Emergent Revascularization After Transposition of an Unexpected Intraosseous Anomalous Subarcuate Loop During Vestibular Schwannoma Surgery: A Case Report.

background and importanceThe presence of an anomalous anteroinferior cerebellar artery (AICA) embedded within the subarcuate fossa increases the difficulty of cerebellopontine angle (CPA) tumor surgery. Iatrogenic injury of posterior fossa arteries can result in serious morbidity. CLINICAL PRESENTATION: A 70-year-old man presented with right-sided hearing loss and facial dysesthesia. Magnetic resonance imaging showed a tumor with solid and cystic components and 35-mm maximum diameter in the right CPA. The AICA traveled just dorsal to the tumor and was well-developed because the ipsilateral vertebral artery and posteroinferior cerebellar artery (PICA) were aplastic. During surgery, we unexpectedly encountered an anomalous loop of the AICA-PICA which was embedded in the subarcuate fossa. This loop was mobilized using an ultrasonic bone curette to enable further tumor resection. However, it occluded immediately after mobilization and required open thrombectomy and end-to-end anastomosis. After revascularization, near-complete tumor resection was achieved without causing facial nerve dysfunction or brainstem/cerebellar infarction. Pathological examination of the resected anomalous loop showed abnormal focal hypertrophy of the adventitia and the presence of external elastic lamina.

conclusionMobilization of an anomalous AICA-PICA loop embedded within the subarcuate fossa during VS resection can result in arterial occlusion which requires thrombectomy and revascularization. Surgeons should be aware of this vascular anomaly and be prepared to deal with its ramifications.