Cerebrovascular Regulation in Preganglionic and Postganglionic Autonomic Insufficiency

Abstract

Cerebral blood flow was measured in four subjects with chronic idiopathic autonomic insufficiency using ⁸⁵Kr inhalation, cerebral A-V samples for scintillation counting, and O₂ content determination. Blood pressure was varied by up or down tilting and L-norepinephrine infusion. In three patients with typical Shy-Drager syndrome and preganglionic denervation, CBF regulation to pressure and Pa CO_CO2 change was intact. In a fourth patient with postganglionic denervation, CBF autoregulation was absent to changes in blood pressure but was preserved normally to increases or decreases in Pa CO_CO2 CBF and CMRO₂, at rest were normal (52.6 cc and 3.1 cc). Hyperventilation to Pa CO_CO2 34.3 mm failed to restore autoregulation to increased blood pressure. The results imply a functional role for postganglionic autonomic fibers in CBF autoregulation.