Anterior approach to the cervical spine: surgical anatomy

Revolutionizing Relief: Cervical Radiculopathy With Neurological Deficits Rescued by Cervical Disc Replacement

Cervical radiculopathy is a common condition characterized by neck pain radiating to the upper and lower limbs, often accompanied by tingling sensations, numbness, and weakness. We present the case of a 32-year-old male who presented with left-sided cervical radiculopathy and neurological deficits. Clinical examination revealed left C5/C6/C7 hypoesthesia, diminished grip strength, reduced power in the left upper and lower extremities, and a positive Spurling test. Magnetic resonance imaging (MRI) of the cervical spine revealed multilevel cervical disc herniations at C4-C5 and C5-C6 levels, resulting in stenosis. The patient underwent anterior cervical discectomies with artificial disc replacement (cervical disc arthroplasty (CDA)) at the C5-C6 level. The surgical procedure was uneventful, and the patient experienced prompt relief from neurological symptoms within two weeks postoperatively. Follow-up radiographs at one week post-surgery demonstrated a preserved range of motion at each operated level with the artificial disc in situ. This case highlights the successful management of cervical radiculopathy with neurological deficits using anterior cervical discectomy and artificial disc replacement. The timely intervention led to the resolution of symptoms and restoration of function, demonstrating the efficacy of this surgical approach in alleviating radicular symptoms and preserving cervical spine mobility. Further studies and long-term follow-up are warranted to validate the long-term outcomes and durability of artificial disc replacement in such cases.

Advantages of 3-dimensional exoscope-assisted anterior cervical spine surgery: A meta-analysis

BACKGROUND

Visual instruments are essential to ensure high-quality surgical outcomes for minimally invasive procedures and have gradually become the focus of research. Recently, a novel visual auxiliary instrument, a 3-dimensional exoscope (EX), has been applied for spinal surgery. However, its advantages over other auxiliary means (OAMs) in anterior cervical surgery need to be assessed.

OBJECTIVE

To compare and evaluate the clinical outcomes of EX and OAMs in anterior cervical spine surgery using a meta-analysis and to provide the latest clinical evidence.

METHODS

PubMed, Embase, Cochrane Library, Web of Science, CNKI, and Wanfang Database were systematically reviewed for relevant literature published prior to January 21, 2023. Two researchers independently screened the literature, extracted data, and assessed bias risk in the included literature. Review Manager software (version 5.4; the Cochrane Collaboration) was used to conduct the meta-analysis.

RESULTS

five studies, one prospective and four retrospective cohort studies, with a total of 349 patients (154 in the EX group and 195 in the OAMs group) were included. A meta-analysis showed that compared to OAMs, EX-assisted anterior cervical spine surgery resulted in less intraoperative hemorrhage [WMD = -8.96, 95% CI (-14.21, -3.71), P = 0.0008]. Nevertheless, no significant differences in VAS scores, JOA scores, operation time, hospitalization time, and complication rate were observed between the two groups (P > 0.05).

CONCLUSION

EX and OAMs are equally safe and effective for anterior cervical spine surgery; however, compared to OAMs, EX results in less intraoperative hemorrhage.

Anatomical Consideration for Anterior Approach of Cervicothoracic Junction: A Computed Tomography Image Analysis

Background

In the cervicothoracic junction (CTJ), there is limited working space to perform the posterior-only approach. Therefore, a combined anterior approach is required in some cases. However, the great vessels and sternum obstruct the anterior corridor and make the anterior approach difficult. We analyzed relevant anatomical structures encountered during the anterior approach in the CTJ and evaluated the feasibility of previously reported surgical corridors.

Methods

We retrospectively examined 49 patients who underwent neck computed tomography angiography between January 2015 and May 2020. Using the coronal images, we measured the intercarotid artery angle (ICAA), intercarotid artery distance (ICAD), shape of the brachiocephalic trunk (BCT), and position of the BCT base. We then measured the most cranial level requiring manubriotomy for the anterior approach (ML), the most caudal level accessible through the superior corridor (SC), and the most caudal level through the inferior corridor (IC) according to the surgeon's line of sight using the sagittal axis image.

Results

The mean ICAA and ICAD were 50.83° ± 15.23° and 33.38 ± 12.11 mm, respectively. Notably, BCT shape was of the convex type in most cases (42.9%), followed by the straight type (36.7%). In addition, the base of BCT was most commonly located inside the body (49%). Moreover, ICAA and ICAD were significantly greater in men. Although men mostly had the BCT base inside the body (64.3%), female mostly had it on the edge of the body (47.6%). Notably, ML showed the highest frequency (16.3%) in the T1 lower and upper bodies. Furthermore, through SC and IC, it was possible to approach the T4 lower body and T6 midbody, respectively. SC showed the highest frequency (16.3%) in the T3 lower body, and IC showed the highest frequency (20.4%) in the T5 midbody.

Conclusions

ICAA and ICAD were larger and higher in men. BCT was convex and located inside the body in most cases. The accessible level of ML, SC, and IC were T1, T3, and T5, respectively. For the anterior approach in the CTJ, preoperative vascular and accessible level analysis of corridors is essential to decide on the appropriate corridor and reduce complications.

