Anatomic considerations of superior laryngeal nerve during anterior cervical spine procedures

Surgical landmarks for identification and preservation of the internal branch of the superior laryngeal nerve

OBJECTIVE

To determine the topographical anatomic features of the internal branch of the superior laryngeal nerve (ibSLN) at the thyrohyoid membrane entrance area in relation to certain consistent anatomical structures.

MATERIALS

METHODS: Twenty-two fresh adult head cadavers (9 male, 13 female; age range 52-95 years) with no signs of abnormality in the neck were dissected to determine the anatomic relationship of ibSLN and superior border of thyroid cartilage, thyroid notch, carotid bifurcation, hyoid corpus, and hyoid greater cornu.

RESULTS

The topographical relationship between ibSLN and superior border of thyroid cartilage, thyroid notch, carotid bifurcation, hyoid corpus, and hyoid greater cornu was identified bilaterally in all cadavers. According to the measures, danger zone and safe zone areas for surgical could be predicted and for surgical manipulations as well.

CONCLUSION

We provided the surgical anatomy and important landmarks for determining the internal branch of superior laryngeal nerve in the thyrohyoid membrane entrance region to avoid surgical damage during surgeries of this region.

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.

Anterior Approach to the Subaxial Cervical Spine: Pearls and Pitfalls

Since its introduction by Smith and Robinson, the anterior approach to the subaxial cervical spine has become one of the standard procedures for numerous cervical spine pathologies, including, but not limited to degenerative disease, trauma, tumor, deformity, and instability. Along with its increasing popularity and improvements in anterior instrumentation techniques, a comprehensive knowledge of the surgical anatomy during the anterior exposure is critical for trainees and experienced spine surgeons alike to minimize the infrequent but potentially devastating risks associated with this approach. Understanding the anatomy and techniques to minimize damage to relevant structures can reduce the risks of developing notable postoperative complications and morbidity.

Anatomic and radiologic relationships of neck structures to cervical spine: implications for anterior surgical approaches

The position of the pharyngolaryngeal framework is very important in choosing the best surgical approach for cervical spine disease. The aim of the present paper is to investigate the position of the hyoid bone and cricoid cartilage in relation to the cervical spine. Moreover, the surgical implications for anterior transcervical approaches to the upper spine and the prevertebral space are discussed. To minimise complication rates and increase surgical effectiveness, the location and extent of the cervical spine disease should be evaluated in the context of the patient’s specific anatomy. A retrospective analysis of 100 cervical spine MRIs was conducted. Patients with diseases that could alter anatomic relationships of cervical structures were excluded. The mid-sagittal view of the hyoid and the inferior margin of the cricoid cartilage were projected perpendicularly to the anterior surface of the cervical vertebrae. The distance between these two landmarks was measured on the same view. The distribution of hyoid projections ranged between C2-C3 and C4-C5 intervertebral space, while the cricoid cartilage ranged between C4-C5 and C7-T1 intervertebral spaces. The mean distance between these two landmarks was 49.1 ± 7.7 mm, with statistically significant differences between males and females. The position of the cricoid cartilage significantly influenced the length of the pharyngolaryngeal framework, while the position of hyoid did not. A wide range of variability in the position of the hyoid bone and the cricoid cartilage in relation to cervical levels exists. This implies that an a priori association of a cervical level to neck structures at risk might be inaccurate. The use of these easily identifiable landmarks on pre-operative imaging may help to guide the choice among different anterior surgical approaches to cervical spine and reduce the risk of surgical complications.

