The extended transbasal approach: A quantitative anatomical and histological study

Since its introduction in 1972 the transbasal approach to the anterior foss a and sphenoethmoidal region has undergone a number of modifications. The e xtended transbasal approach with preservation of olfaction not only improve s exposure of the anterior fossa, but also provides access to the clivus as far inferiorly as the foremen magnum. An anatomical study has been undertaken to photographically demonstrate and quantify the varying degrees of exposure that this technique provides. The pituitary stalk was used as an intracranial target. The amount of exposure was compared using a standard subfrontal approach, a transbasal approach a nd an extended transbasal with preservation of olfaction. In addition, a hi stological study was carried out to investigate the level to which identifi able olfactory nerves extended into the nasal mucosa. The anatomical study demonstrates the area of the "external window of expos ure" can be doubled using a transbasal approach and more than quadrupled us ing the extended transbasal approach, when gaining access to the pituitary stalk. In addition, the study highlights the exposure of other anatomical a reas, such as the medial orbit, the cavernous sinus, the clivus and the ver tebrobasilar complex. The histological study establishes that the olfactory nerves extend only 10 mms below the cribriform plate.