Extended transbasal approach: anatomy, technique, and indications.

Appropriate indications for the transbasal approach have not been clearly established. The focus of this study is to determine the feasibility of maximal exposure of the clivus and surrounding regions via this strategy. Further, we sought to determine the key anatomical landmarks and morphometric data necessary for safe, radical exposure. In 20 injected cadaveric specimens, anatomical observations were made grossly and microscopically with 4-40 x magnification. The three basic variations of the transbasal craniotomy were compared with regard to surgical exposure. Maximum exposure of the ventral clivus could be obtained by total ethmoidectomy and sphenoidectomy through the extensive transbasal craniotomy. The lateral limits of exposure were found to be the optic nerves, intracavernous carotid arteries, and hypoglossal canals. Inferiorly, the foramen magnum is the limit of exposure. Morphometric measurements were determined between the key landmarks and were found helpful in subsequent dissections due to the lack of bony structures in relation to neural and vascular structures within the bone. The keys to optimizing the transbasal approach are beyond the simple initial steps of the craniotomy. Maximal exposure from the suprasellar compartment to the foramen magnum is possible via the extended transbasal approach.