Incidence of vertebral artery injury in patients undergoing cervical spine trauma surgery in correlation with surgical approach: A review

Spinal cord injuries at the cervical spine level represent the most consequential of the related injuries at all levels of the spine. They can trigger permanent unilateral or bilateral damage with conspicuous disability. Regarding unstable injuries, the gold standard approach is open reduction and osteosynthesis, which can select between anterior and posterior surgical access. Each of the aforementioned approaches demonstrates both advantages and disadvantages; thus, it is up to the surgeon to determine the optimal option concerning the patient's safety. Diligent intraoperative control of anatomical reduction is pivotal to obtaining the best feasible postoperative outcomes. Literature data delineate copious complications following surgical intervention in the cervical spine. Indubitably, the most crucial intraoperative complication accounts for vascular injuries, with the most preponderant being the corrosion of the vertebral artery, as it is potentially life-threatening. This paper aims to provide a succinct and compendious review of the existing literature regarding cervical spinal cord injuries and to deduce many inferences concerning the incidence of iatrogenic vertebral artery injuries in relation to the surgical approach for fracture reduction.

Identification of Deep Cervical Fascial Layers During Anterior Cervical Spine Exposure

BACKGROUND

Anterior approaches to the cervical spine are among the most common exposures by which neurosurgeons and orthopedic surgeons access the prevertebral space and ultimately the cervical disk and vertebral bodies. There is a paucity of literature describing the microanatomic fascial planes of the neck with respect to anterior cervical approaches.

OBJECTIVE

To delineate the microanatomic connections of the cervical fascial planes pertinent to anterior cervical exposure.

METHODS

Using a cadaveric model, original illustrations, the Visible Human Project, and an original surgical video, we demonstrate a stepwise method for identifying the correct planes for anterior cervical exposure.

RESULTS

A step-by-step method for identifying the anterior cervical fascial planes intraoperatively is demonstrated.

CONCLUSION

A comprehensive understanding of anterior cervical microsurgical anatomy is vital for performing a methodical yet efficient approach to the prevertebral space while minimizing retraction and iatrogenic injury to the surrounding neurovascular structures.

Incidence and local risk factors of infection after anterior sub-axial cervical spine surgery: retrospective database analysis of 4897 consecutive procedures

INTRODUCTION

The anterior cervical spine approach is safe and effective in many cervical spine pathologies. It is considered one of the most common approaches in spine surgery. Postoperative infections after anterior cervical surgery are rare but serious.

MATERIALS AND METHODS

This study is a retrospective database analysis. In this study, the incidence, and the local risk factors of postoperative infection after anterior-only sub-axial cervical spine surgery in a high-volume spine center were analyzed. The data of patients operated in a teaching hospital is electronically stored in a comprehensive medical database program. Postoperative infection after anterior cervical surgery from C2 to C7 was calculated and analyzed. In the study period, 4897 patients were operated. Twenty-four infections after a primary aseptic operation were detected. Independent local risk factors were estimated.

RESULTS

Postoperative infection occurred in 24/4897 patients (0.49%). The incidence of infection after cervical trauma was 3% (7/229), after spinal cord injury 4.3% (2/46), with myelopathy 1.98% (11/556), and after revision surgery 1.25% (7/560). The incidence showed a significant increase (p = 0.00, 0.01, 0.02). In 14 of the postoperatively infected patients (58.3%) an oesophageal injury was diagnosed. Odds ratios (OR) with a confidence interval (CI) of 95% was calculated. Independent risk factors for the postoperative infections were: Cervical trauma (OR 8.59, 95% CI 3.52-20.93), revision surgery (OR 3.22, 95% CI 1.33-7.82), The presence of cervical myelopathy (OR 6.71, 95% CI 2.99-15.06), and spinal cord injury (OR 9.33, 95% CI 2.13-40.83).

CONCLUSIONS

Postoperative infection after anterior cervical surgery is low (0.49%). In addition to the general risk factor for infection, the local risk factors are trauma, myelopathy, spinal cord injury, and revision surgeries. In the case of postoperative infection, an oesophageal injury should be excluded.

Critical analysis of the evaluation of postoperative dysphagia following an anterior cervical discectomy and fusion

BACKGROUND AND PURPOSE

Postoperative dysphagia is a known complication of anterior cervical discectomy and fusion (ACDF) with reported incidences ranging from 1 to 79%. No standardized guidelines exist for spine surgeons to evaluate postoperative dysphagia after ACDF. A systematic method may be beneficial in distinguishing transient postoperative dysphagia secondary to intubation from those with postoperative complications. This study evaluates the causes, recognition, and clinical evaluation of postoperative dysphagia following ACDF.

METHODS

International classification of disease (ICD) and current procedural terminology (CPT) codes were used to identify ACDF patients and compared to anterior lumbar discectomy and fusion (ALDF), serving as a control group, between the years 2015-2019 and those diagnosed with dysphagia within 1 year. Demographics, operative details, and clinical evaluation were reviewed. Exclusion criteria included history of head and neck procedures, cancer, stroke, radiation, and trauma.

RESULTS

One hundred thirty-one ACDF and 93 ALDF patients met inclusion criteria. Twenty-seven (20.6%) ACDF patients were diagnosed with dysphagia within 1 year. Less than half of the dysphagia patients had the word "dysphagia" documented in their 1-month spine surgeon follow up visit. Only 66% of dysphagia patients had specialist evaluation and one third of those patients were referred by their surgeon. Only six patients received diagnostic barium swallow evaluations.

CONCLUSION

Postoperative dysphagia risk increases in ACDF compared to ALDF, likely due to underlying anatomy. Postoperative dysphagia symptoms are not effectively documented by spine surgeons and as a result underevaluated by dysphagia specialists. Patients may benefit from more extensive pre- and post-operative screening, evaluation, and referral regarding dysphagia symptoms following ACDF.

