Hybrid frame-mask fixation for Gamma Knife radiosurgery of an extracranial vagal schwannoma: illustrative case.

BACKGROUND: Stereotactic radiosurgery requires high precision and stable target immobilization, especially for extracranial lesions prone to motion. Lesions located low in the neck pose unique challenges because of limited access and potential movement from mandibular activity. This case illustrates a novel hybrid fixation technique that combines a stereotactic G-frame with a thermoplastic mask (TPM) via a custom 3D-printed adaptor to ensure immobilization and treatment access for a low-positioned vagal schwannoma treated with Gamma Knife radiosurgery (GKRS). OBSERVATIONS: A 62-year-old male was incidentally diagnosed with a 3.63-cm3 vagal schwannoma in the right carotid space. Over 4 years, the tumor showed progressive growth without neurological deficits. The lesion's low position posed challenges for delivering GKRS with adequate coverage and intrafraction motion stabilization. A custom 3D-printed adaptor was designed to integrate the G-frame with a modified TPM, ensuring target coverage and mandibular restriction during treatment. LESSONS: The novel hybrid personalized fixation strategy, which combines frame-based and mask-based immobilization to enable radiosurgical treatment of low-positioned extracranial lesions, demonstrated feasibility in maintaining secure fixation, reducing intrafraction motion, and enabling successful treatment delivery. The method underscores the importance of innovation and customization in radiosurgery to address anatomical challenges and optimize clinical outcomes. https://thejns.org/doi/10.3171/CASE26251.