Adjustment of the endoscopic third ventriculostomy entry point based on the anatomical relationship between coronal and sagittal sutures.

Object: The coronal suture is often used as an empirical landmark for the entry point for endoscopic third ventriculostomy. The trajectory for the approach is often drawn based on midsagittal MRI findings. However, because the coronal suture is not perpendicular to the midline, this method may be inaccurate.

Methods: The junction of the coronal and sagittal sutures was exposed at the outer table of the cranium of 15 cadavers. An ideal coronal line was established perpendicular to the sagittal suture at the junction of the sagittal and coronal sutures. The distance from this ideal coronal line at the level of the coronal-sagittal junction to the actual coronal suture was measured at 1-cm intervals. The measured distance between the 2 planes was termed the distance to the coronal suture.

Results: The coronal suture bows forward as it moves from medial to lateral. From 1-6 cm lateral to the sagittal suture, the distance to the coronal suture was 0.1, 0.3, 0.5, 0.8, 1.0, and 1.4 cm, respectively. There was no significant difference between the right and left sides.

Conclusions: The position of a bur hole for endoscopic third ventriculostomy should be moved posteriorly with respect to the coronal suture the more laterally it is placed. Although the adjustment is small, it may be crucial. Failure to make this adjustment may result in suboptimal bur hole placement and increase the risk of morbidity.