Anterolateral approach to the upper cervical spine: case report and operative technique Yohan Song, BA1; Suzanne Tharin, MD, PhD2; Vasu Divi, MD1; Laura M. Prolo, MD PhD2; Davud B. Sirjani, MD1 1
Department of Otolaryngology/Head and Neck Surgery Stanford University School of Medicine 801 Welch Rd, Stanford, CA, USA 94305 2
Department of Neurological Surgery Stanford University School of Medicine 300 Pasteur Drive, Boswell Building, A301 Stanford, CA 94305-5327
Corresponding author: Yohan Song Department of Otolaryngology/Head and Neck Surgery Stanford University School of Medicine 801 Welch Rd., 2nd Fl., Stanford CA 94305-5739 [email protected]
Key Words: Anterolateral approach, High cervical spine, Quadrilateral space, Hyoid bone, ACDF
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as an ‘Accepted Article’, doi: 10.1002/hed.23951 This article is protected by copyright. All rights reserved.
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Abstract Background: Transcervical approaches to the upper cervical spine are challenging because several upper anterior neurovascular structures need to be displaced to provide access. Although various techniques have been described, the anterolateral approach is one of the safest and most effective methods available to access the anterior C2-C3 disc space. Despite the approach’s efficacy, however, it can cause postoperative complications due at least partly to inter-surgeon differences in the methods by which the larynx and hypopharynx are displaced medially. Methods/Results: We present a case report of a patient treated with an modified anterolateral approach to C2-C3. The approach provided excellent visualization while protecting vital structures.
The patient recovered without any postoperative dysphagia or other surgical
complications. Conclusions: The anterolateral approach to C2-C3 described herein safely protects the contents of the submandibular triangle while providing a wide exposure for direct access to the C2-C3 disc space.
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Introduction The Smith-Robinson anterior surgical approach to the anterior cervical spine below C3 is well established(1, 2). This method is typically not employed to reach the upper cervical levels because of the risk of damage to the superior laryngeal nerve (SLN), concerns about retraction injury and difficulty in attaining sufficiently wide C2-C3 visualization(3). No alternative approach to the C2-C3 disc space is yet well established likely because the anatomy of the medial upper neck including the mandible, submandibular triangle, and delicate neurovascular structures is more variable than that of the lower neck. Though no single anterior surgical approach provides a straightforward exposure to the spine with minimal risk, other anterior approaches have been described that include the far lateral, transoral, and anterolateral approaches(3-10).
The lateral approach described by
Whitesides, a modification of Henry’s approach to the cervical vertebral artery(11), circumvents the need to dissect delicate neurovascular structures in the anterior upper neck but does not provide the direct anterior view desired to perform a traditional anterior cervical discectomy and placement of interbody graft(12,
13)
.
The transoral approach also avoids the midline
neurovascular structures of the upper neck, but results in a narrow operative field with suboptimal access below the body of C2, potential for oropharyngeal bacterial contamination of the spine, and increased risk of postoperative breathing and swallowing disturbances (14, 15). It is also suboptimal for access below the body of C2. The anterior retropharyngeal approach described by McAffee, also known as the anterolateral or submandibular approach, offers good visualization of the C2-C3 disc space, a large operative field desirable for instrumentation, and low morbidity following surgery(7), but risks injuring the hypoglossal nerve and the marginal mandibular branch of the facial nerve and may result in postoperative dysphagia. If performed correctly, however, the anterolateral approach is a safe and reliable way to reach the upper cervical levels(7, 16).
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The anterolateral approach takes advantage of a natural retropharyngeal space above the SLN and below the hypoglossal nerve. Given the complexity of the approach, however, there is no consensus on the proper way to reach this natural space and surgeons vary in opinion about the best way to dissect the anterior neck. Some authors suggest resecting the submandibular gland during the approach(7, 8), while others prefer preserving the gland(3, 9). Given such differences, continued exploration and subsequent modifications to the approach are warranted to ultimately develop the most effective, consistent, and safest anterolateral approach. In this report, we describe a modified anterolateral approach that safely preserves the contents of the submandibular triangle and provides excellent visualization for direct access to the C2-C3 disc space.
Case Report A 58 year-old gentleman with a history of cervical spondylosis and myelopathy who previously underwent C3-T1 circumferential decompression and instrumented vertebrae suffered a subsequent traumatic C2-C3 facet subluxation and traumatic disc herniation in the setting of multiple postop falls. He presented with new-onset left upper extremity weakness and left arm pain. Physical examination revealed decreased light-touch sensation in the medial left hand and decreased tricep, bicep, and grip strength on the left upper extremity. CT and x-ray of the cervical spine revealed a new subluxation of the left C2-C3 facet, acute disc herniation at C2-C3 with central canal stenosis, and spinal cord compression.
