Placement of cesium-131 permanent brachytherapy seeds in periventricular high-grade gliomas: case report highlighting a novel technique to prevent seed migration. Illustrative cases.

Background: Reirradiation of recurrent high-grade gliomas (HGGs) with external beam radiation therapy is limited by the risk of radiation necrosis (RN). Intraoperative brachytherapy offers a localized radiation approach that minimizes RN risk while maintaining tumor control. However, seed migration has historically limited its use in periventricular regions. The authors present 3 cases of recurrent periventricular HGG (2 IDH-wildtype, MGMT promoter-methylated, EGFR-amplified WHO grade 4 glioblastoma and 1 WHO grade 3 astrocytoma) in which a three-layered barrier was created between the ventricular lining and tumor cavity to prevent seed migration, enabling successful brachytherapy.

Observations: Following maximal safe resection, a three-layered patch separated the resection cavity from the ventricle prior to cesium-131 (131Cs) brachytherapy. Patient 1 received suture-stranded 131Cs (20 seeds), while patients 2 and 3 received 131Cs GammaTile (6 tiles, 4 seeds per tile). A three-layered barrier was formed using Gelfoam, Surgicel, and Adherus. At a median 22-month (range 11-24 months) follow-up, MRI confirmed no seed migration and seeds remained in the cavity. There were no complications associated with the barrier placement.

Lessons: This study highlights the novel use of this technique in preventing 131Cs seed migration in intraoperative brachytherapy, serving as a proof-of-concept study. https://thejns.org/doi/10.3171/CASE25176.