Ansa cervicalis nerve: review of the topographic anatomy and morphology

Cadaver investigation of the usefulness of the transstyloid diaphragm approach for high-position plaque carotid endarterectomy

OBJECTIVES

Patients sometimes present with high cervical internal carotid artery (ICA) stenosis. This study demonstrates the usefulness of the transstyloid approach to expose the distal ICA by dissection of the styloid diaphragm covering the distal cervical ICA for carotid endarterectomy (CEA). In particular, the possible exposure length achieved by this approach was investigated using cadaveric heads.

METHODS

The procedure of the transstyloid diaphragm approach was confirmed in 10 cadaveric heads (20 sides). After the carotid triangle was opened, both the posterior belly of the digastric muscle (PBDM) and the stylohyoid muscle could be divided. Then, the carotid sheath was dissected, and the glossopharyngeal nerve was identified crossing over the distal ICA. The revealed length of the ICA was measured with or without dissection of both the PBDM and the stylohyoid muscle. The specimens were dissected under the surgical microscope.

RESULTS

The transstyloid diaphragm approach was achieved successfully in all specimens. The revealed lengths of the ICA with and without dissection of the styloid diaphragm were 53.7 ± 5.9 mm and 38.8 ± 2.9 mm (mean ± standard deviation), respectively. Therefore, the revealed length of the distal ICA was 14.9 ± 4.5 mm greater using the transstyloid diaphragm approach compared to the regular CEA approach.

CONCLUSIONS

More of the ICA can be revealed by dissection of both the PBDM and the stylohyoid muscle. The transstyloid diaphragm approach might be helpful to reveal the distal ICA in cases of high cervical ICA stenosis.

Selective ansa cervicalis nerve transfer to the marginal mandibular nerve for lower lip reanimation: An anatomical study in cadavers and a case report

BACKGROUND

Donor nerve options for lower lip reanimation are limited in patients undergoing oncological resection of the facial nerve. The ansa cervicalis nerve (ACN) is an advantageously situated donor with great potential but has not been examined in detail. In the current study, the anatomical technical feasibility of selective ACN to marginal mandibular nerve (MMN) transfer for restoration of lower lip tone and symmetry was explored. A clinical case is presented.

METHODS

Dissections were conducted in 21 hemifaces in non-embalmed human cadavers. The maximal harvestable length of ACN was measured and transfer to MMN was simulated. A 28-year-old male underwent ACN-MMN transfer after parotidectomy (carcinoma) and was evaluated 12 months post-operatively (modified Terzis' Lower Lip Grading Scale [25 observers] and photogrammetry).

RESULTS

The harvestable length of ACN was 100 ± 12 mm. A clinically significant anatomical variant ("short ansa") was present in 33% of cases (length: 37 ± 12 mm). Tensionless coaptation was possible in all cases only when using a modification of the surgical technique in "short ansa" cases (using an infrahyoid muscle nerve branch as an extension). The post-operative course of the clinical case was uneventful without complications, with improvement in tone, symmetry, and function at the lower lip at 12-month post-operative follow-up.

CONCLUSIONS

Selective ACN-MMN nerve transfer is anatomically feasible in facial paralysis following oncological ablative procedures. It allows direct nerve coaptation without significant donor site morbidity. The clinical case showed good outcomes 12 months post-operatively. A strategy when encountering the "short ansa" anatomical variant in clinical cases is proposed.

Facial reanimation using the hypoglossal nerve and ansa cervicalis: a short-term retrospective analysis of surgical outcomes

Background

Transferring the hypoglossal nerve to the facial nerve using an end-to-end method is very effective for improving facial motor function. However, this technique may result in hemitongue atrophy. The ansa cervicalis, which arises from the cervical plexus, is also used for facial reanimation. We retrospectively reviewed cases where facial reanimation was performed using the ansa cervicalis to overcome the shortcomings of existing techniques of hypoglossal nerve transfer.

Methods

The records of 15 patients who underwent hypoglossal nerve transfer were retrospectively reviewed. Three methods were used: facial reanimation with hypoglossal nerve transfer (group 1), facial nerve reanimation using the ansa cervicalis (group 2), and sural nerve interposition grafting between the hypoglossal nerve and facial nerve (group 3). In group 1, the ansa cervicalis was coapted to neurotize the distal stump of the hypoglossal nerve in a subset of patients. Clinical outcomes were evaluated using the House-Brackmann (H-B) grading system and Emotrics software.