Anatomical Variations of the Recurrent Laryngeal Nerve and Implications for Injury Prevention during Surgical Procedures of the Neck

Accurate knowledge of anatomical variations of the recurrent laryngeal nerve (RLN) provides information to prevent inadvertent intraoperative injury and ultimately guide best clinical and surgical practices. The present study aims to assess the potential anatomical variability of RLN pertaining to its course, branching pattern, and relationship to the inferior thyroid artery, which makes it vulnerable during surgical procedures of the neck. Fifty-five formalin-fixed cadavers were carefully dissected and examined, with the course of the RLN carefully evaluated and documented bilaterally. Our findings indicate that extra-laryngeal branches coming off the RLN on both the right and left side innervate the esophagus, trachea, and mainly intrinsic laryngeal muscles. On the right side, 89.1% of the cadavers demonstrated 2–5 extra-laryngeal branches. On the left, 74.6% of the cadavers demonstrated 2–3 extra-laryngeal branches. In relation to the inferior thyroid artery (ITA), 67.9% of right RLNs were located anteriorly, while 32.1% were located posteriorly. On the other hand, 32.1% of left RLNs were anterior to the ITA, while 67.9% were related posteriorly. On both sides, 3–5% of RLN crossed in between the branches of the ITA. Anatomical consideration of the variations in the course, branching pattern, and relationship of the RLNs is essential to minimize complications associated with surgical procedures of the neck, especially thyroidectomy and anterior cervical discectomy and fusion (ACDF) surgery. The information gained in this study emphasizes the need to preferentially utilize left-sided approaches for ACDF surgery whenever possible.

Pharyngo-Esophageal Perforations After Anterior Cervical Spine Surgery: Management and Outcomes

OBJECTIVE

To report about the diagnosis, surgical treatment, and postoperative management of pharyngo-esophageal perforations (PEPs) after anterior cervical spine (ACS) surgery in 17 patients.

METHODS

A retrospective multicenter case series of patients surgically treated for PEP after ACS surgery was performed. Data regarding cervical spine pathology and surgery, comorbidities, diagnosis and surgical management of PEP, airway management, antibiotic therapy, postoperative course, and feeding route after repair surgery at discharge and last follow-up were collected.

RESULTS

Seventeen patients were included in the study, for a total of 22 surgical procedures for PEP repair. Seven PEPs (41%) had early onset, whereas 10 (59%) were delayed. All patients underwent PEP surgical repair through an anterior prevascular retrovisceral cervicotomic approach, consisting of multiple layer sutures of the perforation, with flap interposition. Despite the challenging management of these patients, 16 of 17 patients from our series restored oral feeding.

CONCLUSIONS

PEPs are among the most appalling complications of cervical spine surgery. Because of their rarity and heterogeneous presentation, a standardized management is difficult to define. From our experience with the largest case series in the literature, a multidisciplinary approach is advisable to deal with these patients.

Upper cervical anterior fusion with a particular focus on superior laryngeal nerve and hypoglossal nerve

Introduction

During upper cervical anterior fusion involving C2, the branches of the superior laryngeal and hypoglossal nerves traversing the operative field are at risk for injury, mainly from excessive retraction and/or incidental ligation. These injuries would cause postoperative dysphagia and/or dysphonia that are often transient but might sometimes persist for several months. The aim of this study was to describe our modified approach for upper cervical anterior fusion and to examine the surgical outcomes and postoperative complications in a small case series.

Methods

Four patients underwent upper cervical anterior fusion at our institution. Detaching the omohyoid and sternohyoid muscles from the hyoid bone increased the mobility of the hyoid bone and enabled visualization of the thyrohyoid membrane. This maneuver facilitated access to C2 without excessive retraction to the larynx and the hypoglossal nerve traversing above the hyoid bone. Moreover, this maneuver enabled easy identification and dissection of the internal branch of the superior laryngeal nerve piercing the thyrohyoid membrane.

Results

Three patients underwent C2-3 fusion and one patient underwent C2-5 fusion followed by instrumentation. In all patients, wide, adequate exposure of C2 and proper instrumentation was achieved, and both the internal branch of the superior laryngeal nerve and the hypoglossal nerve were identified and preserved. No patient experienced remarkable postoperative dysphagia, dyspnea, and dysphonia. Solid union was achieved in all patients.

Conclusions

The technique of detaching the infrahyoid muscles from the hyoid bone during upper cervical anterior fusion involving C2 reduced the traction force to the larynx and the hypoglossal nerve, enabled easy identification of the internal branch of the superior laryngeal nerve, and prevented postoperative complications, such as dysphagia.

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.

C2-C3 Anterior Cervical Fusion: Technical Report

STUDY DESIGN

Retrospective review of patients at a university hospital.

