38 Endoscopic Endonasal Transphenoidal Approach • Position: The patient is positioned supine with slight rotation towards operating team. • Head: The head is slightly extended and above the heart with Mayfield pins for intra-arachnoidal lesions. • The tip of patient’s nose should be the highest point in the surgical field. • Abdomen is usually prepped for potential fat graft. • Neurophysiological monitoring (electroencephalogram and somatosensory evoked potentials) is often utilized. • Image guidance navigation with stereotactic CT and MRI is often used. • Nasal cavity decongestion with topical vasoconstricting agents (1:1000 Epinephrine, oxymetazoline, or 4% cocaine). • Not applicable. • Close collaboration with an ENT team is favored. ◦ Option 1: Single nare technique with or without turbinate resection. ◦ Option 2 (favored): Bilateral nare technique with or without turbinate resection, which provides a wider viewing angle and area of exposure, more room for skull base instruments, and better haptic feedback. • Depending on the preference of the ENT surgeon, local anesthetic may be injected before or after the patient is draped. • Additionally, cotton pledgets saturated in a topical vasoconstricting agent placed between the middle turbinate and the nasal septum may aid in decongestion. • A 0° rigid endoscope is introduced into the nasal cavities; the inferior turbinates and the nasal septum are the first identifiable landmarks. • The middle turbinates are then moved laterally to allow for increased exposure. If necessary, the middle turbinate can be resected for additional space. • The sphenoid ostium is identified adjacent to the septum near the inferior edge of the superior turbinate. This is approximately 2 cm above the arch of the choana. • Inferior, middle, and superior turbinates. • Choana, sphenoid ostium. • Care is taken during approach to preserve sphenopalatine arteries in anticipation of possible skull base dural reconstruction with a pedicled vascularized nasoseptal flap. Fig. 38.1 Endoscopic endonasal photo depicting sino-nasal landmarks in the right nasal cavity. Fig. 38.2 Endoscopic endonasal photo depicting sino-nasal landmarks deeper in the right nasal cavity. Identification of the superior turbinate. Fig. 38.4 View of right nasal cavity after removal of middle turbinate. Note the location of the vascular pedicle for the nasoseptal flap. Damage to this mucosa should be avoided to preserve the viability of the flap. Fig. 38.5 The right sphenoid ostium has been partially widened. A more limited opening has been employed initially in this specimen due to the high position of the natural ostium (thus its proximity to the skull base superiorly) and the need to protect the nasoseptal flap pedicle inferiorly. The posterior septectomy has also been outlined. Fig. 38.6 The posterior septectomy has been completed. Instruments passed through the left nasal cavity can now be seen from the right. Also note the sphenoidotomy has been further widened as better visualization has been obtained. • This neurovascular pedicle runs horizontally across the sphenoid face and extends from the arch of the choana to the level of the natural sphenoid ostium. • The sphenoid ostium is widened first laterally then superiorly on both sides. The superior turbinate can be trimmed as needed to improve visualization and access. • A small posterior septectomy is then performed to allow binarial access.
38.1 Patient Positioning
38.2 Preoperative Settings
38.3 Skin Incision
38.4 Soft Tissue Dissection, Nasal Phase (Figs. 38.1–38.4)
38.4.1 Critical Structures
38.5 Osteotomy, Sphenoid Phase (Fig. 38.4–38.9)
Abbreviations: IT = inferior turbinate; MT = middle turbinate; NS = nasal septum.
Abbreviations: IT = inferior turbinate; MT = middle turbinate; NS = nasal septum; ST = superior turbinate.
Abbreviations: CA = choanal arch; MTr = middle turbinate resected; NS = nasal septum; NSFP = nasoseptal flap peduncle; SO = sphenoid ostium; ST = superior turbinate.
Abbreviations: NS = nasal septum; PS = posterior septectomy; SOw = widened sphenoid ostium; STt = trimmed superior turbinate.
Abbreviations: PS = posterior septectomy; RSO =right sphenoid ostium; S = suction tube in the contralateral nasal fossa.
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