Collision tumor of the facial nerve: a synchronous seventh nerve schwannoma and neurofibroma.

Objective: To report a novel case of a collision tumor involving an intraparotid neurofibroma and a mastoid segment facial nerve schwannoma.

Methods: Clinical capsule report. Methods: Tertiary academic referral center. Methods: A 29-year-old woman with a 2-year history of an asymptomatic enlarging left infraauricular mass and normal FN function presented to a tertiary care referral center. Computed tomography and magnetic resonance imaging demonstrated a cystic lesion in the deep portion of the parotid gland extending into the stylomastoid foramen. Methods: The patient underwent superficial parotidectomy, and a cystic parotid mass was found to be intrinsic to the intraparotid facial nerve. A portion of the mass was biopsied, and intraoperative frozen section pathology was consistent with a neurofibroma. A mastoidectomy with FN decompression was then performed until a normal-appearing segment was identified just proximal to the second genu. After biopsy, proximal facial nerve stimulation failed to elicit evoked motor potentials, and en bloc resection was performed.

Results: Final pathology demonstrated a schwannoma involving the mastoid segment and a neurofibroma involving the proximal intraparotid facial nerve.

Conclusions: We report the first case of a facial nerve collision tumor involving an intraparotid neurofibroma and a mastoid segment facial nerve schwannoma. Benign FN sheath tumors of the parotid gland are rare but should be considered in the differential diagnosis of a parotid mass.