OBJECTIVE

To describe the anterior approach for cervical discectomy and fusion (ACDF) at C2-C3 level and evaluate its suitability for treatment of instability and degenerative disease in this region.

SUMMARY OF BACKGROUND DATA

The anterior approach is commonly used for ACDF in the lower cervical spine but is used less often in the high cervical spine.

METHODS

We retrospectively reviewed a database of consecutive cervical spine surgeries performed at our institution to identify patients who underwent ACDF at the C2-C3 level during a 10-year period. Demographic data, clinical indications, surgical technique, complications, and immediate results were evaluated.

RESULTS

Of the 11 patients (7 female, 4 male; mean age 46 y) identified, 7 were treated for traumatic fractures and 4 for degenerative disk disease. Three patients treated for myelopathy showed improvement in mean Nurick grade from 3.6 to 1.3. Pain was significantly improved in all patients who had preoperative pain. Solid bony fusion was achieved in 5 of 7 patients at 3-month follow-up. Complications included dysphagia in 4 patients (which resolved in 3), aspiration pneumonia, mild persistent dysphonia, and construct failure at C2 requiring posterior fusion. One patient died of a pulmonary embolism 2 weeks postoperatively.

CONCLUSIONS

ACDF at the C2-C3 level is an option for the treatment of high cervical disease or trauma but is associated with a higher rate of approach-related morbidity. Familiarity with local anatomy may help to reduce complications. ACDF at C2-C3 appears to have a fusion rate similar to ACDF performed at other levels.

Incidence and risk factors for pneumonia following anterior cervical decompression and fusion procedures: an ACS-NSQIP study

BACKGROUND CONTEXT

Postoperative pneumonia has important clinical consequences for both patients and the health-care system. Few studies have examined pneumonia following anterior cervical decompression and fusion (ACDF) procedures.

PURPOSE

This study aimed to determine the incidence and risk factors for development of pneumonia following ACDF procedures.

STUDY DESIGN/SETTING

A retrospective cohort study of data collected prospectively by the American College of Surgeons National Surgical Quality Improvement Program was carried out.

PATIENT SAMPLE

This study comprised 11,353 patients undergoing ACDF procedures during 2011-2013.

OUTCOME MEASURES

The primary outcome was diagnosis of pneumonia in the first 30 postoperative days.

METHODS

Independent risk factors for the development of pneumonia were identified using multivariate regression. Readmission rates were compared between patients who did and did not develop pneumonia using multivariate regression that adjusted for all demographic, comorbidity, and procedural characteristics.

RESULTS

The incidence of pneumonia was 0.45% (95% confidence interval=0.33%-0.57%). In the multivariate analysis, independent risk factors for the development of pneumonia were greater age (p<.001), dependent functional status (relative risk [RR]=5.3, p<.001), chronic obstructive pulmonary disease (RR=4.4, p<.001), and greater operative duration (p=.020). Patients who developed pneumonia following discharge had a higher readmission rate than other patients (72.7% vs. 2.4%, adjusted RR=24.5, p<.001). In total, 10.2% of all readmissions were caused by pneumonia.

CONCLUSIONS

Pneumonia occurs in approximately 1 in 200 patients following ACDF procedures. Patients who are older, are functionally dependent, or have chronic obstructive pulmonary disease are at greater risk. These patients should be counseled, monitored, and targeted with preventative interventions accordingly. Greater operative duration is also an independent risk factor. Approximately three in four patients who develop pneumonia following hospitalization for ACDF procedures are readmitted. This elevated readmission rate has implications for bundled payments and hospital performance reports.

Blood supply of the terminal part of the external branch of the superior laryngeal nerve

PURPOSE

The external laryngeal nerve (ELN) carries motor fibers to the cricothyroid and inferior pharyngeal muscles. Damage to the nerve may cause symptoms such as a monotone voice. One reason for these symptoms may be nerve injury due to inadvertent stretching, ligation or transaction of the nerve during the dissection of the superior pole of the thyroid gland. We hypothesized a new reason for the symptoms, an insufficient arterial blood supply to the nerve, and investigated this hypothesis.

