PLETHSYMOGRAPHIC STUDIES OF THE CEREBRAL CIRCULATION: EVIDENCE FOR CRANIAL NERVE VASOMOTOR ACTIVITY12

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Abstract
Cerebral pulse and intradural volume changes have been recorded from 18 human subjects by a new adaptation of a plethysmographic technique. Vasomotor responses to inhalation of CO2 and O2 mixture, hyperventilation, sleep-walking, and vasomotor drugs were similar to those deduced from nitrous-oxide blood flow measurements. Complicated anesthesia, apprehension and pain produce cerebral vasoconstriction. Pre-ganglionic vasomotor fibers appear to traverse the vagus nerve to the cervical sympathetic ganglia, constituting a cranio-cervical sympathetic system, separate from the thoraco-lumbar sympathetic system. This new system provides a neural control of the cerebral circulation.