Abstract
Purpose
Endoscopic endonasal approach (EEA) is the safest and most effective technique for odontoidectomy. Nevertheless, this kind of approach is yet not largely widespread. The aim of this study is to share with the scientific community some tips and tricks with our ten-year-old learned experience in endoscopic endonasal odontoidectomy (EEO), which remains a challenging surgical approach.
Material and methods
Our case series consists of twenty-one (10 males, 11 females; age range of 34–84 years) retrospectively analyzed patients with ventral spinal cord compression for non-reducible CVJ malformation, treated with EEA from July 2011 to March 2019.
Results
The results have recently been reported in a previous paper. The only intraoperative complication observed was intraoperative cerebrospinal fluid (CSF) leak (9.5%), without any sign of post-operative CSF leak.
Conclusions
Considering our experience, EEO represents a valid and safe technique to decompress neural cervical structures. Despite its technical complexity, mainly due to the use of endoscope and the challenging surgical area, with this study we encourage the use of EEO displaying our experience-based surgical tips and tricks.
Similar content being viewed by others
Avoid common mistakes on your manuscript.
Introduction
The anterior approach to the atlantoaxial region was first described in 1935 by German in dogs and then in 1968 by Greenberg in humans [1]. From that point on, the transoral approach has been used extensively for different type of diseases, including basilar invagination, rheumatoid pannus in rheumatoid arthritis, odontoid fractures or nonunion, tumor and odontoid hypoplasia [2]. This approach was considered the gold standard for several decades; however, it requires retraction or splitting of the soft palate and can result in significant patient morbidity including dysphagia, velopharyngeal insufficiency and the possible need for tracheostomy Several studies began questioning the invasiveness and necessity of the transoral route compared to the less invasive and equally efficient endonasal or transcervical approach [3, 4].
Endoscopic endonasal approach (EEA) to the craniovertebral junction (CVJ) was first described in a cadaveric study by Alfieri et al. in 2002 and then, Kassam et al. in 2005 published the first case report of this procedure [2, 5]. This approach has been proposed to avoid the need to split the soft or hard palate, to retract the tongue, or to perform a glossotomy or mandibulotomy with the related sequelae and possible complications and to provide a more direct, panoramic, and shorter route to the odontoid [6].
In general, endoscopic endonasal odontoidectomy (EEO) requires a complete resection of the anterior arch of C1 to have an unobstructed access to the odontoid, followed by removal of the dens, the anterior atlanto-occipital membrane, and the alar and apical ligaments [2, 7, 8]. The stability of CVJ is intricate and depends on bony, ligamentous, and capsular structures [9]. For this reason, protection of crucial structures has a role in reducing post-operative instability. Various studies suggest that partial preservation of the anterior arch of C1 may reduce the destabilization of CVJ, favor less extensive fixation constructs, decrease the risk of future hardware failure and cranial settling [8, 10].
The aim of this study is to offer some tips and tricks with our ten years experience in EEO, which remains a challenging surgical approach [11, 12].
Material and methods
Our case series consists of twenty-one (10 males, 11 females; age range of 34–84 years) retrospectively analyzed patients with ventral spinal cord compression for non-reducible CVJ malformation, treated with EEA from July 2011 to March 2019 in our Neurosurgical Department. In every case pre-operative cervical magnetic resonance imaging (MRI), to detect spinal cord compression and radiological sign of myelopathy, and cervical spine dynamic X-ray, to evaluate reducibility, were performed (dynamic X-ray was not performed in case of acute presentation).
All patients underwent pre-operative computed tomography angiography (CTA) for intraoperative neuronavigation and to plan an eventual posterior fixation. In the immediate post-operative period, every patient underwent dynamic X-ray and computed tomography (CT) scan control in order to document CVJ decompression and to exclude instability. The clinical and radiological follow-up was scheduled at 1 and 6 months after surgery and then annually.
Results
Our series results have recently been reported in our previous works [11,12,13,14], they are summarized in Fig. 1. The only intraoperative complication observed was intraoperative cerebrospinal fluid (CSF) leak (9.5%), without any sign of post-operative CSF leak.
