"Sagittal Crest": Definition, Stepwise Dissection, and Clinical Implications From a Transorbital Perspective.

BACKGROUND: The recent development of the superior eyelid endoscopic transorbital approach (SETOA) offered a new route for the management of cavernous sinus and middle cranial fossa tumors. As a result, a constant anatomic landmark of the surgical pathway after drilling the medial edge of the greater sphenoid wing (GSW) is represented by a triangular-shaped bone ridge appearing as a "crest." OBJECTIVE: To perform an anatomic study to define this surgical landmark, named the "sagittal crest" (SC) as seen from the transorbital endoscopic view. METHODS: Four adult cadaveric specimens (8 sides) were dissected performing an endoscopic transorbital approach to the middle fossa and the SC was removed to perform interdural opening of the cavernous sinus. Computed tomography scans were made before and after removal of the SC to perform quantitative analysis and building a 3-dimensional model of the bone resection of the GSW via the SETOA. RESULTS: The SC is a bone ridge triangle shaping dorsally the superior orbital fissure resulting as the residual fragment after drilling the lateral aspect of the greater sphenoid wing. Predissection and postdissection computed tomography scans allowed to objectively assess SC features and dimensions (mean 1.08 ± 0.2 cm). CONCLUSION: The SC is a constant anatomic landmark constituted of the residual medial portion of the GSW. Complete resection of this key landmark provides adequate working space and appears to be mandatory during SETOA to guide the subsequent interdural dissection of the lateral wall of cavernous sinus.

Quantitative analysis of progressive removal of nasal structures during endoscopic suprasellar approach.

OBJECTIVES/HYPOTHESIS: Following recent studies measuring working area and surgical freedom of transcranial approaches, we aimed to quantify the gain achieved with progressive removal of nasal structures during the endoscopic endonasal suprasellar approach. STUDY DESIGN: Human cadaveric anatomic study. METHODS: The width of the endoscopic endonasal corridor to the suprasellar area was obtained and measured in five cadaver heads using a computerized tracking system with six steps: 1) standard approach with monolateral lateralization of middle turbinate; 2) standard bilateral lateralization of the middle turbinates; 3) monolateral middle turbinectomy; 4) bilateral middle turbinectomy; 5) monolateral ethmoidectomy; 6) bilateral ethmoidectomy. RESULTS: The progressive removal of nasal structures offers a nonlinear increasing of the working area during the first steps of the procedure. The maximum advantage is offered by bilateral lateralization of the middle turbinates (102.7% increase in exposure), whereas a moderate increase is observed with each following step. Surgical freedom mainly increased during the first part of the approach, that is, with a monolateral right middle turbinectomy (17.9% raise of maneuverability), whereas additional steps did not increase surgical freedom enough to justify an aggressive nasal disruption. CONCLUSIONS: Monolateral turbinectomy on the side of endoscope docking represents the best solution, optimizing working area and surgical freedom (offering increases of 116.9% and 17.9%, respectively). Bilateral turbinectomy, together with a monolateral anterior and posterior ethmoidectomy, can be reserved for selected cases (increases of 148.5% and 24.7%, respectively). Bilateral ethmoidectomy does not significantly improve surgical freedom (0.81%). LEVEL OF EVIDENCE: N/A. Laryngoscope 124:2231-2237, 2014.