Disorders of Consciousness

Abstract

The components of consciousness are classically separated into two major groups: level of arousal and content of thought processes (better known as being awake and aware). Disorders can affect both components or can affect only the content of consciousness. Physicians assess consciousness indirectly by observing a patient’s response to stimuli. This chapter covers the clinical approach to the comatose patient, which discusses history, physical examination (general and neurologic), localization principles, bihemispheric syndromes, and brainstem syndromes. Diagnostic tests discussed include blood tests, tests of other body fluids, and neuroimaging (e.g., computed tomography, magnetic resonance imaging, functional neuroimaging and physiologic testing). Also discussed are prognosis and brain death. Figures illustrate the Full Outline of Unresponsiveness (FOUR) scale, the spectrum of pupil abnormalities and causes, as well as anatomic structures and dorsal and ventral pathways involved with the maintenance of consciousness. Tables include the Glasgow Coma Scale, blood gas abnormalities due to toxins, and prognostic factors in nontraumatic coma. This chapter contains 45 references.