ANATOMICAL STUDY
The Selective Odontoidectomy: Endoscopic Endonasal Approach to the Craniocervical Junction Osman Tanriverdi, MD,* Bekir Tugcu, MD,* Omur Gunaldi, MD,* Sevki Serhat Baydin, MD,* Bulent Timur Demirgil, MD,* Bulent Sam, MD,† Baris Kucukyuruk, MD,‡ and Necmettin Tanriover, MD‡ Objective: The resection of the odontoid process via an extended endoscopic endonasal approach has been recently proposed as an alternative to the microscopic transoral method. We aimed to delineate a minimally invasive endoscopic transnasal odontoidectomy and to describe the endoscopic anatomy of the anterior craniovertebral junction (CVJ). Materials and Methods: The anterior CVJ of 14 fresh adult cadavers were selectively accessed via a binostril endoscopic endonasal approach using 0- and 30-degree endoscopes. Results: The nasopharynx was widely exposed without removing any of the turbinates and without performing a sphenoidotomy. Occipital condyles and lateral masses of the C1 vertebra have been exposed inferiorly at lateral margins of the exposure, in addition to the foramen lacerum, which came into view at the superolateral corner of the operative field. The anterior arch of C1 and the upper 1.5 cm of the odontoid process of C2 have been removed via a minimally invasive endoscopic transnasal approach in all dissections. Conclusions: We propose the selective odontoidectomy as a minimally invasive method for the endoscopic endonasal removal of the odontoid process. By using this approach, turbinates and the sphenoid sinus remain unharmed. In addition, this approach may be used in exposing pathologies situated laterally at the anterior CVJ, such as the lateral masses of atlas and occipital condyles. Key Words: Craniovertebral junction, endoscopic endonasal approach, odontoid process, skull base, surgical anatomy (J Craniofac Surg 2014;25: 1482–1487)
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n cases of congenital basilar impression, rheumatoid arthritis with pannus, or traumatic atlanto-occipital dislocation, removal of the odontoid process may be indicated if brain stem and spinal cord compression are present.1–5 The transoral microscopic approach has been the standard method for reaching the craniovertebral junction (CVJ) and removing the odontoid process.1,6 However, this surgical route may be related to undesirable situations such as frequent From the *Bakirkoy Research and Training Hospital for Neurology, Neurosurgery, and Psychiatry, 2nd Neurosurgery Clinic, Istanbul, Turkey; †Istanbul Headquarters of Forensic Medicine Institute, Ministry of Justice, Istanbul, Turkey; and ‡Istanbul University, Cerrahpaşa Medical Faculty, Department of Neurosurgery, Istanbul, Turkey. Received December 8, 2013. Accepted for publication January 17, 2014. Address correspondence and reprint requests to Necmettin Tanriover, MD, Eflatun sok. Leylak sitesi, B. Blok, D:2, Fenerbahce, Istanbul, Turkey; E-mail: [email protected]; [email protected] The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000788
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tracheostomy requirement, prolonged postoperative intubation secondary to tongue retraction, and postoperative voice problems.7–9 On the other hand, accumulated experience on the standard endoscopic endonasal transsphenoidal approach to the sellar region promoted an extended endoscopic endonasal approach to the anterior CVJ.8–11 On the basis of these anatomic studies, this recently acquired endoscopic approach proved to be clinically successful in removing the odontoid process.1,2,4,12–14 On the other hand, although this method seems to avoid many complications related to microscopic transoral approach, it requires a right middle turbinectomy and a wide anterior sphenoidotomy to use the transnasal corridor. Although the technique and anatomic relationships have been described in many previous reports,1,4,8,10 only a few studies have been focused on a minimally invasive removal of the odontoid process.9 Therefore, we aimed to delineate the potential and limitations of a minimally invasive endoscopic endonasal odontoidectomy and, concomitantly, to describe the endoscopic anatomy of the anterior CVJ.
MATERIALS AND METHODS This study, using 14 fresh adult cadavers, was performed at the Council of the Forensic Medicine in Istanbul Forensic Medicine Institution after receiving permission from the Science Board of the Forensic Medicine Institute. Ten cadavers were men (71.4%) and 4 were women (28.6%). All cadavers were older than 18 years, had no history of head trauma and/or craniofacial surgery, and were dissected at the end of a standard autopsy procedure. Karl Storz 0- and 30-degree, 4-mm, 18-cm and 30-cm rod lens rigid endoscopes (Karl Storz and Co, Tuttlingen, Germany) were used in dissections. The light source and the camera system were attached to the endoscope via a fiber optic cable. Images were transferred to a 21-in monitor, and dissections performed during the study were recorded by a digital video recorder. Karl Storz KassamSnydermann surgery set was used as surgical instruments. TT12C telescopic drill attachment and TT12MH25 drill (Midas Rex, Legend EHS; Medtronic, Fort Worth, TX) were used for bone removal, along with 2-mm Kerrison Rongeurs.
