An in vivo morphometry study on the standard transsylvian trajectory for mesial temporal lobe epilepsy surgery

A safe and appropriate surgical approach to the medial temporal structure is a prerequisite to perform surgeries for temporal lobe epilepsy. We used in vivo morphometry to identify the standard direction for entry into the inferior horn of the lateral ventricle via the Sylvian fissure: an important initial step in performing transsylvian selective amygdalohippocampectomy. 3D magnetic resonance images obtained from 28 patients without intra-parenchymal lesions were re-oriented to demonstrate all points in the Talairach space of the brain. The limen insulae and the midpoint between the hippocampal sulcus and the innominate sulcus on the coronal slice through the posterior edge of the amygdala were defined as the start and target points, respectively. We evaluated the direction of the vector between these two points and its validity in the brain of 12 patients with temporal lobe epilepsy. The direction of the mean approach vector was 52.4° posteriorly and 16.2° inferiorly. The mean approach vector on the axial plane showed the approximate parallelism with the sphenoid ridge in individual cases. The computer simulation revealed that our average approach vector correctly entered the inferior horn of the lateral ventricle in all temporal lobe epilepsy brains. In vivo morphometry may contribute to the further development of safe and minimally-invasive neurosurgical procedures.