Per-segment evaluation of atherosclerotic stenosis of intracranial internal carotid artery

The uneven distribution of intracranial atherosclerotic stenosis (ICAS) along the internal carotid artery (ICA) had been described in early clinicopathological studies, yet large-scale data is lack. This study aimed to determine the distribution pattern of atherosclerotic stenosis for each of 6 segments within intracranial ICA.

This retrospective cohort study utilized prospective data from the secure digital subtraction angiography (DSA) registry from 2011 to 2024. Patients with clinically defined atherosclerotic vascular diseases or atherosclerosis risk factors were included. The degree and distribution pattern of atherosclerotic stenosis for C2-C7 segments were analyzed.

The preliminary analysis included 8,084 patients. The mean (SD) age was 59.88 (12.85) years; 5,493 (67.95%) were men, and 1,475 (18.25%) had ICAS. Site-specific distribution patterns were found on both left and right intracranial ICAs: the C2 segment had the lowest proportion of ICAS (36 (0.45%) on the left side and 30 (0.37%) on the right respectively while C6 had the highest proportion (365 (4.52%) on the left and 392 (4.85%) on the right). The ICAS probability per unit length was also calculated for each segment, and C2 still had the lowest average value with 1.58 per millimeter (mm) on the left, followed by C4 (10.63), C3 (12.04), C7 (28.71), C6 (46.38), and C5 (116.04), and 1.31 per mm on the right, followed by C3 (10.99), C4 (12.51), C7 (35.09), C6 (49.81), and C5 (133.02), respectively.

Compared with the other intracranial ICA segments, the C2 segment had an extremely low proportion of atherosclerotic stenosis.