The patient was initially
immobilized in a halo vest with stabilization and improvement of his symptoms. He subsequently underwent anterior-posterior decompression and instrumented fusion with an anterior surgical approach provided by the Otolaryngology, Head and Neck Surgery service. Preoperative fiberoptic laryngeal examination confirmed intact bilateral vocal cord function, which indicated intact bilateral recurrent laryngeal nerve function and confirmed the
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safety of the contralateral approach. A right anterolateral approach was selected to minimize scar encounters from previous left approaches for anterior cervical discectomies and fusions (ACDF) for the lower cervical levels.
Operative Technique After orotracheal intubation, a right anterolateral approach began with a 10-cm incision over the right neck at the level of the hyoid bone starting from the midline and curving posteriorly in a skin crease (Fig. 1). The tissue was divided down through the platysma. The anterior jugular vein was ligated and divided, the inferior edge of the submandibular gland was identified at approximately the level of the hyoid bone, and the submandibular fascia was opened along its inferior border to expose the inferior submandibular gland (Fig. 2). The fascia was elevated from the level of the hyoid to 1 cm below the mandible in a plane deep to the submandibular fascia and directly on the submandibular gland.
Because the marginal
mandibular nerve resides within the submandibular fascia, it was critical to stay directly on the surface of the gland to avoid injury to this nerve, which could be visualized within the submandibular fascia, and ensure the safety of the nerve as it was reflected superiorly with the skin and fascia envelope. Next, the posterior belly of the digastric muscle was identified underneath the submandibular gland, and traced posteriorly and anteriorly as the submandibular gland was retracted superiorly. The facial vein or retromandibular vein may be encountered and can be divided during the posterior dissection. The anterior belly of the digastric was then exposed immediately above the hyoid bone to increase superior exposure.
Below the incision, a
subplatysmal skin flap was elevated immediately above the strap muscles. The thyrohyoid membrane was identified and the internal branch of the superior laryngeal nerve (iSLN) was
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dissected. Once identified along its neurovascular pedicle, the iSLN was traced out medially to laterally. The SLN marked the inferior border of our approach. Next, the SCM was reflected laterally, and the facial vein was skeletonized, clamped, and divided to allow unrestricted displacement of the submandibular gland within its triangle. At this point, dissection on the external carotid artery (ECA) branches led to the identification of the superior thyroid artery. The lingual artery was also identified and retracted superolaterally. To prevent injury to the hypoglossal nerve, the inferior attachments of the digastric along the hyoid bone were not mobilized. The hypoglossal nerve was then identified immediately below the posterior belly of the digastric as it coursed lateral to the internal carotid artery.
It was
skeletonized along its course into the tongue muscles and the overlying venous plexus (Ranine Veins) were clipped and divided, providing more mobility to the nerve. The hypoglossal nerve marked the superior border of our approach. With the submandibular gland retracted superiorly and medially to the mandible, and the lateral aspect of the hyoid bone exposed, the mobility of the hyoid bone was now restricted by the infrahyoid musculature. Before dividing the strap muscles, the ansa cervicalis branch of the hypoglossal nerve was clipped and divided. This maneuver was performed to limit retraction on the hypoglossal nerve, expand the borders of the exposure, and denervate the ipsilateral strap muscles. Next, the ipsilateral sternohyoid and omohyoid muscles were divided laterally to decrease restriction on the hyoid bone (Fig. 3). With increased mobility, the hyoid bone was elevated superiorly to medially displace the lateral edge of the thyrohyoid membrane. This maneuver widens the approach in the medial direction to provide better visualization of the spine. The C2-C3 disc space now became accessible in a more anterior to posterior direction. The release of the sternohyoid muscle also had increased exposure in the superior inferior direction because it allowed further mobilization of the submandibular triangle that was retracted superior and medially, displacing the contents of the oral cavity (Fig. 4).
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The dissection continued superiorly after the midline spine was palpated. With the use of a Kittners dissector in the retropharyngeal space, the pharyngeal mucosa was reflected medially and the longus colli muscle was identified on the right side.
Additional palpation
allowed identification of the previous hardware, and dissection continued for another 5 cm from the superior edge of the previous hardware to expose the C2-C3 disc space. Cranial nerve IX on the right did not need to be identified because the constrictor muscle was elevated off of the paraspinous region and was protected that nerve structure; that is, we were deep to the muscle that was innervated by cranial nerve IX. After the C2-C3 disc space was identified, several Valsalva maneuvers were performed to ensure hemostasis and nerve monitors were placed in the right submental region to aid with monitoring of cranial nerve XII during retraction. Adequate hypoglossal nerve response from a 0.1-ms stimulus pulse indicated appropriate and preserved nerve function. At this point the Neurosurgical Service took over the procedure for the discectomy and fusion. The patient subsequently underwent staged extension of his posterior instrumentation and arthrodesis to the C2 level without complication. The halo was removed and the patient was discharged in a rigid cervical collar. The patient recovered well with no post-operative complications—notably, with no dysphagia, change of voice, or postoperative pneumonia.
