Imaging Classification of Internal Carotid Artery Hypoplasia Based on Distal Ophthalmic Segment Occlusion

Abstract

Background: Internal carotid artery (ICA) hypoplasia (ICAH) is rare. The classification of ICAH is largely unclear. The aim of the study is to propose a new imaging classification for ICAH based on the occlusion of the distal ophthalmic segment and discuss the clinical and radiological differences between the different types. Materials and Methods: This was a retrospective study of patients with congenital ICAH diagnosed at the Department of Neurology of the China-Japan Friendship Hospital between June 2011 and June 2016. The patients underwent temporal bone computed tomography (CT), brain CT, cranial magnetic resonance imaging, transcranial Doppler, and head and neck CT angiography. Results: A total of 20 ICAH patients were divided into the distal occlusion (12 cases; 60%) and nondistal occlusion (8 cases; 40%) types based on whether the distal ophthalmic segment was occluded. The frequencies of collateral circulation from the circle of Willis (P = .01) and dilated cerebrovascular lesions (P = .001) in the distal occlusion type was higher than in the nondistal occlusion type. Five (25%) patients developed adverse cerebrovascular events during followup: 3 ischemic cases were of the nondistal occlusion type, and 2 cases with subarachnoid hemorrhage were of the distal occlusion type. Conclusions: A novel classification of ICAH was revealed based on the occlusion of the distal ophthalmic segment. The 2 types may show differences in collateral circulation patterns, coexisting cerebrovascular abnormalities, and potential clinical outcomes.