We also report main surgical steps and our tricks to better perform this surgery (Table 1).
Discussion
The team experience for this relatively rare surgical approach indication is now more than ten years old. Taking into account the low rate of complications and the good outcome of our patients, we consider the EEA the safest and most effective technique for odontoidectomy. Nevertheless, this kind of approach is yet not largely widespread. In consideration of this, the objective of this paper is to share with the scientific community our surgical tips and tricks to perform a successful and safe EEO rather than listing our results.
The traditional transoral-transpharyngeal approach is burdened with some disadvantages including deep surgical corridor and a relatively high risk of morbidity, such as post-operative dysphonia, contamination with oral flora, tongue edema, and prolonged intubation [15,16,17,18,19,20,21,22]. Alternative approaches for this route have been proposed through transcervical or endoscopic endonasal route [2, 23]. The transcervical approach through minimally invasive tubular retractors with endoscopically controlled dissection was described by Wolinsky et al. The major limit of this approach is the access to the lower third of the clivus because the angle of attack in relation to the chest makes unable to gain access [23]. The development in endoscopic surgery seems to offer the more favorable route for patient outcomes than the traditional transoral-transpharyngeal approach.
EEO approach was first described by Kassam et al. in 2005 [2]. The endonasal route takes advantage of a natural anatomical corridor to reach a deep-seated area, such as the CVJ, and allows a wide and direct approach to the dens even in cases with severe platybasia and high-positioned odontoid [6, 14]. The advantages, in comparison with the transoral approach, include the surgical trajectory, no need for palatal splitting, no tongue retraction and no oropharyngeal incision. Furthermore, it allows an entirely top-down resection of the clivus and odontoid, thus creating higher dominance during drilling and during the detachment of required ligaments [6]. In this regard, the endoscopic endonasal technique permits a quick removal of the orotracheal tube with a prompt resumption of oral feeding, as yet reported in our case series in 2022 [12].
The surgical technique of EEO needs various tricks and a meticulous surgical planning has a paramount role. Considering that an important limitation of the EEA to the CVJ is the caudal exposure, because of the anatomical limitations superiorly and inferiorly, in the pre-operative phase, it is crucial to predict the lower limit that can be reached. Traditionally, the most used predictor was the nasopalatine line, or Kassam line, that is constructed from the rhinion and the posterior nasal spine and terminates on cervical spine [24]. Recently, different studies considered as more accurate predictor the rhinopalatine line, that is constructed from the midpoint of a line between rhinion and the anterior nasal spine and terminates on C2, intersecting the posterior nasal spine [25,26,27]. A relevant trick in the planning phase is to consider surgical instruments length. It is important not to underestimate the depth of the surgical field because instruments may not be long enough to reach the odontoid region from the nose.
The neuronavigation is a fundamental tool both in the pre-operative planning and during the surgical approach. In particular, the use of CTA sequences could be useful to analyze the carotid course, especially during the preparation of the U-shaped rhinopharyngeal flap. During the positioning phase, the head is always secured in a Mayfield fixation device. It is fundamental to put the head in a more flexed position compared to any other endoscopic endonasal procedure, in order to gain an improved exposure of the odontoid process and to promote the removal of its upper part. Considering that some patients arrive to the surgeon attention with not only spinal cord compression but also myelopathy, intraoperative neurophysiological monitoring is essential. In order to properly flex the patient head and before the preparation of the surgical field, motor evoked (MEP) and somatosensory evoked potentials (SSEP) must be run to avoid any spinal cord damage during positioning phase. In our opinion, MEP and SSEP are useful also during odontoid and pathological tissue resection to avoid any unwanted compression against the spinal cord.
