A, A bicoronal scalp flap has been reflected forward. The pericranium is commonly reflected as a separate layer for later use in closing the floor of the anterior cranial fossa. B, Bone flap and osteotomy. The transcranial-transnasal approach uses only a bifrontal craniotomy bordering the floor of the anterior cranial fossae with-out the osteotomy. A large bifrontal craniotomy and a fronto-orbitozygomatic osteotomy have been completed. The osteotomized segment may extend through the nasal bone and lateral orbital rim, but for most clival lesions a more limited bone flap and osteotomy (dot-ted lines) will usually suffice and can be tailored as needed to deal with involvement of the nasal cavity, paranasal sinuses, or orbit. C, The periorbita has been separated from the walls of the orbit in preparation for the osteotomies. Division of the medial canthal ligament is not necessary for most lesions, but may be required for lesions extending into the lower nasal cavity or orbit. The ligaments should be re-approximated at the end of the procedure. D, The right medial canthal ligament has been divided and the orbital contents retracted laterally to expose the nasolacrimal duct and the anterior ethmoidal branch of the ophthalmic artery at the anterior ethmoidal foramen. E, The osteotomies have been completed and the frontal dura elevated. The dura remains attached at the cribriform plate. The upper part of both orbits are exposed. F, An osteotomy around the cribriform plate leaves it attached to the dura and olfactory bulbs, a maneuver that has been attempted to preserve olfaction, but is infrequently successful. The anterior face of the sphenoid sinus and both sphenoid ostia are exposed between the orbits. (Images courtesy of AL Rhoton, Jr.)