Cervical disc arthroplasty at C2–3: illustrative case

BACKGROUND

Since the beginning of the 21st century, cervical disc arthroplasty (CDA) has been accepted as an alternative to anterior cervical discectomy and fusion for surgical management of disc problems. The published clinical trials of CDA have included patients with radiculopathy or myelopathy caused by one- or two-level disc herniation at C3–7. However, it remains uncertain whether CDA is a viable option for C2–3 disc herniation.

OBSERVATIONS

In this report, a 52-year-old man presented with hand numbness, arm pain, and myelopathic symptoms that were refractory to medical treatment for more than 6 months. The magnetic resonance images demonstrated herniated discs at C2–3, C3–4, and C4–5, causing stenosis. There was no ossification of posterior longitudinal ligament and the spine was mobile, so he received anterior discectomies with artificial disc replacement at each of the C2–3, C3–4, and C4–5 levels. The surgery went smoothly, and his neurological symptoms were promptly relieved. The postoperative radiographs at 24 months demonstrated a preserved range of motion at each level.

LESSONS

To date, this was the first report of CDA performed at C2–3, which also involved three consecutive levels of disc replacement. The report suggested that both C2–3 and three-consecutive-level CDA may be a viable option for cervical disc disease.

Cervical Oblique Corpectomy: Revitalizing the Underused Surgical Approach With Step-By-Step Simulation in Cadavers

ABSTRACT

Recently, the World Federation of Neurosurgical Societies Spine committee recommended that additional research on cost-benefit analysis of various surgical approaches for cervical spondylotic myelopathy be carried out and their efficacy with long-term outcomes be compared. Unfortunately, it is highly probable that the oblique corpectomy (OC) will not be included in cost-benefit investigations due to its infrequent application by neurosurgeons dealing with the spine. In this cadaveric study, head and necks of 5 adult human cadavers stained with colored latex and preserved in 70% alcohol solution were dissected under a table-mounted surgical microscope using 3× to 40× magnifications. The OC approach was performed to simulate real surgery, and the neurovascular structures encountered during the procedure and their relations with each other were examined. Oblique corpectomy was performed unilaterally, although neck dissections were performed bilaterally on 10 sides in all 5 cadavers. At each stage of the dissection, multiple three-dimensional photographs were obtained from different angles and distances. For an optimal OC, both the anterior spinal cord must be sufficiently decompressed and sufficient bone must be left in place to prevent instability in the cervical spine. Oblique corpectomy is a valid and potentially low cost alternative to other anterior and posterior approaches in the surgical treatment of cervical spondylotic myelopathy. However, meticulous cadaver studies are essential before starting real surgical practice on patients in order to perform it effectively and to avoid the risks of the technique.

The Smith-Robinson Approach to the Subaxial Cervical Spine: A Stepwise Microsurgical Technique Using Volumetric Models From Anatomic Dissections

BACKGROUND

The Smith-Robinson1 approach (SRA) is the most widely used route to access the anterior cervical spine. Although several authors have described this approach, there is a lack of the stepwise anatomic description of this operative technique. With the advent of new technologies in neuroanatomy education, such as volumetric models (VMs), the understanding of the spatial relation of the different neurovascular structures can be simplified.

OBJECTIVE

To describe the anatomy of the SRA through the creation of VMs of anatomic dissections.

METHODS

A total of 4 postmortem heads and a cervical replica were used to perform and record the SRA approach to the C4-C5 level. The most relevant steps and anatomy of the SRA were recorded using photogrammetry to construct VM.

RESULTS

The SRA was divided into 6 major steps: positioning, incision of the skin, platysma, and muscle dissection with and without submandibular gland eversion and after microdiscectomy with cage positioning. Anatomic model of the cervical spine and anterior neck multilayer dissection was also integrated to improve the spatial relation of the different structures.

CONCLUSION

In this study, we review the different steps of the classic SRA and its variations to different cervical levels. The VMs presented allow clear visualization of the 360-degree anatomy of this approach. This new way of representing surgical anatomy can be valuable resources for education and surgical planning.

Vertigo caused by longus colli tendonitis: A case report and literature review

RATIONALE

Tendinitis of the longus colli muscle is an aseptic inflammatory process leading to acute posterior neck pain, neck stiffness, and dysphagia or odynophagia. We present a patient exhibiting an infrequent symptom, vertigo. This is the first description of the occurrence of vertigo symptoms caused by longus colli tendinitis.

PATIENT CONCERNS

A 38-year-old man was diagnosed with vertigo, presenting with a 1-month history of dizziness, palpitations, and numbness in the hands.

DIAGNOSIS

Longus colli tendinitis. The diagnosis was established using magnetic resonance imaging fat-suppression sequences.

INTERVENTIONS

Treatment with corticosteroid injections and acupotomy.

OUTCOMES

The symptoms relieved immediately after the treatment and complete resolution of the symptoms was observed after 1 week.

LESSONS

Longus colli tendinitis with vertigo is an under-reported condition in the literature and physicians should be aware of its existence. A lack of familiarity with the anatomy of the prevertebral space and its variable radiographic appearance makes the diagnosis of longus colli tendinitis clinically difficult. Misdiagnosis of this condition may lead to unnecessary interventions in vertigo.

Surgical Landmark of Mandible Angle in the Identification of Cervical Spinal Level

Mandible angle is considered to be a consistently palpable external landmark for the identification of cervical spinal level by a radiographic study. But this anatomical study aimed to determine the positional relationship between mandible angle and cervical spinal level in cadavers. In this study, the cervical spine of 10 adult cadavers with intact head and neck structure, including 6 males and 4 females, was dissected, and the position of mandible angle (MA) relative to the corresponding cervical spinal level was measured when the head was fixed in the flexion, anatomy position, and extension. The difference between the genders and the sides was analyzed. On the basis of the study of the corpse samples, the reference level of cervical spine was approximated to C2/3 intervertebral disc. The result has confirmed MA as a consistent and convenient landmark in the identification of cervical spinal level. Given some external landmarks do not consistently correspond to the exact level of the cervical spine, MA provides the relatively consistent reference point: C2/3 intervertebral disc. The authors hold that MA is a superior external landmark, which can help surgeons to localize the skin incision before anterior cervical spine surgery.

