Transethmoidal approach to the skull base: Surgical anatomy

Introduction: Anterior approaches to the skull base have clear indications in the modern management of previously so-called inoperable cases. In our Neurosurgical Department, with an experience of over 3000 skull base cases, the transethmoidal approach has become the transfacial approach of first choice given itʹs minimal morbidity, versatility and extensive exposure. The aim of this study is to clarify the technique and skull base anatomy from the approaches sight of view as neurosurgeons must be familiar with itʹs anatomy and potential exposure. Methods: Twenty cadaver heads fixed in formalin were used, six of them were additionally colored in the vascular spaces. The transethmoidal approach was performed bilateraly in 5 specimens and unilateraly in 15. The lacrimal duct was preserved and a medial maxillectomy was always performed. Transsphenoidal and transchoanal dissections up to the skull base dissections were performed. Drilling the shell of bone covering the cavernous sinuses, petrous apex and clivus exposed the neurovascular structures immediately underlying. Results: The approach exposed the entire anterior skull base, the contralateral posteromedial orbit, optic nerve, cavernous sinus, foramen rotundum, vidian canal, petrous apex, Dorelloʹs and hypoglossal canals, and the and the carotid in its C3, C4 and C5 portions. Medially the sella, entire clivus, foramen magnum, odontoid process and inferior limit of C1 were exposed. Opening of the dura after drilling showed the prepontine and premedulary spaces and the contralateral CP-angle. Conclusions: Tumors such as chordomas, chondrosarcomas, angiofibromas, fibrous displasia, giant adenomas among others present frequently large extensions in the skull base and towards the sphenoid and preclival areas. They push or surround the neurovascular structures as they erode the bone thus demanding familiarity with the anatomy of this area. The transethmoidal approach provides an excellent cosmetic result, avoids the morbidity of other transfacial approaches, is familiar to most ENT colleagues and provides enough space and contralateral exposure to extensive skull base tumors.