Selective n-Butyl Cyanoacrylate Embolization of a Ruptured Aneurysmal Lesion Arising from a Rete-like Collateral Network of the Posterior Inferior Cerebellar Artery

A 58-year-old woman presented with sudden-onset severe headache and decreased consciousness. Computed tomography revealed posterior fossa–predominant subarachnoid hemorrhage. Digital subtraction angiography demonstrated a rete-like collateral network of the left posterior inferior cerebellar artery, an extremely rare vascular anomaly in which the posterior inferior cerebellar artery trunk divides into a plexiform network of small dysplastic channels before reconstituting into distal branches. A 1.5-mm aneurysmal lesion was identified on one channel of this network by superselective angiography and was considered the bleeding source; given its small size and the fragile dysplastic substrate, a pseudoaneurysm could not be excluded. After emergent hematoma evacuation, the aneurysm-bearing channel was selectively occluded with 25% n-butyl cyanoacrylate (0.2 mL). Post-embolization angiography confirmed exclusion of the lesion with preserved distal posterior inferior cerebellar artery perfusion through the remaining channels. Diffusion-weighted imaging at 48 hours showed no new ischemic lesions in the posterior inferior cerebellar artery perfusion territory. The patient was discharged with a modified Rankin Scale score of 2, which improved to 1 at 7 months. A rete-like collateral network of the posterior inferior cerebellar artery is exceedingly rare. Although a ruptured pseudoaneurysm on a hypoplastic and plexiform posterior inferior cerebellar artery has been reported, a ruptured aneurysmal lesion arising from a focal rete-like collateral network of an otherwise normal posterior inferior cerebellar artery, treated by selective channel occlusion, has not previously been described. The multi-channel architecture of this anomaly may permit selective occlusion of an aneurysm-bearing channel while maintaining distal perfusion; however, the potential risk of brainstem perforator infarction must be carefully considered, and further experience is needed before this strategy can be generalized.