Onyx embolization of a cerebellar arteriovenous malformation fed by the posterior inferior cerebellar artery originating from a vertebral artery fenestration: illustrative case.

backgroundArterial fenestration is a vascular anomaly resulting from failed embryonic fusion. Its association with arteriovenous malformations (AVMs) has been reported, but embolization of an AVM fed by an artery arising from a fenestration has not been described. OBSERVATIONS: A 9-year-old girl presented with intracerebral hemorrhage. Imaging revealed a cerebellar AVM fed mainly by the posterior inferior cerebellar artery (PICA) originating from a vertebral artery (VA) fenestration. Associated anomalies included a type II persistent proatlantal artery and a VA entering the transverse foramen at the C4 level on the same side. Prior to resection, Onyx embolization was performed. A distal access catheter (DAC) was placed proximal to the VA fenestration, and a microcatheter was navigated through the VA fenestration to the distal PICA. Partial embolization was achieved using the simple push technique. The DAC was pulled backward during microcatheter withdrawal to prevent the former from moving forward and injuring the vessel. Complete AVM resection was then performed, and there has been no recurrence observed over the past 4 years. LESSONS: Because the vessel wall near the proximal end of a fenestration is fragile, careful manipulation is required during microcatheter insertion and withdrawal to avoid mechanical stress. https://thejns.org/doi/10.3171/CASE25790.