METHODS

From 36 larynges, 52 sides (26 right and 26 left) were dissected under a surgical Zeiss-OpM1 microscope.

RESULTS

The arterial branch to the external branch of the superior laryngeal nerve originated from the posterior glandular branch of the superior thyroid artery in 26 (50%) sides, from the anterior glandular branch in 23 (44.23%) sides, from its trunk on one (1.92%) side, from the infrahyoid branch on one (1.92%) side and from the bifurcation of the superior thyroid artery at the level of separation of the anterior and posterior glandular branches on one (1.92%) side.

CONCLUSION

Devascularization of the ELN may lead to dysfunction, so this nerve's varied blood supply should be kept in mind when invasive procedures are performed in this region.

Incidence, risk factors, and mortality associated with aspiration in cervical spine surgery

STUDY DESIGN

Retrospective national database analysis.

OBJECTIVE

A population-based database was analyzed to characterize the incidence, mortality, and associated risk factors for aspiration pneumonia in cervical spine surgery.

SUMMARY OF BACKGROUND DATA

Aspiration pneumonia represents a potentially fatal complication of any surgical procedure. The incidence of this complication is not well characterized after cervical spine surgery.

METHODS

Data from the Nationwide Inpatient Sample was obtained from 2002-2009. Patients undergoing anterior cervical fusion, posterior cervical fusion, or posterior cervical decompression for radiculopathy and/or myelopathy were identified. Patient demographics, incidence of aspiration, costs, and mortalities were assessed. Statistical analysis was performed using Student t test for discrete variables and χ test for categorical data. Logistic regression was used to identify independent predictors for aspiration.

RESULTS

A total of 202,694 patients were identified in the Nationwide Inpatient Sample from 2002 to 2009. Of these, 166,633 were anterior cervical fusions (82.2%), 13,298 were posterior cervical fusions (6.6%), and 22,764 were posterior cervical decompressions (11.2%). The overall incidence of aspiration was 5.3 events per 1000 cases. The greatest incidence was demonstrated in posterior cervical fusion-treated patients with 13.7 per 1000 cases, followed by posterior cervical decompressions with 6.4 per 1000 and anterior cervical fusions with 4.5 per 1000. Patients affected by aspiration were significantly older, more frequently male, and had greater comorbidities than unaffected patients (P < 0.001). Patients diagnosed with aspiration demonstrated significantly greater length of stay, costs, and mortality (P < 0.001). Logistic regression analysis demonstrated independent predictors of aspiration to include advanced age (≥65 yr), male sex, congestive heart failure, coagulopathy, neuropsychiatric disorders, and weight loss (P < 0.001).

CONCLUSION

We demonstrated an overall incidence of 5.3 cases of aspiration per 1000 cervical procedures. Patients most commonly affected by aspiration were older males with greater comorbidity. Hospital courses complicated by aspiration had greater length of stay, costs, and mortality. Identification of patients with risk factors for aspiration may assist in early diagnosis and treatment to prevent further morbidity and mortality.

Topographical anatomy of the anterior cervical approach for c2-3 level

PURPOSE

To develop a clinically relevant anterior cervical approach (ACA) to the C2-3 level.

METHODS

Frequently encountered nerves [hypoglossal (HyN), internal (ISLN) and external superior laryngeal nerves (ESLN)] and vessels [lingual (LiA), superior laryngeal (SLA) and superior thyroid arteries (STA)] in the field of high ACA and the anatomic spatial markers [submandibular gland (SMG); sling for digastrics muscle (SDG); hyoid bone (HyB), and thyroid cartilage (ThC)] were evaluated using 18 fresh cadavers. The vertical distance of each structure at the carotid sheath and larynx and each disc for cervical level were measured from the suprasternal notch.

RESULTS

The cervical levels of SDG, SMG and HyB were mostly C3 and that of ThC was C5. The vertical locations of HyN and LiA were not significantly different and the levels corresponded to C2. The levels for ISLN and ESLN were C3 at carotid and C4 and C5 at larynx sides, respectively. The vertical locations of ISLN and HyN were significantly different at carotid (p = 0.001) and larynx (p < 0.001) sides. The vertical locations and cervical levels of SLA and STA at carotid and larynx sides were not significantly different with those of ISLN and ESLN, respectively. The HyN traversed C2 with accompanying LiA. The ISLN passed C3 and C4 from carotid to larynx sides and accompanied SLA.

