INFLUENCE OF DEGREE OF CAROTID-ARTERY STENOSIS AND COLLATERAL PATHWAYS AND EFFECT OF CAROTID ENDARTERECTOMY ON CEREBRAL VASOREACTIVITY

OBJECTIVE: The goal was to determine the influence of the degree of in ternal carotid artery (ICA) stenosis and collateral pathways on cerebr al vasoreactivity (CVR). The effect of carotid endarterectomy on CVR i s also presented. METHODS: For 36 patients with unilateral ICA stenosi s of at least 70%, regional cerebral blood flow (rCBF) and regional CV R (rCVR) were investigated before and after carotid endarterectomy, wi th resting and acetazolamide-challenge single photon emission computed tomographic scans. The degree of ICA stenosis and the status of the c ollateral pathways (sizes of the A1 segment and the posterior communic ating artery) were evaluated by angiography. RESULTS: Thirteen patient s were classified as Type N/N (normal rCBF and normal rCVR), 5 as Type R/N (reduced rCBF and normal rCVR), 6 as Type N/R (normal rCBF and re duced rCVR), and 12 as Type R/R (reduced rCBF and reduced rCVR). The d egree of ICA stenosis correlated with rCVR status. The size of the A1 segment was a second-rank factor and was less effective in affecting r CVR. The size of the posterior communicating artery was not associated with rCVR. The predictive value of reduced rCVR for postoperative imp rovement (100%) was significantly higher than that of reduced rCBF (50 %). CONCLUSION: The present results indicate that the degree of ICA st enosis is a more significant determinant of CVR than are the collatera l pathways in patients with carotid artery stenosis. The high predicti ve rate of reduced rCVR for postoperative improvement implies that ace tazolamide-challenge single photon emission computed tomographic scann ing might be useful in selecting patients with asymptomatic ICA stenos is who might benefit from carotid endarterectomy.