Single-Session Gamma Knife Stereotactic Radiosurgery for Contralateral Vestibular Schwannoma and Trigeminal Neuralgia

Introduction: Gamma Knife stereotactic radiosurgery (SRS) is a well-established treatment modality for both vestibular schwannoma (VS) and trigeminal neuralgia (TN). In rare cases, VS patients present with TN symptoms attributable to mass effect at the trigeminal root entry zone, which typically improves following tumor treatment. We report a patient with contralateral TN and VS, both treated via single session SRS.

Methods: Case report.

Results: A 25-year-old female with a history of Vein of Galen malformation status post coil embolization at age 15 months, requiring serial angiography over many years, and hydrocephalus status post ventriculoperitoneal shunt placement, presented with 13 years of right-sided TN refractory to medical therapy. MRI incidentally identified a hyperintense heterogeneously enhancing 1.6 × 1.2 cm left cerebellopontine angle (CPA) mass with internal auditory canal extension, consistent with VS, as well as expected postoperative changes, and a new small dural arteriovenous fistula adjacent to the torcular herophili. Single session SRS was performed targeting both the right trigeminal nerve and left CPA mass. The left VS was treated with 10 isocenters of radiation to cover a volume of 1.4 cm³ using a dose of 13 Gy to the 50% isodose line, and the right trigeminal nerve was treated with one isocenter of radiation to treat the cisternal segment of the trigeminal nerve covering a volume of 0.1 cm³. The maximum dose to the right trigeminal nerve was 85 Gy. At 12-month follow-up, the patient reported marked improvement in TN symptoms, with successful weaning to maintenance carbamazepine (200mg QID) for breakthrough facial pain prophylaxis. MRI demonstrated expected post-SRS changes of the left CPA mass, including reduction in tumor size, decreased tumor intensity, and a more homogeneous enhancement pattern.

Conclusions: SRS is an efficacious treatment for VS and TN. Its benefits include favorable functional outcomes, excellent tumor control, and minimization of surgical risk. We report the first patient to present with synchronous contralateral VS and TN. Although a mechanism linking the disease processes is not definitively established, extensive radiation exposure in childhood may have predisposed the patient to abnormal posterior fossa development, potentially precipitating both TN and VS. Selection of SRS in this individual allowed for single-session, non-invasive management of two potentially debilitating pathologies, as opposed to staged bilateral suboccipital craniotomies—a particularly advantageous strategy in a patient with a complex history of multiple intracranial interventions.