Epidural subtemporal intertentorial approach to the mesiotemporal lobe and lateral midbrain.

Objective: The mesiotemporal lobe and lateral midbrain reside in a deep and complex anatomical region. The classic intradural subtemporal approach provides good access to this region but has significant risk of iatrogenic injury to the temporal lobe and vein of Labbé. We developed a new approach to this region to decrease the risk of iatrogenic injury. Methods: Anatomical dissection of three adult injected non-formalin fixed cadaveric heads was performed to evaluate the feasibility of performing an epidural subtemporal intertentorial approach (ESIA) to the mesiotemporal lobe and lateral midbrain. The surgical technique was analyzed in detail with accompanying cadaveric images and video used to describe the approach. Results: Tentorial peeling without petrosal drilling during the approach separated the tentorium into two layers, the posterior fossa tentorial leaf (PFTL) and the temporal tentorial leaf (TTL). Dural incision in the medial TTL allowed access to the mesiotemporal lobe, lateral midbrain, crural cistern, and ambient cistern. The lateral portion of the TTL and temporal dura remained intact, protecting the basal temporal lobe and vein of Labbé. Anatomic landmarks to determine the extent of tentorial peeling and site of the durotomy for access to the basal surface of the temporal lobe and lateral midbrain were identified. Conclusion: The ESIA is a novel approach for lesions of the mesiotemporal lobe and lateral midbrain. It provides direct access and a short working distance with reduced risk of iatrogenic injury to the temporal lobe and basal temporal veins.