Results

All patients in group 1 (n = 4) achieved H-B grade IV facial function and showed improvements in the oral commissure angle at rest (preoperative vs. postoperative difference, 6.48° ± 0.77°) and while smiling (13.88° ± 2.00°). In groups 2 and 3, the oral commissure angle slightly improved at rest (group 2: 0.95° ± 0.53°, group 3: 1.35° ± 1.02°) and while smiling (group 2: 2.06° ± 0.67°, group 3: 1.23° ± 0.56°). In group 1, reduced tongue morbidity was found in patients who underwent ansa cervicalis transfer.

Conclusion

Facial reanimation with hypoglossal nerve transfer, in combination with hypoglossal nerve neurotization using the ansa cervicalis for complete facial palsy patients, might enable favorable facial reanimation outcomes and reduce tongue morbidity. Facial reanimation using the ansa cervicalis or sural nerve for incomplete facial palsy patients did not lead to remarkable improvements, but it warrants further investigation.

The anterolateral cervicoatlantooccipital plexus: A novel finding with application to skull base and spine surgery and pain disorders of the head and neck

INTRODUCTION

A novel nerve plexus of the upper neck is described. By exploring how the individual components of this specific anterolateral nerve plexus communicate with each other, patient care may be improved in regard to preoperative diagnosis, intraoperative navigation, and minimally invasive treatments.

MATERIALS AND METHODS

Using a surgical microscope, 11 adult cadaveric heads (22 sides) were dissected. The region of the junction between the atlantooccipital and craniocervical junctions was explored, specifically, the innervation of this region via adjacent nerve connections. Branches from these regional nerve sources were analyzed for interconnections and when found, these branches were documented and measured.

RESULTS

A delicate nerve plexus was found overlying the anterolateral C1-C2 junction in all specimens. The plexus was contributed by the sympathetic trunk, vagus nerve, hypoglossal nerve, and C1 and C2 ventral rami. We termed this plexus the anterolateral cervicoatlantooccipital plexus (ALCAO plexus). On all but two sides (91%), the C2 ventral ramus provided the most input into the plexus with 1 to 2 branches. On two sides, the C1 ventral ramus was the primary contribution and on average, this nerve contributed 1 to 2 branches to the plexus. Interestingly, on eight sides (36.4%), the C1 fibers that are known to travel with the hypoglossal nerve and to be distributed to the geniohyoid and thyrohyoid muscles arose from C1 nerve fibers that first traversed the ALCAO plexus. The sympathetic trunk contributed 1 to 4 lateral branches with the majority of these arising superiorly from the superior cervical ganglion. The vagus nerve contributed 1-2 lateral branches and the hypoglossal nerve contributed 1 to 2 anteromedial branches. This plexus was located more or less lateral to the sympathetic trunk and superior cervical ganglion and medial to the transverse process of C1 and C2. The plexus innervated the rectus capitis lateralis, rectus capitis anterior, lateral atlantooccipital joint and on four sides, the atlantoaxial joint. Additionally, small branches were seen traveling to the anterior atlantoaxial and anterior atlantooccipital membranes on 55% and 77.2% of sides, respectively. On six sides, very small branches from the ALCAO plexus ended in the periosteum over the anterolateral aspect of the anterior arch and transverse process of the C1 vertebra.

CONCLUSION

It is important to recognize that the course of these interneural connections are variable and may pose unforeseen complications during surgical procedures. A comprehensive knowledge of these neural connections is useful when surgery and pathology of the neck and skull base are considered.

Intra-operative monitoring as an adjuvant to standard vagus nerve stimulation implantation

PURPOSE

The treatment of refractory epilepsy by vagus nerve stimulation (VNS) is a well-established therapy. Complications following VNS insertion may be procedure-related or stimulation-related. Herein, we describe our technique of intra-operative neuro-monitoring (IONM) in an attempt to diminish these adverse events.

