Abstract Body: Background: The uneven distribution of intracranial atherosclerotic stenosis (ICAS) along the internal carotid artery (ICA) had been described in early clinicopathological studies, yet related, large-scale data is lack despite the widespread utilization of angiography. This study aimed to determine the distribution pattern of atherosclerotic stenosis for each of 6 segments within intracranial ICA.
Methods: This cross-sectional study utilized prospective data from the secure digital subtraction angiography (DSA) registry at the West China Hospital of Sichuan University from 2011 to 2024. Patients with clinically defined intracranial atherosclerotic vascular diseases or risk factors of atherosclerosis were available. Patients with ICAS having no or only mild stenosis (≤30%) of the ipsilateral extracranial ICA (C1) were included. The degree of stenosis and distribution pattern of atherosclerotic stenosis for each of 6 segments (C2-7) were analyzed. Poisson regression analysis was used to investigate the associated factors with ICAS.
Results: A total of 8,084 patients were included in the preliminary analysis. The mean (SD) age was 59.88 (12.85) years; 5,493 (67.95%) were men, and 1,475 (18.25%) had ICAS. Identical site-specific distribution patterns were found on both left and right intracranial ICA that C2 segment had the lowest proportion of ICAS (36 (0.45%) on the left side and 30 (0.37%) on the right) 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. Poisson regression showed that the C2 segment might be a protective factor for ICAS.
Conclusion: Compared with other segments of intracranial ICA (C3-7), C2 segment has extremely low proportion of atherosclerotic stenosis among all internal ICA segments. This striking segmental differences of ICAS within intracranial ICA may be attributed to the peculiar external support from bony carotid canal that decreases vessel wall stretching and alleviates circumferential stresses, generating a unique atheroprotective hemodynamic microenvironment for this "well-wrapped" C2 segment.