Cerebral Blood Flow in the Monkey

T HE adequacy of the cerebral circulation following interrupt ion of a portion of the extracranial arterial blood supply has been of interest to both physiologists and clinicians. The cerebral angiographic studies carried out by White and Verdura ~2 have clearly demonstra ted the ability of a single major extracranial artery to opacify the entire intracranial vasculature. However, the fact tha t the cerebral vascular bed is filled during either angiography or by pos tmor tem injection techniques does not necessarily imply that a functionally adequate blood supply is being delivered to the brain. 1 A more quanti tat ive method of evaluating the collateral circulation to the brain is to measure cerebral blood flow following interrupt ion of a portion of the extracranial blood supply. F r o m this data one can assess the compensa tory flow in the unoccluded vessel. Another technique which can be applied to this problem is the use of the electroencephalogram (EEG). Both Wise et al. 13 and Meyer et al. 6 have shown tha t the E E G can be used to reflect the development of cerebral ischemia secondary to decreased perfusion. The present s tudy was designed to investigate further the relationship of extracranial arterial occlusion to the development of cerebral ischemia. Quant i ta t ive determinations of flow were made from a single internal carotid artery and the compensatory increases in flow detenuined during successive occlusion of the remaining extracranial vessels. In addition, simultaneous E E G recordings were made at vary ing levels of arterial pressure in order to determine the functional