RESULTS Endoscopic Anatomy and Surgical Technique Cadaveric heads were positioned in a neutral angle, which promoted anatomic orientation of the surgeon and promoted a safer muscle dissection.10 Initially, middle and inferior turbinates were retracted laterally on both sides to facilitate a passage to the sphenoethmoidal recess between the nasal septum and the lower medial part of the middle turbinate. The endoscope was carried further posterior and inferior through this passage to expose the posterior nasal aperture, the choana, and the sphenoid ostium, located approximately 15 mm superior to the choana (Figs. 1, 2). Next, the endoscope was advanced along the lower edge of the inferior turbinate to identify
The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
FIGURE 1. Endoscopic view within the right nostril with a 0-degree endoscope. 1, The middle turbinate; 2, the nasal septum; 3,the choana.
3 structures: from lateral to medial, the Eustachian tube, located in the lateral part of the nasopharynx; Rosenmüller fossa, situated just behind and medial to this canal; and the prominence of anterior tubercle of atlas, located deeper in the medial part. At this point, we resected the posterior 1.5-cm part of the nasal septum, ensuring a satisfactory working channel through both nostrils and application of bilateral instruments (Fig. 3). After this, the vomer and the anterior wall of the sphenoid sinus were visualized through a submucosal dissection (Fig. 4). Just below this, the nasopharyngeal compartment of the clivus, located from the level of the choana to the level of the anterior arch of the C1 vertebra, was exposed (Fig. 5). At this point, we checked the position of the anterior tubercle of C1 and the odontoid process by fluoroscopy (Fig. 6). The nasopharyngeal mucosa was removed with a reversed U incision, with lateral margins extending toward the Eustachian
FIGURE 2. The view of the inferior and middle turbinates, the posterior nasal aperture (choana), and the sphenoethmoidal recess situated medial to the middle turbinate in the right nostril. 1, The inferior turbinate; 2, the nasal septum; 3, the choana; 4, the sphenoethmoidal recess; 5, the middle turbinate.
The Selective Odontoidectomy
FIGURE 3. Subperiosteal mucosal dissection has been carried out until the anterior edge of the vomer, after which the dissection has been continued as a binostril approach. 1, Vomer; 2, the nasal septal mucosa. Asterisk indicates the surgical scissor.
tubes (Fig. 7). Paraspinal muscles, longus capitis and longus colli, were exposed deep to the nasopharyngeal mucosa, and both muscles were separated to have a view of the anterior tubercle of C1 and the atlanto-occipital membrane (Fig. 8). The Eustachian tube is an important landmark during this stage of the procedure because the cervical segment of the retropharyngeal carotid artery is located directly at its posterolateral side. Therefore, the dissection should stay medial to the Eustachian tube to prevent any damage to the carotid artery. The resection of the anterior arch of C1 was performed using a 3-mm diamond drill with a telescopic attachment (TT12C, Midas Rex, Legend EHS; Medtronic, Fort Worth, TX) and exposed the odontoid process of axis (Figs. 9–11). We were able to differentiate the odontoid process from the anterior arch of C1 by
FIGURE 4. The endoscope has been directed inferiorly with regard to Figure 3. Note that the anterior wall of the sphenoid sinus has not been opened. 1, The vomer; 2, the inferior turbinate; 3, the rhinopharyngeal mucosa; 4, the hard palate.
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FIGURE 5. The endoscope has been advanced medial to the inferior turbinate and parallel to the hard palate to have a view of the nasopharyngeal mucosa and orifices of Eustachian tubes that constitute lateral limits of the exposure. 1, The vomer; 2, the clivus; 3, orifices of Eustachian tubes; 4, the Rosenmüller fossa; 5, the rhinopharyngeal mucosa; 6, the hard palate; 7, the soft palate.
its more compact consistency. The atlantoaxial ligaments could also be seen at the posterior margin of the anterior arch of C1and help the surgeon to differentiate the transition from C1 to C2. We were able to remove the upper 15 mm of the odontoid process in all heads with the help of an electronic drill with a telescopic attachment (TT12C-TT12MH25, Midas Rex, Legend EHS; Medtronic, Fort Worth, TX). The transverse ligament came into view deep to the odontoid process (Figs. 12, 13). At the lateral margin of the operative exposure, lateral masses of the C1 vertebra and occipital condyles were identified inferiorly, just medial to the Eustachian tubes. Removal of the transverse ligament exposed the dura anterior to the pontomedullary junction (Fig. 14), and further opening the dura in the midline revealed the vertebral artery and the structures within the pontomedullary cisterns (Fig. 15).
FIGURE 6. The radiographic confirmation that the odontoid process can be accessed.
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FIGURE 7. U-shaped incision along the nasopharyngeal mucosa. 1, The rhinopharyngeal mucosa; 2, orifices of Eustachian tubes; 3, the hard palate.
