rCBF was measured by 133Xenon inhalation at rest and during pCO2 manipulation in 19 patients prior to and at various times after STA-MCA bypass surgery. The resting flow increased gradually postoperatively, seemingly more due to progressive clinical recovery from the original neurologic disability than due to the surgical intervention. CO2 reactivity increased in some patients, more in those who preoperatively had the poorest reactivity. The negative relationship between preoperative reactivity and postoperative change in reactivity was highly significant. These observations are consistent with the interpretation that the surgery did not significantly affect the resting flow level but did augment the collateral reserve in those cases in which it had been most severely impaired by the arterial lesion.

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Carotid endarterectomy may carry a substantial risk of morbidity and mortality from major stroke, thus offsetting any statistical benefit in reduction of future stroke. Because of the disturbing ranges in the incidence of stroke morbidity and mortality reported from the several institutional series studying carotid endarterectomy, the authors undertook a prospective review of 142 consecutive carotid endarterectomies performed for symptomatic atherosclerotic occlusive vascular disease on the neurosurgical service. The University of Alabama Hospital. Preoperative risk assessment was performed in each case according to the Mayo Clinic classification system. The overall mortality rate was 1.4% and the major stroke morbidity rate was 0.7%, for a combined major morbidity and mortality rate of 2.1%. The incidence of minor neurological morbidity was 1.4%. There was no morbidity or mortality in the Grade I and II (low-risk) patient groups. This low combined major morbidity and mortality rate of 2.1% for carotid endarterectomy causes the surgical stroke-free survival curve to intersect the medical stroke-free survival curve at an earlier point in time, and thus demonstrates the greater reduction in risk of stroke which accrues over time for the surgically treated patient.

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