SURG-42. Evaluating brainstem biopsy outcomes: Insights from frame-Based, MRI-Guided, and robot-Assisted techniques

Abstract In modern oncology, where tissue diagnosis is fundamental, brainstem lesions present unique challenges due to their deep location and surgical risks; however, technological advancements have significantly improved the precision and safety of biopsy procedures. This study evaluates the clinical outcomes of stereotactic biopsies of brainstem lesions using frame-based, MRI-guided, and robot-assisted techniques. Clinical outcomes were collected from brainstem biopsies performed between 2011 and 2025 by a single surgeon using the Cosman-Roberts-Wells (CRW) frame (frame-based), the Clearpoint XG frame (MRI-guided), or the Globus Excelsius GPS (robotic assistance). Of the 22 brainstem biopsies, five were frame-based, nine were MRI-guided, and four were robot-assisted. Procedural times were comparable across techniques (Frame:166.4±28.2 minutes, MRI:179.8±48.6 minutes, Robot:136.3±35.7 minutes, p=0.27). Stereotactic accuracy was not calculated for frame-based biopsies due to the absence of intra-operative imaging, while MRI and robotic biopsies demonstrated comparable radial errors (1.08±0.54 vs. 1.48±0.54, p=0.32). More samples were obtained in MRI-guided and robotic biopsies than in frame-based procedures (1.2±0.4 vs. 2.94±0.73, p<0.0001), attributed to additional samples taken after confirming stereotactic accuracy via intra-operative imaging. A definitive diagnosis was established in 20 of 22 lesions (91%), including isocitrate dehydrogenase-mutated astrocytomas, H3K27 gliomas, glioblastomas, pilocytic astrocytomas, and demyelinating diseases. The two undiagnosed patients were monitored due to confirmed stereotactic accuracy during the procedure. One surgical morbidity occurred in a patient with recurrent H3K27 glioma, who developed a hematoma at the entry site requiring evacuation. Hospital stays were similar across methods (median of 3 days, p=0.66), and there were 5 out of 22 (21.7%) 30-day readmissions, all due to corticosteroid-related complications. In conclusion, the pathology of brainstem lesions is diverse and tissue diagnosis is essential; compared to traditional frame-based biopsy, MRI-guided and robotic-aided techniques allow intra-operative confirmation of stereotactic accuracy, thereby enabling real-time decision-making and optimized patient management.