Rhabdomyolysis resulting in concurrent Horner's syndrome and brachial plexopathy: a case report

This case report describes a 29-year-old male who presented with immediate onset of Horner's syndrome and ipsilateral brachial plexopathy after sleeping with his arm dangling outside a car window for 8 h. Outside workup and imaging revealed rhabdomyolysis of the left neck musculature. Subsequent electrodiagnostic testing and high-resolution brachial plexus magnetic resonance imaging at the authors' institution attributed the Horner's syndrome and concurrent brachial plexopathy to rhabdomyolysis of the longus colli and scalene musculature, which had compressed-and consequently scar tethered-the cervical sympathetic trunk and brachial plexus. This case of co-existent Horner's syndrome and brachial plexopathy demonstrates the role of high-resolution brachial plexus MRI in diagnosing plexopathy and the importance of being familiar with plexus and paravertebral muscle anatomy.

Anatomic Relationship Between Right Recurrent Laryngeal Nerve and Cervical Fascia and Its Application Significance in Anterior Cervical Spine Surgical Approach

STUDY DESIGN

An anatomic study of anterior cervical dissection of 42 embalmed cadavers.

OBJECTIVE

The aim was to study the anatomic relationship between recurrent laryngeal nerve (RLN) and cervical fascia combined with the requirements in anterior cervical spine surgery (ACSS).

SUMMARY OF BACKGROUND DATA

There has been no systematic research about how to avoid RLN injury in anterior cervical spine surgical approach from the aspect of the anatomic relationship between RLN and cervical fascia.

METHODS

Forty-two adult cadavers were dissected to observe the relationships between RLN and different cervical fascia layers.

RESULTS

RLN pierced out the alar fascia from the inner edge of the carotid sheath in all cases, and the piercing position in 22 cases (52.4%) was located at the lower segment of T1. The enter point into visceral fascia of RLN was located at C7-T1 in 25 cases (59.5%). The middle layer of deep cervical fascia exhibited the most stable anatomic relationship with RLN at the carotid sheath confluence site. Pulling visceral sheath leftwards would significantly increase the RLN tension.

CONCLUSION

Using the close and stable relationship between RLN and cervical fascia could help to avoid RLN injury in anterior cervical spine surgical approach.

LEVEL OF EVIDENCE

4.

Rare Complications of Cervical Spine Surgery: Horner's Syndrome

STUDY DESIGN

A multicenter retrospective case series.

OBJECTIVE

Horner's syndrome is a known complication of anterior cervical spinal surgery, but it is rarely encountered in clinical practice. To better understand the incidence, risks, and neurologic outcomes associated with Horner's syndrome, a multicenter study was performed to review a large collective experience with this rare complication.

METHODS

We conducted a retrospective multicenter case series study involving 21 high-volume surgical centers from the AOSpine North America Clinical Research Network. Medical records for 17 625 patients who received subaxial cervical spine surgery from 2005 to 2011 were reviewed to identify occurrence of 21 predefined treatment complications. Descriptive statistics were provided for baseline patient characteristics. Paired t test was used to analyze changes in clinical outcomes at follow-up compared to preoperative status.

RESULTS

In total, 8887 patients who underwent anterior cervical spine surgery at the participating institutions were screened. Postoperative Horner's syndrome was identified in 5 (0.06%) patients. All patients experienced the complication following anterior cervical discectomy and fusion. The sympathetic trunk appeared to be more vulnerable when operating on midcervical levels (C5, C6), and most patients experienced at least a partial recovery without further treatment.

CONCLUSIONS

This collective experience suggests that Horner's syndrome is an exceedingly rare complication following anterior cervical spine surgery. Injury to the sympathetic trunk may be limited by maintaining a midline surgical trajectory when possible, and performing careful dissection and retraction of the longus colli muscle when lateral exposure is necessary, especially at caudal cervical levels.

A Multicenter Review of Superior Laryngeal Nerve Injury Following Anterior Cervical Spine Surgery

STUDY DESIGN

A retrospective multicenter case-series study; case report and review of the literature.

OBJECTIVE

The anatomy and function of the superior laryngeal nerve (SLN) are well described; however, the consequences of SLN injury remain variable and poorly defined. The prevalence of SLN injury as a consequence of cervical spine surgery is difficult to discern as its clinical manifestations are often inconstant and frequently of a subclinical degree. A multicenter study was performed to better delineate the risk factors, prevalence, and outcomes of SLN injury.

METHODS

A retrospective multicenter case-series study involving 21 high-volume surgical centers from the AO Spine North America Clinical Research Network. Medical records for 17 625 patients who received subaxial cervical spine surgery from 2005 to 2011 were reviewed to identify occurrence of 21 predefined treatment complications. Descriptive statistics were provided for baseline patient characteristics. A retrospective review of the neurosurgical literature on SLN injury was also performed.

RESULTS

A total of 8887 patients who underwent anterior cervical spine surgery at the participating institutions were screened, and 1 case of SLN palsy was identified. The prevalence ranged from 0% to 1.25% across all centers. The patient identified underwent a C4 corpectomy. The SLN injury was identified after the patient demonstrated difficulty swallowing postoperatively. He underwent placement of a percutaneous gastrostomy tube and his SLN palsy resolved by 6 weeks.