CONCLUSIONS

The C2-3 level can be exposed through the space between the HyN and the ISLN by retracting the LiA superiorly, the SLA inferiorly, the HyB medially, and the carotid sheath laterally.

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.

Clinically relevant anatomy of high anterior cervical approach

STUDY DESIGN

An anatomic study of anterior cervical dissection of 11 embalmed cadavers and measurement of structures relative to cervical spine.

OBJECTIVE

To determine the anatomic relationship of the hypoglossal nerve (HN), internal and external superior laryngeal nerves (ESLNs), superior thyroid artery (STA), and superior laryngeal artery (SLA) to cervical spine and demonstrate any vulnerability.

SUMMARY OF BACKGROUND DATA

The anterior approach is a common approach to the cervical spine. Much of the operative morbidity in high cervical region is related to neurovascular injury leading to dysphagia, dysphonia, impaired high-pitch phonation, and impaired cough reflex.

METHODS

Eleven adult cadavers (5 male/6 female) were dissected bilaterally to expose structures of the high anterior cervical region.

RESULTS

The HN consistently traveled toward the midline at C2-3 and was safe caudal to C3-4. In 95% of dissections, the internal superior laryngeal nerve (ISLN) was exposed within 1 cm of C3-4. The path of the ESLN was variable, but it was safe above C3-4 and below C6-7. The ESLN was deep to the STA, and it was less bulky and tauter than the ISLN in all dissections. The origin of the STA was quite variable along the carotid artery, but it was most commonly located at C4. Two anatomic variants of the SLA were observed. In 15 dissections, the SLA branched off the superior thyroid. In six dissections, the SLA branched directly from external carotid artery. There was no appreciable side-to-side variation in the neurovascular structures studied.

CONCLUSION

On the basis this study, spine surgeons can have enhanced knowledge of high anterior cervical anatomy. The neurovascular structures in this study did not demonstrate side-to-side anatomic variation; therefore, patient pathology and surgeon preference should dictate the operative side.

Anterior single screw fixation of odontoid fracture with intraoperative Iso-C 3-dimensional imaging

PURPOSE

The purpose of this study was to assess the value of isocentric C-arm three-dimensional (Iso-C 3D) fluoroscopy for the insertion of an anterior odontoid screw. The results of the Iso-C 3D group were compared with that of an historic control group using conventional fluoroscopy.

METHODS

Twenty-nine patients diagnosed with type II or rostral-type III odontoid fractures were treated with a single anterior screw fixation in this study. The Iso-C 3D group included 13 patients and the other 16 patients were in the historic control group. All operations were performed by a single surgeon using standard procedure and manner. The clinical and radiographic results were recorded and compared between the two groups.

RESULTS

The fluoroscopy time in the Iso-C 3D group was 42.9 s as compared to 68.1 s in the control group (P < 0.01). The mean operative time was 91.5 min in the Iso-C 3D group when compared with 81.6 min in the control group (P = 0.20). The rate of bony fusion was 96.6% (28/29), the failure rate of reduction or fixation was 13.8% (7.7% in Iso-C 3D group; 18.8% in control group). The Smiley-Webster scale showed that 90% of patients achieved good or better outcomes

CONCLUSIONS

In conclusion, this technique can be safely extended to the treatment of technically difficult to treat spinal injuries and at the same time reduce total radiation exposure time both for the patient and the surgeon.

Topographic anatomy of the internal laryngeal nerve: surgical considerations

BACKGROUND

This study is focused on the topographic features of the internal branch of the superior laryngeal nerve (ibSLN) at the thyrohyoid membrane area using as anatomic landmarks the posterior border of the thyrohyoid muscle and the superior border of the thyroid cartilage.

METHODS

Thirty-six fresh adult cadavers were dissected to determine the topography and branching pattern of the ibSLN and the superior laryngeal artery.

