Abstract 3013: Cerebral Perfusion Parameter Differences in Clinically Relevant Categories of Carotid Stenosis/Occlusion.

Abstract

Hypothesis: To determine whether clinically relevant categories of carotid stenosis are associated with changes in cerebral blood flow. Methods: We examined a consecutive cohort of stroke patients with confirmed stroke on DWI imaging who underwent CT angiography (CTA) and perfusion CT imaging on presentation with acute symptoms. Degree of carotid stenosis was measured per NASCET criteria on CTA. Perfusion CT was analyzed to calculate relative mean transit time (rMTT), relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) of normal brain tissue ipsilateral to carotid disease. Measurements excluded areas of infarction to avoid confounding hemispheric perfusion changes with local changes due to distal cerebral artery occlusion(s), and subjects with MCA occlusions on any side were excluded. Results: The cohort consisted of 119 patients. Of these 8.4% had 100% ipsilateral carotid occlusion, 1.7% had near-occlusion, 5% had 70-99% stenosis, 5.9% had 50-69% stenosis, and 79% had <50% stenosis. Subjects with 100% carotid occlusion had a higher rMTT (median 1.503, IQR 0.974 to 2.44; p=0.02) when compared to the expected normal rMTT of 1.0. These patients also had a lower rCBF (median 0.708, IQR 0.553 to 1.116; p=0.048) when compared to the expected normal rCBF of 1.0. Perfusion parameters of subjects with carotid near-occlusion did not differ significantly from the expected normal values. Subjects with 70-99% stenosis had slightly higher rMTT (median 1.246, IQR 1.034 to 1.422; p=0.031) and slightly higher rCBV (median 1.088, IQR 1.046 to 1.142; p=0.031) when compared to the expected normal of 1.0. Subjects with 50-69% carotid stenosis and <50% stenosis did not have significantly different perfusion parameters when compared to expected normal values. Conclusions: This is the first reported correlation between clinically relevant categories of carotid stenosis and perfusion parameters measured by perfusion CT imaging of the brain. Subjects with 100% occlusion appeared to have hemodynamically significant changes in perfusion (increased rMTT by ∼50%, decreased rCBF by ∼30%). Patients with 70-99% stenosis had less pronounced changes in rMTT, and no change in rCBF. Interestingly, patients with carotid near-occlusion showed no significant change in perfusion parameters, suggesting that this subgroup of patients may have developed sufficient collateral circulation. Patients with 0-69% stenosis had no significant changes in perfusion parameters. These findings may have significant implications in our approach to patients with carotid occlusion/stenosis and need to be confirmed in larger patient populations.