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

Abstract

Pineal region tumors are associated with the ventricular system. Endoscopic third ventriculostomy (ETV) is often performed at the same time as tumor biopsy. To investigate the volume of brain possibly undergoing injury and forniceal stretching during ETV and tumor biopsy. 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. 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. 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.