DISCUSSION Anterior approaches for the CVJ lesions and the removal of the odontoid process, through the transoral microscopic route, have been reported to be advantageous over lateral and posterolateral approaches because of providing a direct route to the lesion, avoidance of neural tissue retraction, and low rate of lower cranial nerve injury.15–23 However, frequent need for tracheostomy to obtain a safe airway and facilitate the postoperative recovery period, possible velopharyngeal insufficiency due to the separation of the soft palate, and upper respiratory tract and tongue problems due to prolonged compression necessitated an alternative approach to avoid these undesired situations.1,8,13,24 Hence, endoscopy found its use next to the microscope in the treatment of CVJ lesions and the removal of the odontoid process
FIGURE 8. The anterior arch of the C1 vertebra has been exposed. 1, The clivus; 2, the atlanto-occipital membrane; 3, the anterior arch of the C1 vertebra; 4, orifices of Eustachian tubes; 5, the soft palate; 6, the hard palate; 7, the inferior margin of the vomer (the base of the sphenoid sinus).
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
FIGURE 9. Drilling of the anterior arch of the C1 vertebra. 1, The anterior arch of C1; 2, atlanto-occipital membrane. Asterisk indicates suction; double asterisk, tip of the drill attachment.
by providing increased illumination and visualization of the operative field and the ability to look around anatomic corners.25–28 Subsequently, the anatomic study of Alfieri et al8 and the seminal clinical report of Kassam et al1 described the removal of the odontoid process via a fully endoscopic endonasal approach, which included the resection of the right middle turbinate and/or opening at least the floor of the sphenoid sinus. In 1998, Cappabianca et al29,30 proposed the term functional endoscopic pituitary surgery and underlined the protection of the normal nasal airflow by performing a minimally invasive approach and causing less harm to nasal structures. As the name implies, this concept has been proposed mainly for pituitary surgeries, but we believe that the idea also applies for the endoscopic endonasal removal of the odontoid process. Similarly, Kassam et al31 cited the
FIGURE 10. The odontoid process has been exposed after the partial resection of the C1 vertebra. 1, The odontoid process; 2, the tip of the odontoid process; 3, the inferior margin of the C1 anterior arch.
The Selective Odontoidectomy
FIGURE 11. Drilling of the odontoid process.
minimally invasive approach in skull base procedures as “access and visualization through the narrowest practical corridor providing maximum effective action at the target with minimal disruption of normal tissues.” However, although many studies reported their experience and technique for the endoscopic endonasal removal of the odontoid process,2,4,5,10–14,32 only a few of them focused on a minimally invasive method for removing the odontoid process.9 Similar to the work of Messina et al,9 our results suggest that the removal of the upper 1.5 cm of the odontoid process is feasible via a minimally invasive endoscopic binostril approach, namely, the selective odontoidectomy, which does not necessitate the resection of turbinates and opening of the sphenoid sinus. The rationale for the selective odontoidectomy is 2-fold: first, avoidance of exposing critical neurovascular structures may lead to decreased perioperative complications, and second, protecting the nasal structures may be related to increased patient quality of life.
FIGURE 12. The view of the transverse membrane after the resection of the odontoid process. 1, The transverse membrane.
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FIGURE 13. Magnified view of Figure 12. 1, The transverse membrane.
Endoscopic endonasal skull base approaches may be related to epistaxis, cerebrospinal fluid leakage (CSFL), injury to carotid or vertebral arteries, cranial nerve deficits, and pseudoaneurysms.33 Current standard technique for endoscopic endonasal removal of the odontoid process has been reported to include wide sphenoidotomy both to increase surgical working corridor and to expose carotid canals as important landmarks.1,31 On the other hand, the same group also stated that vascular and neural complications in endoscopic skull base surgery increase as the procedure becomes more complex.31 Similar to this, Cavallo et al34 determined that CSFLs after extended endoscopic approaches are higher compared with that after standard endoscopic pituitary surgery. We believe that conclusions of these experienced groups may be interpreted as that a limited resection to expose surrounding structures may lead to better results in terms of CSFL and neurovascular complications. In this modern neurosurgical era, patient quality of life becomes more important each day after. Turbinates consisting of large mucosal
FIGURE 14. The dura comes into view after the transverse membrane has been removed. 1, The transverse membrane; 2, the dura.
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surfaces and arteriovenous anastomoses have important contributions to nasal air conditioning; hence, turbinectomy reduces nasal resistance and causes an impaired respiratory function.35,36 Aggressive resection of the turbinates has been reported to cause reduced nasal humidity and temperature and disrupted airflow, which may create complaints such as nasal dryness, crusting, recurrent nosebleed, and hyposmia.37 Specifically, the middle turbinate has been suggested to have an important role in humidification and heating of the inspired air, which is directed to the olfactory area.35 The middle turbinate was proposed to protect the middle meatus from a turbulent airflow, thus supporting mucociliary clearance.35 Therefore, some authors determined to reject routine resection of the middle turbinate because of the risk for anosmia and atrophic rhinitis.38,39 As expected, endoscopic endonasal selective odontoidectomy has its limitations. The hard palate seems to be the most important factor limiting the caudal extension of the approach. A nasopalatine line, connecting the most inferior point on the nasal bone to the most posterior point on the hard palate at the midsagittal plane, has been proposed so that the intersection of this line with the vertebral column was found to be related to the inferior aspect of the body of C2.40 Although structures situated inferior to this intersection can be seen with angled endoscopes, surgical intervention to these regions is highly challenging and requires angled telescopic drill attachments. The presence of a shallow sphenoid sinus floor can be another limitation for the selective odontoidectomy. In these cases, such as patients with platybasia, the back end of the clivus hinders the odontoid process so that the surgeon should first open the inferior part of the sphenoid sinus floor and then drill the floor all the way back to the anterior arch of the C1 vertebra.