METHODS

This retrospective study describes 66 consecutive patients between the ages of 3 and 12 years who had undergone primary VNS implantation. The study population consisted of two cohorts, one in which the VNS device was implanted according to the standard described technique and a second group in which IONM was used as an adjuvant during the VNS device placement. Prior to VNS insertion, a Pediatric Voice Handicap Index (PVHI) was performed to assess voice-related quality of life, and this was repeated at 3 months following VNS insertion.

RESULTS

Sixty-six patients underwent the VNS implantation. Forty-three patients had a "standard" VNS insertion technique performed, whereas 23 had IONM performed during the VNS implantation. There were significant changes in the PVHI scores across both cohorts at 3-month follow-up. There were no statistically significant differences in PVHI scores between the monitored group and non-monitored group at 3-month follow up.

CONCLUSIONS

IONM can be used during VNS insertions to ensure correct placement of the leads on CNX. IONM may minimise vocal cord stimulation by placing the lead coils on the area of nerve eliciting the least amount of vocal cord EMG response. IONM however does not appear to improve voice outcomes at early follow up.

Normal anatomy, variants and factors associated with the cervical vagus nerve topography: a high-resolution ultrasound study

PURPOSE

To describe the cervical vagus nerve (CVN) topography at the thyroid lobe (TL) level using high-resolution ultrasound and to investigate the possible association with anthropometric data, TL size, and thyroid disease.

METHODS

We prospectively examined 550 CVNs in 275 (205 female, 70 male) individuals with normal thyroid (53/275, 19.3%), multinodular disease (167/275, 60.7%), and Hashimoto thyroiditis (55/275, 20%). The CVN location relative to the common carotid artery was recorded as typical (lateral position) and atypical (anterior, medial, and posterior position). The shortest distance between CVN and TL margin, the TL dimensions, and volume were measured.

RESULTS

Normal thyroid subjects had lateral-positioned right CVNs in 100% and lateral/anterior/medial left CVNs in 81.1%, 15.1%, and 3.8%, respectively. CVN types did not differ significantly bilaterally between study groups. Asymmetry in CVN topography in all subjects was found in 22.2%, of which anterior CVN was the most common atypical position (64%), especially on the left side (82%). Significant gender, age, body mass, and BMI differences among CVN types were observed on the left side only. Among CVN types, no difference in TL dimensions, volume, and CVN-TL distance was found in all study groups. A weak negative correlation was recorded between CVN-thyroid distance and TL volume only on the left side (r = - 0.147, p = 0.01).

CONCLUSION

Asymmetry in CVN topography is mainly due to the increased incidence of the anterior location of CVN on the left side. Age and anthropometric parameters are different on the left side possibly due to the increased prevalence of left CVN variants.

Ultrasound Localization and Percutaneous Electrical Stimulation of the Hypoglossal Nerve and Ansa Cervicalis

OBJECTIVE

Hypoglossal nerve stimulation for obstructive sleep apnea (OSA) can be effective for appropriately selected patients, but current patient selection criteria are complex and still result in a proportion of nonresponders. Ansa cervicalis stimulation of the infrahyoid cervical strap muscles has recently been proposed as a new form of respiratory neurostimulation (RNS) therapy for OSA treatment. We hypothesized that percutaneous stimulation of both nerves in humans with temporary electrodes would make testing of the physiologic response to different RNS strategies possible.

STUDY DESIGN

Nonrandomized acute physiology study.

SETTING

Tertiary care hospital.

METHODS

Fifteen participants with OSA underwent ultrasonography and placement of percutaneous electrodes proximal to the medial division of the hypoglossal nerve and the branch of the ansa cervicalis innervating the sternothyroid muscle (ACST). Procedural success was documented in each participant, as were any failures or procedural complication.

RESULTS

The hypoglossal nerve was successfully localized in 15 of 15 (100%) participants and successfully stimulated in 13 of 15 (86.7%). The ACST was successfully localized in 15 of 15 (100%) participants and successfully stimulated in 14 of 15 (93.3%). Stimulation failure of the hypoglossal nerve was due to suboptimal electrode placement in 1 participant and electrode displacement in the other 2 cases. No complications occurred.

CONCLUSIONS

The hypoglossal nerve and ACST can be safely stimulated via percutaneous electrode placement. Larger trials of percutaneous stimulation may help to identify responders to different RNS therapies for OSA with temporary or permanent percutaneous electrodes. Techniques for electrode design, nerve localization, and electrode placement are described.

