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Definitions

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Consciousness is usually described as having two components: arousal and awareness. Many terms are used to describe the continuum of consciousness ranging from alert to comatose. The alert patient is awake and immediately responsive to all stimuli. Stupor is a condition in which the patient is less alert but still responds with stimulation. An obtunded patient appears to be asleep much of the time but still responds to noxious stimuli. The comatose patient appears asleep and does not respond to stimuli. A vegetative state is a state of arousal without awareness in which the patient may open his or her eyes, track objects, chew and swallow, but not respond to auditory stimuli or appear to sense pain. Often, terms used to describe states of consciousness lack consistent definitions, and a clear description of a patient’s state of arousal and awareness results in more precise communication.

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The Neurologic Examination

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The neurologic examination includes assessment of level of consciousness, brainstem reflexes, and motor activity. The Glasgow Coma Scale (GCS) (Table 36–1) was designed to assess level of consciousness in patients with head injury. A patient with a GCS of 8 or lower is generally considered to be comatose. Brainstem reflexes, including pupillary response to light, corneal reflexes, oculocephalic reflex (doll’s eyes), vestibuloocular reflex (cold calorics), breathing patterns, and cough and gag reflexes, are further used to accurately describe the level of consciousness and localize the level of brainstem dysfunction. Motor responses may be described as spontaneous or induced by noxious stimuli, purposeful or nonpurposeful, unilateral or bilateral, and upper or lower extremity. The patient may display withdrawal from a stimulus, abnormal flexion (decorticate rigidity), abnormal extension (decerebrate rigidity), or absence of motor activity.

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Table Graphic Jump Location
Table 36–1. Glasgow Coma Scale.
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Etiology

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The differential diagnosis of altered states of consciousness is broad (Table 36–2), and while the etiology may be obvious, as in trauma, a history, physical examination, laboratory studies, and imaging studies may be required to establish a diagnosis. Metabolic etiologies (eg, sodium or glucose abnormalities) and pharmacologic causes (eg, sedatives or illicit drugs) should be excluded. Onset and progression of symptoms may provide important clues; for example, neoplasms often present with a progressive course, while vascular occlusions often present with abrupt changes. Associated symptoms and conditions such as recent fevers or a history of diabetes may also aid in diagnosis.

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Table Graphic Jump Location
Table 36–2. Etiology of Altered State of Consciousness.

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