THE RELATIONSHIP of the circle of Willis to the cerebral blood flow (CBF) has provided considerable speculation.1-4 Circle dynamics have been evaluated by altering or occluding the principal supply vessels.5-8 The majority of these insults to the CBF were limited to periods of only a few minutes to prevent ischemia and possible brain damage. In general, the results from these acute situations were similar, with species differences accounting for most of the variations observed.
Although acute changes in circle dynamics test the temporary effectiveness of this anastomotic arrangement, in more common situations the demands placed upon the circle are the result of chronic, long-term alterations in either the supply vessels or of the circle itself. The present work was undertaken to evaluate pressure relationships existing within the circle of Willis following chronic alteration of the normal supply routes.
The dog was selected because of size, availability, and
Knapp FM, Mitchell WK. Chronic Occlusion Studies of the Canine Circle of Willis. Arch Neurol. 1967;16(3):326–334. doi:10.1001/archneur.1967.00470210102011
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