The autoregulation of cerebral blood flow, the cerebrovascular reactivity and their interaction in the Shy-Drager syndrome.

The experimental study of the autoregulation of cerebral blood flow (CBF), of the cerebrovascular reactivity and of their interaction is performed in a confirmed case of Shy-Drager syndrome, by means of the xenon-clearance technique. The basal mean regional CBF is slightly depressed. The cerebrovascular reactivities to variation in paCO2 and to local cerebral activation are maintained. The inferior threshold of breaking of autoregulation is raised. A competition between the effects on CBF of autoregulation loss and of metabolic regulation is demonstrated. The latency of operation of the autoregulation is evoked by the analysis of the CBF measurements and is confirmed by the simultaneous EEG study.