AbstractBackground and PurposeThe influence of intracranial arteriosclerosis (ICAR) on acute ischaemic stroke (AIS) prognosis is unclear. This study explored its impact, focusing on ICAR subtypes categorized by intracranial carotid artery calcification (ICAC) patterns: intimal or atherosclerotic versus internal elastic lamina calcification or non‐atherosclerotic. The aim was to determine their effect on AIS prognosis in patients undergoing endovascular treatment (EVT).MethodsThis prospective cohort study included consecutive AIS patients with anterior circulation large vessel occlusion undergoing EVT. ICAC, the hallmark of ICAR, was assessed using non‐contrast computed tomography to quantify volume and establish the predominant ICAR subtype. The primary outcome was long‐term functional outcome, measured by the 90‐day modified Rankin Scale score. Secondary outcomes included first‐pass effect, revascularization degree, symptomatic intracranial haemorrhage and 24‐h infarct volume. Multivariate‐adjusted linear and logistic regression models were used to assess the association of ICAC volume and subtype with these outcomes.ResultsFrom January 2021 to February 2022, 181 patients were included, of whom 172 (95%) had ICAC. Internal elastic lamina calcification was the predominant subtype in 103 (57%), intimal in 52 (29%) and mixed in 17 (9%). The intimal or atherosclerotic ICAC pattern was linked to poorer functional outcomes (adjusted odds ratio 2.12, 95% confidence interval [CI] 1.10–4.09), decreased first‐pass effect probability (adjusted odds ratio 0.42, 95% CI 0.21–0.84) and higher infarct volume (adjusted β value 22.11, 95% CI 0.55–43.67).ConclusionsA predominant intimal ICAC subtype, linked to underlying atherosclerosis, correlated with larger infarct volume and poorer 90‐day functional outcomes in EVT‐treated AIS patients. Intracranial atherosclerosis appears to be a relevant factor hampering clinical benefits post‐EVT.