Background The morphology of the basilar artery tip (BAT) varies between patients. The morphologic anatomy of the BAT could affect the efficacy of mechanical thrombectomy (MT).

Methods 108 patients with acute distal basilar artery occlusion (dBAO) who underwent MT from January 2013 to December 2021 were retrospectively analyzed. These patients were divided into two groups based on their BAT morphology: those with symmetrical cranial or caudal fusion of the BAT (symmetric group) and those with asymmetrical fusion of the BAT (asymmetric group). Morphological variables and angiographic and clinical outcomes were compared between the two groups.

Results Of the 108 enrolled patients, 42 were in the asymmetric group. Compared with the symmetric group, the asymmetric group had significantly larger BAT diameter (mean 3.5±1.0 mm vs 4.3±1.1 mm, P=0.001) and basilar artery tip/trunk ratio (1.2±0.2 vs 1.7±0.2, P<0.001). The asymmetric group showed a significantly lower rate of complete reperfusion (71.2% vs 40.5%, P=0.002) and first pass effect (FPE) (51.5% vs 21.4%, P=0.002) than the symmetric group. The BAT asymmetry was an independent predictor of failed FPE (OR 0.299, 95% CI 0.098 to 0.918, P=0.035) and failed complete reperfusion (OR 0.275, 95% CI 0.087 to 0.873, P=0.029).

Conclusions The efficacy of MT for dBAO differs according to the anatomic morphology of the BAT. The asymmetric BAT was frequently encountered in dBAO patients and was independently associated with a reduced likelihood of complete reperfusion and FPE.