CONCLUSIONS

This multicenter study demonstrates that identification of SLN injury occurs very infrequently. Symptomatic SLN injury is an exceedingly rare complication of anterior cervical spine surgery. The SLN is particularly vulnerable when exposing the more rostral levels of the cervical spine. Careful dissection and retraction of the longus coli may decrease the risk of SLN injury during anterior cervical surgery.

Surface Landmarks do not Correspond to Exact Levels of the Cervical Spine: References According to the Sex, Age and Height

Objective

A general orientation along the cervical spine could be estimated by external landmarks, and it was useful, quick and less exposable to radiation, but, sometimes it gave reference confusion of target cervical level. The authors reviewed the corresponding between the neck external landmarks and cervical levels.

Methods

Totally 1,031 cervical lateral radiographs of different patients were reviewed in single university hospital. Its compositions were 534 of males and 497 females; 86 of second decades (10-19 years-old), 169 of third decades, 159 of fourth decades, 209 of fifth decades, 275 of sixth decades, and 133 of more than seventh decades (>60 years-old). Reference external landmarks (mandible, hyoid bone, thyroid cartilage, and cricothyroid membrane) with compounding factors were reviewed.

Results

The reference levels of cervical landmarks were C2.13 with mandible angle, C3.54 with hyoid bone, C5.12 with thyroid cartilage, and C6.01 with cricothyroid membrane. The reference levels of cervical landmarks were differently observed by sex, age, and somatometric measurement (height) accordingly mandible angle from C1 to C3, hyoid bone from disc level of C2 and C3 to C5, thyroid cartilage from disc level of C3 and C4 to C7, and cricothyroid membrane from C4 to disc level of C7 and T1.

Conclusion

Surface landmarks only provide general reference points, but not correspond to exact levels of the cervical spine. Intraoperative fluoroscopy ensures a more precise placement to the targeted cervical level.

Probabilistic mapping of the cervical sympathetic trunk ganglia

The goal of this study was to create a heat map indicating the probabilistic location of major ganglia of the cervical sympathetic trunk (CST). Detailed dissections of human cadaveric specimens, followed by spatial registration and analysis of the cervical sympathetic ganglia in the neck and upper thorax regions (C1-T1) were performed in 104 neck specimens (both sides from 52 cadavers). Unbiased parametric mapping, visualized with a heat map, revealed a general pattern of two major ganglia located on both sides of the neck: The superior cervical ganglion (SCG) was located 80-90 mm superior to the point at which the vertebral artery entered the transverse foramen (VA-TF); the stellate ganglion (SG) was located approximately 10 mm inferior to the VA-TF in 80% of our sample, or surrounding the VA-TF in the remaining 20% of our sample. In between these ganglia, a highly variable number of smaller and less prevalent ganglia were present on either side of the neck. The middle ganglia on the right side of the neck were located closer to the SCG, possibly indicative of the middle cervical ganglion. On the left side the middle ganglia were located closer to the SG, perhaps indicative of the vertebral ganglion or the inferior cervical ganglion. Individual specimens could be classified into one of seven different patterns of cervical trunks. The results may help surgeons and anesthesiologists more accurately target and preserve these structures during medical procedures.

How to reduce recurrent laryngeal nerve palsy in anterior cervical spine surgery: a prospective observational study

BACKGROUND

Recurrent laryngeal nerve palsy (RLNP) occurs as a complication during anterior cervical spine surgery. In 2005 the authors demonstrated the high incidence of asymptomatic RLNP in a right-sided approach.

OBJECTIVE

This follow-up prospective observational study was designed to test 2 options said to reduce the rate of RLNP: reduced endotracheal cuff pressure and sinistral approach.

METHODS

Two hundred forty-two patients in whom anterior cervical spine surgery was performed were examined postoperatively with indirect laryngoscopy to evaluate the status of the vocal cords. All patients had a left-sided approach but 1 group (A, 149 patients) was operated on with an additional reduction of endotracheal cuff pressure to below 20 mm Hg. In 93 patients we could not reduce the cuff pressure. This group served as a control group (B). Both groups were compared with a historic control group with a right-sided approach and no cuff pressure reduction. In cases of vocal cord malfunction a follow-up examination was done 3 months later.

RESULTS

Group A (low cuff pressure) had a total rate of persisting symptomatic and asymptomatic RLNP of 1.3% and group B had a rate of 6.5% (normal cuff pressure). Compared with the historic study (N = 120) with a right-sided approach and a total rate of persisting RLNP of 13.3% in the left-sided approach, a marked reduction to 6.5% and 1.3% with an additional reduction of cuff pressure was seen.

CONCLUSION

The left-sided approach in anterior cervical spine surgery reduces the incidence of postoperative and permanent RLNP significantly. Endotracheal cuff pressure reduction used additionally decreases the rate of RLNP even more. These results indicate that anterior cervical spine surgery should be performed with a left-sided approach and, if possible, with an additional reduction of the endotracheal cuff pressure while the retractors are inserted.

Anatomical anomalies of the laryngeal branches of the vagus nerve in pigs (Sus scrofa)

To delineate the anomaly and frequency of their occurrence in a pig model, we reported the topography of the vagus laryngeal branches and compared the differences with humans. Thirty sides of cervical vagus nerve in 15 fresh cadavers (Sus scrofa) were microdissected. We measured the branch diameters and lengths of the laryngeal branches using a Vernier caliper with a resolution of 0.01 mm. Two patterns of the vagus laryngeal branches were shown: 56.7% with the cranial laryngeal nerve (CLN) and 43.3% without the CLN. The diameters and the length of the CLN were not affected by the side of the neck (P > 0.05), but the diameters of the recurrent laryngeal nerve (RLN) and the nodose ganglion were significantly different between left and right sides (P < 0.05). The left RLN was thinner than the right side in diameter (P < 0.05). Four of the 30 sides had anastomoses between the vagus and the cervical sympathetic chain. There were some differences between the pig anatomy and human anatomy, but the patterns were largely similar. The similarities support the utility of this model, which is closer in size to humans than the standard rodent models.

