The endoscopic endonasal approach to cranio-cervical junction: the complete panel

Abstract

We aim to establish a complete summary on the Endoscopic Endonasal Approach (EEA) to Cranio Cervical Junction (CCJ): evolution since first description, criteria to predict the feasibility and limitations, anatomical landmarks, indications and biomechanical evaluation after performing the approach. A comprehensive literature search to identify all available literature published between March 2002 and June 2015, the articles were divided into four categories according to their main purpose: 1- surgical technique, 2- anatomical landmarks and limitations, 3- literature reviews to identify main indications, 4- biomechanical studies. Thereafter, we demonstrate the approach step-by-step, using 1 fresh and 3 silicon injected embalmed cadaveric specimen heads. 61 articles and one poster were identified. The approach was first described on cadaveric study in 2002, and firstly used to perform odontoidectomy in 2005. The main indication is odontoid rheumatoid pannus and basilar invagination. The nasopalatine line (NPL), the superior nostril-hard palate Line (SN-HP), the naso-axial line (NAxL), the rhinopalatine Line (RPL) and other methods were described to predict the anatomical feasibility of the approach. The craniocervical fusion is potentially unnecessary after removal of < 75% of one occipital condyle. A recent cadaveric study stated the possibility of C1-C2 fusion via EEA. This paper reviews all available clinical and anatomical studies on the EEA to CCJ. The approach marked a significant evolution since its first description in 2002. Because of its lesser complications compared to the transoral approach, the EEA became when feasible, the approach of choice to the ventral CCJ.

Keywords: Craniocervical junction; endonasal; endoscopic; odontoidectomy; transnasal.

Figure 1

(A) 0° endoscope is introduced in left nostril of fresh head specimen the free end of the middle turbinate leads to the superior lateral aspect of the choana: (Alfieri et al) IT= inferior turbinate; MT= Middle turbinate; NF= Nasal floor; NS = Nasal septum; Co= Choana; ET= Eustachian tube; (B) removal of 1-2 cm of posterior nasal septum, the endoscope is placed on midline. RMF = Rosenmüller fossa; SPT = Soft palate; NPX = Nasopharynx; the line drawn between the upper edges of the eustachian tubes ostia (dashed line) crosses the ventral margin of foramina magnum “landmark” (Alfieri et al 2002); (C) mucosal-muscular flap was done and pushed into mouth cavity VSJ= Spheno-vomer junction; AAOM= Anterior Atlanto-occipital membrane (or ligament)

Figure 2

(A) bone exposure after removal of AAOM: PhT = Pharyngeal tubercle of clivus; FM = Foramina magnum; OdT= Odontoid tip; C1 = Anterior arch of C1; (B) embalmed specimen: removal of anterior arch of C1 apL = Apical ligament; OD= Odontoid process; (C) the odontoid process was hollowed out and removed; the clivus was partially drilled in order to well demonstrate the apical ligament (ApL); the C1 superior articular process was also partially drilled on each side to show the Alar ligaments (ALL) TL = transverse portion of cruciate ligament

Figure 3

(A) the apical ligament was removed; the alar ligaments were cut out. The C2 body and was partially drilled CxL= Cruciate ligament; Occ = occipital condyle; (B) removal of cruciate ligament TcM= Tectorial membrane; (C) intradural view (sutures were applied on dura by transoral route for demonstration purpose C1Nv = C1 ventral nerve roots; DnL= dentate ligament; ASA = Anterior spinal artery; VA= vertebral artery; PICA= Posterior inferior cerebellar artery; AICA = Anterior inferior cerebellar artery; BA = Basilar artery

Figure 4

Lines predicting the inferior limits of EEA to CCJ, NPL (green), SN-HP Line (blue), NAxL (yellow), RPL (Purple), the hard palate line (HPL) is also shown in dashed red