First stage in predicative measure for transnasal transsphenoidal approach to petrous apex cholesterol granuloma

Pneumatization Patterns of the Petrous Apex and Lateral Sphenoid Recess

Introduction  The petrous apex poses a challenge for surgical intervention due to poor access. As intraoperative image guidance and surgical instrumentation improve, newer endoscopic approaches are increasingly favored. This study aims to provide normative data on the anatomy of the lateral sphenoid sinus recess and petrous apex. These normative data could assist in determining the efficacy of a transnasal transsphenoidal approach to lesions of the anteroinferior petrous apex. Methods  This is a retrospective study investigating normative data on all maxillofacial computed tomography (CT) scans performed at a level I trauma center over a 6-month period. All appropriate images had the pneumatization pattern of the petrous apex and lateral recess of the sphenoid sinus reviewed by a single otologist and graded bilaterally. These were then analyzed in SPSS; Pearson correlation analyses and χ ² test were used. Results  A total of 481 patients were identified, yielding a total of 962 temporal bones and sphenoid sinuses for analysis. Eighty-eight percent of sides analyzed had a nonpneumatized lateral recess. The petrous apex was nonpneumatized in 54% of sides analyzed. There was a correlation noted between the degree of pneumatization of the petrous apex and pneumatization of the lateral recess of the sphenoid. Conclusion  This study is the first to provide normative data comparing pneumatization of the petrous apex and sphenoid sinus. These data may support future work evaluating the utility of an endonasal approach to the petrous apex.

Development of a snake-like dexterous manipulator for skull base surgery

Petrous apex lesions constitute considerable surgical challenges due to their location in the skull base and close relationship with critical structures such as inner ear, carotid arteries, facial nerves and jugular bulb. These lesions often cannot be treated completely with rigid tools due to the limited accessibility. We are aiming to develop a snake-like manipulator to assist surgeons with the infralabyrinthine treatment of petrous apex lesions with increased dexterity. This snake-like dexterous manipulator (SDM) with 3.3 mm outer diameter and 40 mm working length was designed including a tool channel with a diameter of 1.8 mm and an endoscope channel with a diameter of 0.7 mm. The SDM can be actuated in one plane and two directions enabling the C- and S-shaped bends and rotated around its longitudinal axis. The constant curvature modeling was implemented to predict the deflection in one direction. Experiments were carried out with optical microscope to find out different bending modes. Experimental bending modes were in a good agreement with the theoretical ones in terms of the bending behavior. However tip position prediction showed discrepancies up to 1 mm in X and 2 mm in Z axes.