Blood pressure changes due to the progressive closing of each of the carotid and each of the vertebral arteries were studied at various arterial levels, including femoral and one lingual, both linguals, and lingual and branch of the middle cerebral artery. The changes in lingual artery pressure were closely related to changes in systemic pressure, especially with regard to the degree of recovery which followed the initial drop in pressure caused by clamping one or more of the main arteries to the brain. The anastomotic nature of the circle of Willis was demonstrated in animals in which the posterior communicating artery or the basilar artery had been clipped. Under these experimental conditions, clipping of the basilar artery removed all functional connections between the carotid and vertebral circulations. Qualitatively, the lingual artery pressure appeared to be a good reflection of pressure in an arterial branch in the cerebral cortex. Quantitatively, the cortical pressure remained significantly higher than the lingual pressure until the last main artery to the brain was closed.
The Hemodynamic Importance of the Geometry of Bifurcations in the Circle of Willis (Glass Model Studies)
