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 faps.

45.2 Indications

•Extradural lesions originating from the clivus or petroclival fssure 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 fxed with Mayfeld 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 foor of the sella.

•Middle third of clivus (Sphenoidal): From the foor of the sella to the foor of the sphenoid sinus.

•Inferior third of clivus (Nasopharyngeal): From the foor 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%).

○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 fap

○The nasal septal fap 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 beneft identifcation of landmarks: sella, paraclival internal carotid artery (ICA), foor of the sphenoid sinus.

○The maxillary crest is fattened 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 foor 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

-Superfcial 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.

•Atlanto-occipital membrane

○It has to be resected to expose the foramen magnum and atlas (C1) anterior arch.

•Dura is incised on the midline, then it is opened like a book and resected from the inside out if needed.

45.7 Bony Drilling Landmarks (Fig. 45.5)

•Lateral limit

○Paraclival ICA, foramen lacerum, petroclival fssure, jugular tubercle, hypoglossal canal, occipital condyle.

•Inferior limit

○Upper part of C1 anterior arch.

•Condylectomy

○Lateral limit: An imaginary line extending inferiorly from the junction of petroclival fssure and foramen lacerum.

○Deep limit: Anterior cortical bone of intracranial aspect of hypoglossal canal.

45.8 Dural Opening (Fig. 45.5)

•The basilar plexus is located between two layers of dura (hemostatic agents can easily control venous bleeding).

45.8.1 Critical Structures

•Abducens nerve.

•Hypoglossal nerve.

•Vertebrobasilar system.

45.9 Intradural Exposure (Fig. 45.5)

•Parenchymal structures: Ventral medulla and pontomedullary junction.

•Arachnoidal layer: Premedullary cistern.

•Arteries: Vertebral arteries, vertebrobasilar junction, posterior inferior cerebellar artery (PICA), anterior spinal arteries.

•Cranial nerves: Hypoglossal nerve and lower cranial nerves (dorsal to vertebral artery), anterior root of the frst cervical nerve (C1) (ventral to vertebral artery).

45.10 Pearls

•Extended nasoseptal fap is useful for large clival defects.

•Preparation of the thigh for fascia lata harvesting and the abdomen for fat graft.

•Maxillary antrostomy is needed to store the fap during the operation away from the surgical feld.

•Posterior septectomy can be minimized since most of the binarial work is done posteriorly.

•Drilling the maxillary crest is important to obtain more caudal binarial access.

•Sphenoidotomy is typically not necessary for tumors limited to the inferior clivus.

•It is key to remove the fascia and muscle layers widely to reach the petroclival fssure laterally and to identify the lower aspect of the foramen lacerum.

•Drilling should include jugular tubercle and medial aspect of the occipital condyle, following the above described landmarks.

•Ultrasonic bone curette is useful for drilling these areas.

•A well-done medial condylectomy provides access to the lateral wall of the foramen magnum, involves just a quarter of the condylar volume, and carries no risk of craniocervical instability.

•The vertebral artery enters the posterior fossa just behind the condyle and can be accessible after medial condylectomy.

•Wide dural opening is recommended for meningiomas to facilitate recognition of neurovascular structures and extracapsular dissection.

•Microsurgical-like techniques are used for extracapsular dissection.

•Angled scopes are benefcial to look around corners and identify residual tumor, specially within the hypoglossal canal.

•Extensive dural resection is performed for meningiomas.

•Multilayer reconstruction: inlay collagen layer, onlay fascial lata graft, fat graft reinforcement, and vascularized extended nasoseptal fap plus nasal packing and postoperative lumbar drain (3 days).

References

1.Fernandez-Miranda JC, Morera VA, Snyderman CH, Gardner P.

Endoscopic endonasal transclival approach to the jugular tubercle. Neurosurgery 2012;71(1, Suppl Operative):146–158, discussion 158–159.

2.Morera VA, Fernandez-Miranda JC, Prevedello DM, et al.

“Far-medial” expanded endonasal approach to the inferior third of the clivus: the transcondylar and transjugular tubercle approaches. Neurosurgery 2010;66(6, Suppl Opera- tive)211–219, discussion 219–220.

3.Wang WH, Abhinav K, Wang E, et al. Endoscopic endonasal transclival transcondylar approach for foramen magnum meningiomas: anatomical considerations and technical note. Neurosurgery 2015.

4.Vaz-Guimaraes Filho F, Fernandez-Miranda JC, Wang EW. Endoscopic endonasal “far-medial” transclival approach: surgical anatomy and technique. Oper Tech Otolaryngol—

Head Neck Surg 2013; 24(4):222–228.