Endoscopic Endonasal Approach to the Lateral Wall of the Cavernous Sinus: A Cadaveric Feasibility Study

Objective: A transcranial extradural approach to the middle cranial fossa (MCF) requires separation of the dural layers of the lateral wall of the cavernous sinus. The authors tested the feasibility of an endonasal approach for this separation. Methods: A cadaveric feasibility study was conducted on the sides of 14 dry skulls and 10 fresh cadaveric heads. An endonasal, transsphenoidal, transpterygoid approach was taken to the MCF. The maxillary struts and medial greater wing of the sphenoid below the superior orbital fissure were drilled with transposition of the maxillary nerve. The lateral cavernous dural layers were split at the maxillary nerve with separation of the temporal lobe dura and exposure of the MCF bony base. The integrity of the cranial nerves and inner and outer dural layers of the lateral cavernous wall was checked. Different measurements of bony landmarks were obtained. Results: The integrity of the dural layers of the lateral cavernous wall and the cranial nerves were preserved in 10 heads. The mean area of the bony corridor was 4.68 +/- 0.97 cm(2), the V2-to-V3 distance was 15.21 +/- 3.36 mm medially and 18.21 +/- 3.45 mm laterally, and the vidian canal length was 13.01 +/- 3.06 mm. Conclusions: Endonasal endoscopic separation of the lateral cavernous dural layers is feasible without crossing the motor cranial nerves, allowing better exposure of the MCF.