Association of Tortuous Common Carotid Artery with Abnormal Distribution of the Ansa Cervicalis: A Case Report

In the current study, we display a rare association of an aberrant innervation of the sternocleidomastoid muscle by the ansa cervicalis (AC) with a tortuous common carotid artery (TCCA). In specific, in a male cadaver we observed on the right side of the cervical region, a nerval branch of remarkable size originating from the most distal part of the AC's superior root and after piercing the superior belly of the omohyoid muscle innervated the distal portion of the sternocleidomastoid muscle. Furthermore, we noticed a tortuous course of the initial part of the right common carotid artery. We discuss the surgical significance of the awareness of AC's variations during neurotisation of the recurrent laryngeal nerve in cases of its damage, as well as the importance of aberrant innervation of the sternocleidomastoid muscle by AC for the preservation of muscle's functionality after accessory nerve's damage. Furthermore, we highlight the fact, that the knowledge of the relatively uncommon variant, such as TCCA is crucial for the physician in order to proceed more effectively in differential diagnosis of a palpable mass of the anterior cervical region or deal with symptoms such as dyspnea, dysphagia or symptoms of cerebrovascular insufficiency.

Thyrohyoideus muscle innervation in the horse

OBJECTIVE

To describe the innervation of the thyrohyoideus (TH) muscle and to confirm our findings with stimulation of first cervical (C1) nerve branches.

STUDY DESIGN

Ex vivo phase 1 and clinical phase 2.

ANIMALS

Fourteen head and neck specimens and 17 client-owned horses.

METHODS

In phase 1, the cranial nerve (CN) XII and the C1 nerve were dissected with their branches in 20 dissections were performed on 14 specimens (6 left and right side and 8 only left or right) Anatomy was noted. Samples of nerve bifurcations were collected for histological confirmation of anatomical findings. First cervical nerve branches were stimulated in horses undergoing cervical nerve graft to treat laryngeal hemiplegia.

RESULTS

The nerve innervating the TH muscle arose directly from the C1 nerve in 17 of 20 dissections, from an anastomotic branch between CN XII and the C1 nerve in two of 20 dissections, and from the C1 nerve and the anastomotic branch in one of 20 dissections. No direct connection between the TH muscle and CN XII was found. Histological examination revealed that the anastomosis was composed of C1 nerve fibers passing over to CN XII. First cervical stimulation resulted in TH muscle contraction in 16 of 17 horses.

CONCLUSIONS

The innervation of the TH muscle originated from the C1 nerve according to dissection, histological, and conduction studies, with variation in the branching pattern.

CLINICAL SIGNIFICANCE

Care should be taken to preserve the C1 nerve during prosthetic laryngoplasty. The surgical technique for C1 nerve grafts should be reconsidered in light of these findings, along with new options to treat dorsal displacement of the soft palate..

An Anatomic Variant of the Ansa Cervicalis Precluding Its Use as a Donor Nerve

BACKGROUND

The ansa cervicalis is useful for cranial nerve repair, and may be harvested without apparent morbidity. Herein we report an unusual and surgically relevant anatomic variant of the ansa cervicalis.

METHODS

An adult male with left parotid adenoid cystic carcinoma underwent parotidectomy with upper-division facial nerve resection and planned interposition repair using the ansa cervicalis. The ipsilateral hypoglossal nerve was identified, together with a descending branch producing strap muscle contraction when stimulated. This presumed descendens hypoglossi was unusually large in caliber; further dissection revealed continuity with the vagus nerve.

RESULTS

Ansa cervicalis harvest was aborted when its separation from vagus nerve epineurium was not possible. The sural nerve was alternatively harvested. The patient awoke with left vocal fold palsy, which completely resolved within 3 months.

CONCLUSION

Anatomic variants of the ansa cervicalis exist that may preclude graft harvest and place the vagus nerve at risk of inadvertent injury.

Ansa cervicalis: a comprehensive review of its anatomy, variations, pathology, and surgical applications

The ansa cervicalis is a neural loop in the neck formed by connecting the superior root from the cervical spinal nerves (C1-2) and the inferior root descending from C2-C3. It has various anatomical variations and can be an important acknowledgment in specific operations of the neck region. This is a review the anatomy, variations, pathology and clinical applications of the ansa cervicalis.

