Safe Entry Zones to the Thalamus: A Systematic Review and Meta-Analysis of Classifications and Surgical Approaches with a Proposed Theoretical Framework

Background: Surgical access to the thalamus is complex because of its deep location and proximity to eloquent structures. Traditional classifications provide limited safety guidance. This review assesses classifications, surgical approaches, outcomes across entry zones, and suggests a framework combining accessibility and functional safety. Methods: We conducted a systematic review and meta-analysis in accordance with PRISMA 2020 guidelines. PubMed and Scopus were searched for English-language studies published between 2000 and 2025. Data were extracted on surgical approaches, entry zones, and outcomes. Meta-analysis was performed in Jamovi (v2.3) using odds ratios or mean differences with 95% confidence intervals. Results: Thirty studies encompassing 952 patients were analyzed, with gliomas (61%) and vascular lesions (38%) predominating. Surgical corridors included endoscopic (26%) and interhemispheric transcallosal (14%) among others. Overall, 46% of patients improved, 33% remained stable, 18% worsened, and mortality was 8%, with recurrence in 8%. Corridor-specific analyses showed improvement rates of 41% for transfrontal, 45% for occipital, and 61% for interhemispheric transcallosal approaches, though differences were not statistically significant. Endoscopic surgery achieved similar improvement rates (~45%) but was associated with higher odds of deterioration (OR ≈ 3.2) and mortality (OR ≈ 5.9) compared with open surgery. Conclusion: Thalamic surgery remains technically demanding, with outcomes shaped by both anatomical access and functional resilience of the nuclei involved. This review proposes a framework that integrates these dimensions, offering a basis for more systematic corridor selection. Further prospective validation is needed to translate this concept into clinical practice. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany