Management of Intraosseous Subarcuate Loop of the Anterior Inferior Cerebellar Artery during Trigeminal Schwannoma Resection: Operative Case and Anatomical Correlation

Introduction: The intraosseous subarcuate loop is an anatomical variant of the Anterior Inferior Cerebellar Artery (AICA), in which the artery gives off the subarcuate artery at the apex of the loop while being entrapped in the homonymous fossa of the temporal bone. This represents an additional surgical challenge, often unexpected during surgery of the cerebellopontine angle (CPA). The occurrence of the intradural intraosseous variation ranges between 0.6% [1] and 4% [2]. We 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 anterior reverse petrosectomy. Illustration of the same anatomical variation in an anatomical specimen is also provided.

Case History: A 42-year-old male presented with intermittent right trigeminal neuropathy. MRI identified an extra-axial dumbbell-shaped heterogeneously contrast-enhancing mass lesion extending from the right Meckel’s cave into the CPA. The 3D-CISS sequence demonstrated a possible vascular loop of the right AICA within the bone of the Subarcuate Fossa (SF), at the level of the suprameatal tubercle posterior to the lesion. Physical examination was negative for any focal neurologic deficits. A right retrosigmoid craniotomy with reverse anterior petrosectomy with drilling of the suprameatal tubercle was performed. The subarcuate artery was coagulated and divided and the intraosseous loop of the AICA was safely mobilized. The steps were additionally illustrated with the same anatomical variation in an anatomical specimen. 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 from surgery with mild ipsilateral trigeminal sensory loss and no new neurologic deficits.

Conclusion: The intraosseous AICA loop in the subarcuate fossa is a relatively common anatomical variation. Identification and safe mobilization is essential to avoid intraoperative lesion of AICA.

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Artikel online veröffentlicht:
05. Februar 2024