14 - Disturbances of consciousness and sleep–wake functions

Summary

Introduction

Quantitative and qualitative alterations of consciousness are frequently observed in stroke patients, rarely in the absence of major sensorimotor deficits (’inobvious stroke’; Dunne et al. 1986). Disorders of wakefulness and delirium (acute confusional state), often in combination, are the most common disorders of consciousness in patients with acute stroke. In prospective studies, decreased levels of wakefulness – ranging from somnolence (hypersomnia) to coma – can be observed in 15–25% of patients (Bassetti, 2000; Bogousslavsky et al., 1988b; Melo et al., 1992), and acute confusional states are seen in up to 48% of patients (Gustafson et al., 1991). Less often, stroke causes coma-like states (akinetic mutism, locked-in syndrome), vegetative state, or other sleep–wake disturbances.

Analysis of disturbances of consciousness and sleep–wake functions in stroke patients is of clinical interest. First, the presence of an altered consciousness may suggest topography or etiology of stroke. A severe impairment of wakefulness favours the presence of large hemispheric or (bilateral) brainstem strokes, whereas an acute confusional state is suggestive of a supratentorial stroke. In addition, a decreased level of consciousness is relatively common in patients with intracerebral hemorrhage (Bogousslavsky et al., 1988a), cardioembolic stroke (Kittner et al.,1990), and intracranial dissections (Bassetti et al., 1994a), being conversely rare in those with lacunar strokes. Secondly, patients with altered consciousness require different monitoring and therapeutical strategies. Early detection and prompt surgical treatment of patients with decreased levels of consciousness due to cerebellar stroke and large hemispheric stroke was shown, for example, to improve prognosis (Hornig et al., 1994; Mathew et al., 1995; Schwab et al., 1998).