S urgical resection of the hippocampus is the standard of care for medically intractable temporal lobe epilepsy 46 and significantly improves seizure control and quality of life.14,42 The 2 most common surgical approaches are anterior temporal lobectomy and selective amygdalohippocampectomy, both of which are performed through a standard temporal craniotomy. Despite the marked success of these approaches, craniotomy for the treatment of temporal lobe epilepsy is not without risk. Complications range from cosmetic disfigurement to permanent neurological and cognitive disability (Table 1). Though uncommon, these complications significantly diminish quality of life for affected patients. Alternative strategies that minimize these risks while still achieving an adequate hippocampectomy, the principle goal of surgery, could further improve patient outcomes.Minimally invasive approaches have the potential to access the hippocampus with minimal disruption of the lateral temporal cortex and white matter pathways. For instance, stereotactic radiofrequency ablation permits hippocampal lesioning with 16-38 ablations through a single occipital bur hole. 29,35 Likewise, endoscopic approaches may provide access to the hippocampus and permit resection under direct visualization. The present cadaveric study examines the feasibility of a transorbital approach to the mesial temporal lobe using endoscopic visualization and image guidance. Unlike the occipital approach, the transorbital route affords the surgeon a short working distance and early access to the anterior portion of the hippocampus. We present the quantitative metrics of transorbital endoscopic amygdalohippocampectomy (TEA) predicted by predissection neuroimaging in relation to the measurements taken during the dissections. These measurements are compared with scans from 10 patients with epilepsy for clinical validation of the angles of exposure. Object. Resection of the hippocampus is the standard of care for medically intractable epilepsy in patients with mesial temporal sclerosis. Although temporal craniotomy in this setting is highly successful, the procedure carries certain immutable risks and may be associated with cognitive deficits related to cortical and white matter disruption. Alternative surgical approaches may reduce some of these risks by preserving the lateral temporal lobe. This study examined the feasibility of transorbital endoscopic amygdalohippocampectomy (TEA) as an alternative to open craniotomy in cadaveric specimens.Methods. TEA dissections were performed in 4 hemispheres from 2 injected cadaveric specimens fixed in alcohol. Quantitative predictions of the limits of exposure based on predissection imaging were compared with intradissection measurements. The extent of resection and angles of exposure during the dissection and on postdissection imaging were recorded. These measurements were validated with MRI studies from 10 epilepsy patients undergoing standard surgical evaluations.Results. The transorbital approach permitted direct access to t...