VESTIBULAR SCHWANNOMA TUMOURS (ACOUSTIC NEUROMA)
This tumor accounts for around 8 % of all intracranial tumors and has an incidence of 13/million per year (Tos and Thomsen 1984). Although sometimes called acoustic neuromas, these are Schwann cell tumors. They usually arise from the vestibular nerve but can develop on the fifth cranial nerve and less often on the ninth and tenth nerves.
Within the spinal canal, they usually arise on the dorsal spinal root. Familial and bilateral vestibular schwannomas are features of neurofibromatosis type 2 (NF2). About 4 % of vestibular schwannomas are bilateral, and all patients with bilateral tumors have NF2. Sporadic vestibular schwannoma is typically seen in the fifth and sixth decades of life, which is about 20 years later than in patients with NF2. The clinical features and diagnostic criteria for NF2. Although vestibular schwannoma in NF2 is usually bilateral, it can be unilateral. Those mosaics for an NF2 gene mutation may present with milder- and later-onset disease.
Multiple extracranial schwannomas (cutaneous and spinal) without vestibular schwannomas may be inherited as a dominant trait (Evans et al. 1997) and may be caused by germline mutations in SMARCB1. Occasionally SMARCB1 mutations. (Smith et al. 2011).