7.1 Overview
Cognition includes memory, language, orientation, judgment, conducting of interpersonal relationships, performance of actions (praxis), and problem solving. Cognitive disorders reflect disruption in one or more of these domains, and are also frequently complicated by behavioral symptoms. Cognitive disorders exemplify the complex interfaces among neurology, medicine, and psychiatry, in that medical or neurological conditions often lead to cognitive disorders that, in turn, are associated with behavioral symptoms. It can be argued that of all psychiatric conditions, cognitive disorders best demonstrate how biological insults result in behavioral symptomatology. The clinician must carefully assess the history and context of the presentation of these disorders before arriving at a diagnosis and treatment plan. Advances in molecular biology, diagnostic techniques, and medication management have significantly improved the ability to recognize and treat cognitive disorders.
In the text revision of the fourth edition of the
Diagnostic Statistical Manual of Mental Disorders (DSM-IV-TR), three groups of disorders—delirium, dementia, and the amnestic disorders— are characterized by the primary symptom common to all the disorders, which is an impairment in cognition (as in memory, language, or attention). Although DSM-IV-TR acknowledges that other psychiatric disorders can exhibit some cognitive impairment as a symptom, cognitive impairment is the cardinal symptom in delirium, dementia, and the amnestic disorders. Within each of these diagnostic categories, DSM-IV-TR delimits specific types (
Table 7.1-1).
In the past, these conditions were classified under the heading “organic mental disorders” or “organic brain disorders.” Traditionally, those disorders had an identifiable pathological condition such as brain tumor, cerebrovascular disease, or drug intoxication. Those brain disorders with no generally accepted organic basis (e.g., depression) were called functional disorders.
This century-old distinction between organic and functional disorders is outdated and has been deleted from the nomenclature. Every psychiatric disorder has an organic (i.e., biological or chemical) component. Because of this reassessment, the concept of functional disorders has been determined to be misleading, and the term functional and its historical opposite, organic, are not used in DSM-IV-TR.
A further indication that the dichotomy is no longer valid is the revival of the term neuropsychiatry, which emphasizes the somatic substructure on which mental operations and emotions are based; it is concerned with the psychopathological accompaniments of brain dysfunction as observed in seizure disorders, for example. Neuropsychiatry focuses on the psychiatric aspects of neurological disorders and the role of brain dysfunction in psychiatric disorders.
CLASSIFICATION
For each of the three major groups—delirium, dementia, and amnestic disorders—there are subcategories based on etiology. They are defined and summarized as follows.
Delirium
Delirium is marked by short-term confusion and changes in cognition. There are four subcategories, based on several causes: (1) general medical condition (e.g., infection), (2) substance induced (e.g., cocaine, opioids, phencyclidine [PCP]), (3) multiple causes (e.g., head trauma and kidney disease), and (4) delirium not otherwise specified (e.g., sleep deprivation).
Dementia
Dementia is marked by severe impairment in memory, judgment, orientation, and cognition. There are six subcategories: (1) dementia of the Alzheimer’s type, which usually occurs in persons older than 65 years of age and is manifested by progressive intellectual disorientation and dementia, delusions, or depression; (2) vascular dementia, caused by vessel thrombosis or hemorrhage; (3) other medical conditions (e.g., human immunodeficiency virus disease, head trauma, Pick’s disease, and Creutzfeldt-Jakob disease, which is caused by a slow-growing, transmittable virus); (4) substance induced, caused by toxin or medication (e.g., gasoline fumes, atropine); (5) multiple etiologies; and (6) not otherwise specified (if cause is unknown).
Amnestic Disorder
Amnestic disorder is marked by memory impairment and forgetfulness. The three subcategories are (1) caused by medical condition (hypoxia), (2) caused by toxin or medication (e.g., marijuana, diazepam), and (3) not otherwise specified.
Cognitive Disorder Not Otherwise Specified
Cognitive disorder not otherwise specified is a DSM-IV-TR category that allows for the diagnosis of a cognitive disorder that does not meet the criteria for delirium, dementia, or amnestic disorders (
Table 7.1-2). The cause of these syndromes is presumed to involve a specific general medical condition, a pharmacologically active agent, or possibly both.
CLINICAL EVALUATION
During the history taking, the clinician seeks to elicit the development of the illness. Subtle cognitive disorders, fluctuating symptoms, and progressing disease processes may be tracked effectively. The clinician should obtain a detailed rendition of changes in the patient’s daily routine involving such factors as self-care, job responsibilities, and work habits; meal preparation; shopping and personal support; interactions with friends; hobbies and sports; reading interests; religious, social, and recreational activities; and ability to maintain personal finances. Understanding the life history of each patient provides an invaluable source of baseline data regarding changes in function, such as attention and concentration, intellectual abilities, personality, motor skills, and mood and perception. The examiner seeks to find the particular pursuits that the patient considers most important, or central, to his or her lifestyle and attempts to discern how those pursuits have been affected by the emerging clinical condition. Such a method provides the opportunity to appraise both the impact of the illness and the patient-specific baseline for monitoring the effects of future therapies.
Mental Status Examination
After taking a thorough history, the clinician’s primary tool is the assessment of the patient’s mental status. As with the physical examination, the mental status examination is a means of surveying functions and abilities to allow a definition of personal strengths and weaknesses. It is a repeatable, structured assessment of symptoms and signs that promotes effective communication between clinicians. It also establishes the basis for future comparison, essential for documenting therapeutic effectiveness, and it allows comparisons between different patients, with a generalization of findings from one patient to another.
