Management of Intraosseous Subarcuate Loop of the Anterior Inferior Cerebellar Artery During Trigeminal Schwannoma Resection: 2-Dimensional Operative Video

The intraosseous subarcuate loop is an anatomic variant of the anterior inferior cerebellar artery (AICA), in which theartery gives off the subarcuate artery at the apex of the loop, entrapped in the subarcuate fossa (SF) of the temporal bone. First reported by Tanriover and Rhoton,1few others2-5have addressed this additional challenge during cerebell opontineangle surgery, occurring in 0.6%-4%.3,6We present a case of the safe mobilization of the intraosseous variant of the AICA and resection of a trigeminal schwannoma through a retrosigmoid approach with reverse anterior petrosectomy. Il-lustration of the same anatomic variation in a specimen is also provided.A 42-year-old male patient presented with intermittent right trigeminal neuropathy. MRI identified an extra-axialdumbbell-shaped heterogeneously contrast-enhancing lesion extending from the right Meckel cave into the cerebellopontine angle. The 3D-CISS sequence demonstrated a possible vascular loop of the right AICA within the SF.Physical examination was negative. Documented and verified informed consent was obtained.A right retrosigmoid craniotomy with reverse anterior petrosectomy was performed. The subarcuate artery was co-agulated and divided, and the intraosseous loop of the AICA was safely mobilized, with the steps demonstrated on aspecimen. The extra-axial mass was exposed, and gross total resection was achieved. The Doppler signal in AICA was appropriate at the end of the operation. The patient recovered well with mild ipsilateral trigeminal sensory loss and nonew neurological deficits. Intraosseous AICA loop in the SF is a relatively common anatomic variation. Identification and safe mobilization are essential to avoid intraoperative lesion of AICA