Duplicated Vagus Nerve in Adolescence: Case Report and Review of Literature

BACKGROUND

Vagus nerve stimulation (VNS) has become an increasingly popular procedure for the treatment of epilepsy and depression. Significant complications or side effects associated with VNS surgery may result from either the inadvertent direct injury to the vagus nerve as part of the surgical approach, placement of the electrode, or the concomitant stimulation of vagal efferent fibers. To mitigate these effects, the recognition of anatomic variants that may place the nerve at increased risk is necessary.

CASE DESCRIPTION

During microsurgical dissection of the carotid sheath for the implantation of a vagus nerve stimulator in a 17-year-old male patient with refractory epilepsy, additional nonidentified nerve tissue was found running parallel to the vagus nerve. These fibers were two thirds of the thickness of the vagus nerve and ran medial to it, from the most superior to the most inferior aspect of the carotid sheath dissection, found at a distance of at least 4 cm in a craniocaudal direction. This duplicated nerve did not appear to branch from the vagal trunk nor exit the sheath but rather paralleled the course of the vagus nerve. The parallel course and the proximity of the unidentified nerve make this structure likely to be a duplicated vagus nerve.

CONCLUSIONS

This is the first reported case of cervical vagus nerve duplication presented in the literature. Surgeons performing VNS implantations should be cognizant of this potential anomaly in order to avoid inadvertent injury to the nerve.

Sternocleidomastoid innervation from an aberrant nerve arising from the hypoglossal nerve: a prospective study of 160 neck dissections

BACKGROUND

Anatomical variants of the spinal root of the accessory nerve and cervical plexus are well known but other variants are exceptionally rare.

METHODS

A prospective study of 160 selective neck dissections was undertaken following an index case, where a presumed C1 nerve (travelling with the hypoglossal nerve) was found to innervate sternocleidomastoid (SCM). A search was subsequently made for this variant while not compromising the neck dissection surgery itself. Eight cases could not be included due to metastatic disease precluding safe dissection in this area. A nerve stimulator was used to confirm the motor supply to SCM.

RESULTS

This nerve variant was found in 4/160 necks (2.5 %). In all cases, it originated directly from the hypoglossal nerve and stimulation resulted in isolated SCM contraction. No accessory nerve anomalies were found.

CONCLUSION

This finding adds to the knowledge of variants in this area. Meticulous dissection and preservation of all nerves, where possible, is important for optimising functional outcomes following surgery.

Surface Electromyographic Activity in Total Laryngectomy Patients following Laryngeal Nerve Transfer to Neck Strap Muscles

Hands-free triggering and pitch control would improve electrolarynx devices, which are inconvenient to use and sound unnatural. The present study tested the strategy of salvaging voice-related neural signals for hands-free electrolarynx control either by transferring cut recurrent laryngeal nerves (RLNs) to denervated neck strap muscles or by preserving strap muscles with their normal innervation. An RLN nerve transfer was performed at the time of total laryngectomy in 8 individuals, and in 5 of these subjects, strap muscles with intact ansa cervicalis innervation were also preserved for comparison. Neck surface electromyography performed over the strap muscles was used periodically for more than 1 year on phonatory and nonphonatory tasks. Signals were eventually obtained in all subjects from both RLN-innervated and ansa-innervated strap muscles that correlated with speech production. After 1 year, RLN-driven signals were larger than ansa-driven signals in magnitude, and their timing appeared better correlated with intended phonation. The results show that neck surface electromyography is an effective control source for hands-free electrolarynx activation, and that RLN transfer may provide the best approach for obtaining phonation-related activity.

Results of ansa to recurrent laryngeal nerve reinnervation

Objective

We sought to describe the results of ansa cervicalis to recurrent laryngeal nerve (ansa-RLN) reinnervation for unilateral vocal fold paralysis.

Study Design

A chart review was performed on patients undergoing ansa-RLN reinnervation for unilateral vocal cord paralysis at a tertiary care center. Patient perceptions of preoperative and postoperative voice quality was surveyed. Acoustic and visual parameters were assessed from videostroboscopy.