CONCLUSIONS Cappabianca et al33 stressed that the best strategy in endoscopic surgery to deal with surgical complications is to avoid them. Our aim in this cadaveric study was to demonstrate the feasibility of a minimally invasive approach in endoscopic endonasal removal of the odontoid process, namely, the selective odontoidectomy that does not need removal of turbinates and sphenoidotomy. We believe that this study, along with previous ones, would encourage widespread use of similar surgical interventions to the CVJ.
FIGURE 15. The view of the intradural space after the opening of the dura. 1, Vertebral artery; 2, vertebrobasillar junction.
© 2014 Mutaz B. Habal, MD
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
REFERENCES 1. Kassam AB, Snyderman C, Gardner P, et al. The expanded endonasal approach: a fully endoscopic transnasal approach and resection of the odontoid process: technical case report. Neurosurgery 2005;57(suppl 1):E213 2. Laufer I, Greenfield JP, Anand VK, et al. Endonasal endoscopic resection of the odontoid process in a nonachondroplastic dwarf with juvenile rheumatoid arthritis: feasibility of the approach and utility of the intraoperative Iso-C three-dimensional navigation. Case report. J Neurosurg Spine 2008;8:376–380 3. Mummaneni PV, Haid RW. Transoral odontoidectomy. Neurosurgery 2005;56:1045–1050 4. Nayak JV, Gardner PA, Vescan AD, et al. Experience with the expanded endonasal approach for resection of the odontoid process in rheumatoid disease. Am J Rhinol 2007;21:601–606 5. Wu JC, Huang WC, Cheng H, et al. Endoscopic transnasal transclival odontoidectomy: a new approach to decompression: technical case report. Neurosurgery 2008;63(suppl 1):ONSE92–ONSE94 6. Tun K, Kaptanoglu E, Cemil B, et al. A neurosurgical view of anatomical evaluation of anterior C1-C2 for safer transoral odontoidectomy. Eur Spine J 2008;17:853–856 7. Abuzayed B, Tanriover N, Ozlen F, et al. Endoscopic endonasal transsphenoidal approach to the sellar region: results of endoscopic dissection on 30 cadavers. Turk Neurosurg 2009;19:237–244 8. Alfieri A, Jho HD, Tschabitscher M. Endoscopic endonasal approach to the ventral cranio-cervical junction: anatomical study. Acta Neurochir (Wien) 2002;144:219–225 9. Messina A, Bruno MC, Decq P, et al. Pure endoscopic endonasal odontoidectomy: anatomical study. Neurosurg Rev 2007;30:189–194 10. Abuzayed B, Tanriover N, Gazioglu N, et al. Extended endoscopic endonasal approach to the anterior cranio-vertebral junction: anatomic study. Turk Neurosurg 2009;19:249–255 11. Cavallo LM, Cappabianca P, Messina A, et al. The extended endoscopic endonasal approach to the clivus and cranio-vertebral junction: anatomical study. Childs Nerv Syst 2007;23:665–671 12. Gempt J, Lehmberg J, Meyer B, et al. Endoscopic transnasal resection of the odontoid in a patient with severe brainstem compression. Acta Neurochir (Wien) 2010;152:559–560 13. Leng LZ, Anand VK, Hartl R, et al. Endonasal endoscopic resection of an os odontoideum to decompress the cervicomedullary junction: a minimal access surgical technique. Spine (Phila Pa 1976) 2009;34:E139–E143 14. Magrini S, Pasquini E, Mazzatenta D, et al. Endoscopic endonasal odontoidectomy in a patient affected by Down syndrome: technical case report. Neurosurgery 2008;63: E373–E374 15. al-Mefty O, Borba LA, Aoki N, et al. The transcondylar approach to extradural nonneoplastic lesions of the craniovertebral junction. J Neurosurg 1996;84:1–6 16. Bertalanffy H, Seeger W. The dorsolateral, suboccipital, transcondylar approach to the lower clivus and anterior portion of the craniocervical junction. Neurosurgery 1991;29:815–821 17. Crockard HA, Sen CN. The transoral approach for the management of intradural lesions at the craniovertebral junction: review of 7 cases. Neurosurgery 1991;28:88–97 18. Goel A, Desai K, Muzumdar D. Surgery on anterior foramen magnum meningiomas using a conventional posterior suboccipital approach: a report on an experience with 17 cases. Neurosurgery 2001;49:102–106 19. Kingdom TT, Nockels RP, Kaplan MJ. Transoral-transpharyngeal approach to the craniocervical junction. Otolaryngol Head Neck Surg 1995;113:393–400
