Disturbances of the sleep-waking cycle in patients with vascular brain stem lesions.

Continuous polygraphic recordings of six patients with vascular brain stem lesions were evaluated to investigate the relationship between 1) the localization or extent of the lesions and the alteration of the sleep-waking cycle, and 2) the evolution of the clinical condition and the sleep-waking cycle. Absent REM sleep and severely disorganized NREM sleep were associated with extensive pontine lesions involving the pontine tegmentum. In "locked-in" syndrome, the neural mechanisms responsible for both REM and NREM sleep continued to function, but the sleep-waking cycle was disturbed and marked by sleep-onset REM periods. Lesions in the lower brain stem resulted in absent slow-wave sleep and sleep-onset REM, suggesting that vascular lesions may involve the neural mechanisms responsible for slow-wave sleep. In general, the acute stage of illness was marked by increased awakenings and time spent awake, absent REM sleep, and little or no slow-wave sleep. These results indicate that continuous polygraphic recordings can reveal severe abnormalities due to vascular lesions of the brain stem whereas the waking EEG can only detect mild abnormalities. Improvement in the organization of the sleep-waking cycle in successive polygraphic examinations is likely to be followed by an improvement of the clinical condition. Continuous polygraphic recording is thus a valuable prognostic indicator for vascular brain stem lesions.