184 - Trigeminal Schwannomas

Abstract

Trigeminal schwannomas (TSs) are slow-growing skull base tumors arising from the peripheral nerve sheath of the trigeminal nerve. The vast majority of cases are histologically benign schwannomas, and malignant cases are exceedingly rare. Patients predominantly present with sensory trigeminal signs and symptoms. Tumors may be located at the cerebellopontine angle (in the posterior fossa) or the Meckel cave or cavernous sinus (in the middle fossa); can extend along the peripheral branches into the orbit, pterygopalatine, or infratemporal fossa; or may occur in any combination of these. In symptomatic tumors with mass effect, total surgical resection is the treatment of choice. Surgical approaches are tailored according to the extension of each individual tumor within intracranial/extracranial compartments. Tumors extending to multiple fossae are a surgical challenge. Extradural skull base approaches increase the success rate for resection in ganglionic or combined ganglionic-cisternal tumors. Endoscopic endonasal approaches may also be used, especially when dealing with the extensions into the pterygopalatine and subtemporal fossae. Gross total surgical resection of TSs results in cure. Surgical complications are not rare, the most common being variable degrees of persistent trigeminal hypoesthesia. Any small residual tumor will continue to grow. Radiosurgery can be used as an adjuvant treatment in recurrent, residual, or inoperable cases with excellent results. The aim of radiosurgery is tumor growth control, with possible decrease in tumor size and possible decrease of symptoms, without causing additional neurological deficits. Small to midsize tumors can also be effectively managed with radiosurgery alone. Some authors advocate radiosurgery for even larger tumors, but the risk of treatment failure or treatment side effects increases in parallel with the volumetric size.