A non-NF2 case of schwannomas of vestibular and trigeminal nerves with different genetic alterations of NF2 gene: case report
We report a patient with 2 separate schwannomas, a vestibular schwannoma and a trigeminal schwannoma, that were attached to each other and appeared to be a single tumor on imaging studies. The patient, without any family history of neurofibromatosis, presented with a progressive hearing loss and mild left facial nerve palsy. Magnetic resonance imaging showed a snowman-like tumor in the left cerebellopontine angle. Surgical exposure revealed that the tumor consisted of 2 "kissing" schwannomas, a trigeminal and vestibular schwannoma. Molecular genetic analysis detected a 1-base pair deletion at exon 10 of the neurofibromatosis type 2 (NF2) gene in the trigeminal schwannoma, but not in the acoustic schwannoma. However, loss of heterozygosity at chromosome 22q (D22S282 and D22S929) was detected in both tumors, losing the same allele. Multiple schwannomas in non-NF2 patients are extremely rare, and possible causes include simple coincidence or germline genetic alteration of adjacent gene on chromosome 22q, similar to the cause recently suggested in familial schwannomatosis. Although not always possible, molecular genetic examination may help to understand the underlying mechanism and would be warranted in such cases.