Epidural and subdural interdural approach to the lateral wall of the cavernous sinus for preserving the laterocavernous sinus in trigeminal schwannoma

Evacuation of middle fossa trigeminal schwannomas (TS) warrants a subtemporal interdural approach through the lateral wall of the cavernous sinus (CS). The dura comprises the dura propria, which follows the trigeminal nerve and becomes the epineurium, and periosteal layer. The interdural approach involves peeling off the dura propria and exposing the epineural sheath. The venous route around the CS is often obstructed due to TS progression. The interdural approach based on venous route preservation remains to be discussed. The laterocavernous sinus (LCS) is formed in these layers, draining to either the medial or lateral route. In the lateral route, the LCS drains to the pterygoid plexus via the middle cranial fossa foramen. Exposure of the interdural space disturbs the lateral route’s venous flow. We describe an operative strategy for venous route preservation in the TS via the LCS lateral route. The venous route can be preserved by peeling off the dura propria from the posterior end of the foramen ovale short of the venous drainage route to the pterygoid plexus epidurally and then cutting from the middle cranial fossa dura posterior to the venous route subdurally to the exposed interdural space. This technique helps in avoiding postoperative venous complications.