Frameless VarioGuide biopsy for pediatric brainstem lesions in the molecular era: diagnostic performance and workflow characteristics in a comparative single-center series

Abstract Background Molecular characterization has become essential for the diagnosis and treatment of pediatric brainstem lesions. While frame-based stereotactic and robotic-assisted biopsies are well established, comparative data on frameless VarioGuide biopsy for pediatric brainstem lesions remain scarce. This study evaluated the diagnostic performance, safety, and workflow characteristics of frameless VarioGuide biopsy compared with frame-based stereotactic and ROSA-assisted techniques. Methods We retrospectively reviewed all pediatric patients (≤ 18 years) who underwent stereotactic biopsy of a brainstem lesion at a single tertiary neurosurgical center between 2016 and 2026. Patients were grouped according to biopsy technique (frameless VarioGuide, frame-based stereotaxy, or ROSA-assisted biopsy). Diagnostic yield, molecular diagnostic yield, complications, operative times, and workflow parameters were analyzed. Results Twenty-two pediatric patients met inclusion criteria. Six underwent frameless VarioGuide biopsy, nine frame-based stereotactic biopsy, and seven ROSA-assisted biopsy. Overall diagnostic and molecular diagnostic yields were 95%. Diagnostic and molecular diagnostic yields were 100% with VarioGuide, 89% with frame-based stereotactic biopsy, and 100% with ROSA-assisted biopsy, without statistically significant differences between groups ( p = 0.62). Median operative times were similar among groups (32, 36, and 25 min, respectively; p = 0.28). However, preoperative setup time differed significantly, with the shortest duration observed in the VarioGuide cohort (40.5 min) compared with ROSA-assisted biopsy (64 min) and frame-based stereotaxy (112 min; p = 0.002). Despite the absence of intraoperative neuropathological assessment, all VarioGuide procedures yielded diagnostically and molecular-pathologically informative tissue. No procedure-related hemorrhage, infection, permanent neurological deficit, or procedure-related mortality were observed. Conclusions In this exploratory single-center cohort, frameless VarioGuide biopsy achieved high diagnostic and molecular diagnostic yields without permanent procedure-related morbidity and was associated with shorter preoperative setup time. These findings support further evaluation of frameless VarioGuide biopsy as a workflow-efficient approach for tissue acquisition in pediatric brainstem lesions.