One- vs Two-Burr-Hole Technique for Combined Endoscopic Third Ventriculostomy and Pineal Region Biopsy: Volumetric Analysis of Brain at Risk.

Background: Pineal region tumors are associated with the ventricular system. Endoscopic third ventriculostomy (ETV) is often performed at the same time as tumor biopsy.

Objective: To investigate the volume of brain possibly undergoing injury and forniceal stretching during ETV and tumor biopsy.

Methods: We performed a retrospective review of preoperative magnetic resonance imagings (MRIs) and computed tomography (CTs) of patients with pineal region masses and used volumetric image-guided navigation to simulate a 1-burr-hole vs a 2-burr-hole approach through the brain parenchyma. We compared the volumes of parenchyma and fornix at the risk of injury.

Results: The ideal entry point for ETV using 2 burr holes was a mean ± standard deviation (SD) of 25.8 ± 6 mm from the midline and 11.4 ± 9 mm behind the coronal suture. The ideal entry point using 2 burr holes for tumor biopsy was 25.7 ± 8 mm from the midline and 53.7 ± 14 mm anterior to the coronal suture. With 1 burr hole, the mean ± SD volume of brain parenchyma at risk was 852 ± 440 mm3. The volume of brain parenchyma at risk with 2 burr holes was 2159 ± 474 mm3 (P < .001; paired t-test). The use of 1 burr hole predisposed the fornix to 14 ± 3 mm of possible stretch, which was minimized with the 2-burr-hole approach.

Conclusion: Using 1 burr hole for both the ETV and tumor biopsy is less likely to traumatize the brain parenchyma than using 2 burr holes. However, 1 burr hole predisposes the fornix to stretch injury. We recommend tailoring the entry to each patient according to their anatomy rather than using a 1-size-fits-all approach.