The first step is to create two nostrils field to permit a four hands job. The surgeon then follows the inferior turbinate to reach the choanas and through them exposes the rhino-pharynx mucosa. As yet reported in our previous study, the drilling of the posterior nasal spine, situated between soft and hard palate, could be helpful to expand the route of access to the dens [12]. In the approaching phase, authors like Wu, Hankinson or Iacoangeli, proposed a midline linear incision or the direct skeletonizing of rhinopharyngeal mucosa [10, 28, 29]. In contrast, Magrini and then Mazzatenta et al. purposed a U-shaped rhinopharyngeal flap. The advantage of the flap is seen in case of accidental or planned intraoperative CSF leak to perform a waterproof plastic repair (Fig. 2). However, this is a complex and time-consuming maneuver and could cause blood loss; in our series we use a fiber laser (CH fiber laser [Dornier MedTech, Munich, Germany]) for the flap harvesting. This tool permits a clean cut, facilitating the detachment of the pharyngobasilar fascia. Never underestimate the strength necessary to detach the rhinopharyngeal flap; in this regard, other useful surgical tools to help during this maneuver are the mucosal debrider and an S-shaped curved aspirator. The real major risk is represented by a possible irregular midline carotid artery loop that could be dramatically injured during the flap preparation. This risk is limited by performing pre-operative CTA study and neuronavigation [6, 30]. At the end of surgery, the use of a posterior nasal mechanical compression with a Foley catheter is a helpful trick to improve the U-shaped flap adhesion in the post-operative phase [12].
After the exposure of C1–C2 anterior surface, in addition to usual high-speed drill, the use of an ultrasonic bone curette to remove the tip and the base of the odontoid is another relevant trick (Figs. 3 and 4). The ultrasonic bone curette is a comfortable tool in the endonasal approach to the CVJ because it provides a bone emulsification‐irrigation‐suction mechanism in single‐hand and can reach deep field thanks to multiple size handle. It provides a selective bone emulsification based on longitudinal and torsional oscillation with a minimal thermal damage [13].
A debated argument regarding bone removal phase is occipitocervical stability. In contrast with the alternative approaches, like the transoral route, in which the entire C1 anterior ring and the base of the odontoid process are resected, or the transcervical route, in which the body and odontoid of C2 are resected, the EEA can give a great contribution to decrease the post-operative risk of spinal instability preserving the C1 anterior arch and resecting only the odontoid or the focal abnormality. Atlas ring integrity is an important element for craniocervical stability, in particular preventing the C1–C2 subluxation [15, 31]. Several authors performed a posterior C1–C2 fixation after an EEO with anterior C1 arch preservation, thus conserving more cervical mobility as compared to an occipitocervical fusion. As demonstrated (Iacoangeli et al.), the C1–C2 fixation has not to be systematically performed in old and frail patients with no evidence of pre-operative occipitocervical instability [10, 32, 33]. Furthermore, as reported by Iacoangeli, it could be considered safe to preserve the half‐lower medial part of the arch to keep a solid continuity of the ring and to obtain a better access to the odontoid tip. When an adequate decompression is not obtainable without a total transection of the C1 anterior arch, a posterior fixation may be required [10, 14].
At the end of surgery, intraoperative CT scan could have a relevant role, showing the extent of bone removal and thus decompression effectiveness [12]. Asymmetrical bony removal, neuronavigation malfunctioning, missing of some part of the dethatched odontoid tip or subtotal tumor resection are problem that can be easily addressed with the use of intraoperative imaging.
Conclusion
Considering our experience, EEO represents a valid and safe technique to decompress neural cervical structures. Nevertheless, this approach is not widespread because its technical complexity, mainly due to the use of endoscope and the challenging surgical area. With this study, along with our previous one, we encourage the use of this technique displaying our experience-based surgical tips and tricks.
