Background: Augmentation of collateral flow is proposed as a method to reduce ischemic injury in the posterior circulation. However, collateral formation in basilar artery stenosis (BAS) and basilar artery occlusion (BAO) has not been studied thoroughly.
Methods: We identified 24 consecutive patients admitted over a 4-year period with angiographically demonstrated BAS of more than 50% or occlusion. Angiographic images were reviewed for pattern of collaterals by a blinded reviewer. A new grading system by Qureshi  (Qureshi AI (2012) J Neuroimaging in press) was utilized for grading. Grades I and II had retrograde filling of the basilar artery through PCA with or without filling of the superior cerebellar artery, respectively. Grades III and IV were bilateral or unilateral anastomoses of cerebellar arteries or PCAs, respectively. Risk factors such as age, gender, race/ethnicities, co-morbidities, NIHSS sore on admission and discharge, tPA administration, in-hospital complications, and discharge status measured by the modified Rankin score were ascertained.
Results: THE COLLATERALS WERE CATEGORIZED AS: Grade I A (n = 8), Grade IIIA (n = 5), and none (n = 11). No patient had Grade II collaterals. Grade IA collaterals were more frequent in patients with BAO than those with BAS. The rate of good outcomes (mRS 0-2) at discharge was significantly higher among patients with IA collaterals compared with patients with grade IIIA collaterals (62% vs. 20%). The rate of good outcomes was 54% of patients without collaterals.
Conclusions: The pattern of collateral formation in BAS and BAO varies and is associated with patient outcomes.
Keywords: Qureshi grading scale; basilar artery occlusion; basilar artery stenosis; collaterals; posterior circulation collaterals.