Bilateral internal superior laryngeal nerve palsy of traumatic cervical injury patient who presented as loss of cough reflex after anterior cervical discectomy with fusion

Injury to the bilateral internal branch of superior laryngeal nerve (ibSLN) brings on an impairment of the laryngeal cough reflex that could potentially result in aspiration pneumonia and other respiratory illnesses. We describe a patient with traumatic cervical injury who underwent bilateral ibSLN palsy after anterior cervical discectomy with fusion (ACDF). An 75-year-old man visited with cervical spine fracture and he underwent ACDF through a right side approach. During the post-operative days, he complained of high pitched tone defect, and occasional coughing during meals. With a suspicion of SLN injury and for the work up for the cause of aspiration, we performed several studies. According to the study results, he was diagnosed as right SLN and left ibSLN palsy. We managed him for protecting from silent aspiration. Swallowing study was repeated and no evidence of aspiration was found. The patient was discharged with incomplete recovery of a high pitched tone and improved state of neurologic status. The SLN is an important structure; therefore, spine surgeons need to be concerned and be cautious about SLN injury during high cervical neck dissection, especially around the level of C3-C4 and a suspicious condition of a contralateral nerve injury.

Operative techniques for cervical radiculopathy and myelopathy

The surgical treatment of cervical spondylosis and resulting cervical radiculopathy or myelopathy has evolved over the past century. Surgical options for dorsal decompression of the cervical spine includes the traditional laminectomy and laminoplasty, first described in Asia in the 1970's. More recently the dorsal approch has been explored in terms of minimally invasive options including foraminotomies for nerve root descompression. Ventral decompression and fusion techniques are also described in the article, including traditional anterior cervical discectomy and fusion, strut grafting and cervical disc arthroplasty. Overall, the outcome from surgery is determined by choosing the correct surgery for the correct patient and pathology and this is what we hope to explain in this brief review.

Dysphagia after anterior cervical spine surgery: incidence and risk factors

OBJECTIVE

To evaluate risk factors for the development of dysphagia after anterior cervical surgery.

METHODS

The records of 249 patients who underwent anterior cervical surgery were reviewed. The presence and severity of dysphagia were assessed with the Dysphagia Disability Index 6 weeks and 3, 6, and 12 months after surgery. Age; sex; ethnicity; cigarette smoking; previous cervical surgeries; reoperation for same pathology; type of procedure, incision, and instrumentation; number and levels involved; side of procedure, length of surgery; and use of postoperative bracing were analyzed.

RESULTS

During the first 6 months after surgery, 27 (10.8%) patients developed dysphagia. From these patients the presence of dysphagia at 6 weeks and at 3 and 6 months was 88.8%, 29.6%, and 7.4%, respectively. By 12 months, dysphagia had resolved in all cases. The mean age of patients with dysphagia was 55 years (SD 12.98) and 50 years (SD 12.07) in patients without dysphagia (P = 0.05). Dysphagic patients had an average of 2.2 (SD 1.15) levels operated compared with 1.84 (SD 0.950) in nondysphagic patients (P = 0.05). Patients who developed dysphagia were most often treated at C4-5 (67%) and C5-6 (81%: P < 0.001). Although mean operative time was slightly longer in patients with dysphagia (186 minutes) compared with those without (169 minutes), the difference was not significant.

CONCLUSIONS

In our patients, the incidence of dysphagia was low, and it had completely resolved at 12 months in all cases. Risk factors for dysphagia were multilevel procedures, involvement of C4-5 and C5-6, and age.

Anterior fixation of odontoid fractures in an elderly population

OBJECT

Fractures of the odontoid process are the most common fractures of the cervical spine in patients over the age of 70 years. The incidence of fracture nonunion in this population has been estimated to be 20-fold greater than that in patients under the age of 50 years if surgical stabilization is not used. Anterior and posterior approaches have both been advocated, with excellent results reported, but surgeons should understand the drawbacks of the various techniques before employing them in clinical practice.

METHODS

A retrospective review was undertaken to identify patients who had direct fixation of an odontoid fracture at a single institution from 1991 to 2006. Patients were followed up using flexion-extension radiographs, and stability was evaluated as bone union, fibrous union, or nonunion. Patients with bone or fibrous union were classified as stable. In addition, the incidence of procedure- and nonprocedure-related complications was extracted from the medical record.

RESULTS

Of the 57 patients over age 70 who underwent placement of an odontoid screw, 42 underwent follow-up from 3 to 62 months (mean 15 months). Stability was confirmed in 81% of these patients. In patients with fixation using 2 screws, 96% demonstrated stability on radiographs at final follow-up. Only 56% of patients with fixation using a single screw demonstrated stability on radiographs. In the immediate postoperative period, 25% of patients required a feeding tube and 19% had aspiration pneumonia that required antibiotic treatment.

CONCLUSIONS

Direct fixation of Type II odontoid fractures showed stability rates > 80% in this challenging population. Significantly higher stabilization rates were achieved when 2 screws were placed. The anterior approach was associated with a relatively high dysphagia rate, and patients must be counseled about this risk before surgery.

