Chapter 20. Delirium and Other Acute Confusional States

Delirium and Other Acute Confusional States: Introduction

The striking event in which a patient with previously intact mentality becomes acutely confused is observed almost daily on the medical, surgical, and emergency wards of a general hospital. Occurring, as it often does, during an infection with fever or in the course of a toxic or metabolic disorder (such as renal or hepatic failure) or as an effect of medication, drugs, or alcohol, it never fails to create grave problems for the physician, nursing personnel, and family. The physician has to cope with the problem of diagnosis, often without the advantage of a lucid history, and any program of therapy is constantly impeded by the patient’s inattention, agitation, sleeplessness, and inability to cooperate. Nurses are burdened with the need to provide satisfactory care and a safe immediate environment for the patient, and at the same time, maintain a tranquil atmosphere for other patients. The family must be supported as it faces the frightening specter of a deranged mind with peculiar behaviors and all it signifies.

These difficulties are magnified when the patient arrives in the emergency ward, having behaved in some irrational way, and the clinical analysis must begin without knowledge of the patient’s background and underlying medical illnesses. It is our view that such patients should be admitted to a general medical or neurologic ward. Transfer of the patient to a psychiatric service is undertaken only if the behavioral disorder proves impossible to manage on a general hospital service.

Definition of Terms

The definition of normal and abnormal states of mind is difficult because the terms used to describe them have been given so many different meanings in both medical and non-medical writings. Compounding the difficulty is the fact that the pathophysiology of the confusional states and delirium is not fully understood, and the definitions depend to some extent on their clinical causes and relationships, with all the imprecision that this entails. The following nomenclature has proved useful to us and is employed in this and subsequent chapters.

Confusion is a general term denoting the patient’s incapacity to think with customary speed, clarity, and coherence. Its most conspicuous attributes are impaired attention and power of concentration, disorientation—which may be manifest or is demonstrated only by direct questioning—an inability to properly register immediate events and to recall them later, a reduction in the amount and a disruption in the quality of all mental activity, including the normally constant inner ideation and sometimes, by the appearance of bewilderment. Thinking, speech, and the performance of goal-directed actions are impersistent or abruptly arrested by the intrusion of irrelevant thoughts or distracted by the slightest external stimulus. Reduced perceptiveness and accompanying visual and auditory illusions or hallucinations and paranoid delusions (a psychosis) are variable features that may be appended to the picture.

These psychologic disturbances may appear in many contexts. Confusion, as defined in this way, is an essential ingredient of the state called delirium (discussed further on), in which agitation, hallucinations, and sometimes tremulousness accompany the confusional state. Also, as pointed out in Chap. 17, a confusional state may appear at any stage in the evolution and resolution of a number of diseases that lead to drowsiness, stupor, and coma—typically in the metabolic encephalopathies but also in diseases affecting those parts of the brain that maintain normal arousal.

Confusion is also a characteristic feature of the chronic syndrome of dementia, where it is the product of a progressive failure of cognition, language, memory, and other intellectual functions; there it is the long-standing and progressive nature of the mental confusion that differentiates dementia from the acute confusional and delirious states that carry quite different implications. Finally, intense emotional disturbances, of either manic or depressive type, may interfere with attentiveness and coherence of thinking and thereby produce an apparent confusional state.

Special restricted forms of what could be called confusion appear as a result of certain focal cerebral lesions, particularly of the frontal, parietal, and temporal lobe association areas. Then, instead of a global inattention and incoherence, there are specific and circumscribed syndromes, such as unilateral neglect of self or of the environment, inability to identify persons or objects, and sensorimotor defects as described in Chap. 22. Yet another special form of confusion arises as a result of disordered language function, which also alters the stream of thought; this aphasia is a consequence of lesions in the language areas of the left temporal lobe. These are considered separately in Chap. 23.

The many mental and behavioral aberrations that are seen in confused patients, and their occurrence in various combinations and clinical contexts, make it unlikely that all forms of confusion derive from a single elementary psychologic abnormality such as a disturbance of attention. While attention is near the core of confusion, phenomena as diverse as drowsiness and stupor, hallucinations and delusions, disorders of perception and registration, impersistence and perseveration, and so forth are not easily reduced to a disorder of one psychologic or physiologic mechanism. It seems more likely to us that a number of separable disorders of function are involved. Indeed, one view of the confusional state that we find attractive conceptualizes confusion as a loss of the integrative functions among all the elementary and localizable cerebral functions such as symbolic language, memory retrieval, and apperception (the interpretation of primary perceptions). All of these are included under the rubric of the confusional state, for want of a better term.

We reserve the term delirium to denote a special agitated type of confusional state. In addition to many of the negative elements of incoherent thinking mentioned above, delirium is characterized by a prominent disorder of perception; hallucinations and vivid dreams; a kaleidoscopic array of strange and absurd fantasies and delusions; inability to sleep; a tendency to twitch, tremble, and convulse; and intense fear or other emotional reactions. Delirium is distinguished not only by extreme inattentiveness but also by a state of heightened alertness—i.e., an increased readiness to respond to stimuli—and by overactivity of psychomotor and autonomic nervous system functions, sometimes striking in degree. Implicit in the term delirium are its nonmedical connotations as well—namely, intense agitation, or frenzied excitement, and trembling. This distinction between delirium and other acute confusional states is not universally accepted. Many authors attach no particular significance to the autonomic and psychomotor overactivity and the hallucinatory and dream-like features of delirium, or to the underactivity and somnolence that characterize most other confusional states. All such states are categorized together as we continue to find it useful to set delirium apart from other nondescript confusional states because the two conditions are manifestly different and tend to occur in different clinical contexts. Nevertheless, implicit in both designations is the idea of an acute, transient, and usually completely reversible disorder.

An impairment of memory is often included among the symptoms of delirium and other confusional states. Registration and recall are indeed greatly impaired in the states under discussion, but they are affected in proportion to the degree of inattention and the inability to register new material. The term amnesia, however, refers more precisely to an isolated loss of past memories as well as to an inability to form new ones, despite an alert state of mind and normal attentiveness. Amnesia further presupposes an ability of the patient to grasp the meaning of what is going on around him. The failure in the amnesic state is one of retention, recall, and reproduction and must be distinguished from states of drowsiness, acute confusion, and delirium, in which information and events seem never to have been adequately perceived and registered in the first place. In both a confusional state and in amnesia, the patient will be left with a permanent gap in memory for his acute illness.

In a similar way, the term dementia (literally, an undoing of the mind) denotes a deterioration of all intellectual or cognitive functions with little or no disturbance of consciousness or perception. Implied in dementia is the idea of a gradual degradation of mental powers in a person who formerly possessed a normal mind. Amentia, by contrast, indicates a congenital feeblemindedness more commonly referred to as mental retardation, or more properly, developmental cognitive delay. Dementia and amnesia are discussed more explicitly in Chap. 21.

Observable Aspects of Behavior and Intellect in Confusion, Delirium, Amnesia, and Dementia

The intellectual, emotional, and behavioral activities of the human organism are so complex and varied that one may question the feasibility of using derangements of these activities as reliable indicators of cerebral disease. Certainly they do not have the same tangibility and ease of anatomic and physiologic interpretation as sensory and motor paralysis or aphasia. Yet one observes patterns of disturbed higher cerebrocortical function with such regularity as to make them clinically useful in identifying certain diseases. Some of these disturbances gain specificity because they are combined in certain ways to form syndromes.

The components of mentation and behavior that lend themselves to bedside observation and examination are (1) the processes of attention; (2) perception and apperception (awareness and interpretation of sensory stimuli); (3) the capacity to memorize and recall events of the recent and distant past; (4) the ability to think and reason; (5) temperament, mood, and emotion; (6) initiative, impulse, and drive; (7) social behavior; and (8) insight. Of these, the first two are sensory, the third and fourth are cognitive, the fifth is affective, the sixth is conative or volitional, the seventh refers to the patient’s relationships with those around him, and the last refers to the patient’s capacity to assess his own functioning. Each component of behavior and intellect has its objective side, expressed in the behavioral responses produced by certain stimuli, and its subjective side, expressed in the thinking and feeling described by the patient in relation to the stimuli. Less accessible to the examiner, but nevertheless possible to study by questioning of the patient, are the memories, planning, and other psychic activities that continuously occupy the mind of an alert person. They, too, are disordered or quantitatively diminished by cerebral disease.