Cognition
When testing cognitive functions, the clinician should evaluate memory, visuospatial and constructional abilities, and reading, writing, and mathematical abilities. Assessment of abstraction ability is also valuable; however, whereas a patient’s performance on tasks such as proverb interpretation may be a useful bedside projective test in some patients, the specific interpretation may result from a variety of factors, such as poor education, low intelligence, and failure to understand the concept of proverbs, as well as from a broad array of primary and secondary psychopathological disturbances.
PATHOLOGY AND LABORATORY EXAMINATION
As with all medical tests, psychiatric evaluations such as the mental status examination must be interpreted in the overall context of thorough clinical and laboratory assessment. Psychiatric and neuropsychiatric patients require careful physical examination, especially when issues exist involving etiologically related or comorbid medical conditions. When consulting internists and other medical specialists, the clinician must ask specific questions to focus the differential diagnostic process and use the consultation most effectively. In particular, most systemic medical or primary cerebral diseases that lead to psychopathological disturbances also manifest with a variety of peripheral or central abnormalities.
A screening laboratory evaluation is sought initially and may be followed by a variety of ancillary tests to increase the diagnostic specificity.
Table 7.1-3 lists such procedures, some of which are described in subsequent sections.
7.2 Delirium
Delirium is defined by the acute onset of fluctuating cognitive impairment and a disturbance of consciousness with reduced ability to attend. Delirium is a syndrome, not a disease, and it has many causes, all of which result in a similar pattern of signs and symptoms relating to the patient’s level of consciousness and cognitive impairment. Delirium is underrecognized by health care workers. Part of the problem is that the syndrome has a variety of other names. The intent of the text revision of the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) was to help consolidate the myriad of terms into a single diagnostic label.
In DSM-IV-TR, delirium is “characterized by a disturbance of consciousness and a change in cognition that develop over a short … time.” The hallmark symptom of delirium is an impairment of consciousness, usually occurring in association with global impairments of cognitive functions. Abnormalities of mood, perception, and behavior are common psychiatric symptoms; tremor, asterixis, nystagmus, incoordination, and urinary incontinence are common neurological symptoms. Classically, delirium has a sudden onset (hours or days), a brief and fluctuating course, and rapid improvement when the causative factor is identified and eliminated, but each of these characteristic features can vary in individual patients. Physicians must recognize delirium to identify and treat the underlying cause and avert the development of delirium-related complications such as accidental injury because of the patient’s clouded consciousness.
EPIDEMIOLOGY
Delirium is a common disorder. According to DSM-IV-TR, the point prevalence of delirium in the general population is 0.4 percent for people 18 years of age and older and 1.1 percent for people 55 and older. Approximately 10 to 30 percent of medically ill patients who are hospitalized exhibit delirium. Approximately 30 percent of patients in surgical intensive care units and cardiac intensive care units and 40 to 50 percent of patients who are recovering from surgery for hip fractures have an episode of delirium. The highest rate of delirium is found in postcardiotomy patients—more than 90 percent in some studies. An estimated 20 percent of patients with severe burns and 30 to 40 percent of patients with acquired immune deficiency syndrome (AIDS) have episodes of delirium while they are hospitalized. Delirium develops in 80 percent of terminally ill patients. The causes of postoperative delirium include the stress of surgery, postoperative pain, insomnia, pain medication, electrolyte imbalances, infection, fever, and blood loss.
Numerous factors can increase a patient’s risk for delirium. These range from extremes of age to the number of medications taken. Advanced age is a major risk factor for the development of delirium. Approximately 30 to 40 percent of hospitalized patients older than age 65 years have an episode of delirium, and another 10 to 15 percent of elderly persons exhibit delirium on admission to the hospital. Of nursing home residents older than age 75 years, 60 percent have repeated episodes of delirium. Other predisposing factors for the development of delirium are preexisting brain damage (e.g., dementia, cerebrovascular disease, tumor), a history of delirium, alcohol dependence,
diabetes, cancer, sensory impairment (e.g., blindness), and malnutrition. Male gender is an independent risk factor for delirium according to DSM-IV-TR.
Delirium is a poor prognostic sign. Rates of institutionalization are increased threefold for patients 65 years and older who exhibit delirium while in the hospital. The 3-month mortality rate of patients who have an episode of delirium is estimated to be 23 to 33 percent. The 1-year mortality rate for patients who have an episode of delirium may be as high as 50 percent. Elderly patients who experience delirium while hospitalized have a 20 to 75 percent mortality rate during that hospitalization. After discharge, up to 15 percent of these persons die within a 1-month period, and 25 percent die within 6 months.
ETIOLOGY
The major causes of delirium are central nervous system disease (e.g., epilepsy), systemic disease (e.g., cardiac failure), and either intoxication or withdrawal from pharmacological or toxic agents. When evaluating patients with delirium, clinicians should assume that any drug that a patient has taken may be etiologically relevant to the delirium.
DIAGNOSIS AND CLINICAL FEATURES
The syndrome of delirium is almost always caused by one or more systemic or cerebral derangements that affect brain function.
The DSM-IV-TR gives separate diagnostic criteria for each type of delirium: (1) delirium due to a general medical condition (
Table 7.2-1), (2) substance intoxication delirium (
Table 7.2-2), (3) substance withdrawal delirium (
Table 7.2-3), (4) delirium due to multiple etiologies (
Table 7.2-4), and (5) delirium not otherwise specified (
Table 7.2-5) for a delirium of unknown cause or of causes not listed, such as sensory deprivation. The syndrome, however, is the same, regardless of cause.
