LAUSR

BACKGROUND Petroclival tumors and ventro-lateral lesions of the pons present unique surgical challenges. Our cadaveric study provides qualitative and quantitative anatomic comparison for an anterior petrous apicectomy through the transcranial middle fossa (TMF) and expanded endoscopic transphenoidal-transclival (EETT) approaches. METHODS In 10 silicone-injected heads, the petrous apex and clivus were drilled extradurally using middle fossa and endonasal approaches. With in situ and frameless stereotactic navigation, we defined consistent points to compare working areas, bone removal volumes, approach angles, and surgical freedom. RESULTS Mean exposed TMF area (21.03 ± 3.46 cm2) achieved a 44.71 ± 4.13° working angle to the brainstem between cranial nerves (CNs) V and VI. Kawase's rhomboid area measured 1.76 ± 0.34 cm2 and bone removal averaged 1.20 ± 0.12 cm3 at the petrous apex. Surgical freedom on the lateral brainstem was higher halfway between CNs V and VI at the center of the rhomboid compared to midline at the basilar sulcus (P < 0.01). After clivectomy and petrous apicectomy, mean exposed EETT area was 5.29 ± 0.66 cm2. Approach from either nostril showed no statistically significant differences in surgical freedom at the foramen lacerum and midpoint basilar sulcus. At the petrous apex, bone volume removed and area exposed were significantly larger for TMF approach (P< 0.001). CONCLUSIONS Expanded transclival anterior petrosectomy through the TMF approach provides an adequate corridor to lesions in the upper ventro-lateral pons. The EETT approach better fits midline lesions not extending laterally beyond CN VI and C3 carotid when evaluating normal anatomical parameters.