45 Endoscopic Endonasal Transclival Approach with Transcondylar Extension
45.1 Introduction
The endoscopic endonasal transclival approach is a midline endoscopic approach, which provides a great surgical exposure through a minimally invasive procedure. The approach can be tailored according to the pathology, which has to be treated.
When needed, it can provide the exposure of the whole clivus. Transcondylar extension enables the surgeon to extend the resection laterally.
The approach is suitable to treat both extra and intradural lesions, with the possibility to harvest wide mucosal reconstruction flaps.
45.2 Indications
• Extradural lesions originating from the clivus or petroclival fissure with predominant ventral extension: chordomas, chondrosarcomas.
• Intradural midline lesion ventral to pons and medulla located in between the vertebral arteries: ventral foramen magnum meningiomas, jugular tubercle meningiomas, epidermoid and neuroenteric cysts.
• Intra-axial lesions located in the ventral aspect of the medulla and ponto-medullary junction: cavernomas.
45.3 Patient Positioning
• Position: The patient is positioned supine with the head fixed with Mayfield holder.
• Body: The body is placed parallel to the horizontal.
• Head position: Position of the head is neutral, slightly rotated toward the surgeon.
45.4 Clival Division (Fig. 45.1)
Clivus may be classically divided into three anatomical segments.
• Superior third of clivus (Sellar): From the posterior clinoid and dorsum sella to the level of the floor of the sella.
• Middle third of clivus (Sphenoidal): From the floor of the sella to the floor of the sphenoid sinus.
• Inferior third of clivus (Nasopharyngeal): From the floor of the sphenoid sinus to the foramen magnum.
45.5 Approach To The Nasal Cavity (Figs. 45.2, 45.3)
• Nasal decongestion with topical oxymetazoline (0.05%).
Fig. 45.2 The anatomic structures of the nasal cavity. (A) The superficial view of the right nostril. (B) The deeper view of the right nostril demonstrates the direct access to nasopharynx (corresponding to the inferior clivus). (C) The middle turbinate is resected to gain more space for endoscopy and better exposure. The posterior nasal artery is located approximately halfway between sphenoid ostium and choana. The yellow dotted line illustrates the incision of nasal septal flap starting from sphenoid ostium and choana. (D) The nasal septal flap is reflected laterally and the sphenoid rostrum can be identified.Abbreviations: CH = choana; ET = Eustachian tube; IT = inferior turbinate; MT = middle turbinate; NP = nasopharynx; NSF = nasal septal flap; PNA = posterior nasal artery; SE = septum; SO = sphenoid ostium; SR = sphenoid rostrum; ST = superior turbinate; V = vomer.
• Inferior turbinate
◦ The inferior turbinate is lateralized to gain a better access to the nasopharynx.
• Middle turbinate
◦ The middle turbinate’s inferior portion is resected to gain more space for endoscopy (optional).
• Nasal septal flap
◦ The nasal septal flap is elevated at the contralateral side of the main part of the tumor or from the most favorable side if prominent septal spurs.
◦ Pedicle vessel:
– Posterior nasal artery (may bifurcate early in 2 branches).
– Branch of sphenopalatine artery.
– Halfway between sphenoid ostium and choana.
◦ It is temporally stored in the sphenoid sinus or maxillary sinus.
• Sphenoid sinus
◦ The posterior nasal septum and the vomer are detached from the sphenoid rostrum.
◦ Posterior third septectomy provides binarial access.
◦ A wide sphenoidotomy would benefit identification of landmarks: sella, paraclival internal carotid artery (ICA), floor of the sphenoid sinus.
• Maxillary crest
◦ The maxillary crest is flattened to the level of the hard palate for more inferior access.
45.6 Soft Tissue Dissection (Fig. 45.4)
• Nasopharyngeal mucosa and basopharyngeal fascia
◦ They are elevated from the floor of the sphenoid sinus, using a combination of electrocautery and blunt dissection.
◦ Lateral extension is carried out up to the Eustachian tubes.
◦ Arteries: Palatovaginal artery (aka palatosphenoidal or pharyngeal artery).
• Muscular Layer
◦ Longus capitis major
– Superficial layer.
– Attached to the superior clival line.
◦ Rectus capitis anterior
– Deep layer.
– Attached to the inferior clival line (same level as supracondylar groove and hypoglossal canal).
◦ The two muscle layers are elevated and resected together.
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