Discussion
The anterolateral approach is an effective procedure to reach the high cervical spine by providing wider exposure with less postoperative morbidity compared to other anterior cervical approaches(7). To our knowledge there are many publications in the literature describing the anterolateral surgical approach for C2-C3 disc herniations(4-6,
18-29)
. Russo et al. described a
strategy to reach the C2-C3 level through a quadrilateral space defined by the hypoglossal
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nerve superiorly, iSLN inferiorly, stylopharyngeus muscle medially, and carotid sheath laterally(3). They found that the C2-C3 space could be approached safely without injuring any neural structures. In a more recent study, however, Park et al. found that displacing midline structures widened the aforementioned quadrilateral space(30), and suggested redefining the quadrilateral space by the hypoglossal nerve superiorly, iSLN inferiorly, hyoid bone medially, and the carotid sheath laterally. In this report, we suggest additional modifications to the anterolateral approach that can even further increase the extent of the borders. Dividing the ipsilateral sternohyoid along with the omohyoid musculature allowed increased mobility of the hyoid bone superiorly with subsequent medial displacement of the thyrohyoid membrane. This maneuver further widened the quadrilateral space defined by Park et al. in the medial direction, and allowed us to approach the spine in a more anterior to posterior fashion. Thus, we suggest redefining the quadrilateral space as the hypoglossal nerve/hyoid bone superiorly, iSLN inferiorly, the thyrohyoid membrane medially, and the carotid sheath laterally. Sternohyoid muscle division leads to a less invasive exposure because it allows submandibular triangle mobilization superiorly and protects the hypoglossal nerve from stretch injury. Functionally, unilateral strap muscle division did not lead to any swallowing disturbances in our patient. Although the literature on the anterolateral approach seldom discusses ansa cervicalis transection, we believe that it is actually a common practice among surgeons because it provides a wider exposure and leads to decreased retraction on the hypoglossal nerve.
As
such, dividing the strap muscle that has already been denervated does not create additional morbidity associated with the surgery, and improves the exposure in the medial direction through thyrohyoid membrane displacement. The location of the hyoid bone relative to the mandible is highly variable among patients(31, 32) making the anterior approach difficult to implement in a consistent and predictable manner.
The hyoid location affects the cervicomental angle formed by the horizontal plane of
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the submental region and the vertical plane of the neck(33).
With previously described
approaches, the exposure becomes more difficult in patients with unfavorable cervicomental angles leading to a hyoid bone positioned higher in the neck. This limits the extent of the approach and increases the risk of hypoglossal nerve injury because the hypoglossal nerve is pushed superiorly and the hyoid bone is pushed inferiorly in an attempt to increase the extent of the approach. We believe our modified approach addresses the variability in the cervicomental angles among patients by dividing the infrahyoid strap muscles and moving the hyoid bone superiorly. This maneuver not only provides a wider consistent exposure by eliminating the hyoid-mental space, but also reduces hypoglossal nerve injury risk while protecting the contents of the submandibular triangle by displacing them out of the operative field. The marginal mandibular nerve has a variable location within the upper part of the submandibular triangle residing between the platysma and the facial vein and artery. The nerve is not found traversing the tissues inferiorly to the lower edge of the submandibular gland. For that reason, it is safest to start reflecting the superior skin envelope by dividing the facial vein and dissecting directly on top of the submandibular gland.
Attempts to directly visualize and
dissect the nerve can damage its blood supply and cause nerve injury. Although it is considered a relatively safe procedure, the anterolateral approach can sometimes lead to postoperative complications. For example, hypoglossal nerve injury is a recognized complication to the approach that can lead to ipsilateral hemitongue palsy. Fortunately, the complication is rare. A retrospective study of 40 patients who underwent an anterolateral approach found only one long-term case of hypoglossal nerve injury(34). Another retrospective study similarly reported one incident out of 15 patients of permanent hypoglossal nerve palsy with corresponding dysphagia and dysarthria(9). The authors believed the injury was due to excessive retraction on the nerve during a long surgical case. Another recognized complication to the approach is SLN injury. Fortunately, this complication also is rare. One study reported an incidence of only 1% of SLN injury following an anterolateral approach(35).
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Certain modified versions of the approach can predispose patients to complications.
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For
instance, resecting the submandibular gland to increase exposure can lead to marginal mandibular nerve damage with corresponding permanent lower lip muscle weakness(7, 36). In our experience, submandibular gland resection is not necessary and the retraction needed on the superior skin/fascial envelope to provide exposure for the submandibular gland resection can lead to stretch injury of the marginal mandibular nerve. We were able to safely preserve the marginal mandibular nerve by gently elevating the submandibular fascia and folding it superiorly to protect the nerve from damage. While the window between the hypoglossal nerve and SLN provides access to C2-C3, the location of the SLN may prevent adequate simultaneous exposure to lower levels. Exposure to the lower levels would require further dissection of the inferior skin flap with a second window of exposure created as the hypopharynx and larynx is rotated off the spine with the release of the middle and inferior constrictor. Although our patient was orally intubated, these patients often undergo fiberoptic nasal intubation because of the inability to extend the neck during intubation. Nasal intubation might improve transcervical access with the jaw in the closed position. It can also minimize the risk of extubation during the displacement of the right level 1B into the oral cavity.