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20. Oya S, Tsutsumi K, Shigeno T, et al. Posterolateral odontoidectomy for irreducible atlantoaxial dislocation: a technical case report. Spine J 2004;4:591–594 21. Spetzler RF, Grahm TW. The far-lateral approach to the inferior clivus and upper cervical region. Technical note. Barrow Neurol Inst Q 1990;6:35–38 22. Ture U, Pamir MN. Extreme lateral-transatlas approach for resection of the dens of the axis. J Neurosurg 2002;96(suppl 1):73–82 23. Ziyal I. Extended frontal approach to anterior, middle, and posterior clivus: an anatomical study. Turk Nöroşirurji Dergisi 1999;9:7–11 24. Ibrahim AG, Crockard HA. Basilar impression and osteogenesis imperfecta: a 21-year retrospective review of outcomes in 20 patients. J Neurosurg Spine 2007;7:594–600 25. McCoul ED, Anand VK, Bedrosian JC, et al. Endoscopic skull base surgery and its impact on sinonasal-related quality of life. Int Forum Allergy Rhinol 2012;2:174–181 26. Welch WC, Kassam A. Endoscopically assisted transoral-transpharyngeal approach to the craniovertebral junction. Neurosurgery. 2003;52:1511–1512 27. Frempong-Boadu AK, Faunce WA, Fessler RG. Endoscopically assisted transoral-transpharyngeal approach to the craniovertebral junction. Neurosurgery 2002;51(suppl 5):S60–S66 28. Prevedello DM, Doglietto F, Jane JA Jr, et al. History of endoscopic skull base surgery: its evolution and current reality. J Neurosurg 2007;107:206–213 29. Cappabianca P, Alfieri A, de Divitiis E. Endoscopic endonasal transsphenoidal approach to the sella: towards functional endoscopic pituitary surgery (FEPS). Minim Invasive Neurosurg 1998;41:66–73 30. Cappabianca P, Alfieri A, Colao A, et al. Endoscopic endonasal transsphenoidal approach: an additional reason in support of surgery in the management of pituitary lesions. Skull Base Surg 1999;9:109–117 31. Kassam AB, Prevedello DM, Carrau RL, et al. Endoscopic endonasal skull base surgery: analysis of complications in the authors’ initial 800 patients. J Neurosurg 2011;114:1544–1568 32. Schwartz TH, Fraser JF, Brown S, et al. Endoscopic cranial base surgery: classification of operative approaches. Neurosurgery 2008;62:991–1002 33. Cappabianca P, Cavallo LM, Colao A, et al. Surgical complications associated with the endoscopic endonasal transsphenoidal approach for pituitary adenomas. J Neurosurg. 2002;97: 293–298 34. Cavallo LM, Messina A, Esposito F, et al. Skull base reconstruction in the extended endoscopic transsphenoidal approach for suprasellar lesions. J Neurosurg. 2007;107:713–720 35. Lindemann J, Keck T, Wiesmiller KM, et al. Numerical simulation of intranasal air flow and temperature after resection of the turbinates. Rhinology 2005;43:24–28 36. Mygind N. Applied physiology of the nose. In: Mygind N, ed. Nasal Allergy. Oxford, England: Blackwell Scientific Publications, 1979:39–56 37. Lindemann J, Leiacker R, Sikora T, et al. Impact of unilateral sinus surgery with resection of the turbinates by means of midfacial degloving on nasal air conditioning. Laryngoscope 2002;112: 2062–2066 38. Kennedy DW. Functional endoscopic sinus surgery. Technique. Arch Otolaryngol 1985;111:643–649 39. Stammberger H. Operative techniques. Chicago: WB Saunders Publisher, 1991 40. de Almeida JR, Zanation AM, Snyderman CH, et al. Defining the nasopalatine line: the limit for endonasal surgery of the spine. Laryngoscope. 2009;119:239–244
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The Selective Odontoidectomy: Endoscopic Endonasal Approach to the Craniocervical Junction Osman Tanriverdi, MD,* Bekir Tugcu, MD,* Omur Gunaldi, MD,* Sevki Serhat Baydin, MD,* Bulent Timur Demirgil, MD,* Bulent Sam, MD,† Baris Kucukyuruk, MD,‡ and Necmettin Tanriover, MD‡ Objective: The resection of the odontoid process via an extended endoscopic endonasal approach has been recently proposed as an alternative to the microscopic transoral method. We aimed to delineate a minimally invasive endoscopic transnasal odontoidectomy and to describe the endoscopic anatomy of the anterior craniovertebral junction (CVJ). Materials and Methods: The anterior CVJ of 14 fresh adult cadavers were selectively accessed via a binostril endoscopic endonasal approach using 0- and 30-degree endoscopes. Results: The nasopharynx was widely exposed without removing any of the turbinates and without performing a sphenoidotomy. Occipital condyles and lateral masses of the C1 vertebra have been exposed inferiorly at lateral margins of the exposure, in addition to the foramen lacerum, which came into view at the superolateral corner of the operative field. The anterior arch of C1 and the upper 1.5 cm of the odontoid process of C2 have been removed via a minimally invasive endoscopic transnasal approach in all dissections. Conclusions: We propose the selective odontoidectomy as a minimally invasive method for the endoscopic endonasal removal of the odontoid process. By using this approach, turbinates and the sphenoid sinus remain unharmed. In addition, this approach may be used in exposing pathologies situated laterally at the anterior CVJ, such as the lateral masses of atlas and occipital condyles. Key Words: Craniovertebral junction, endoscopic endonasal approach, odontoid process, skull base, surgical anatomy (J Craniofac Surg 2014;25: 1482–1487)
