Transorbital Transsylvian Selective Amygdalohippocampectomy: A Feasibility Anatomic Investigation

Several surgical techniques have been developed to treat mesial temporal lobe epilepsy, the most common form of drug-resistant epilepsy. Although surgical treatment for mesial temporal lobe epilepsy has proven to be highly effective in controlling seizures and improving patients' quality of life, it carries potential risk to critical neurovascular structures, which can result in significant complications. With the advent of endoscopic techniques, the transorbital route has emerged as a potential alternative for mesial temporal lobe surgery. This study aims to assess the feasibility, potential advantages, and disadvantages of the transorbital transsylvian selective amygdalohippocampectomy (TTSA) and to provide a step-by-step anatomic description of this approach.

A TTSA was performed on three injected cadaveric specimens (six sides). Computer tomography and MRI scans were performed before and after each dissection to demonstrate the extent of amygdalohippocampectomy. Neuronavigation was used to identify the optimal trajectory and the position of intra-axial structures, including the amygdala and hippocampus. For each side, a TTSA was performed and all the anatomic landmarks verified from the standard transcranial perspective through a frontotemporal craniotomy.

The dissection procedure was organized into four sequential steps: (1) the extradural approach, (2) identification and opening of the sylvian fissure, (3) identification and removal of the amygdala, and (4) identification and removal of the hippocampus and parahippocampal gyrus. The intradural steps were performed in accordance with the technique described by Yasargil. Furthermore, a unique and educational comparison between the transorbital anatomic view and the related standard transcranial perspective was provided.

The described technique represents an innovative and feasible approach for amygdalohippocampectomy, achieving comparable surgical resection with traditional open surgery in cadaveric specimens, with potential advantages for neurological and neuropsychological outcomes. However, clinical series and further studies are imperative to validate these findings.