Results

From a total of 25 study patients, 15 patients underwent both preoperative and postoperativ video stroboscopies. In stroboscopies within 6 months, the average improvement in overall severity, roughness, and breathiness was 69, 79, and 100 percent, respectively. In stroboscopies after 6 months, the average improvement in overall severity, roughness, and breathiness was 63, 66, and 100 percent, respectively. Postoperatively, all patients had reinnervation of the vocal fold.

Conclusions

Voice outcomes were improved in patients with preoperative and postoperative stroboscopies.

Significance

Ansa-RLN reinnervation should be considered as a treatment for unilateral vocal fold paralysis.

Unilateral anatomical variation of the ansa cervicalis

The ansa cervicalis is a loop of nerves that is usually formed by the union of ventral rami of spinal nerves C1, C2, and C3. It is located in the carotid triangle of the neck, lying superficial to the carotid sheath. During routine dissection, unilateral variation of the ansa cervicalis was observed. The superior root, arising from hypoglossal nerve, was initially bifurcated and later united to form a single superior root. IN addition, the inferior root consisted of fibres arising from the spinal accessory nerve, C1, C2 and C3 spinal nerves that joined separately. Fibres from the spinal accessory and C1 joined to form a single root. Thus, a 'triple form' of ansa cervicalis was observed. An interconnection was observed between the C2 and C3 fibres. Knowledge of such anatomical variations is important for surgery, clinical intervention or trauma involving the carotid triangle or the structures within or deep to this region.

The "vagal ansa": a source of complication in vagus nerve stimulation

A 16-year-old boy underwent vagus nerve stimulation for treatment-resistant multifocal epilepsy. During intraoperative system diagnostics, vigorous contraction of the ipsilateral sternomastoid muscle was observed. On re-exploration, a thin nerve fiber passing from the vagus to the sternomastoid was found hooked up in the upper electrode. Detailed inspection revealed an abnormal course of the superior root of the ansa cervicalis, which descended down as a single nerve trunk with the vagus and separated to join the inferior root. The authors discuss the variation in the course of the ansa cervicalis and how this could be a reason for postoperative neck muscle contractions.

Innervation of the lower third of the sternocleidomastoid muscle by the ansa cervicalis through the C1 descendens hypoglossal branch: a previously unreported anatomical variant

We describe a previously unreported anatomical variant (found during a routine neck dissection) in which the lower third of the sternocleidomastoid was innervated by the C1 branch of the ansa cervicalis (descendens hypoglossi).

Rare case of double looped ansa cervicalis associated with its deep position in the carotid triangle of the neck

Ansa cervicalis (AC) frequently shows its variations in the formation and distribution pattern. However, variation in its looping pattern associated with abnormal topographic disposition is relatively rare. Knowledge on the possible deviations in the looping pattern is clinically important, to avoid iatrogenic injuries in surgical procedures. We report here a concurrent rare case of double looped AC located deep to internal jugular vein. Anatomy of its superior root was normal, but the usual appearance of inferior root had gone astray due to formation of double loop. AC is being popularly used for nerve reconstructive surgery in treating paralyzed larynx, tongue hemiatrophy. Anatomical variation of it may potentially jeopardize the surgical procedures. Therefore, it is essential to the surgeons to be familiar with its unusual variations.

An anatomical variation in the formation of the inferior root of ansa cervicalis

During regular dissections, we observed an unusual organization of the inferior root of Ansa Cervicalis (AC). The superior root of ansa arose normally from the hypoglossal nerve. The ventral ramus of the C2 spinal nerve divided into two branches. One of its branches joined the superior root independently to form a loop at a higher level. Another branch ran along the vagus nerve, joined with the ventral ramus of C3 spinal nerve, finally connected with the superior root and formed the second loop at a lower level. No variation was found in formation of superior root. Knowledge on the possible deviations in the formation of these roots is clinically important, to prevent iatrogenic injuries in surgical procedures such as thyroplasties, arytenoids adductions, and Teflon injections.

