Temporal Bone Histopathology in Neurofibromatosis Type 2

Objectives/Hypothesis: To describe the histopathologic findings in the temporal bone in patients with neurofibromatosis type 2 (NF2). The literature contains limited data on otopathology of NF2. Study Design: Basic science study. Methods: Twenty-six temporal bones from 16 patients with NF2 were examined by light microscopy. The diagnosis of NF2 was made on the basis of bilateral cochleovestibular schwannomas. Clinical information was obtained from review of the medical records. Results: The tumors were multicentric in origin in 19 of 26 (73%) ears. Typically, tumors were seen arising within the internal auditory canal and from various locations within the labyrinth. The majority of schwannomas showed high cellularity with involvement of the labyrinth. Most cases showed significant degrees of degeneration of sensory and neural elements within the cochlea. Fusion tumors were sometimes seen as a result of a schwannoma merging with an adjacent meningioma. Fifteen of 26 (58%) ears showed facial nerve involvement by schwannoma. Conclusions: Cochleovestibular schwannomas in NF2 are aggressive neoplasms; they are often multicentric and demonstrate a propensity to involve the labyrinth. There is often associated secondary degeneration within the cochlea. These features make total removal of these tumors and their removal with preservation of hearing more difficult than with sporadic unilateral cochleovestibular schwannoma.