Obstructive hydrocephalus due to posterior third ventricle pathology: One or two burr hole approaches for ETV and biopsy

Endoscopic third ventriculostomy (ETV) and tumor biopsy is a frequent procedure for third ventricular tumors. While some authors favor one approach to achieve both goals, others support the selection of two approaches to avoid fornical damage and venous hemorrhage. Here the authors present their experience with both techniques. A retrospective analysis was conducted on cases which underwent an ETV and a tumor procedure in lesions of the posterior third ventricle from 2011 to 2025. Patient records, pre- and postoperative imaging and intraoperative video recordings were retrospectively analyzed. Twenty-six patients met the inclusion criteria: 13 were treated with one, the other 13 with two approaches. The surgical goal of ETV and tumor biopsy/resection was achieved in all cases. No procedure was abandoned. No postoperative complication was observed. Intraoperative forniceal injury was observed in 8/26 patients (31%). Intraoperative bleeding was found in 81% (21/26 cases). In 19% of cases (5/26 cases), intraoperative bleeding required a longer irrigation time but no switch to dry field technique or open surgery was needed. On follow up, three patients required ventriculoperitoneal shunt placement. Thus, ETV success scored 88.5% (23/26 cases). On 2D MRI, the mean intertrajectory angle was smaller in the one-burr-hole group than in the two-burr-hole group (41.8° ± 3.5° vs. 48.7° ± 5.4°; p = 0.001). Lesions of the posterior third ventricle causing obstructive hydrocephalus are ideal candidates for an endoscopic approach. The overall success rate is very high with acceptable surgical risks. In this cohort, larger intertrajectory angles were associated with selection of a two-burr-hole approach. The approximate 45° value was derived post hoc and requires external validation.