Disturbances of Attention

Critical to clear thinking is a process of maintaining awareness of one or a limited number of external stimuli or internal thoughts for a fixed period of time and to simultaneously disregard the numerous distracting sensations and ideas that constantly bombard the nervous system. Without this ability to focus or “pay attention” and have an “attention span,” a coherent stream of thought or action is not possible. The undue interruption of these activities by the intrusion of other thoughts or actions is termed inattention, or distractibility. Two essential components are embodied in the attention mechanism: one, a continuous state of alertness that is normally present throughout waking life (and underlies self-awareness); the other, a process of selecting from the myriad sensations and thoughts those that are relevant to the immediate situation to the exclusion of others.

The confused patient may demonstrate inattention in almost every task undertaken. If the degree of confusion is slight, the patient may report a difficulty with concentration. If severe, there is a parallel lack of insight and the problem is evident by observing easy distractibility by ambient stimuli and by impersistence and perseveration in conversation and motor tasks. Restated, attention has such a pervasive effect on all other aspects of mental performance that it is often difficult to determine whether the confused patient also has primary disorders of memory, executive, or visuospatial function. Indeed, retentive memory may be severely reduced in confusional states. Furthermore, the ability to carry out a series of actions or mental operations wherein one is required to hold in memory the result of the previous operation (“working memory”) is intimately tied to attention and is particularly prone to disruption in confusional states.

The general ability to persist in a motor or mental task emphasizes an executive side of attention, but here one encounters a problem because the term attention has been applied to a number of seemingly different mental activities. One can view attention as a separate and unique cerebral function or simply a way of referring to the persistence or impersistence of any activity. We would argue that the entire cerebrum participates in attentiveness and the frontal and perhaps the parietal lobes are responsible for directing its content, but that the thalamocortical system is in a special way responsible for its raw maintenance. Mesulam, who has thought substantially about this problem, considers the frontal and parietal lobes to be at the nexus of an “attentional matrix”; in his model, the prefrontal, parietal association, and limbic cortices direct and modulate attention in an executive manner. Certainly, the temporal lobes and other regions are involved as well.

Attention to a particular sensory modality requires the participation of the sensory cortex, which must simultaneously initiate the perceptive and apperceptive processes discussed later. What are called “modality” and “domain-specific” attentions (for example, face or object recognition) are more complex, and disorders of these functions result in unique types of inattention, such as agnosia and anosognosia (lack of recognition of a part of the body, as discussed in Chap. 22). These are not derived from the all-encompassing loss of attention that is part of general confusional states but can instead be viewed as highly restricted forms of disruption of insight.

Disturbances of Perception

The process of acquiring through the senses a knowledge of the world or, of one’s self by cohering what is experienced into apperception, involves much more than the simple sensory process of being aware of the attributes of a stimulus. New visual stimuli, for example, activate the striate cortex and visual association areas, wherein are probably stored the coded past representations of these and similar classes of stimuli. Recognition involves the reactivation of this system by the same or similar stimuli at a later time. Essential elements in the perceptual process are the maintenance of attention, the selective focusing on a stimulus, elimination of all extraneous stimuli, and identification of the stimulus by recognizing its relationship to remembered experience.

