Background: One of the serious complications associated with endoscopic ventriculostomy (ETV) is memory impairment cause by injury of the memory pathway at the foramen of Monro. The optimal landmark of burr hole for the endoscope entry point decreases the risk of traumatizing important anatomical structures around the foramen of Monro.
Objective: To define the optimal landmark of entry site for ETV in Thai patients in order to reduce postoperative complications.
Material and Method: The practical entry point was obtained from 3D reconstructive postoperative cranial CT scans of patients who underwent an ETV procedure. Favorable practical entry point is associated with intraoperative uninjured anatomical structures around the foramen of Monro. In addition, the ideal entry point was obtained from mergence of cranial
MR images and CT scans.
Results: The mean perpendicular distance from the favorable practical entry point was 2.91 cm lateral to the midline and 0.96
cm anterior to the coronal suture. The mean perpendicular distance from the ideal entry point was 2.51 cm lateral to the
midline and 0.24 cm posterior to the coronal suture.
Conclusion: The authors suggest that the optimal entry point for ETV is 2.5 cm perpendicular to the midline and centered at
the coronal suture, especially in Thai people.

Keywords: Endoscopic third ventriculostomy, Entry point, Midline, Coronal suture, Obstructive hydrocephalus