Conclusion We report a modified anterolateral approach to C2-C3 that protects vital neurovascular structures while expanding the borders of the operative field for wide anterior midline access. . When performed correctly, the approach can be effective and designed to limit risk of stretch injury to the hypoglossal, marginal mandibular and superior laryngeal nerves.
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FIGURE LEGEND Figure 1. Photograph showing patient position and markings indicating the location of noted head and neck structures. The head is extended at 15° and rotated 30° away from the operative side. The incision starts at the top of the hyoid cartilage and extends to 3 cm inferior to the submandibular angle. Figure 2. This intraoperative photograph rotated counter-clockwise from Figure 2 shows the submandibular gland (SMG) fascia, facial vein, platysma, and inferior edge of the SMG. The marginal mandibular nerve has a variable location within the upper part of the submandibular triangle located between the platystma and facial vein/artery. As such, it is safest to start reflecting the superior skin envelope by dividing the facial vein and dissecting directly on top of the submandibular gland. The inferior border of the SMG is the site at which the fascia should be entered and dissected off of the SMG.
Figure 3: This intraoperative photograph shows the hypoglossal nerve (CNXII) and superior laryngeal nerve (SLN). The infrahyoid muscles have been cut. The circles with “1” indicate the cut edges of the omohyoid muscle, and the circle with “2” indicates the cut edge of the sternohyoid muscle. The strap muscles have been cut because the tension in these muscles on the hyoid bone restricts access. The thyrohyoid muscle is deep to the strap muscles, and was not divided during the operation because the internal branch of the SLN penetrates the thyrohyoid muscle as it courses to the thyrohyoid membrane. Figure 4: This intraoperative photograph shows our access. The hyoid bone and hypoglossal nerve are located deep to the region marked by the dashed rectangle with one asterisk. The carotid artery is located deep to the region marked with the dashed rectangle with two asterisks. The thyohyoid membrane is located deep to the region marked with a dashed rectangle with three asterisks. The internal branch of the superior laryngeal nerve (iSLN) is shown, as well as the superior thyroid artery and facial vein. The contents of the submandibular triangle and CNXII were retracted and protected as a complex. The borders of our access were CNXII/hyoid bone superiorly, iSLN inferiorly, thyrohyoid membrane medially, and carotid artery laterally.
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14. Hadley MN, Spetzler RF, Sonntag VK. The transoral approach to the superior cervical spine. A review of 53 cases of extradural cervicomedullary compression. Journal of neurosurgery 1989;71(1):16-23. 15. Kingdom TT, Nockels RP, Kaplan MJ. Transoral-transpharyngeal approach to the craniocervical junction. Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery 1995;113(4):393-400. 16. Murphey F, Simmons JC, Brunson B. Surgical treatment of laterally ruptured cervical disc. Review of 648 cases, 1939 to 1972. Journal of neurosurgery 1973;38(6):679-83. 17. Apfelbaum RI, Kriskovich MD, Haller JR. On the incidence, cause, and prevention of recurrent laryngeal nerve palsies during anterior cervical spine surgery. Spine 2000;25(22):2906-12. 18. Antich PA, Sanjuan AC, Girvent FM, Simo JD. High cervical disc herniation and Brown-Sequard syndrome. A case report and review of the literature. The Journal of bone and joint surgery British volume 1999;81(3):462-3. 19. Chen TY. The clinical presentation of uppermost cervical disc protrusion. Spine 2000;25(4):439-42. 20. Chen TY, Lui TN. Retrodental fibrocartilaginous mass. Report of a case. Spine 1997;22(8):920-3. 21. Espersen JO, Buhl M, Eriksen EF, et al. Treatment of cervical disc disease using Cloward's technique. I. General results, effect of different operative methods and complications in 1,106 patients. Acta neurochirurgica 1984;70(1-2):97-114. 22. Jomin M, Lesoin F, Lozes G, Thomas CE, 3rd, Rousseaux M, Clarisse J. Herniated cervical discs. Analysis of a series of 230 cases. Acta neurochirurgica 1986;79(2-4):107-13. 23. Nishizawa S, Ryu H, Yokoyama T, Uemura K. Myelopathy caused by retroodontoid disc hernia: case report. Neurosurgery 1996;39(6):1256-9. 24. Nishizawa S, Yokoyama T, Yokota N, Kaneko M. High cervical disc lesions in elderly patients--presentation and surgical approach. Acta neurochirurgica 1999;141(2):119-26. 25. Rosenberg WS, Rosenberg AE, Poletti CE. Cervical disc herniation presenting as a mass lesion posterior to the odontoid process. Report of two cases. Journal of neurosurgery 1991;75(6):954-9. 26. Ture U, Guclu B, Naderi S. Anterolateral extradural approach for C2-C3 disc herniation: technical case report. Neurosurgical review 2008;31(1):117-21; discussion 121. 27. Shim CS, Jung TG, Lee SH. Transcorporeal approach for disc herniation at the C2-C3 level: a technical case report. Journal of spinal disorders & techniques 2009;22(6):459-62.
