Refinement of the extradural anterior clinoidectomy: surgical anatomy of the orbitotemporal periosteal fold.

OBJECTIVE: Extradural removal of the anterior clinoid process is technically challenging because of the limited exposure. In our study of the extradural anterior clinoidectomy, we describe anatomic details and landmarks to facilitate sectioning of the orbitotemporal periosteal fold and elevation of the temporal fossa dura from the superior orbital fissure. We assess the morbidity associated with these procedures as well as compare the indications, advantages, and disadvantages of intra-versus extradural clinoidectomy.
METHODS: Of five formalin-fixed cadaveric heads, four were used for cadaveric dissections and one was used for histological examination.
RESULTS: Sectioning of the orbitotemporal periosteal fold revealed a cleavage plane between the temporal fossa dura and a thin layer of connective tissue that covers the superior orbital fissure. The lacrimal nerve coursed immediately medial to this surgically created cleavage plane. The superior orbital vein crossed laterally under the cranial nerves, which pass through the superior orbital fissure. This vein is particularly vulnerable as it is composed only of endothelium and a basal membrane.
CONCLUSION: Both intra- and extradural techniques for anterior clinoidectomy are important parts of the neurosurgical armamentarium. Sharp incision of the orbitotemporal periosteal fold to increase the extradural exposure of the anterior clinoid process should be made at the level of the sphenoid ridge and restricted to the periosteal bridge. Subsequent blunt elevation of the temporal fossa dura should be performed; however, peeling of the temporal fossa dura should be limited to avoid cranial nerve morbidity.