References
Greenberg AD, Scoville WB, Davey LM (1968) Transoral decompression of atlanto-axial dislocation due to odontoid hypoplasia report of two cases. J Neurosurg 28:266–269. https://doi.org/10.3171/jns.1968.28.3.0266
Kassam AB, Snyderman C, Gardner P et al (2005) The expanded endonasal approach: a fully endoscopic transnasal approach and resection of the odontoid process: technical case report. Neurosurgery. https://doi.org/10.1227/01.NEU.0000163687.64774.E4
Tang D, Roxbury C, D’Anza B et al (2018) Technical notes on the endoscopic endonasal approach to the craniovertebral junction for odontoidectomy. Am J Rhinol Allergy. https://doi.org/10.1177/1945892418762659
Butenschoen VM, Wostrack M, Meyer B, Gempt J (2021) Endoscopic transnasal odontoidectomy for ventral decompression of the craniovertebral junction: surgical technique and clinical outcome in a case series of 19 patients. Oper Neurosurg 20:24–31. https://doi.org/10.1093/ons/opaa331
Alfieri A, Jho HD, Tschabitscher M (2002) Endoscopic endonasal approach to the ventral cranio-cervical junction: anatomical study. Acta Neurochir (Wien). https://doi.org/10.1007/s007010200029
Mazzatenta D, Zoli M, Mascari C, et al (2014) Endoscopic endonasal odontoidectomy: Clinical series. Spine (Phila Pa 1976) 39, 846–853. https://doi.org/10.1097/BRS.0000000000000271
Nayak JV, Gardner PA, Vescan AD et al (2007) Experience with the expanded endonasal approach for resection of the odontoid process in rheumatoid disease. Am J Rhinol 21:601–606. https://doi.org/10.2500/ajr.2007.21.3089
Algattas HN, Okonkwo DO, Snyderman C et al (2021) Staged repositioning in endoscopic endonasal odontoidectomy maximizes decompression while allowing preservation of the C1 anterior arch: a technical note. World Neurosurg 151:118–123. https://doi.org/10.1016/j.wneu.2021.04.105
Radcliff KE, Hussain MM, Moldavsky M et al (2015) In vitro biomechanics of the craniocervical junction—a sequential sectioning of its stabilizing structures. Spine J 15:1618–1628. https://doi.org/10.1016/j.spinee.2015.02.004
Iacoangeli M, Nasi D, Colasanti R et al (2017) Endoscopic endonasal odontoidectomy with anterior c1 arch preservation in rheumatoid arthritis: long-term follow-up and further technical improvement by anterior endoscopic C1–C2 screw fixation and fusion. World Neurosurg 107:820–829. https://doi.org/10.1016/j.wneu.2017.08.063
Zenga F, Pacca P, Tardivo V et al (2016) Endoscopic endonasal approach to the odontoid pathologies. World Neurosurg. https://doi.org/10.1016/j.wneu.2016.02.011
Penner F, De Marco R, Di Perna G et al (2022) Endoscopic endonasal odontoidectomy: a long-term follow-up results for a cohort of 21 patients. Eur Spine J. https://doi.org/10.1007/s00586-022-07308-6
Zenga F, Villaret AB, Fontanella MM, Nicolai P (2013) Endoscopic transnasal odontoidectomy using ultrasonic bone curette: technical case report. Neurol India 61:69–72. https://doi.org/10.4103/0028-3886.108015
Zenga F, Marengo N, Pacca P et al (2015) C1 anterior arch preservation in transnasal odontoidectomy using three-dimensional endoscope: a case report. Surg Neurol Int. https://doi.org/10.4103/2152-7806.172696
Baird CJ, Conway JE, Sciubba DM et al (2009) Radiographic and anatomic basis of endoscopic anterior craniocervical decompression: a comparison of endonasal, transoral, and transcervical approaches. Neurosurgery 65:158–164. https://doi.org/10.1227/01.NEU.0000345641.97181.ED
Crockard HA (1985) The transoral approach to the base of the brain and upper cervical cord. Ann R Coll Surg Engl 67(5):321
Crockard HA (1995) Transoral surgery: some lessons learned. Br J Neurosurg. https://doi.org/10.1080/02688699550041304
Crockard HA, Pozo JL, Ransford AO et al (1986) Transoral decompression and posterior fusion for rheumatoid atlanto-axial subluxation. J Bone Jt Surg Ser B. https://doi.org/10.1302/0301-620x.68b3.3733795