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28. Fei Z, Fan C, Ngo S, Xu J, Wang J. Dynamic evaluation of cervical disc herniation using kinetic MRI. Journal of clinical neuroscience : official journal of the Neurosurgical Society of Australasia 2011;18(2):232-6. 29. Kotil K, Sengoz A. The management in the C2-C3 disc herniations: a clinical study. Turkish neurosurgery 2011;21(1):15-21. 30. Park SA, Lee JH, Nam YS, An X, Han SH, Ha KY. Topographical anatomy of the anterior cervical approach for c2-3 level. European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society 2013;22(7):1497-503. 31. Tsuchiya M, Lowe AA, Pae EK, Fleetham JA. Obstructive sleep apnea subtypes by cluster analysis. American journal of orthodontics and dentofacial orthopedics : official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 1992;101(6):533-42. 32. Battagel JM, Johal A, L'Estrange PR, Croft CB, Kotecha B. Changes in airway and hyoid position in response to mandibular protrusion in subjects with obstructive sleep apnoea (OSA). European journal of orthodontics 1999;21(4):363-76. 33. Prendiville S, Kokoska MS, Hollenbeak CS, et al. A comparative study of surgical techniques on the cervicomental angle in human cadavers. Archives of facial plastic surgery 2002;4(4):236-42. 34. Saunders RL, Bernini PM, Shirreffs TG, Jr., Reeves AG. Central corpectomy for cervical spondylotic myelopathy: a consecutive series with long-term follow-up evaluation. Journal of neurosurgery 1991;74(2):163-70. 35. Bulger RF, Rejowski JE, Beatty RA. Vocal cord paralysis associated with anterior cervical fusion: considerations for prevention and treatment. Journal of neurosurgery 1985;62(5):657-61. 36. Hsu AK, Kutler DI. Indications, techniques, and complications of major salivary gland extirpation. Oral and maxillofacial surgery clinics of North America 2009;21(3):313-21.
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177x114mm (300 x 300 DPI)
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254x168mm (300 x 300 DPI)
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254x168mm (300 x 300 DPI)
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254x167mm (300 x 300 DPI)
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Department of Otolaryngology/Head and Neck Surgery Stanford University School of Medicine 801 Welch Rd, Stanford, CA, USA 94305 2
Department of Neurological Surgery Stanford University School of Medicine 300 Pasteur Drive, Boswell Building, A301 Stanford, CA 94305-5327
Corresponding author: Yohan Song Department of Otolaryngology/Head and Neck Surgery Stanford University School of Medicine 801 Welch Rd., 2nd Fl., Stanford CA 94305-5739 [email protected]
Key Words: Anterolateral approach, High cervical spine, Quadrilateral space, Hyoid bone, ACDF
This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as an ‘Accepted Article’, doi: 10.1002/hed.23951 This article is protected by copyright. All rights reserved.
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Abstract Background: Transcervical approaches to the upper cervical spine are challenging because several upper anterior neurovascular structures need to be displaced to provide access. Although various techniques have been described, the anterolateral approach is one of the safest and most effective methods available to access the anterior C2-C3 disc space. Despite the approach’s efficacy, however, it can cause postoperative complications due at least partly to inter-surgeon differences in the methods by which the larynx and hypopharynx are displaced medially. Methods/Results: We present a case report of a patient treated with an modified anterolateral approach to C2-C3. The approach provided excellent visualization while protecting vital structures.
The patient recovered without any postoperative dysphagia or other surgical
complications. Conclusions: The anterolateral approach to C2-C3 described herein safely protects the contents of the submandibular triangle while providing a wide exposure for direct access to the C2-C3 disc space.
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Introduction The Smith-Robinson anterior surgical approach to the anterior cervical spine below C3 is well established(1, 2). This method is typically not employed to reach the upper cervical levels because of the risk of damage to the superior laryngeal nerve (SLN), concerns about retraction injury and difficulty in attaining sufficiently wide C2-C3 visualization(3). No alternative approach to the C2-C3 disc space is yet well established likely because the anatomy of the medial upper neck including the mandible, submandibular triangle, and delicate neurovascular structures is more variable than that of the lower neck. Though no single anterior surgical approach provides a straightforward exposure to the spine with minimal risk, other anterior approaches have been described that include the far lateral, transoral, and anterolateral approaches(3-10).
The lateral approach described by
Whitesides, a modification of Henry’s approach to the cervical vertebral artery(11), circumvents the need to dissect delicate neurovascular structures in the anterior upper neck but does not provide the direct anterior view desired to perform a traditional anterior cervical discectomy and placement of interbody graft(12,
13)
.
