Risk factors, infarct patterns and outcome differ between anterior and posterior circulation strokes attributed to intracranial large artery atherosclerotic steno-occlusive disease

Intracranial large artery atherosclerotic steno-occlusive disease (ICLAS) is the leading cause of acute ischemic stroke (AIS). The differences between anterior circulation stroke (ACS) and posterior circulation stroke (PCS) based on the TOAST classification have been well studied. However, data on the differences between ACS and PCS related to ICLAS are scarce, particularly from Saudi Arabia (SA). This study aimed to investigate the differences in demographics and clinico-radiological characteristics between patients with ACS and PCS attributed to ICLAS.This retrospective study included data for patients with ICLAS-related AIS grouped into two phenotypes as ACS and PCS. Demographics and clinico-radiological characteristics were compared between defined phenotypes using the chi-square test. The difference in the distribution of risk factors and radiological variables was ascertained by estimating the odds ratios (ORs) and 95 % confidence intervals (CI).Data pertaining to 147 patients were included. Anterior circulation was involved in 66 % of patients. Territorial infarct pattern (68.7 %) was the most prevalent infarct pattern and artery to artery embolization (49 %) was the most prevalent mechanism for AIS. Watershed infarct pattern due to hemodynamic impairment was more prevalent in ACS than PCS (P = 0.0011). Diabetes mellitus (P = 0.02) and perforator infarct pattern (P = 0.001) were more prevalent in PCS than ACS. Baseline NIHSS, stroke severity and discharge status were statistically different between two phenotypes. Patients with infarction in posterior circulation have better functional outcome than those having in anterior circulation.AIS attributed to ICLAS differs between ACS and PCS. Observed differences in risk factors' distribution, infarct pattern, underlying mechanism and outcome between two phenotypes carry important therapeutic and prognostic implications.