Clinical Characteristics

Delirium is a clinical syndrome characterized by acute onset and fluctuating course. It is characterized by disturbances of consciousness, attention, cognition, thought, language, memory, orientation, perception, sleep-wake cycle, behavior, mood, and affect (American Psychiatric Association 2000) (see Table 5-1). The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR; American Psychiatric Association 2000), criteria for the diagnosis of delirium were derived from studies in adults (Liptzin et al. 1993) and are applicable in children and adolescents (Turkel and Tavare 2003) (see Table 5-2). Children may be especially susceptible to delirium due to febrile illnesses or medications (American Psychiatric Association 2000). Visual, auditory, and tactile hallucinations sometimes occur, as do delusions, although these are not needed for the diagnosis of delirium (Francis et al. 1990).

Delirium reflects neuronal dysfunction in susceptible areas of the cerebrum and reticular activating system, with relative sparing of the cerebellum (McGowan and Locala 2003). Many cortical and subcortical functions are altered in delirium. The prefrontal cortex and thalamus, which are critical in integrating higher cortical functions and behaviors, and the mesocortical dopaminergic pathway, which selectively modulates the role of the frontal cortex in maintaining and shifting attention, are particularly affected (Rummans et al. 1995). Memory impairment may be associated with disturbance of the basal forebrain cholinergic pathways. Changes in the level of consciousness may be associated with pontine cholinergic pathways that project to the forebrain and brain stem (Rummans et al. 1995).

The pattern and frequency of symptoms may vary within a delirium episode, with fewer symptoms present during the early or subclinical phases and during the later resolving phases than during the most fulminant phase, when symptoms are numerous and prominent. Most deliria are multifacto-rial, and the relative importance of differing etiologies occurring at different points in time within an episode of delirium may alter symptom expression. The symptoms of delirium that occur most consistently may result from a perturbation of critical neural circuitry, irrespective of etiology, and variation in symptoms may indicate the effects on neural circuits more related to differences in etiology or individual differences in brain structure, function, or response to illness (Trzepacz 2000).

In a study of the sensitivity and specificity of DSM-IV diagnostic criteria, Cole et al. (1993) found that inattention or clouding of consciousness was most sensitive for the diagnosis of delirium. Recognizing impaired attention in very young patients is difficult unless the examiner is familiar with engaging small children. Children present with irritability, withdrawal, and problems regulating state rather than the cognitive and behavioral changes seen in adults.

The inability to pay attention to external and internal stimuli predisposes an individual to disorientation. Ongoing attention is needed to reliably perceive passage of time, change in location, and recall of people in the environment. Typically, the sense of time is the first aspect of orientation to be distorted; however, time is a concept that young children have

Table 5-1. DSM-IV-TR diagnostic criteria for delirium

A. Disturbance of consciousness (i.e., reduced clarity of awareness of the environment) with reduced ability to focus, sustain, or shift attention.

B. A change in cognition (such as memory deficit, disorientation, language disturbance) or the development of a perceptual disturbance that is not better accounted for by a preexisting, established, or evolving dementia.

C. The disturbance develops over a short period of time (usually hours to days) and tends to fluctuate during the course of the day.

D. There is evidence from the history, physical examination, or laboratory findings that the disturbance is caused by the direct physiological consequences of a general medical condition.

Coding note: If delirium is superimposed on a preexisting vascular dementia, indicate the delirium by coding 290.41 vascular dementia, with delirium.

Coding note: Include the name of the general medical condition on Axis I, e.g., 293.0 delirium due to hepatic encephalopathy; also code the general medical condition on Axis III (see DSM-IV-TR Appendix G for codes).

Table 5-2. Clinical presentation of pediatric delirium (tf =84)

not yet developed, and questions of orientation are difficult to assess in the very young.

Sleep disturbance is a common feature of delirium. The sleep-wake cycle may be reversed, or sleep may be fragmented and limited. Melatonin is related to the regulation of circadian rhythms, and changes in levels of melatonin may have a role in the sleep disturbance of delirium (Balan et al. 2003).

Most studies of delirium have emphasized risk factors and outcomes rather than the incidence or pattern of specific symptoms. Delirium is presumed to be the same syndrome across all ages, although the symptom profile and course may differ (Leent-jens et al. 2008). Turkel et al. (2006) reported that sleep-wake disturbance, fluctuating symptoms, im paired attention, irritability, agitation, affective lability, and confusion were more often noted in children; that impaired memory, depressed mood, speech disturbance, delusions, and paranoia were more common in adults; and that impaired alertness, apathy, anxiety, disorientation, and hallucinations occurred similarly in both children and adults.

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