The transoral approach also avoids the midline
neurovascular structures of the upper neck, but results in a narrow operative field with suboptimal access below the body of C2, potential for oropharyngeal bacterial contamination of the spine, and increased risk of postoperative breathing and swallowing disturbances (14, 15). It is also suboptimal for access below the body of C2. The anterior retropharyngeal approach described by McAffee, also known as the anterolateral or submandibular approach, offers good visualization of the C2-C3 disc space, a large operative field desirable for instrumentation, and low morbidity following surgery(7), but risks injuring the hypoglossal nerve and the marginal mandibular branch of the facial nerve and may result in postoperative dysphagia. If performed correctly, however, the anterolateral approach is a safe and reliable way to reach the upper cervical levels(7, 16).
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The anterolateral approach takes advantage of a natural retropharyngeal space above the SLN and below the hypoglossal nerve. Given the complexity of the approach, however, there is no consensus on the proper way to reach this natural space and surgeons vary in opinion about the best way to dissect the anterior neck. Some authors suggest resecting the submandibular gland during the approach(7, 8), while others prefer preserving the gland(3, 9). Given such differences, continued exploration and subsequent modifications to the approach are warranted to ultimately develop the most effective, consistent, and safest anterolateral approach. In this report, we describe a modified anterolateral approach that safely preserves the contents of the submandibular triangle and provides excellent visualization for direct access to the C2-C3 disc space.
Case Report A 58 year-old gentleman with a history of cervical spondylosis and myelopathy who previously underwent C3-T1 circumferential decompression and instrumented vertebrae suffered a subsequent traumatic C2-C3 facet subluxation and traumatic disc herniation in the setting of multiple postop falls. He presented with new-onset left upper extremity weakness and left arm pain. Physical examination revealed decreased light-touch sensation in the medial left hand and decreased tricep, bicep, and grip strength on the left upper extremity. CT and x-ray of the cervical spine revealed a new subluxation of the left C2-C3 facet, acute disc herniation at C2-C3 with central canal stenosis, and spinal cord compression.
The patient was initially
immobilized in a halo vest with stabilization and improvement of his symptoms. He subsequently underwent anterior-posterior decompression and instrumented fusion with an anterior surgical approach provided by the Otolaryngology, Head and Neck Surgery service. Preoperative fiberoptic laryngeal examination confirmed intact bilateral vocal cord function, which indicated intact bilateral recurrent laryngeal nerve function and confirmed the
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safety of the contralateral approach. A right anterolateral approach was selected to minimize scar encounters from previous left approaches for anterior cervical discectomies and fusions (ACDF) for the lower cervical levels.
Operative Technique After orotracheal intubation, a right anterolateral approach began with a 10-cm incision over the right neck at the level of the hyoid bone starting from the midline and curving posteriorly in a skin crease (Fig. 1). The tissue was divided down through the platysma. The anterior jugular vein was ligated and divided, the inferior edge of the submandibular gland was identified at approximately the level of the hyoid bone, and the submandibular fascia was opened along its inferior border to expose the inferior submandibular gland (Fig. 2). The fascia was elevated from the level of the hyoid to 1 cm below the mandible in a plane deep to the submandibular fascia and directly on the submandibular gland.
Because the marginal
mandibular nerve resides within the submandibular fascia, it was critical to stay directly on the surface of the gland to avoid injury to this nerve, which could be visualized within the submandibular fascia, and ensure the safety of the nerve as it was reflected superiorly with the skin and fascia envelope. Next, the posterior belly of the digastric muscle was identified underneath the submandibular gland, and traced posteriorly and anteriorly as the submandibular gland was retracted superiorly. The facial vein or retromandibular vein may be encountered and can be divided during the posterior dissection. The anterior belly of the digastric was then exposed immediately above the hyoid bone to increase superior exposure.
Below the incision, a
subplatysmal skin flap was elevated immediately above the strap muscles. The thyrohyoid membrane was identified and the internal branch of the superior laryngeal nerve (iSLN) was
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dissected. Once identified along its neurovascular pedicle, the iSLN was traced out medially to laterally. The SLN marked the inferior border of our approach. Next, the SCM was reflected laterally, and the facial vein was skeletonized, clamped, and divided to allow unrestricted displacement of the submandibular gland within its triangle. At this point, dissection on the external carotid artery (ECA) branches led to the identification of the superior thyroid artery. The lingual artery was also identified and retracted superolaterally. To prevent injury to the hypoglossal nerve, the inferior attachments of the digastric along the hyoid bone were not mobilized. The hypoglossal nerve was then identified immediately below the posterior belly of the digastric as it coursed lateral to the internal carotid artery.
