“A Pure Endoscopic Transpterional Approach (Eta): Cadaveric Feasibility Study and Report of One Clinical Case”

Background: A minimally invasive pure endoscopic pterional centered approach (transpterional) to the antero-lateral skull base has not been described yet.

Objective: To determine the feasibility of a pure endoscopic combined extra-intradural transpterional approach to lesions of the antero-lateral skull base.

Method and Results: 8 ETA approaches were performed in 4 Fresh cadaveric heads using rigid 4mm, 0o and 30o endoscopes. . A 3 cm incision in the temporal hairline was done through skin and temporal muscle allowing the exposure of the pterion. A 2 × 2 cm bone flap was elevated exposing the lateral aspect of the sphenoid wing. Under endoscopic vision the sphenoid wing and the lateral orbital wall were drilled until the superior orbital fissure and its meningo-orbital fold were fully exposed. The dural fold was cut and the temporal dura reflected from the anterior clinoid process (ACP) and the lateral wall of the cavernous sinus followed by an extradural removal of the ACP and optic strut with unroofing of the optic canal. This provided sufficient surgical space to allow comfortable bimanual manoeuvrability under endoscopic vision. Optionally, a 1 cm incision was made in the lateral aspect of the eyebrow and used as a separate port for the endoscope or surgical instruments. A linear opening of the dura along the sylvian fissure was made toward the optic nerve sheath and the carotid distal dural ring. The sylvian fissure was opened and the neurovascular structures of the anterolateral skull base were explored. Structures that can be reached and manipulated during this approach include the clinoidal segment of the ICA, the intradural ICA, the posterior communicating artery, the anterior communicating artery, the A1 segment,of the ACA, the full MCA tree, the optic nerve and chiasm and the third cranial nerve. The membrane of Liliquist could be opened allowing a full endoscpic view of the basilar tip and both P1 segments.

Our initial clinical experience is one case of an extra and intradural biopsy for an Aspergillus abscess of the canvernous sinus, without complications.

Conclusion: ETA allows an adequate access to the antero-lateral skull base under proper endoscopic visualization. Our preliminary experience with a biopsy of the cavernous sinus demonstrates the clinical feasibility of this approach. However more experience is needed to evaluate the utility and safety of this approach for more complex lesions of the antero-lateral skull base.