Anterolateral Routes to the Skull Base—The Frontotemporal Approaches and Exposure of the Sellar and Parasellar Regions

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. Of five formalin-fixed cadaveric heads, four were used for cadaveric dissections and one was used for histological examination. 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. 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.

Objective To describe the microanatomy of the meningo-orbital band (MOB) and its associated membranes, and propose a stepwise method for their detachment while minimizing potential complications. Design Cadaveric and prospective clinical. Setting Microneurosurgery Skull Base Laboratory, Weill Cornell Medical College (New York, NY) and Shiroyama Hospital (Osaka, Japan). Participants Five preserved cadaveric heads (10 sides) and five patients requiring surgical detachment of the MOB in 2012. Results MOB detachment and subsequent extradural anterior clinoidectomies were successfully performed on five clinical cases. Detachment of the MOB was accomplished using a four-step dissection based on the structure's detailed microanatomy and included (1) partial removal of the lateral wall of the superior orbital fissure, (2) incising of the lateral periosteal dura of the superior orbital fissure, (3) peeling off the dura propria of the temporal lobe from the inner cavernous membrane, and (4) fully detaching the exposed MOB from the periorbita. Conclusion Understanding the complex microanatomy of these structures enabled a safe and effective stepwise detachment of the MOB. We recommend that surgeons possess sufficient anatomical knowledge before surgically manipulating this structure.

Objective We propose a stepwise decompression of the optic nerve (ON) through a supraorbital minicraniotomy and describe the surgical anatomy of the ON as seen through this approach. We also discuss the clinical applications of this approach. Methods Supraorbital approaches were performed on 10 preserved cadaveric heads (20 sides). First, 3.5-cm skin incisions were made along the supraciliary arch from the medial third of the orbit and extended laterally. A 2 × 3-cm bone flap was fashioned and extradural dissections were completed. A 180-degree unroofing of the ON was achieved, and the length and width of the proximal and distal portions of the optic canal (OC) were measured. Results The supraorbital minicraniotomy allowed for identification of the anterior clinoid process and other surgical landmarks and adequate drilling of the roof of the OC with a comfortable working angle. A 25-degree contralateral head rotation facilitated visualization of the ON. Conclusion The supraorbital approach is a minimally invasive and cosmetically favorable alternative to more extended approaches with longer operative times used for the management of ON decompression in posttraumatic or compressive optic neuropathy from skull base pathologies extending into the OC. The relative ease of this approach provides a relatively short learning curve for developing neurosurgeons.