Multiple Unilateral Vestibular Schwannomas: Segmental NF2 or Sporadic Occurrence?

OBJECTIVE To report a case of a patient presenting with two separate unilateral vestibular schwannomas (VSs) without other stigmata of neurofibromatosis type 2 (NF2). STUDY DESIGN This article discusses a case report and review of the literature. SETTING Tertiary academic referral center. PARTICIPANTS A 41-year-old female was referred for evaluation of a left-sided 1.8-cm cerebellopontine angle tumor centered on the porus acusticus and a separate ipsilateral 3-mm intracanalicular tumor appearing to arise from the superior vestibular nerve. The patient denied a family history of NF2. Neurotologic examination was unremarkable and close review of magnetic resonance imaging did not find any other stigmata of NF2. RESULTS The patient underwent left-sided retrosigmoid craniotomy with gross total resection of both tumors. Final pathology confirmed benign schwannoma. The INI1/SMARCB1 staining pattern did not suggest NF2 or schwannomatosis. CONCLUSIONS This is only the third report of a case with multiple unilateral VSs occurring in a patient without other features of NF2. Herein, the authors review the two other reports and discuss potential mechanisms for this rare phenomenon.