Hydrocephalus after Gamma Knife Surgery for Vestibular Schwannoma Resolved by Tumor Removal without Cerebrospinal Fluid Diversion: Report of Two Cases

Hydrocephalus following Gamma Knife surgery for vestibular schwannoma is typically treated with cerebrospinal fluid diversion. However, additional cerebrospinal fluid diversion (shunt placement) causes a lifelong risk of shunt malfunction and infection. We report two cases of vestibular schwannoma in which the hydrocephalus with progressive tumor growth after Gamma Knife surgery was treated by an initial tumor removal, resolving hydrocephalus without cerebrospinal fluid diversion and causing long-term tumor control. Patient 1 underwent Gamma Knife surgery for a 22-mm tumor vestibular schwannoma of Koos grade III and developed symptomatic hydrocephalus with progressive tumor growth. Tumor removal at 17 months after Gamma Knife surgery resolved the hydrocephalus without tumor recurrence 8 years after surgery. Patient 2 underwent Gamma Knife surgery for an 18-mm tumor vestibular schwannoma of Koos grade IV and developed rapid tumor growth and symptomatic hydrocephalus 2 years after Gamma Knife surgery. Patient 2 underwent subtotal tumor removal at 40 months after Gamma Knife surgery resolving hydrocephalus without residual tumor progression at 14 years after Gamma Knife surgery. Subtotal tumor removal may be a primary treatment option in patients with vestibular schwannoma treated with Gamma Knife surgery and developing hydrocephalus with tumor progression. This might help avoid cerebrospinal fluid diversion with long-term tumor control.