The perception of stimuli undergoes predictable derangement in disease. Most often there is a reduction in the number of perceptions in a given unit of time and a failure to synthesize them properly and to relate them to the ongoing activities of the mind. Or, there may be inattentiveness and fluctuations of attention, distractibility (pertinent and irrelevant stimuli having equal value), and inability to concentrate and persist in an assigned task. This often leads to disorientation in time and place. Qualitative changes also appear, mainly in the form of sensory distortions, causing misinterpretations of environmental stimuli (illusions) and misidentifications of persons; these, at least in part, form the basis of hallucinatory experience in which the patient reports and reacts to environmental stimuli that are not evident to the examiner. There is an inability to perceive simultaneously all elements of a large complex of stimuli, a defect that has been termed “failure of subjective organization.” These major disturbances in the perceptual sphere, traditionally referred to as “clouding of the sensorium,” are characteristic of delirium, and other confusional states.

More specific partial losses of perception are manifest in the “neglect syndromes.” The most dramatic examples are observed with right parietal lesions, which render a patient unaware of the left half of his body and the environment on the left side. There are numerous other examples of focal cerebral lesions that disturb or distort sensory perceptions, each subject to neurologic testing; these are discussed in Chap. 22. Their close connection to spatial experience makes them understandable as alterations of apperception in the spatial-sensory sphere.

Disturbances of Memory

The retention of learned information and experiences is involved in all mental activities. Memory may be arbitrarily subdivided into several parts: (1) registration; (2) fixation, mnemonic integration, and retention; (3) recognition and recall; and (4) reproduction. As stated above, there is a failure of learning and memory in patients with impaired perception and attention because the material to be learned was never registered and assimilated in the first place. In almost all circumstances, the formation of new memories and the ability to recall old ones are disturbed in tandem.

In the Korsakoff amnesic syndrome, newly presented material appears to be correctly registered but cannot be retained for more than a few minutes (anterograde amnesia, or failure of learning). In this syndrome, there is always an associated defect in the recall and reproduction of memories that had been formed several days, weeks, or even years before the onset of the illness (retrograde amnesia). The fabrication of stories, called confabulation, constitutes a third feature of the syndrome but is neither specific nor invariably present. Intact retention with failure of recall (retrograde amnesia without anterograde amnesia) when it is severe and extends to all events of past life and even personal identity, is usually a manifestation of hysteria or malingering. Certain other characteristic defects occur in almost all memory disorders, for example, the relative retention of older memories in preference to newer ones (Ribot’s rule). Chapter 22 discusses this subject more fully.

Disturbances of Thinking

Thinking, the highest order of intellectual activity, remains the most elusive of all mental operations. If by thinking one means the selective ordering of symbols for learning, organizing information, and problem solving, as well as the capacity to reason and form sound judgments, then the working units of this type of mental activity are words and numbers. The substitution of words and numbers for the objects for which they stand (symbolization) is a fundamental part of the process. These symbols are formed into ideas or concepts, and the arrangement of new and remembered ideas into certain orders or relationships constitutes an intricate part of thought, presently beyond the scope of analysis. Reference is made further on to Luria’s analysis of the steps involved in problem solving in connection with frontal lobe function, but actually, as he points out, the whole cerebrum is implicated in all forms of thinking. In a general way, one may examine thinking in terms of its speed and efficiency, ideational content, coherence and logical relationships of ideas, and the quantity and quality of associations to a given idea. Feelings and behaviors engendered by an idea are more in the realm of emotion and affect. Aphasic disturbances are uncommon in global confusional and delirious states, but Geschwind has emphasized misnaming as an important feature among the “nonaphasic disorders of speech” in these conditions. Spontaneous speech is normal, but there may be slight inaccuracies in repetition that are most likely the result of inattention rather than a focal cerebral lesion.

Disorders of thinking are quite prominent in delirium and other confusional states, in mania, dementia, and schizophrenia. In confusional states of all types, the organization of thought processes is disrupted, with fragmentation, repetition, and perseveration; this is spoken of as an “incoherence of thinking.” Derangements of thinking may also take the form of a flight of ideas; patients move too facilely from one idea to another, and their associations are numerous, and loosely linked. This is a common feature of hypomanic and manic states, and of some schizophrenic psychoses. The opposite condition, poverty of ideas, is characteristic both of depressive illnesses, in which it is combined with gloomy thoughts, of schizophrenia, and of dementing diseases, in which it is part of a reduction of all inner psychic intellectual activity. This overall reduction in thought and action is the most prominent feature of diseases that damage the frontal lobes.