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n cases of congenital basilar impression, rheumatoid arthritis with pannus, or traumatic atlanto-occipital dislocation, removal of the odontoid process may be indicated if brain stem and spinal cord compression are present.1–5 The transoral microscopic approach has been the standard method for reaching the craniovertebral junction (CVJ) and removing the odontoid process.1,6 However, this surgical route may be related to undesirable situations such as frequent From the *Bakirkoy Research and Training Hospital for Neurology, Neurosurgery, and Psychiatry, 2nd Neurosurgery Clinic, Istanbul, Turkey; †Istanbul Headquarters of Forensic Medicine Institute, Ministry of Justice, Istanbul, Turkey; and ‡Istanbul University, Cerrahpaşa Medical Faculty, Department of Neurosurgery, Istanbul, Turkey. Received December 8, 2013. Accepted for publication January 17, 2014. Address correspondence and reprint requests to Necmettin Tanriover, MD, Eflatun sok. Leylak sitesi, B. Blok, D:2, Fenerbahce, Istanbul, Turkey; E-mail: [email protected]; [email protected] The authors report no conflicts of interest. Copyright © 2014 by Mutaz B. Habal, MD ISSN: 1049-2275 DOI: 10.1097/SCS.0000000000000788
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tracheostomy requirement, prolonged postoperative intubation secondary to tongue retraction, and postoperative voice problems.7–9 On the other hand, accumulated experience on the standard endoscopic endonasal transsphenoidal approach to the sellar region promoted an extended endoscopic endonasal approach to the anterior CVJ.8–11 On the basis of these anatomic studies, this recently acquired endoscopic approach proved to be clinically successful in removing the odontoid process.1,2,4,12–14 On the other hand, although this method seems to avoid many complications related to microscopic transoral approach, it requires a right middle turbinectomy and a wide anterior sphenoidotomy to use the transnasal corridor. Although the technique and anatomic relationships have been described in many previous reports,1,4,8,10 only a few studies have been focused on a minimally invasive removal of the odontoid process.9 Therefore, we aimed to delineate the potential and limitations of a minimally invasive endoscopic endonasal odontoidectomy and, concomitantly, to describe the endoscopic anatomy of the anterior CVJ.
MATERIALS AND METHODS This study, using 14 fresh adult cadavers, was performed at the Council of the Forensic Medicine in Istanbul Forensic Medicine Institution after receiving permission from the Science Board of the Forensic Medicine Institute. Ten cadavers were men (71.4%) and 4 were women (28.6%). All cadavers were older than 18 years, had no history of head trauma and/or craniofacial surgery, and were dissected at the end of a standard autopsy procedure. Karl Storz 0- and 30-degree, 4-mm, 18-cm and 30-cm rod lens rigid endoscopes (Karl Storz and Co, Tuttlingen, Germany) were used in dissections. The light source and the camera system were attached to the endoscope via a fiber optic cable. Images were transferred to a 21-in monitor, and dissections performed during the study were recorded by a digital video recorder. Karl Storz KassamSnydermann surgery set was used as surgical instruments. TT12C telescopic drill attachment and TT12MH25 drill (Midas Rex, Legend EHS; Medtronic, Fort Worth, TX) were used for bone removal, along with 2-mm Kerrison Rongeurs.
RESULTS Endoscopic Anatomy and Surgical Technique Cadaveric heads were positioned in a neutral angle, which promoted anatomic orientation of the surgeon and promoted a safer muscle dissection.10 Initially, middle and inferior turbinates were retracted laterally on both sides to facilitate a passage to the sphenoethmoidal recess between the nasal septum and the lower medial part of the middle turbinate. The endoscope was carried further posterior and inferior through this passage to expose the posterior nasal aperture, the choana, and the sphenoid ostium, located approximately 15 mm superior to the choana (Figs. 1, 2). Next, the endoscope was advanced along the lower edge of the inferior turbinate to identify
The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
Copyright © 2014 Mutaz B. Habal, MD. Unauthorized reproduction of this article is prohibited.
The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
FIGURE 1. Endoscopic view within the right nostril with a 0-degree endoscope. 1, The middle turbinate; 2, the nasal septum; 3,the choana.
