EXTRADURAL TOTAL PETROUS APEX RESECTION WITH TRIGEMINAL TRANSLOCATIONFOR IMPROVED EXPOSURE OF THE POSTERIOR CAVERNOUS SINUS AND PETROCLIVAL REGION

We have analyzed a strategy for improved exposure of the posterior cav ernous sinus and petroclival region through an extradural subtemporal approach to be utilized in the removal pf neoplastic processes with in volvement of the apical petrous bone and posterior cavemous sinus. Thi s surgical approach includes the following elements for improved expos ure or me posterior cavemous sinus through the middle fossa corridor: (1) maximal extradural exposure and mobilization of the trigeminal ner ve complex, allowing its elevation and anterior displacement, (2) comp lete extradural removal of the anterior petrous pyramid from the porus acoustious to-the petrous apex under direct vision, (3) total exposur e of the abducens nerve from the posterior fossa to its point of cross over the intracavernous carotid artery, and (4) wide extradural expos ure of the cavernous carotid artery in the foramen lacerum region. Thi s strategy can be combined with other related approaches; specifically , frontotemporal or posterior transpetrosal exposures for extensive le sions. Microsurgical dissection and morphometric analysis were perform ed in 20 fixed cadaver specimens for the purposes of validating the me thod for clinical application and determining the key elements to maxi mization of exposure. The trigeminal complex could be anteromedially r etracted 4.8 mm +/- 1.3 (range = 3 to 6 mm) without skeletonization of V-2 and V-3. Liberating these two divisions from their bony canals to their first peripheral branch (10.4 mm +/- 2.5 and 5.4 mm +/- 1.1, re spectively) resulted in increased mobilization an average of 9.1 mm +/ - 1.7 (7 to 14 mm). Further mobilization is achieved by dividing the a ttachment between the trigeminal connective tissue sheath and the fibr ous carotid ring at the foramen lacerum. An average of 13.0 mm +/- 3.1 (7 to 20 mm) of the posterior intracavemous carotid artery was expose d. Detailed microanatomic observations and a comprehensive morphometri c analysis of the relevant anatomic relationships were made.