RESULTS

The ibSLN prior to thyrohyoid membrane's penetration was divided into 3 or 2 branches, in 72.22% and 27.78% of cases. The trifurcated ibSLN was more common than the bifurcated in both sexes and in both sides of the neck. In over 80% of cases the ibSLN penetrated the thyrohyoid membrane 0.1 to 0.9 cm far from the posterior border of the thyrohyoid muscle and 0.1 to 1.2 cm far from the superior border of the thyroid cartilage.

CONCLUSIONS

We provide a schematic overview of the ibSLN penetration zone at the thyrohyoid membrane, the so-called danger zone, to avoid ibSLN damage.

Papel da videoendoscopia da laringe no diagnóstico de lesão do nervo laríngeo recorrente na abordagem cervical anterior

INTRODUÇÃO: o reconhecimento da lesão do nervo laríngeo recorrente (NLR) após tratamento cirúrgico de hérnia discal cervical via anterior é importante na evolução clínica do paciente e, em especial, nos casos de reintervenção. O real papel da videoendoscopia da laringe (VEL) de rotina no pós-operatório não tem sido completamente estudado. OBJETIVO: identificar a prevalência de lesões do NLR em pacientes sintomáticos ou não através da VEL após cirurgia de hérnia cervical via anterior. MÉTODOS: no período de Junho de 2009 a Julho de 2010 selecionamos 30 pacientes submetidos a tratamento cirúrgico de hérnia discal no Hospital São Lucas da PUC-RS. Realizou-se avaliação por VEL no pré-operatório e no décimo dia após a cirurgia. Pacientes que apresentaram um resultado anormal da VEL foram considerados com lesão do NLR e foram reavaliados mensalmente até a recuperação espontânea, ou no período máximo de seis meses, quando a lesão foi considerada definitiva. RESULTADOS: encontramos evidência de lesão do NLR em 3/30 (10%) dos pacientes, sendo que todos se apresentavam assintomáticos no momento do exame. Dentre as lesões, 2/30 (66,6%) ocorreram após abordagem cirúrgica pelo lado direito e 1/30 (33,3%) pelo lado esquerdo. Não encontramos nenhuma lesão definitiva, sendo o período máximo de recuperação de 120 dias. CONCLUSÃO: a avaliação por VEL no período pós-operatório pode ser útil para diagnosticar lesões do NLR, principalmente em pacientes assintomáticos. A falta de suspeita clínica não exclui a possibilidade de lesão do LNR.

Anterior Fixation of the Axis

BACKGROUND:

Although anterior fixation of the axis is not commonly performed, plate fixation of C2 is an important technique for treating select upper cervical traumatic injuries and is also useful in the surgical management of spondylosis.

OBJECTIVE:

To report the technique and outcomes of C2 anterior plate fixation for a series of patients in which the majority presented with symptomatic degenerative spondylosis.

METHODS:

Forty-six consecutive patients underwent single or multilevel fusions over a 7-year period; 30 of these had advanced degenerative disease manifested by myelopathy or deformity. Exposure was achieved with rostral extension of the standard anterior cervical exposure via careful soft tissue dissection, mobilization of the superior thyroid artery, and the use of a table-mounted retractor. It was not necessary to remove the submandibular gland, section the digastric muscle, or make additional skin incisions.

RESULTS:

Screws were placed an average of 4.6 mm (± 2.3 mm) from the inferior C2 endplate with a mean sagittal trajectory of 15.7° (± 7.6 °).

Short- and long-term procedure-related mortality was 4.4%, and perioperative morbidity was 8.9%. Patients remained intubated an average of 2.5 days following surgery. Dysphagia was initially reported by 15.2% of patients but resolved by the 8th postoperative week in all patients. Arthrodesis was achieved in all patients available for long-term follow-up. Multilevel fusions were not associated with longer hospitalization or morbidity.

CONCLUSION:

Anterior plate fixation of the axis for degenerative disease can be accomplished with acceptable morbidity employing an extension of the standard anterolateral route.

