"Far-medial" expanded endonasal approach to the inferior third of the clivus: the transcondylar and transjugular tubercle approaches.
OBJECTIVE
The endoscopic endonasal transclival approach is a valid alternative for treatment of lesions in the clivus. The major limitation of this approach is a significant lateral extension of the tumor. We aim to identify a safe corridor through the occipital condyle to provide more lateral exposure of the foramen magnum.


METHODS
Sixteen parameters were measured in 25 adult skulls to analyze the exact extension of a safe corridor through the condyle. Endonasal endoscopic anatomic dissections were carried out in nine colored latex-injected heads.


RESULTS
Drilling at the lateral inferior clival area exposed two compartments divided by the hypoglossal canal: the jugular tubercle (superior) and the condylar (inferior). Completion of a unilateral ventromedial condyle resection opens a 3.5 mm (transverse length) * 10 mm (vertical length) lateral surgical corridor, facilitating direct access to the vertebral artery at its dural entry point into the posterior fossa. The supracondylar groove is a reliable landmark for locating the hypoglossal canal in relation to the condyle. The hypoglossal canal is used as the posterior limit of the condyle removal to preserve more than half of the condylar mass. The transjugular tubercle approach is accomplished by drilling above the hypoglossal canal, and increases the vertical length of the lateral surgical corridor by 8 mm, allowing for visualization of the distal cisternal segment of the lower cranial nerves.


CONCLUSIONS
The transcondylar and transjugular tubercle "far medial" expansions of the endoscopic endonasal approach to the inferior third of the clivus provide a unique surgical corridor to the ventrolateral surface of the ponto- and cervicomedullary junctions.
Morera
Victor A
VA
Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Fernandez-Miranda
Juan C
JC
Prevedello
Daniel M
DM
Madhok
Ricky
R
Barges-Coll
Juan
J
Gardner
Paul
P
Carrau
Ricardo
R
Snyderman
Carl H
CH
Rhoton
Albert L
AL
Kassam
Amin B
AB
D001933:Brain Stem / Q000033:anatomy & histology / Q000601:surgery; D002102:Cadaver; D003388:Cranial Fossa, Posterior / Q000033:anatomy & histology / Q000601:surgery*; D003399:Craniotomy / Q000379:methods* / Q000592:standards; D004210:Dissection / Q000379:methods; D004724:Endoscopy / Q000379:methods*; D006801:Humans; D007002:Hypoglossal Nerve / Q000033:anatomy & histology / Q000601:surgery; D007431:Intraoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D007601:Jugular Veins / Q000033:anatomy & histology / Q000601:surgery; D009296:Nasal Cavity / Q000033:anatomy & histology / Q000601:surgery*; D019635:Neurosurgical Procedures / Q000379:methods / Q000592:standards; D009777:Occipital Bone / Q000033:anatomy & histology / Q000601:surgery*; D019292:Skull Base Neoplasms / Q000473:pathology / Q000601:surgery; D014711:Vertebral Artery / Q000033:anatomy & histology / Q000601:surgery