Neuroanatomy of cervical sympathetic trunk: a cadaveric study

To reduce the risk of iatrogenic injury to sympathetic chain during anterior and anterolateral approaches to the cervical spine, its location has to be well defined and known by surgeons. We analyzed the course of sympathetic chain and its ganglia from C7 up to its entry into the cranial base and its relationship mainly with the longus colli (LC). Formalin fixed 20 human cadavers were dissected under operating microscope. Measurement of the dimensions of the ganglia, distance of the trunk to the LC, and the angles identifying the course of the chain were performed. Superior and inferior cervical/cervicothoracic ganglion were observed in all specimens, the middle cervical ganglion was observed in 48% of the specimens. The middle ganglion consisted of two ganglia in 10% of the dissected sides. Forty percent of the inferior cervical/cervicothoracic ganglion was at the C7 level, 25% was at C7-Th1 disc level, and 35% was at Th1 level. Vertebral ganglion was detected in only 8% of the specimens. The course of the sympathetic trunk converges medially descending from upper cervical levels to the lower levels. Anterior surgical approach to the cervical spine is a commonly used procedure. Although Horner syndrome due to sympathetic injury is not a common sequence of cervical operations, our findings support the current few reports on the subject and should be useful to any surgeon who operates in the cervical region to avoid this uncommon complication.

Submandibular approach to the C2–3 disc level: microsurgical anatomy with clinical application

Object

Approaching the C2–3 disc level is challenging because of its location behind the mandible and the vital neurovascular structures overlying the area. The purpose of this study was to illustrate in a stepwise fashion the microsurgical anatomy of the submandibular approach to the C2–3 disc.

Methods

Ten adult formalin-fixed cadaveric specimens (20 sides) were studied. Particular attention was paid to the structures limiting the exposure. The authors measured the distance between the inferior border of the mandible and the marginal mandibular branch of the facial nerve running inferior to the mandible, the distance between the horizontal segment of the hypoglossal nerve and the hyoid bone, and the distance between the horizontal segment of the hypoglossal nerve and the mandible. They compared the location of the superior laryngeal nerve with regard to the submandibular and the standard Smith-Robinson approaches. A clinical case illustrating the usefulness of the surgical technique in this region is presented.

Results

The mean distance between the inferior border of the mandible and the lowest point of the marginal mandibular branch of the facial nerve was 6.7 ± 1.69 mm. The hypoglossal nerve's mean distance above the hyoid bone was 8.4 ± 1.78 mm and below the mandible was 19.6 ± 6.39 mm. The internal branch of the superior laryngeal nerve, with respect to the cervical spine, always entered the thyrohyoid membrane just inferior to the C-3 vertebral body. The superior laryngeal nerve was found to be an impediment to approaching the C2–3 disc through the standard Smith-Robinson approach.

Conclusions

The submandibular approach provides excellent exposure, with a perpendicular view of the C2–3 disc level. This approach is one of the options to be considered when dealing with high cervical pathologies.

Cervical corpectomy and strut grafting

Cervical corpectomy and strut grafting is a deceptively simple procedure that has been performed for many years for a variety of cervical spine disorders (infection, neoplastic disease, and trauma) but most commonly for cervical spondylosis. The procedure requires attention to detail to ensure adequate decompression of the neural structures and avoiding injury to the soft tissues of the neck and the vertebral artery in the transverse foramina. The following description of the technique is one we have successfully used for cervical corpectomy and strut grafting. We also discuss patient selection criteria, avoidance of common complications, and postoperative management.

Ansa cervicalis as a variant of spinal accessory nerve plexus: a case report

The ansa cervicalis is a neural loop in the neck formed by the union of two main nerve roots, namely superior and inferior roots, derived from ventral rami of the cervical nerves. With the expanding use of the ansa cervicalis for reinnervation procedures and the fact that it is located in the vicinity of major nerves and vessels of the neck, knowledge of the topography and morphology of this loop is quite necessary in the modern era. Any variation in the course, contributing roots or branching pattern of the ansa cervicalis, potentially alters and perhaps complicates the course of the procedures involving this nerve such as neurorrhaphy, skull base surgery, neck dissection, and anterior cervical spinal approach. Here, we present an unusual case of an ansa cervicalis encountered upon routine dissection of an adult male cadaver. In this case, the inferior root of the ansa cervicalis was formed by the joining of two rootlets, one originating from spinal accessory nerve and the other from a branch of the cervical plexus to the sternocleidomastoid muscle. The fibers traversing the branch of spinal accessory nerve were derived from the first segments of the cervical spinal cord. This case demonstrates a variant of the spinal accessory nerve plexus that contributed to the formation of the ansa cervicalis. Review of the literature was performed to reveal the possible clinical aspects of this anatomical variation.

Surgical anatomy of the cervical sympathetic trunk

Lack of knowledge of the anatomy of the cervical sympathetic trunk (CST) may complicate surgical procedures on the cervical spine. This study aims to define linear and angular relations of the CST with respect to consistent structures around it, including the number and size of the cervical ganglia, the distances between the CST and the longus colli muscle and the anterior tubercles of the transverse processes of cervical vertebrae. Morphometric parameters of the 24 CSTs of 12 adults were measured on both sides. The CST had superior, middle, and inferior (or cervicothoracic) ganglia in 20.8% of specimens; superior and inferior (or cervicothoracic) ganglia in 45.8%; superior, middle, vertebral, inferior, or cervicothoracic ganglia in 12.5%, and superior, vertebral, inferior or cervicothoracic ganglia in 20.8% of specimens. The superior ganglion was observed in all specimens, the middle ganglion and vertebral ganglion were each observed in 33.3%. There was no difference between the number of superior and vertebral ganglia between the right and left sides. The average distance between the CST and the medial border of the ipsilateral longus colli muscle (LCM) was 17.2 mm at C3 and 12.4 mm at C7. As the CSTs converged caudally, the LCMs diverged. The average distance between the anterior tubercles of transverse processes of the cervical vertebrae and the lateral borders of the ipsilateral CST was 3.4 mm at C4, 3.2 mm at C5, and 3.9 mm at C6. The presence of a vertebral ganglion and variations, such as the localization of the CST within the carotid sheath, are important. The anatomical landmarks described should assist the spinal surgeon to avoid injury of the CST.

