Prevalence and Risk Factors of Intracranial Atherosclerosis in an Asymptomatic Korean Population

BACKGROUND AND PURPOSE Intracranial atherosclerosis (ICAS) is one of the major risk factors for ischemic stroke, particularly in Asian populations. We investigated the prevalence and risk factors of ICAS in asymptomatic subjects. METHODS We prospectively evaluated 835 asymptomatic Korean adults who voluntarily visited a tertiary referral hospital for a health screening examination that included brain magnetic resonance angiography. The subjects had no history of stroke or transient ischemic attacks; those who had potential cardiac sources of emboli were excluded. ICAS and extracranial atherosclerosis were defined as a reduction in luminal diameter of at least 50%. Vascular risk factors were screened through questionnaires, interviews, and examinations. RESULTS ICAS was found in 25 subjects (3.0%) and extracranial atherosclerosis was found in 4 patients (0.5%). No patient had combined lesions. ICAS was distributed in 31 arteries in 25 subjects: anterior cerebral arteries (5 subjects, 16%), middle cerebral arteries (16 subjects, 52%), posterior cerebral arteries (8 subjects, 26%), and distal internal carotid arteries (2 subjects, 7%). The ratio of ICAS of the anterior circulation (23 of 31 arteries with ICAS, 74%) to that of the posterior circulation (8 of 31 arteries with ICAS, 26%) was 3:1. The ratio of ICAS (23 of 27 arteries with atherosclerosis in the anterior circulation, 85%) to extracranial atherosclerosis (4 of 27 arteries with therosclerosis in the anterior circulation, 15%) was 6:1. An older age [odds ratio (OR)=1.05, 95% confidence interval (CI)=1.00-1.10] and hypertension (OR=2.41, 95% CI=1.01-5.72) were independent risk factors for ICAS. CONCLUSIONS ICAS is more prevalent than extracranial atherosclerosis among neurologically asymptomatic Korean adults. Subjects with ICAS are significantly older and have an increased frequency of hypertension compared to those subjects without atherosclerotic stenosis.