Birds on a wire: Gamma Knife radiosurgery for two schwannomas along the same cranial nerve. Illustrative case.

backgroundFor small- to medium-sized vestibular schwannomas, especially in patients with preserved hearing and no mass-effect symptoms, Gamma Knife radiosurgery (GKRS) is a preferred initial treatment. It provides effective tumor control and long-term hearing preservation. In the event of a tumor progression, reirradiation remains an option. A rare occurrence is the development of a second schwannoma along the same nerve. In such cases, repeat GKRS can be challenging, as it requires balancing local control with minimizing integral radiation dose and potential toxicity from reirradiation. The authors highlight the feasibility of repeat GKRS and the dosimetric considerations involved in radiating a second schwannoma along the same nerve. OBSERVATIONS: A 35-year-old woman with a history of headaches and a right-sided vestibular schwannoma underwent GKRS as treatment for the tumor. After being under surveillance from 2013 to 2025, the patient's vestibular schwannoma remained stable. After experiencing a worsening right-sided tinnitus, an updated MRI study revealed a new intracanalicular nodular formation along the nerve, which was treated with GKRS. LESSONS: This case demonstrates the safety and efficacy of GKRS as a retreatment option in the rare occurrence of a second vestibular schwannoma developing along the same cranial nerve. https://thejns.org/doi/10.3171/CASE25667.