Correlation between severity of carotid stenosis and vascular reserve measured by acetazolamide brain perfusion single photon emission computed tomography.

Few studies have investigated the relationship between the degree of stenosis of the internal carotid artery (ICA) and cerebrovascular reserve (CVR). This study examined that relationship. A total of 56 ICAs in 43 patients were included. Computed tomography scan or magnetic resonance imaging showed no evidence of infarction in any of these patients. Both iodine-123-N-isopropyl-p-iodoamphetamine ((123)IMP)-single photon emission computed tomography (SPECT) in the resting state and (123)IMP-SPECT with acetazolamide (ACZ) enhancement were performed. Quantitated cerebral blood flow (CBF) images were acquired with the (123)IMP autoradiography technique. The mean CBF without ACZ administration (resting CBF) and CVR in the middle cerebral artery territory were calculated using stereotactic extraction estimation (SEE) analysis software. The degree of stenosis in the origin of the ICA was calculated from intra-arterial digital subtraction angiography. Resting CBF was not correlated with the degree of ICA stenosis; however, nonlinear regression analysis (second-order equation) showed a moderate correlation between CVR and the degree of ICA stenosis. In 72% of the cases with a CVR <30%, ICA stenosis was >74%. Using the SEE method, CVR was moderately correlated with the degree of ICA stenosis. Our findings indicate that evaluating CVR by ACZ-enhanced (123)IMP-SPECT in patients with ICA stenosis is of clinical value.