Di LN, Fortuna A, Guidetti B (1982) Craniovertebral junction malformations. Clinicoradiological findings, long term results, and surgical indications in 63 cases. J Neurosurg 57(5):603–608. https://doi.org/10.3171/jns.1982.57.5.0603
Kingdom TT, Nockels RP (1995) Transoral-transpharyngeal approach to the craniocervical junction. Otolaryngol Head Neck Surg. https://doi.org/10.1016/S0194-5998(95)70074-9
Mummaneni PV, Haid RW (2005) Transoral odontoidectomy. Neurosurgery 56(5):1045–1050. https://doi.org/10.1227/01.NEU.0000158202.60442.FA
Frempong-Boadu AK, Faunce WA, Fessler RG (2002) Endoscopically assisted transoral-transpharyngeal approach to the craniovertebral junction. Neurosurgery. https://doi.org/10.1097/00006123-200211002-00009
Wolinsky JP, Sciubba DM, Suk I, Gokaslan ZL (2007) Endoscopic image-guided odontoidectomy for decompression of basilar invagination via a standard anterior cervical approach technical note. J Neurosurg Spine. https://doi.org/10.3171/spi.2007.6.2.184
De AJR, Zanation AM, Snyderman CH et al (2009) Defining the nasopalatine line: the limit for endonasal surgery of the spine. Laryngoscope 119(2):239–244. https://doi.org/10.1002/lary.20108
Aldana PR, Naseri I, La CE (2012) The naso-axial line: a new method of accurately predicting the inferior limit of the endoscopic endonasal approach to the craniovertebral junction. Neurosurgery. https://doi.org/10.1227/NEU.0b013e318266e488
Liu JK, Patel J, Goldstein IM, Eloy JA (2015) Endoscopic endonasal transclival transodontoid approach for ventral decompression of the craniovertebral junction: operative technique and nuances. Neurosurg Focus. https://doi.org/10.3171/2015.1.FOCUS14813
La CE, Aldana PR, Ferroli P et al (2015) The rhinopalatine line as a reliable predictor of the inferior extent of endonasal odontoidectomies. Neurosurg Focus. https://doi.org/10.3171/2015.1.FOCUS14777
Wu JC, Huang WC, Cheng H et al (2008) Endoscopic transnasal transclival odontoidectomy: a new approach to decompression: technical case report. Neurosurgery. https://doi.org/10.1227/01.neu.0000313115.51071.d5
Hankinson TC, Grunstein E, Gardner P et al (2010) Transnasal odontoid resection followed by posterior decompression and occipitocervical fusion in children with Chiari malformation Type I and ventral brainstem compression. J Neurosurg Pediatr 5(6):549–553. https://doi.org/10.3171/2010.2.PEDS09362
Magrini S, Pasquini E, Mazzatenta D et al (2008) Endoscopic endonasal odontoidectomy in a patient affected by down syndrome: technical case report. Neurosurgery. https://doi.org/10.1227/01.NEU.0000315285.84524.74
Koller H, Resch H, Tauber M et al (2010) A biomechanical rationale for Cl-ring osteosynthesis as treatment for displaced Jefferson burst fractures with incompetency of the transverse atlantal ligament. Eur Spine J. https://doi.org/10.1007/s00586-010-1380-3
Gladi M, Iacoangeli M, Specchia N et al (2012) Endoscopic transnasal odontoid resection to decompress the bulbo-medullary junction: A reliable anterior minimally invasive technique without posterior fusion. Eur Spine J. https://doi.org/10.1007/s00586-012-2220-4
Duntze J, Eap C, Kleiber JC et al (2014) Advantages and limitations of endoscopic endonasal odontoidectomy. A series of nine cases. Orthop Traumatol Surg Res. https://doi.org/10.1016/j.otsr.2014.07.017
Funding
Open access funding provided by Università degli Studi di Torino within the CRUI-CARE Agreement.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
None of the authors has any potential conflict of interest.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Portonero, I., Lo Bue, E., Penner, F. et al. Lesson learned in endoscopic endonasal dens resection for C1–C2 spinal cord decompression. Eur Spine J 33, 438–443 (2024). https://doi.org/10.1007/s00586-023-08001-y
Received:
Revised:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00586-023-08001-y