A related condition of slowed thought, or bradyphrenia, is comparable to the bradykinesia of extrapyramidal disorders. The two often coexist and the patient, for example with Parkinson’s disease, can articulate that thinking is so slow as to be virtually blocked. The content of thought is not much altered, but it may be rendered almost useless when slowed to this degree. The outward manifestation of bradyphrenia is what one would expect, a delay in response and slowness in gathering one’s thoughts to express ideas.

Thinking may be distorted in such a way that ideas are not checked against reality. When a false belief is maintained in spite of convincing evidence to the contrary, the patient is said to have a delusion. This abnormality is common to several illnesses, particularly bipolar, schizophrenic, and paranoid states, as well as the early stages of dementia. Often the story related by the patient has internal logic but is patently absurd. Psychotic patients may believe that ideas have been implanted in their minds by some outside agency, such as the internet, radio, television, or atomic energy; these thought control or “passivity feelings” are highly characteristic of schizophrenia, and sometimes of manic episodes. Also diagnostic of some forms of schizophrenia are distortions of logical thought, such as gaps in sequential thinking, intrusion of irrelevant ideas, and condensation of associations. Chapter 53 discusses these aspects of psychoses.

Disturbances of Emotion, Mood, and Affect

The emotional life of the patient is expressed in a variety of ways. It is widely appreciated that there are marked individual differences in basic temperament in the normal population; throughout their lives some persons are cheerful, gregarious, optimistic, and free from worry, whereas others are just the opposite. The state of emotionality, and changes that are uncharacteristic to the individual lend themselves to observation and have clinical significance. Furthermore, some inherent personality traits may precede the development of overt mental disease. For example, the volatile, cyclothymic person is said to be liable to bipolar disease, and the suspicious, withdrawn, introverted person to schizophrenia and paranoia, but there are frequent exceptions to these statements.

Strong, persistent emotional states, such as fear and anxiety, may occur as reactions to life situations and are accompanied by numerous derangements of visceral function. If excessive, prolonged, and disproportionate to the stimulus, they are usually manifestations of an anxiety state or depression. In depression, almost all stimuli also tend to enhance the somber mood of unhappiness. Affective displays that are excessively labile and poorly controlled or uninhibited are a common manifestation of many cerebral diseases, particularly those involving the corticopontine and corticobulbar pathways. This disorder constitutes part of the syndrome of spastic bulbar (pseudobulbar) palsy, as discussed in Chap. 25, but it may occur independently of any problem with brainstem function. Affect being the external appearance of emotional life, the pseudobulbar state is characterized by a relative disconnection between the patient’s reported emotional feelings and the outward display, most often being in the same general direction, but excessive in appearance. Conversely, all emotional feeling and expression may be lacking, as in states of profound apathy or depression. Or excessive cheerfulness may be maintained in the face of serious, potentially fatal disease or other adversity—a pathologic euphoria. Finally, a patient’s emotional responses may be inappropriate to the stimulus, e.g., a depressing or morbid thought may seem amusing and be attended by a smile, a bizarre affective state as in schizophrenia.

Temperament, mood, and other emotional experiences are evaluated by observing the patient’s behavior and appearance while questioning him about his feelings. For these purposes, it is convenient to divide emotionality into mood and affect. By mood is meant the prevailing internal emotional state of an individual. By contrast, affect (or feeling) refers to the outward emotional reactions evoked by a thought or an environmental stimulus. As such, it is the observable aspect of emotion. Emotionality may only be inferred from a person’s affect and any more accurate assessment of the emotional state is made largely by the patient’s self-report. It may be cheerful and optimistic or gloomy and melancholic. The patient’s language (e.g., the adjectives used), facial expression, attitude, posture, and speed of movement reflect prevailing mood. These distinctions are at times rather tenuous, but they are clinically valuable because pathologic processes may dissociate the two to an extreme degree, as mentioned above. Chapter 25 more fully discusses the emotional disturbances relating to neurologic disease and Chap. 57 addresses depression.