Borderzone ischemia

Abstract

Positron emission tomography was used to measure cerebral perfusion and metabolism in 7 patients with severe carotid stenosis. None of the patients had sustained a major stroke, and all had a normal neurological examination except 1 patient with a mild neurological deficit from a capsular lacuna. Cerebral blood flow (CBF), cerebral blood volume, the cerebral blood flow/cerebral blood volume ratio, oxygen metabolism, and the fractional extraction of oxygen by the brain were measured in the cerebral cortex of both hemispheres in the anterior and middle cerebral artery distributions, in the borderzone regions between the anterior and middle cerebral arteries (anterior borderzone), and between the middle cerebral and posterior cerebral arteries (posterior borderzone). Results obtained in patients were compared, using Student's t test, to those obtained in 6 neurologically normal, elderly volunteers. Cerebral blood flow and the cerebral blood flow/cerebral blood volume ratio were both significantly decreased (p < 0.025 and p < 0.005, respectively) in the anterior borderzone ipsilateral to the carotid stenosis. In the same region there was a tendency toward a rising fractional extraction of oxygen with the oxygen metabolism maintained in the low‐normal range. Cerebral blood flow was also significantly decreased (p < 0.05) in the contralateral anterior borderzone. Hemodynamic and metabolic variables in other vascular territories were not significantly different from values obtained in the control group. These data indicate that the anterior borderzone may be selectively vulnerable to severe carotid stenosis, which produces, in this region, diminished perfusion, lowered hemodynamic reserve, and a tendency towards a rising fractional extraction of oxygen.