Relationship between the internal laryngeal nerve and the triticeal cartilage: a potentially unrecognized compression site during anterior cervical spine and carotid endarterectomy operations

OBJECTIVE

The triticeal cartilage has received scant attention in the literature. To date, its relationship to the nearby internal laryngeal nerve has not been studied. Therefore, to elucidate further this anatomic relationship and its potential surgical implications, this study was performed.

METHODS

Eighty-six adult cadaveric sides underwent dissection of the internal laryngeal nerve near its penetration of the thyrohyoid membrane. The relationship of this nerve to the triticeal cartilage was documented. Measurements and histological analysis were performed on all cartilage specimens.

RESULTS

We identified triticeal cartilage in 51% of the specimens and found it to be hyaline in nature. The triticeal cartilage was located in the upper, middle, and lower thirds of the thyrohyoid membrane in 14%, 66%, and 20% of sides, respectively. Regardless of the position of the triticeal cartilage within the thyrohyoid membrane, the internal laryngeal nerve crossed directly over the triticeal cartilage on 59% of sides.

CONCLUSION

When present, the internal laryngeal nerve will cross over the triticeal cartilage in the majority of individuals. This relationship should be borne in mind during surgical manipulation in this area and when placing retractors during anterior neck operations including cervical discectomy/fusion and carotid endarterectomy. Compression of the internal laryngeal nerve against the solid triticeal cartilage can cause laryngeal nerve palsy and increase the risk of resultant postoperative aspiration.

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.

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.

Preoperative Laryngeal Nerve Screening for Revision Anterior Cervical Spine Procedures

Objectives:

Anterior cervical spine procedures carry an inherent risk of recurrent laryngeal nerve (RLN) injury. Patients with persistent RLN paresis may be asymptomatic because of compensation from the opposite side. If such patients undergo an opposite-side anterior approach for revision surgery, they are at risk for a second RLN injury, creating the potential for bilateral vocal fold paresis and possible need for tracheotomy. A program of routine screening for laryngeal paresis was implemented for these patients. This retrospective study reviews the results of this screening process.

Methods:

Patients referred for preoperative laryngeal nerve screening were identified. Their charts were reviewed for the results of the videolaryngoscopic examination, and for any recommendations made based on the findings. Relevant history and other physical findings were recorded.

Results:

Fifty screening laryngeal examinations were performed in 47 patients, of whom 31 (66%) had previously undergone a single anterior cervical approach procedure, and 16 (34%) had undergone more than one. Thirteen of the examinations (26%) revealed abnormal laryngeal findings, including paresis or paralysis in 11 cases (22%), of which 5 were asymptomatic. The findings resulted in a recommendation of a cervical approach from the already-involved side. None of the revision procedures resulted in bilateral vocal fold paralysis. The risk of laryngeal nerve injury appears to increase as higher cervical levels are approached.

Conclusions:

Minimally symptomatic injuries of the laryngeal nerves from prior neck surgery create a potential serious risk of bilateral vocal fold paralysis with subsequent procedures. Preoperative laryngeal screening is a simple and effective method for reducing this risk.

Surgical anatomy of the external branch of the superior laryngeal nerve and its clinical significance in head and neck surgery

Injury of the external branch of the superior laryngeal nerve (EBSLN) increases the morbidity following a variety of neck procedures and can have catastrophic consequences in people who use their voice professionally. Identification and preservation of the EBSLN are thus important in thyroidectomy, parathyroidectomy, carotid endarterectomy, and anterior cervical spine procedures, where the nerve is at risk. There are large variations in the anatomical course of the EBSLN, which makes the intraoperative identification of the nerve challenging. The topographic relationship of the EBSLN to the superior thyroid artery and the upper pole of the thyroid gland are considered by many authors to be the key point for identifying the nerve during surgery of the neck. The classifications by Cernea et al. ([1992a] Head Neck 14:380-383; [1992b] Am. J. Surg. 164:634-639) and by Kierner et al. ([1998] Arch. Otolaryngol. Head Neck Surg. 124:301-303), as well as clinically important connections are discussed in detail. Along with sound anatomical knowledge, neuromonitoring is helpful in identifying the EBSLN during neck procedures. The clinical signs of EBSLN injury include hoarseness, decreased voice projection, decreased pitch range, and fatigue after extensive voice use. Videostroboscopy, electromyography, voice analysis, and electroglottography can provide crucial information on the function of the EBSLN following neck surgery.