3 structures: from lateral to medial, the Eustachian tube, located in the lateral part of the nasopharynx; Rosenmüller fossa, situated just behind and medial to this canal; and the prominence of anterior tubercle of atlas, located deeper in the medial part. At this point, we resected the posterior 1.5-cm part of the nasal septum, ensuring a satisfactory working channel through both nostrils and application of bilateral instruments (Fig. 3). After this, the vomer and the anterior wall of the sphenoid sinus were visualized through a submucosal dissection (Fig. 4). Just below this, the nasopharyngeal compartment of the clivus, located from the level of the choana to the level of the anterior arch of the C1 vertebra, was exposed (Fig. 5). At this point, we checked the position of the anterior tubercle of C1 and the odontoid process by fluoroscopy (Fig. 6). The nasopharyngeal mucosa was removed with a reversed U incision, with lateral margins extending toward the Eustachian
FIGURE 2. The view of the inferior and middle turbinates, the posterior nasal aperture (choana), and the sphenoethmoidal recess situated medial to the middle turbinate in the right nostril. 1, The inferior turbinate; 2, the nasal septum; 3, the choana; 4, the sphenoethmoidal recess; 5, the middle turbinate.
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FIGURE 3. Subperiosteal mucosal dissection has been carried out until the anterior edge of the vomer, after which the dissection has been continued as a binostril approach. 1, Vomer; 2, the nasal septal mucosa. Asterisk indicates the surgical scissor.
tubes (Fig. 7). Paraspinal muscles, longus capitis and longus colli, were exposed deep to the nasopharyngeal mucosa, and both muscles were separated to have a view of the anterior tubercle of C1 and the atlanto-occipital membrane (Fig. 8). The Eustachian tube is an important landmark during this stage of the procedure because the cervical segment of the retropharyngeal carotid artery is located directly at its posterolateral side. Therefore, the dissection should stay medial to the Eustachian tube to prevent any damage to the carotid artery. The resection of the anterior arch of C1 was performed using a 3-mm diamond drill with a telescopic attachment (TT12C, Midas Rex, Legend EHS; Medtronic, Fort Worth, TX) and exposed the odontoid process of axis (Figs. 9–11). We were able to differentiate the odontoid process from the anterior arch of C1 by
FIGURE 4. The endoscope has been directed inferiorly with regard to Figure 3. Note that the anterior wall of the sphenoid sinus has not been opened. 1, The vomer; 2, the inferior turbinate; 3, the rhinopharyngeal mucosa; 4, the hard palate.
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FIGURE 5. The endoscope has been advanced medial to the inferior turbinate and parallel to the hard palate to have a view of the nasopharyngeal mucosa and orifices of Eustachian tubes that constitute lateral limits of the exposure. 1, The vomer; 2, the clivus; 3, orifices of Eustachian tubes; 4, the Rosenmüller fossa; 5, the rhinopharyngeal mucosa; 6, the hard palate; 7, the soft palate.
its more compact consistency. The atlantoaxial ligaments could also be seen at the posterior margin of the anterior arch of C1and help the surgeon to differentiate the transition from C1 to C2. We were able to remove the upper 15 mm of the odontoid process in all heads with the help of an electronic drill with a telescopic attachment (TT12C-TT12MH25, Midas Rex, Legend EHS; Medtronic, Fort Worth, TX). The transverse ligament came into view deep to the odontoid process (Figs. 12, 13). At the lateral margin of the operative exposure, lateral masses of the C1 vertebra and occipital condyles were identified inferiorly, just medial to the Eustachian tubes. Removal of the transverse ligament exposed the dura anterior to the pontomedullary junction (Fig. 14), and further opening the dura in the midline revealed the vertebral artery and the structures within the pontomedullary cisterns (Fig. 15).
FIGURE 6. The radiographic confirmation that the odontoid process can be accessed.
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FIGURE 7. U-shaped incision along the nasopharyngeal mucosa. 1, The rhinopharyngeal mucosa; 2, orifices of Eustachian tubes; 3, the hard palate.
DISCUSSION Anterior approaches for the CVJ lesions and the removal of the odontoid process, through the transoral microscopic route, have been reported to be advantageous over lateral and posterolateral approaches because of providing a direct route to the lesion, avoidance of neural tissue retraction, and low rate of lower cranial nerve injury.15–23 However, frequent need for tracheostomy to obtain a safe airway and facilitate the postoperative recovery period, possible velopharyngeal insufficiency due to the separation of the soft palate, and upper respiratory tract and tongue problems due to prolonged compression necessitated an alternative approach to avoid these undesired situations.1,8,13,24 Hence, endoscopy found its use next to the microscope in the treatment of CVJ lesions and the removal of the odontoid process
FIGURE 8. The anterior arch of the C1 vertebra has been exposed. 1, The clivus; 2, the atlanto-occipital membrane; 3, the anterior arch of the C1 vertebra; 4, orifices of Eustachian tubes; 5, the soft palate; 6, the hard palate; 7, the inferior margin of the vomer (the base of the sphenoid sinus).
