Distribution of nonvestibular cranial nerve schwannomas in neurofibromatosis 2
To describe the prevalence and location of cranial nerve schwannomas, other than bilateral vestibular schwannoma, in patients with neurofibromatosis 2 (NF2). The NF2 Natural History Consortium prospectively gathered cranial magnetic resonance imaging for 83 patients across 3 annual evaluations. The time between the first and last evaluation was approximately 3 years. Forty-two patients (51%) had nonvestibular cranial nerve schwannomas (NVSs). Of these, 25 (60%) also had cranial meningiomas. Twenty-one of those without NVS (25% of 83) had at least 1 meningioma. The average size of the NVS was 0.4 cubic centimeters. Overall, there was no significant change in NVS size from Year 1 to Year 3 or from Year 1 to Year 2. The most common locations of the NVS were occulomotor and trigeminal. A family history of NF2 did not predict NVS location or growth. Nonvestibular cranial nerve schwannoma usually affect cranial nerves III and V, as was the case in our NF2 sample. Fortunately, neuropathies associated with these tumors are rare. In contrast, lower cranial nerve schwannomas, although also rare, are associated with swallowing difficulty, aspiration, and other sequelae.