22 Transcondylar/Transjugular Tuberculum (“Far-Medial”) Approach

The transcondylar/transjugular tuberculum approach is the extreme lateral extension of the lower transclival approach. ¹ It was developed to resect clival and petroclival lesions with lateral extension and has been currently employed to treat chordomas, chondrosarcomas, meningiomas, and other lesions located medial to the plane passing along lower cranial nerves and acoustic-facial bundle. ^{1 , 2} This approach has been called “far-medial” in relation to the possibility to reach the area of the jugular foramen through a medial transnasal perspective, as an alternative to classical neurosurgical routes such as the far-lateral approach. Skull base teams dealing with lesions of this area should master and eventually combine the far-medial and classical transcranial approaches. ^{3 – 5}

The far-medial approach consists in the combination of two pathways contiguous to the hypoglossal canal, the transcondylar and the transjugular tuberculum, which are created by removing the bone of the occipital condyle and the jugular tuberculum that lie immediately below and above the hypoglossal canal, respectively. The former route leads to the vertebral artery, posterior inferior cerebellar artery, and spinal root of the accessory nerve, whereas the latter one paves the way toward the anterior inferior cerebellar artery, lower cranial nerves (glossopharyngeal, vagus, and cranial root of the accessory nerve), and acoustic-facial bundle (facial and vestibulocochlear nerve). Of note, the corridor through this area of the skull base is bounded and crossed by several venous vessels and plexuses (i.e., inferior petrosal sinus, petroclival vein, plexus of the hypoglossal canal) converging toward the internal jugular vein. ² Therefore, intense venous bleeding should be expected and properly managed.

In addition to the anatomical landmarks discussed for transclival and transodontoid approaches, the far-medial approach requires early identification of the position and orientation of the hypoglossal canal. This can be achieved by sequentially using the tail of the inferior turbinate, anterior rectus capitis muscle, and a bony depression in its cranial insertion (i.e., supracondylar groove) as landmarks for the external opening of the hypoglossal canal. ¹ The internal end can be identified by performing a subperiosteal removal of the lateral edge of the lower clivus until a funnel-shaped dural fold comes into view, allowing the localization of the canal before to start the bone removal.

Being based on the removal of thick bony structures, the far-medial approach is particularly useful in bony-originated tumors, such as chordomas and chondrosarcomas, which arise from the clivus or the petroclival junction and grow predominantly within the bone. It is worth mentioning that the farmedial approach is a challenging route by virtue of several factors: (1) it exploits a deep and diagonal surgical corridor, which requires dedicated instruments, high expertise, and remarkable precision in endoscopic transnasal maneuvers; (2) it crosses a number of important neurovascular structures, whose injury could lead to severe complications for the patient ^{1 , 2 , 6} ; (3) it includes partial removal of the bony framework of the craniocervical junction, thus requiring careful assessment of the need for occipitocervical fusion ² ; (4) being an extension of the lower transclival approach, the difficulty to obtain a watertight closure of the dura is further remarked.

Related posts:

1 Classification of Endoscopic Transnasal Approaches to the Skull Base and Adjacent Areas 9 Transsellar Approach 10 Transsellar Transdorsal Approach 17 Medial Transcavernous Approach 18 Lateral Transcavernous Approach 21 The Suprapetrous (Meckel’s Cave) Approach

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