© 2014 Mutaz B. Habal, MD
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The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
FIGURE 9. Drilling of the anterior arch of the C1 vertebra. 1, The anterior arch of C1; 2, atlanto-occipital membrane. Asterisk indicates suction; double asterisk, tip of the drill attachment.
by providing increased illumination and visualization of the operative field and the ability to look around anatomic corners.25–28 Subsequently, the anatomic study of Alfieri et al8 and the seminal clinical report of Kassam et al1 described the removal of the odontoid process via a fully endoscopic endonasal approach, which included the resection of the right middle turbinate and/or opening at least the floor of the sphenoid sinus. In 1998, Cappabianca et al29,30 proposed the term functional endoscopic pituitary surgery and underlined the protection of the normal nasal airflow by performing a minimally invasive approach and causing less harm to nasal structures. As the name implies, this concept has been proposed mainly for pituitary surgeries, but we believe that the idea also applies for the endoscopic endonasal removal of the odontoid process. Similarly, Kassam et al31 cited the
FIGURE 10. The odontoid process has been exposed after the partial resection of the C1 vertebra. 1, The odontoid process; 2, the tip of the odontoid process; 3, the inferior margin of the C1 anterior arch.
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FIGURE 11. Drilling of the odontoid process.
minimally invasive approach in skull base procedures as “access and visualization through the narrowest practical corridor providing maximum effective action at the target with minimal disruption of normal tissues.” However, although many studies reported their experience and technique for the endoscopic endonasal removal of the odontoid process,2,4,5,10–14,32 only a few of them focused on a minimally invasive method for removing the odontoid process.9 Similar to the work of Messina et al,9 our results suggest that the removal of the upper 1.5 cm of the odontoid process is feasible via a minimally invasive endoscopic binostril approach, namely, the selective odontoidectomy, which does not necessitate the resection of turbinates and opening of the sphenoid sinus. The rationale for the selective odontoidectomy is 2-fold: first, avoidance of exposing critical neurovascular structures may lead to decreased perioperative complications, and second, protecting the nasal structures may be related to increased patient quality of life.
FIGURE 12. The view of the transverse membrane after the resection of the odontoid process. 1, The transverse membrane.
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FIGURE 13. Magnified view of Figure 12. 1, The transverse membrane.
Endoscopic endonasal skull base approaches may be related to epistaxis, cerebrospinal fluid leakage (CSFL), injury to carotid or vertebral arteries, cranial nerve deficits, and pseudoaneurysms.33 Current standard technique for endoscopic endonasal removal of the odontoid process has been reported to include wide sphenoidotomy both to increase surgical working corridor and to expose carotid canals as important landmarks.1,31 On the other hand, the same group also stated that vascular and neural complications in endoscopic skull base surgery increase as the procedure becomes more complex.31 Similar to this, Cavallo et al34 determined that CSFLs after extended endoscopic approaches are higher compared with that after standard endoscopic pituitary surgery. We believe that conclusions of these experienced groups may be interpreted as that a limited resection to expose surrounding structures may lead to better results in terms of CSFL and neurovascular complications. In this modern neurosurgical era, patient quality of life becomes more important each day after. Turbinates consisting of large mucosal
FIGURE 14. The dura comes into view after the transverse membrane has been removed. 1, The transverse membrane; 2, the dura.
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surfaces and arteriovenous anastomoses have important contributions to nasal air conditioning; hence, turbinectomy reduces nasal resistance and causes an impaired respiratory function.35,36 Aggressive resection of the turbinates has been reported to cause reduced nasal humidity and temperature and disrupted airflow, which may create complaints such as nasal dryness, crusting, recurrent nosebleed, and hyposmia.37 Specifically, the middle turbinate has been suggested to have an important role in humidification and heating of the inspired air, which is directed to the olfactory area.35 The middle turbinate was proposed to protect the middle meatus from a turbulent airflow, thus supporting mucociliary clearance.35 Therefore, some authors determined to reject routine resection of the middle turbinate because of the risk for anosmia and atrophic rhinitis.38,39 As expected, endoscopic endonasal selective odontoidectomy has its limitations. The hard palate seems to be the most important factor limiting the caudal extension of the approach. A nasopalatine line, connecting the most inferior point on the nasal bone to the most posterior point on the hard palate at the midsagittal plane, has been proposed so that the intersection of this line with the vertebral column was found to be related to the inferior aspect of the body of C2.40 Although structures situated inferior to this intersection can be seen with angled endoscopes, surgical intervention to these regions is highly challenging and requires angled telescopic drill attachments. The presence of a shallow sphenoid sinus floor can be another limitation for the selective odontoidectomy. In these cases, such as patients with platybasia, the back end of the clivus hinders the odontoid process so that the surgeon should first open the inferior part of the sphenoid sinus floor and then drill the floor all the way back to the anterior arch of the C1 vertebra.
CONCLUSIONS Cappabianca et al33 stressed that the best strategy in endoscopic surgery to deal with surgical complications is to avoid them. Our aim in this cadaveric study was to demonstrate the feasibility of a minimally invasive approach in endoscopic endonasal removal of the odontoid process, namely, the selective odontoidectomy that does not need removal of turbinates and sphenoidotomy. We believe that this study, along with previous ones, would encourage widespread use of similar surgical interventions to the CVJ.
FIGURE 15. The view of the intradural space after the opening of the dura. 1, Vertebral artery; 2, vertebrobasillar junction.
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The Journal of Craniofacial Surgery • Volume 25, Number 4, July 2014
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