Recurrent laryngeal nerve palsy during anterior cervical spine surgery: a prospective study

Object. Recurrent laryngeal nerve (RLN) palsy is a well-known complication of cervical spine surgery. Nearly all previous studies were performed without laryngoscopy in asymptomatic patients. This prospective study was undertaken to discern the true incidence of RLN palsy. Because not every RLN palsy is associated with hoarseness, the authors conducted a prospective study involving the use of pre- and postoperative laryngoscopy.

Methods. Prior to anterior cervical spine surgery preoperative indirect laryngoscopy was performed in 123 patients to evaluate the status of the vocal cords as a sign of function of the RLN. To assess postoperative status in 120 patients laryngoscopy was repeated, and in cases of vocal cord malfunction follow-up examination was conducted 3 months later.

In the group of 120 patients who attended follow-up examination, two (1.6%) had experienced a preoperative RLN palsy without hoarseness. Postoperatively the rate of clinically symptomatic RLN palsy was 8.3%, and the incidence of RLN palsy not associated with hoarseness (that is, clinically unapparent without laryngoscopy) was 15.9% (overall incidence 24.2%). At 3-month follow-up evaluation the rate had decreased to 2.5% in cases with hoarseness and 10.8% without hoarseness. Thus, the overall rate of early persisting RLN palsy was 11.3%.

Conclusions. Laryngoscopy revealed that the true incidence of initial and persisting RLN palsy after anterior cervical spine surgery was much higher than anticipated. Especially in cases without hoarseness this could be proven, but the initial incidence of hoarseness was higher than expected. Only one third of new RLN palsy cases could be detected without laryngoscopy. Resolution of hoarseness was approximately 70% in those with preoperative hoarseness. The true rate of RLN palsy underscores the necessity to reevaluate the surgery- and intubation-related techniques for anterior cervical spine surgery and to reassess the degree of presurgical patient counseling.

Study of some "intrinsic risk factors" that can enhance an iatrogenic injury of the external branch of the superior laryngeal nerve

OBJECTIVE

This study evaluates some "intrinsic risk factors" for a surgical injury of the external branch of superior laryngeal nerve (EBSLN) based on its anatomic relationship with the thyroid gland.

STUDY DESIGN AND SETTING

Seventy-two neck dissections were performed in 36 fresh human adult cadavers. Every EBSLN was dissected and categorized using Cernea's classification. All data regarding gender, ethnicity, stature, side of the neck, and volume of hemi thyroid were collected and statistically analyzed by the chi(2)-test and analysis of variance.

RESULTS

Although no statistical differences were observed between genders (P = 0.3770), ethnicities (P = 0.9780) or sides of the neck (P = 0.2523), statistical significance was reached regarding the nerve type when the groups were divided by stature (P = 0.0006) and glandular volume (P = 0.0007).

CONCLUSION

Individual stature and volume of the hemi thyroid gland are probably involved in risk of the surgical EBSLN injury.

SIGNIFICANCE

Surgeons should be aware of these anatomic findings in order to obtain a good voice-related outcome in the thyroidectomies.

Anatomic considerations of superior laryngeal nerve during anterior cervical spine procedures

STUDY DESIGN

Cadavers were dissected anatomically to identify the course of the superior laryngeal nerve relative to the spinal column.

OBJECTIVE

To illustrate the anatomic relation of the SLN with respect to its vulnerability during anterior cervical spine procedures.

SUMMARY OF BACKGROUND DATA

There is ample literature referencing the superior laryngeal nerve with respect to head and neck surgery. Detailed descriptions of the anatomy of the recurrent laryngeal nerve are quite extensive in both the spine and head and neck literature. To the authors' best knowledge, no similar reports have delineated the anatomic relation of the superior laryngeal nerve in procedures on the anterior aspect of the cervical spine.

METHODS

Ten dissections were carried out on human cadavers to show the course of the superior laryngeal nerve. Particular attention was directed to the internal branch of the superior laryngeal nerve to show the overall anatomic relation relative to standard landmarks. These landmarks included the superior laryngeal and superior thyroid arteries, the split of the superior laryngeal nerve, and the intervertebral disc space.

RESULTS

The superior laryngeal nerve originates from the vagus nerve in the carotid sheath and bifurcates into internal and external branches. Distally, the internal branch of the superior laryngeal nerve courses in close proximity with the superior laryngeal artery and inserts within 1 cm superior to the superior laryngeal artery into the thyrohyoid membrane. With respect to the cervical spine, the distal of portion of the internal branch of the superior laryngeal nerve is located between the C3 and C4 vertebral bodies.

CONCLUSIONS

The internal branch of the superior laryngeal nerve supplies innervation to the mucosa of the larynx and has an important sensory reflex that serves to protect the lungs from aspiration. Injury to this nerve can predispose the patient to life-threatening pneumonia. It is therefore imperative for the surgeon to recognize the location and course of this nerve to avoid injuring it. Injury most commonly occurs either by excessive retraction in different planes or by accidental ligation of the nerve.