It was
skeletonized along its course into the tongue muscles and the overlying venous plexus (Ranine Veins) were clipped and divided, providing more mobility to the nerve. The hypoglossal nerve marked the superior border of our approach. With the submandibular gland retracted superiorly and medially to the mandible, and the lateral aspect of the hyoid bone exposed, the mobility of the hyoid bone was now restricted by the infrahyoid musculature. Before dividing the strap muscles, the ansa cervicalis branch of the hypoglossal nerve was clipped and divided. This maneuver was performed to limit retraction on the hypoglossal nerve, expand the borders of the exposure, and denervate the ipsilateral strap muscles. Next, the ipsilateral sternohyoid and omohyoid muscles were divided laterally to decrease restriction on the hyoid bone (Fig. 3). With increased mobility, the hyoid bone was elevated superiorly to medially displace the lateral edge of the thyrohyoid membrane. This maneuver widens the approach in the medial direction to provide better visualization of the spine. The C2-C3 disc space now became accessible in a more anterior to posterior direction. The release of the sternohyoid muscle also had increased exposure in the superior inferior direction because it allowed further mobilization of the submandibular triangle that was retracted superior and medially, displacing the contents of the oral cavity (Fig. 4).
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The dissection continued superiorly after the midline spine was palpated. With the use of a Kittners dissector in the retropharyngeal space, the pharyngeal mucosa was reflected medially and the longus colli muscle was identified on the right side.
Additional palpation
allowed identification of the previous hardware, and dissection continued for another 5 cm from the superior edge of the previous hardware to expose the C2-C3 disc space. Cranial nerve IX on the right did not need to be identified because the constrictor muscle was elevated off of the paraspinous region and was protected that nerve structure; that is, we were deep to the muscle that was innervated by cranial nerve IX. After the C2-C3 disc space was identified, several Valsalva maneuvers were performed to ensure hemostasis and nerve monitors were placed in the right submental region to aid with monitoring of cranial nerve XII during retraction. Adequate hypoglossal nerve response from a 0.1-ms stimulus pulse indicated appropriate and preserved nerve function. At this point the Neurosurgical Service took over the procedure for the discectomy and fusion. The patient subsequently underwent staged extension of his posterior instrumentation and arthrodesis to the C2 level without complication. The halo was removed and the patient was discharged in a rigid cervical collar. The patient recovered well with no post-operative complications—notably, with no dysphagia, change of voice, or postoperative pneumonia.
Discussion
The anterolateral approach is an effective procedure to reach the high cervical spine by providing wider exposure with less postoperative morbidity compared to other anterior cervical approaches(7). To our knowledge there are many publications in the literature describing the anterolateral surgical approach for C2-C3 disc herniations(4-6,
18-29)
. Russo et al. described a
strategy to reach the C2-C3 level through a quadrilateral space defined by the hypoglossal
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nerve superiorly, iSLN inferiorly, stylopharyngeus muscle medially, and carotid sheath laterally(3). They found that the C2-C3 space could be approached safely without injuring any neural structures. In a more recent study, however, Park et al. found that displacing midline structures widened the aforementioned quadrilateral space(30), and suggested redefining the quadrilateral space by the hypoglossal nerve superiorly, iSLN inferiorly, hyoid bone medially, and the carotid sheath laterally. In this report, we suggest additional modifications to the anterolateral approach that can even further increase the extent of the borders. Dividing the ipsilateral sternohyoid along with the omohyoid musculature allowed increased mobility of the hyoid bone superiorly with subsequent medial displacement of the thyrohyoid membrane. This maneuver further widened the quadrilateral space defined by Park et al. in the medial direction, and allowed us to approach the spine in a more anterior to posterior fashion. Thus, we suggest redefining the quadrilateral space as the hypoglossal nerve/hyoid bone superiorly, iSLN inferiorly, the thyrohyoid membrane medially, and the carotid sheath laterally. Sternohyoid muscle division leads to a less invasive exposure because it allows submandibular triangle mobilization superiorly and protects the hypoglossal nerve from stretch injury. Functionally, unilateral strap muscle division did not lead to any swallowing disturbances in our patient. Although the literature on the anterolateral approach seldom discusses ansa cervicalis transection, we believe that it is actually a common practice among surgeons because it provides a wider exposure and leads to decreased retraction on the hypoglossal nerve.
As
such, dividing the strap muscle that has already been denervated does not create additional morbidity associated with the surgery, and improves the exposure in the medial direction through thyrohyoid membrane displacement. The location of the hyoid bone relative to the mandible is highly variable among patients(31, 32) making the anterior approach difficult to implement in a consistent and predictable manner.
The hyoid location affects the cervicomental angle formed by the horizontal plane of
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the submental region and the vertical plane of the neck(33).
