Chapter 20 Transclival Approach

10.1055/b-0037-143526

Chapter 20 Transclival Approach

Joaquim Enseñat, Elena D′avella, Isam Alobid, Matteo de Notaris, Alberto Prats-Galino

Introduction

The endoscopic endonasal approach to the clivus represents an increasingly important surgical corridor for skull base surgery. It provides surgical access to the ventral midline skull base of the middle and posterior fossa. Although the approach is mostly used for removal of chordomas, the same surgical principles can be applied to a variety of pathologies. Cadaveric studies have documented the extensive exposure through the endoscopic endonasal transclival approach, and description of surgical technique have supported the successful treatment of complex skull base pathologies. The anatomic limits of clivectomy are the floor of the sella superiorly, the foramen magnum inferiorly, and the internal carotid artery laterally. Removal of the clival bone can be limited to a transdorsum approach for exposure of the interpeduncular fossa or can be extended to the lower clivus for tumors of the foramen magnum region. Important anatomic landmarks during the approach are the sella, the opticocarotid recess, the dorsum sellae, the vidian nerve, and the paraclival carotid artery. Skull base reconstruction is performed with a multilayered technique together with a pedicled nasoseptal flap. Major complications of the transclival approach are cerebrospinal fluid (CSF) leak and damage to the internal carotid artery, vertebrobasilar complex, and abducens nerve.

20.1 Indications

The endoscopic endonasal transclival approach is used for lesions involving the clivus or the retroclival region:1–10

Clival chordomas.
Chondrosarcomas.
Cholesterol granulomas.
Craniopharyngiomas in the retrosellar area.
Clival meningiomas.
Vascular lesions (brainstem cavernomas, posterior circulation aneurysms).
Other clival lesions (mucoceles, ossifying fibromas, osteogenic sarcomas, adenocarcinomas, plasmacytomas, metastases, fibrous dysplasia, neuroenteric cysts).

20.2 Surgical Steps

20.2.1 Patient Positioning

The patient is placed in a supine position with the head fixed in a three-pin Mayfield holder and elevated 20 to 30 degrees, slightly rotated toward the side of the surgeon and slightly more flexed than for a common endoscopic procedure for a sellar lesion, to improve the field of view toward the clivus. Anatomic landmarks of the following steps can be consulted in Table 20.1 .

**Table 20.1 Anatomic landmarks to be exposed for each surgical step during the endoscopic endonasal transclival approach**
Nasal phase	Sphenoidal phase	Transclival approach	Intradural exposure
Middle turbinate	Anterior wall of sphenoid sinus	Dorsum sellae	Floor of III ventricle
Maxillary ostium	Sphenoid floor	Vomer–sphenoid junction	Oculomotor nerve
Sphenopalatine artery	Clival recess	Pterygoid plate	Superior cerebellar artery
Sphenoid rostrum	Medial opticocarotid	Pterygoid canal	Posterior cerebral artery
	recess
	Clivocarotid	Vidian nerve	Posterior
	protuberance		communicating artery
		Petrous internal carotid artery	Cerebral peduncle
		Rhinopharyngeal mucosa	Trochlear nerve
		Longus capitis muscle	Basilar artery
		Longus colli muscle	Ventral surface of brainstem
		Foramen magnum	Abducens nerve
			Vertebral artery
			Trigeminal nerve
			Anteroinferior cerebellar artery
			Lower cranial nerves
			Jugular foramen
			Posterior inferior cerebellar artery
			Hypoglossal nerve

20.2.2 Nasal and Sphenoidal Steps

A standard nasal access set used in endoscopic paranasal sinus surgery is used for the initial and extradural part of the procedure. Resection of one, usually the right, or both middle turbinates is performed. A large middle meatal antrostomy can be created to store the nasal septal flap and keep it safe during the procedure. The nasoseptal flap, pedicled at the sphenopalatine bundle, is created on one side following the Hadad technique11 (see Chapter 34). The posterior half of the nasal septum is removed to widely expose the rostrum (see Chapter 5). The sphenoid rostrum and anterior wall of sphenoid sinus are removed. The sphenoid floor is drilled flush with the clival recess and the clival bone is exposed. By drilling the lateral recess of the sphenoid, the medial and lateral opticocarotid recesses and the clivocarotid protuberances are visualized and are important surgical landmarks for the rest of the procedure ( Fig. 20.1 ).

**Fig. 20.1** By drilling the lateral recess of the sphenoid, the medial opticocarotid recess and clivocarotid protuberances are visualized. dm, dura mater; ET, eustachian tube; ICAc, clival internal carotid artery; ICAs: sellar internal carotid artery; MT: middle turbinate; PG: pituitary gland.

20.2.3 Transclival Approach

At this point, the tumor will often be visible, especially if the clivus is eroded anteriorly. When the lesion is not visible, its location is confirmed by intraoperative navigation, and drilling of the upper clivus can be started. Removal of the clival bone is initiated with a diamond burr drill and continued carefully with a Kerrison punch.

In cases of tumor extension to the upper clivus only (sphenoidal segment of the clivus), the expanded endonasal approach consists of removal of upper part of the clivus and the dorsum sellae.

For lesions extending to the foramen magnum region, bone removal should be extended to the lower part of the clivus. The vomer–sphenoid junction, the medial pterygoid plate, and vidian canal are identified in a medial to lateral direction ( Fig. 20.2 ). The vomer and inferior wall of sphenoid sinus are removed.

**Fig. 20.2** For lesions extending to the foramen magnum region, bony removal should be extended to the lower part of the clivus. The vomer–sphenoid junction, the pterygoid plate, and vidian canal are identified in a medial to lateral direction. iwsphs, inferior wall of sphenoid sinus; SS, sphenoidal sinus; V, vomer; VC, vidian canal; VSJ, vomer–sphenoid junction.

The vidian nerve in the pterygoid canal can be identified and the canal is drilled along its inferior circumference until the petrous internal carotid artery at the lacerum segment is encountered ( Fig. 20.3 ). Then, the rhinopharyngeal mucosa is dissected and the longus capitis and longus colli muscles are lateralized ( Fig. 20.4 ).

**Fig. 20.3** The vidian nerve in the pterygoid canal can be identified (blue dots) and the canal is drilled until the petrous internal carotid artery at the lacerum segment is encountered. C, clivus; Co, choana; FL, foramen lacerum; ICAc, clival internal carotid artery; ICAs, sellar internal carotid artery; PG, pituitary gland; VN, vidian nerve; VSJ, vomer–sphenoid junction.

**Fig. 20.4** The rhinopharyngeal mucosa is dissected and the longus capitis and longus colli muscles are lateralized. C, clivus; ET, eustachian tube; iwsphs, inferior wall of sphenoid sinus; RPhx, rhinopharyngeal mucosa.

The limits of clivectomy are the floor of the sella superiorly, the foramen magnum inferiorly, and the internal carotid artery laterally ( Fig. 20.5 ).