Continuous and Dynamic Facial Nerve Mapping During Surgery of Cerebellopontine Angle Tumors: Clinical Pilot Series

Abstract

Objective: To evaluate a new surgical tool combining suction and monopolar neurostimulation (stimulation sucker) for cerebellopontine angle (CPA) tumors. The usefulness for continuous (time) and dynamic (space) facial nerve mapping was studied.

Methods: Patients operated on with the stimulation sucker for a CPA tumor between April 2016 and May 2017 in a tertiary care center were identified. Clinical charts were retrospectively evaluated. The minimum follow-up time of patients was 12 months.

Results: The study population included 17 patients with tumor (6 women and 11 men). The age range was from 2 to 77 years (mean age, 45.7 years; standard error of the mean, 22.7 years). Most CPA tumors were large (Koos grade 4) vestibular schwannomas (n = 10); other pathologies included petrous meningioma (n = 1), metastasis (n = 1), medulloblastoma (n = 2), ependymoma (n = 2), and pilocytic astrocytoma (n = 1). One patient with trigeminal neuralgia served as the normal control subject. No complications because of the stimulation sucker were encountered. Clinical and radiologic outcomes compared favorably with institutional experience and literature. The stimulation sucker allowed for continuous (time) mapping of the facial nerve at the site of resection (space). This real-time feedback allowed early identification of the facial nerve. Handling and ergonomy were excellent and workflow improved. The shortcomings compared with a bayonet-shaped bipolar probe were decreased visibility of neurovascular structures and lower spatial discrimination. The new device did not simplify delicate at the brainstem and on the nerve. We think it should be considered as a complementary tool in the surgeon's armamentarium.

Conclusions: Until now, nerve damage as assessed by neuromonitoring (e.g., facial nerve electromyography, motor evoked potential) served as surrogate for nerve function. This concept should be challenged. The studied stimulation sucker detected the facial nerve earlier than conventional techniques, preventing harm by surgical trauma. A larger, prospective study is warranted to better define its role in CPA surgery.

Keywords: Acoustic neuroma; Cerebellopontine angle tumor; Facial nerve monitoring; Intraoperative; Skull base; Vestibular schwannoma.