbed Sleep-Wake Cycle. Patients with delirium have disturbances of the normal diurnal or circadian rhythm and experience disruption of their day-night cycle. This most commonly manifests as excessive daytime drowsiness or sleeping, and sometimes wakefulness and alertness at night. There may be “sundowning,” or agitation and restlessness occurring during the night.

  
  
• 7.
  

  Altered Psychomotor Activity. Delirium can be hypoactive, hyperactive, or mixed in their psychomotor activity. The most common are hypoactive with psychomotor retardation and often accompanying lethargy and decreased arousal. The less common hyperactive subtype often has accompanying agitation, perceptual disturbances, and overactivity of the autonomic nervous system.

  
  
• 8.
  

  Disorientation and Memory Impairment. Disorientation is one of the most common findings in delirium. Disorientation is not specific for delirium, however, and it occurs in dementia and amnesia as well. Among patients with delirium, recent memory is disrupted in large part by the decreased registration caused by attentional problems. In delirium, reduplicative paramnesia, a specific memory-related disorder, results from decreased integration of recent observations with past memories. Persons or places are “replaced” in this condition. For example, they tend to relocate the hospital closer to their homes.

  
  
• 9.
  

  Other Cognitive Deficits. Patients with delirium have cognitive deficits in writing and in visuospatial abilities. Writing disturbance result in poorly formed letters and words and a tendency to disturbed spatial orientation or direction of written sentences or phrases. These patients also manifest difficulties with visuospatial constructions, such as drawings, and with complex visual processing, such as visual object recognition and environmental orientation.

  
  
• 10.
  

  Behavioral and Emotional Abnormalities. Patients with delirium may have delusions, or false beliefs, that are poorly systematized and paranoid with a persecutory content. Other patients with delirium exhibit marked emotional lability or may become agitated, depressed, or quite apathetic.

Characteristics on MSX

The examiner begins with the neurobehavioral history and behavioral observations. A history of a fairly abrupt change in mental status is usually the most salient aspect of presentation. Behavioral observations then focus on overt signs of disturbed attention, fluctuations, and altered arousal. Delirium is evident in observed ease of distractibility and inability to stay on track or with the interview without having to be constantly brought back. The patient may have overt evidence of altered arousal, particularly lethargy or a tendency to fall asleep during the interview, necessitating stimulation to maintain alertness. They may be hypoactive and psychomotor slowed, or there may be hyperactivity. If conversation is elicited, the examiner listens for the organization and coherence of their verbal output. Finally, the examination should evaluate for behavior disturbances, including agitation and irritability, signs of perceptual alterations such as responding to hallucinations, and changes in emotional lability and mood.

The examiner then proceeds to evaluate attention with specific testing. The most common are assessments of orientation and recitation tasks. Orientation for time and place can be disturbed from attention deficits, as in delirium, or from memory impairment, as in dementia. Ask the patient for time, date including year, and place, including city. Patients should be within 4 hours of time and a few days of the date and know the city if not the exact place that they are at. The most common recitation task is repetition of digits forward, delivered one per second in a steady voice beginning with four digits and gradually increasing (or decreasing) the number of digits as needed (see Chapter 7 ). The patient must repeat the entire sequence immediately after presentation. The examiner gives them two trials at each level, with a normal performance of at least five (preferably six) digits forward. Similar recitation tasks are letters forward and reversal tasks such as digits backward, spelling backward (e.g., the word “world”), or counting backward (by 3 from 20 or by 7 from 100). These tasks are harder than forward recitation and involve other aspects of mental control, particularly working memory, a frontal executive ability. Other attentional tests are continuous performance tasks, such as the “A vigilance test,” in which the patient must indicate whenever the letter “A” appears among 20 random letters presented one per second, or in a string of written letters. There should be no errors of omission or commission.

Considering that attention is required for instrumental cognitive functions, attentional deficits may preclude completion of tests in other cognitive domains. Nevertheless, the examiner should screen language, memory, visuospatial abilities, and executive functions. A language examination should listen for evidence of aphasia and obtain a written sample from the patient. The written sample can reveal linguistic disturbances, or the graphomotor alterations described for delirium. A simple memory test for these patients is to ask them to remember the examiner’s name or three words for 5 minutes, and simple visuospatial screening involves having them copy a simple construction, such as cube. The examiner may screen for executive dysfunction with simple alternating hand movements between one hand fisted and the other open palm down on the table.

The usual mental status scales may differentiate delirium from other cognitive disturbances, and there are a number of targeted delirium scales that can augment the mental status examination (MSX) (see Mariz J, Castanho TC, Teixeira J, Sousa N, Cerreia Santos N. Delirium diagnostic and screening instruments in the emergency department: an up-to-date systematic review. Geriatrics . 2006;1(3):22). The Confusion Assessment Method (CAM) is a widely used instrument for screening for and diagnosing delirium, which requires an acute (hours to days) and fluctuating course and difficulty focusing plus either disorganized, irrelevant thinking for an alteration in arousal. There are a number of variants or modifications of the original CAM. The Delirium Rating Scale-Revised-98, a revision of the earlier Delirium Rating Scale, is a 16-item scale with 13 severity items and three diagnostic items that reliably distinguish delirium from dementia, depression, and schizophrenia. Other scales have unique aspects. For example, the Delirium Triage Screen assesses level of consciousness and attention in less than 1 minute; the Richmond Agitation-Sedation Scale has a 10-level scale that assesses level of arousal; and the Neelon and Champagne Confusion Scale combines both behavioral and physiologic signs of delirium. The diagnosis of delirium may be facilitated by the use of these instruments; however, the best assessment remains a careful MSX focusing on abnormal attention and other specific areas disturbed in delirium, as described earlier.

The physical examination may show evidence of systemic or medical illness, meningismus, signs of increased intracranial pressure, or focal neurologic abnormalities. Delirium is associated with three nonspecific movement abnormalities: an action or sustention tremor of high frequency, asterixis, or brief lapses in tonic posture, especially at the wrist; multifocal myoclonus or shock-like jerks; choreiform movements; dysarthria; and gait instability. There may be agitation or psychomotor retardation, apathy, waxy flexibility, catatonia, carphologia (“lint-picking” behavior), and autonomic hyperactivity.

Dementia

Dementia is an age-related disorder that is growing in importance in proportion to the increasing age of our population. Dementia is an acquired impairment in multiple areas of intellectual function not due to delirium and includes a compromise in memory, language, and other cognitive functions. These cognitive impairments are generally severe enough to interfere with quality of life, social adjustment, and elder independence. Alzheimer disease (AD) is the most common cause of dementia. AD affects at least 6% of people over age 65 years and, in some studies, nearly half of those over age 85 years. More than 5.5 million Americans have AD, and the numbers may reach 14 million by the year 2050 in proportion to the aging population. Furthermore, AD costs approximately 90 billion health care dollars per year and is one of the greatest causes for the loss of independence in the elderly.

After memory loss, language impairment is the second most common disability among patients with AD. The pattern of language changes in AD constitutes a specific loss of linguistic competencies involving semantic aspects rather than syntactic or phonologic abilities. The first abnormality is word-finding difficulty with a decreased ability to generate lists of words in a given category. Perception and spatial abilities are additionally impaired early in the usual course of the disease. With disease progression, there is eventual prominent involvement of executive operations and attributes, as well as a more global impairment in all cognitive domains. The application of the National Institute on Aging-Alzheimer Association criteria facilitates making the diagnosis of AD and are summarized in Box 3.2 .

BOX 3.2

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