Surgical anatomy of the midface and the midline skull base

Abstract

Midline transfacial approaches (those directed through the mouth, nose and paranasal sinuses) provide an optimum route for exposing extradural lesions located in the midline skull base, including the clivus, the upper cervical spine, and selected intradural lesions situated in front of the lower brainstem and the upper cervical spinal cord. The major advantage of the midline transfacial approaches, which include the transnasal, transmaxillary, transoral, and extended frontal approaches and their various modifications and extensions, is the direct anterior surgical access through the large spaces within the nasal cavity, nasopharynx, paranasal sinuses, and oral cavity, which are devoid of significant neurovascular structures. However, these midline routes are transversely narrow, and their lateral margins are restricted by the critical neurovascular structures. The nasal cavity is limited by the orbital contents, pterygopalatine ganglion, and descending palatine artery; the nasopharynx by the Eustachian tube, internal carotid artery, and internal jugular vein; the sphenoid sinus by the optic nerve, cavernous sinus, intracavernous internal carotid artery, and occasionally the maxillary nerve and nerve of the pterygoid canal; and the clivus by the inferior petrosal sinus, abducens and hypoglossal nerves, and occipital condyle. An improved understanding of the anatomical limits of the surgical approaches is indispensable in completing these procedures with acceptable morbidity.