Intracranial carotid artery calcification subtype and collaterals in patients undergoing endovascular thrombectomy

Background and aims: Distinct subtypes of intracranial carotid artery calcification (ICAC) have been found (i.e., medial and intimal), which may differentially be associated with the formation of collaterals. We investigated the association of ICAC subtype with collateral status in patients undergoing endovascular thrombectomy (EVT) for ischemic stroke. We further investigated whether ICAC subtype modified the association between collateral status and functional outcome.Methods: We used data from 2701 patients with ischemic stroke undergoing EVT. Presence and subtype of ICAC were assessed on baseline non-contrast CT. Collateral status was assessed on baseline CT angiography using a visual scale from 0 (absent) to 3 (good). We investigated the association of ICAC subtype with collateral status using ordinal and binary logistic regression. Next, we assessed whether ICAC subtype modified the association between collateral status and functional outcome (modified Rankin Scale, 0-6).Results: Compared to patients without ICAC, we found no association of intimal or medial ICAC with collateral status (ordinal variable). When collateral grades were dichotomized (3 versus 0-2), we found that intimal ICAC was significantly associated with good collaterals in comparison to patients without ICAC (aOR, 1.41 [95% CI:1.06-1.89]) or with medial ICAC (aOR, 1.50 [95%CI:1.14-1.97]). The association between higher collateral grade and better functional outcome was significantly modified by ICAC subtype (p for interaction = 0.01).Conclusions: Patients with intimal ICAC are more likely to have good collaterals and benefit more from an extensive collateral circulation in terms of functional outcome after EVT.