Trigeminal schwannomas are rare benign tumors representing the most common nonvestibular schwannoma, and 0.07 to 0.36% of all intracranial tumors. They may occur sporadically but case reports suggest patients with neurofibromatosis type 2 (NF-2) have an increased propensity to form these tumors in addition to the more commonly found vestibular schwannomas.
Schwannomas emerge from the peripheral nerve sheath, distal to the oligodendroglia–Schwann cell junction. The trigeminal nerve (cerebellpontine angle) and the gasserian ganglion (cavernous sinus and Meckel’s cave) are the most common sites for intracranial schwannomas after the vestibular nerve. Similar to vestibular schwannomas, gross total resection of a trigeminal schwannoma portends a good prognosis regarding long-term tumor free survival; however, if only partial resection is achieved, recurrence is common.
The operative approach and difficulty of resection is highly dependent on the location of the tumor along the trigeminal nerve. Jefferson’s classification proposed in 1959, which categorized the tumor based on the segment of the nerve affected. The Jefferson classification schema categorizes tumors into four types. Root type tumors are those arising from the nerve root and involve the posterior fossa. Ganglion type tumors are those that originate from the gasserian ganglion and are confined to the middle fossa. Dumbbell tumors are larger tumors involving the middle and posterio...