Same-territory chronic infarcts are common in intracranial atherosclerosis and are associated with future recurrence

Background Intracranial atherosclerotic disease (ICAD) has a high risk of symptomatic recurrence. We investigated the prevalence of same-territory chronic infarcts among symptomatic ICAD patients, and their ability to discriminate between absence and presence of future same-territory ischaemic events. Methods In a retrospective analysis of prospectively collected data from two Australian stroke centres, patients were followed for recurrent ischaemia over 12 months. Ability to discriminate between absence and presence of recurrent stroke/TIA (Area-under-curve (AUC) in receiver-operating-characteristic analysis) and degree of model fit (Bayesian information criterion (BIC)) were compared for prognostic characteristics of chronic same-territory stroke, >70% stenosis and CT-perfusion hypoperfusion. Results From 2019 to 2020, 135 patients had symptomatic ICAD, mean age 73.8 (SD±13.2) and 57/135 (42%) female, of whom 29/135 (21%) had chronic same-territory infarcts. Over a 12-month follow-up period, recurrent cerebrovascular events occurred in 9/29 (31%) patients with, and in 11/106 (10%) without, chronic same-territory stroke (OR 3.9 95% CI 1.4 to 10.6, p=0.008). In discrimination and model fit analysis, BIC indicated strong evidence for improved model fit, for same-territory chronic infarction (AUC 0.64) vs >70% stenosis (AUC 0.58, p=0.59; BIC difference 4.7). In n=99 with CT-perfusion, chronic infarct showed better fit than CT-perfusion hypoperfusion (0.64 vs 0.61, p=0.79; BIC difference 2.8). Chronic infarct alone also outperformed all combinations of chronic infarct, hypoperfusion and >70% stenosis in model fit. Conclusions Chronic same-territory infarcts are common among patients presenting with symptomatic ICAD and can better discriminate future same-territory ischaemic cerebrovascular events over a 12-month period than stenosis>70% and hypoperfusion on CTP.