With previously described
approaches, the exposure becomes more difficult in patients with unfavorable cervicomental angles leading to a hyoid bone positioned higher in the neck. This limits the extent of the approach and increases the risk of hypoglossal nerve injury because the hypoglossal nerve is pushed superiorly and the hyoid bone is pushed inferiorly in an attempt to increase the extent of the approach. We believe our modified approach addresses the variability in the cervicomental angles among patients by dividing the infrahyoid strap muscles and moving the hyoid bone superiorly. This maneuver not only provides a wider consistent exposure by eliminating the hyoid-mental space, but also reduces hypoglossal nerve injury risk while protecting the contents of the submandibular triangle by displacing them out of the operative field. The marginal mandibular nerve has a variable location within the upper part of the submandibular triangle residing between the platysma and the facial vein and artery. The nerve is not found traversing the tissues inferiorly to the lower edge of the submandibular gland. For that reason, it is safest to start reflecting the superior skin envelope by dividing the facial vein and dissecting directly on top of the submandibular gland.
Attempts to directly visualize and
dissect the nerve can damage its blood supply and cause nerve injury. Although it is considered a relatively safe procedure, the anterolateral approach can sometimes lead to postoperative complications. For example, hypoglossal nerve injury is a recognized complication to the approach that can lead to ipsilateral hemitongue palsy. Fortunately, the complication is rare. A retrospective study of 40 patients who underwent an anterolateral approach found only one long-term case of hypoglossal nerve injury(34). Another retrospective study similarly reported one incident out of 15 patients of permanent hypoglossal nerve palsy with corresponding dysphagia and dysarthria(9). The authors believed the injury was due to excessive retraction on the nerve during a long surgical case. Another recognized complication to the approach is SLN injury. Fortunately, this complication also is rare. One study reported an incidence of only 1% of SLN injury following an anterolateral approach(35).
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Certain modified versions of the approach can predispose patients to complications.
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For
instance, resecting the submandibular gland to increase exposure can lead to marginal mandibular nerve damage with corresponding permanent lower lip muscle weakness(7, 36). In our experience, submandibular gland resection is not necessary and the retraction needed on the superior skin/fascial envelope to provide exposure for the submandibular gland resection can lead to stretch injury of the marginal mandibular nerve. We were able to safely preserve the marginal mandibular nerve by gently elevating the submandibular fascia and folding it superiorly to protect the nerve from damage. While the window between the hypoglossal nerve and SLN provides access to C2-C3, the location of the SLN may prevent adequate simultaneous exposure to lower levels. Exposure to the lower levels would require further dissection of the inferior skin flap with a second window of exposure created as the hypopharynx and larynx is rotated off the spine with the release of the middle and inferior constrictor. Although our patient was orally intubated, these patients often undergo fiberoptic nasal intubation because of the inability to extend the neck during intubation. Nasal intubation might improve transcervical access with the jaw in the closed position. It can also minimize the risk of extubation during the displacement of the right level 1B into the oral cavity.
Conclusion We report a modified anterolateral approach to C2-C3 that protects vital neurovascular structures while expanding the borders of the operative field for wide anterior midline access. . When performed correctly, the approach can be effective and designed to limit risk of stretch injury to the hypoglossal, marginal mandibular and superior laryngeal nerves.
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FIGURE LEGEND Figure 1. Photograph showing patient position and markings indicating the location of noted head and neck structures. The head is extended at 15° and rotated 30° away from the operative side. The incision starts at the top of the hyoid cartilage and extends to 3 cm inferior to the submandibular angle. Figure 2. This intraoperative photograph rotated counter-clockwise from Figure 2 shows the submandibular gland (SMG) fascia, facial vein, platysma, and inferior edge of the SMG. The marginal mandibular nerve has a variable location within the upper part of the submandibular triangle located between the platystma and facial vein/artery. As such, it is safest to start reflecting the superior skin envelope by dividing the facial vein and dissecting directly on top of the submandibular gland. The inferior border of the SMG is the site at which the fascia should be entered and dissected off of the SMG.
Figure 3: This intraoperative photograph shows the hypoglossal nerve (CNXII) and superior laryngeal nerve (SLN). The infrahyoid muscles have been cut. The circles with “1” indicate the cut edges of the omohyoid muscle, and the circle with “2” indicates the cut edge of the sternohyoid muscle. The strap muscles have been cut because the tension in these muscles on the hyoid bone restricts access. The thyrohyoid muscle is deep to the strap muscles, and was not divided during the operation because the internal branch of the SLN penetrates the thyrohyoid muscle as it courses to the thyrohyoid membrane. Figure 4: This intraoperative photograph shows our access. The hyoid bone and hypoglossal nerve are located deep to the region marked by the dashed rectangle with one asterisk. The carotid artery is located deep to the region marked with the dashed rectangle with two asterisks. The thyohyoid membrane is located deep to the region marked with a dashed rectangle with three asterisks. The internal branch of the superior laryngeal nerve (iSLN) is shown, as well as the superior thyroid artery and facial vein. The contents of the submandibular triangle and CNXII were retracted and protected as a complex. The borders of our access were CNXII/hyoid bone superiorly, iSLN inferiorly, thyrohyoid membrane medially, and carotid artery laterally.
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177x114mm (300 x 300 DPI)
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254x168mm (300 x 300 DPI)
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254x168mm (300 x 300 DPI)
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254x167mm (300 x 300 DPI)
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