Risk factors and stroke mechanisms in atherosclerotic stroke: intracranial compared with extracranial and anterior compared with posterior circulation disease.

Background and Purpose: The aim of this study was to investigate differences in risk factors and stroke mechanisms between intracranial atherosclerosis (ICAS) and extracranial atherosclerosis (ECAS) and between anterior and posterior circulation atherosclerosis.
Methods: A multicenter, prospective, Web-based registry was performed on atherosclerotic strokes using diffusionweighted magnetic resonance imaging and magnetic resonance angiography. Stroke mechanisms were categorized as artery-to-artery embolism, in situ thrombo-occlusion, local branch occlusion, or hemodynamic impairment.
Results: Onethousand patients were enrolled from 9 university hospitals. Age (odds ratio [OR], 1.033; 95% confidence interval [CI], 1.018-1.049), male gender (OR, 3.399; 95% CI, 2.335-4.949), and hyperlipidemia (OR, 1.502; 95% CI, 1.117-2.018) were factors favoring ECAS (vs ICAS), whereas hypertension (OR, 1.826; 95% CI, 1.274-2.618; P=0.001) and diabetes mellitus (OR, 1.490; 95% CI, 1.105-2.010; P=0.009) were related to posterior (vs anterior) circulation diseases. Metabolic syndrome was a factor related to ICAS (vs ECAS) only in posterior circulation strokes (OR, 2.433; 95% CI, 1.005-5.890; P=0.007). Stroke mechanisms included arterytoartery embolism (59.7%), local branch occlusion (14.9%), in situ thrombo-occlusion (13.7%), hemodynamic impairment (0.9%), and mixed (10.8%). Anterior ICAS was more often associated with artery-to-artery embolism (51.8% vs 34.0%) and less often associated with local branch occlusion (12.3% vs 40.4%) than posterior ICAS (P<0.001).
Conclusions: The prevalence of risk factors and stroke mechanisms differ between ICAS and ECAS, and between anterior and posterior circulation atherosclerosis. Posterior ICAS seems to be closely associated with metabolic derangement and local branch occlusion. Prevention and management strategies may have to consider these differences.