Stereotactic radiosurgery for fourth ventricle brain metastases: tumor control outcomes and the need for CSF diversion. Patient series.

backgroundStereotactic radiosurgery is a favorable alternative to surgery for intracranial cerebral metastases. Fourth ventricle (V4) metastases are challenging because of the location and surrounding structures, with a high risk for obstructive hydrocephalus and brainstem compression. Here, the authors evaluate the effectiveness in terms of safety, tumor control rates, and permanent cerebrospinal fluid (CSF) diversion of primary Gamma Knife radiosurgery (GKRS) in treating V4 metastases. OBSERVATIONS: Eleven of 1060 patients had V4 brain metastases. No patients had pre-GKRS hydrocephalus. The mean tumor volume was 3.3 cm3, treatment dose was 18 Gy to the 50.5% isodose line (average 14 shots), conformity index was 1.4, and volume of brainstem receiving greater than 12 Gy was 0.2 cm3. Eight patients had radiographic and clinical follow-ups. The average time to initial follow-up was 3.1 months. Karnofsy Performance Status did not change from the initial consultation to the post-GKRS follow-up. No patients developed hydrocephalus or required permanent CSF diversion. One patient required transient external ventricular drain placement; however, neurological symptoms resolved with steroid therapy. Seven patients received steroid therapy post-GKRS. Seven patients had radiographic disease control at the 6-month follow-up. One patient had tumor progression at 6 months and underwent surgery. LESSONS: Primary GKRS for V4 metastases with a close follow-up is safe and optimizes quality of life for patients with significant cancer burden. https://thejns.org/doi/10.3171/CASE24293.