Anatomical and surgical considerations of the external branch of the superior laryngeal nerve: a systematic review

The anatomical course of the external branch of the superior laryngeal nerve (EBSLN) is variable, and a consistent approach to its preservation during thyroid surgery is needed to reduce risk of post-operative voice impairment. Despite agreement that careful dissection in the region of the superior thyroid pole is required, there is no accepted 'best' approach, nor any universal acknowledgement that location of the EBSLN is actually necessary. The popular cernea classification of EBSLN has limitations, including its decreased reliability with increased thyroid size and its irrelevance in cases of 'buried' variants. * Recent work has identified factors such as ethnicity and stature in the prevalence of EBSLN variants. Consistent approaches to the post-operative detection of EBSLN injury are needed to build an accurate picture of the incidence of surgical nerve injury. Then a standardised approach to EBSLN preservation may emerge.

Surgical anatomy of the internal branch of the superior laryngeal nerve

The internal branch of the superior laryngeal nerve (ibSLN) may be injured during anterior approaches to the cervical spine, resulting in loss of laryngeal cough reflex, and, in turn, the risk of aspiration pneumonia. Such a risk dictates the knowledge regarding anatomical details of this nerve. In this study, 24 ibSLN of 12 formaldehyde fixed adult male cadavers were used. Linear and angular parameters were measured using a Vernier caliper, with a sensitivity of 0.1 mm, and a 1 degrees goniometer. The diameter and the length of the ibSLN were measured as 2.1+/-0.2 mm and 57.2+/-7.7 mm, respectively. The ibSLN originates from the vagus nerve at the C1 level in 5 cases (20.83%), at the C2 level in 14 cases (58.34%), and at the C2-3 intervertebral disc level in 5 cases (20.83%) of the specimens. The distance between the origin of ibSLN and the bifurcation of carotid artery was 35.2+/-12.9 mm. The distance between the ibSLN and midline was 24.2+/-3.3 mm, 20.2+/-3.6 mm, and 15.9+/-4.3 mm at the level of C2-3, C3-4, and at the C4-5 intervertebral disc level, respectively. The angles of ibSLN were mean 19.6+/-2.6 degrees medially with sagittal plane, and 23.6+/-2.6 degrees anteriorly with coronal plane. At the area between the thyroid cartilage and the hyoid bone the ibSLN is the only nerve which traverses lateral to medial. It is accompanied by the superior laryngeal artery, a branch of the superior thyroid artery. The ibSLN is under the risk of injury as a result of cutting or compression of the blades of the retractor at this level. The morphometric data regarding the ibSLN, information regarding the distances between the nerve, and the other consistent structures may help us identify this nerve, and to avoid the nerve injury.

The superior laryngeal nerve: function and dysfunction

Despite long-standing clinical interest in SLN dysfunction, most aspects of this entity continue to require clarification. The replacement of the laryngeal mirror by flexible fiberoptic and rigid rod-lens laryngoscopy (including stroboscopy) and the resulting improvement in laryngeal visualization and documentation of examination has not resulted in a better definition of characteristic signs. Symptoms are often vague, and most are shared with other voice disorders. Under the circumstances, there is good reason to suppose that SLN dysfunction yields a clinical picture at least as heterogeneous as recurrent laryngeal nerve injury and a good deal more subtle. Faced with significant inconsistencies in clinical presentation, the clinician is hard-pressed to draw conclusions regarding prevalence, patterns of dysfunction, natural history, treatment, and even about its overall significance. EMG. used judiciously and complemented by frequency range testing, seems to hold more promise as a means of reliable diagnosis than laryngoscopic examination and may serve to resolve some of the confusion surrounding SLN dysfunction. It is equally important that the otolaryngologist guard against falling into the easy habit of attributing vocal disturbance that cannot be otherwise explained to SLN dysfunction in the absence of EMG evidence. If ambiguities surrounding SLN paralysis and paresis are to be clarified, diagnostic rigor is essential.