A comprehensive review with potential significance during skull base and neck operations, Part II: glossopharyngeal, vagus, accessory, and hypoglossal nerves and cervical spinal nerves 1-4

Knowledge of the possible neural interconnections found between the lower cranial and upper cervical nerves may prove useful to surgeons who operate on the skull base and upper neck regions in order to avoid inadvertent traction or transection. We review the literature regarding the anatomy, function, and clinical implications of the complex neural networks formed by interconnections between the lower cranial and upper cervical nerves. A review of germane anatomic and clinical literature was performed. The review is organized into two parts. Part I discusses the anastomoses between the trigeminal, facial, and vestibulocochlear nerves or their branches and other nerve trunks or branches in the vicinity. Part II deals with the anastomoses between the glossopharyngeal, vagus, accessory and hypoglossal nerves and their branches or between these nerves and the first four cervical spinal nerves; the contribution of the autonomic nervous system to these neural plexuses is also briefly reviewed. Part II is presented in this article. Extensive and variable neural anastomoses exist between the lower cranial nerves and between the upper cervical nerves in such a way that these nerves with their extra-axial communications can be collectively considered a plexus.

Relationship between the ansa cervicalis and the omohyoid muscle: clinical consequences in parathyroid surgery

PURPOSE

To determine the position of the lower loop of the ansa cervicalis (AC) compared to the inferior edge of the omohyoid muscle to guide minimally invasive surgery for the lateral oblique approach of parathyroid glands.

METHODS

Authors performed 36 anatomical dissections in the laboratory of anatomy (Laboratoire d'Anatomie Des Alpes Françaises) of the Grenoble medical school in 2012 on human cadavers. They independently measured the distance between the caudal extremity of the AC and the lower edge of the superior belly of the omohyoid muscle. Then, they controlled this measure on pictures.

RESULTS

The study shows a majority of long AC (under the omohyoid muscle) in 66.7 % of cases. In addition, the AC was located on an average value of 0.1 cm below the lower edge of the omohyoid muscle (median -0.5 cm). Thus, two-thirds of AC are between 0 and -2 cm under the omohyoid muscle. Furthermore, the AC is generally non-symmetrical: there is a mean difference of 1.3 cm between the left and right AC. In this series, there are as many long AC on the right side as on the left side.

CONCLUSIONS

These results are in contradiction with literature data. To preserve the ansa cervicalis and its phonatory functions, it is necessary for the surgeon to perform a systematic per operative identification of the AC because the position of the AC is mainly under the omohyoid muscle and because of an asymmetry. Per operative neurostimulation and/or magnified lenses might be helpful during the surgical approach.

Some unusual types of formation of the ansa cervicalis in humans and proposal of a new morphological classification

Ansa cervicalis (ansa hypoglossi) is a peripheral nerve structure-the primary choice for laryngeal reinnervation. Because the ansa formation is quite variable in humans, it is an object of a number of proposed classifications. Two interesting cases of formation of the ansa cervicalis were found during routine anatomical dissections. In the first case the unusual ansa had three basic roots-a superior one from the hypoglossal nerve, an aberrant middle root from the vagus nerve and an inferior root, coming from the cervical ventral branches. In the second case an ansa was described having roots from the vagus nerve and cervical ventral branches. Based on the reported variations and extensive review of the pertinent literature, a new morphological classification of the ansa cervicalis formation in human is proposed here.

Clinical significance of vagus nerve variation in radiofrequency ablation of thyroid nodules

OBJECTIVES

To evaluate the types and incidence of vagus nerve variations and to assess factors related to the vulnerability of vagus nerves during the radiofrequency (RF) ablation of thyroid nodules.

METHODS

Bilateral vagus nerves of 304 consecutive patients who underwent ultrasound of the neck were assessed. Two radiologists evaluated vagus nerve type (types 1-4; lateral/anterior/medial/posterior), the shortest distance between the thyroid gland and vagus nerve, and thyroid contour. Vagus nerve vulnerability was defined as a vagus nerve located within 2 mm of the thyroid gland through the ex vivo experiments, and factors associated with vulnerability were assessed.

RESULTS

We were unable to find one vagus nerve. Of the 607 vagus nerves, 467 (76.9%) were type 1, 128 (21.1%) were type 2, 10 (1.6%) were type 3, and 2 (0.3%) were type 4, with 81 (13.3%) being vulnerable. Univariate analysis showed that sex, location, thyroid contour and type were significantly associated with vagus nerve vulnerability. Multivariate analysis showed that bulging contour caused by thyroid nodules (P = 0.001), vagus nerve types 2/4 (P < 0.001) and type 3 (P < 0.001) were independent predictors.

CONCLUSION

The operator should pay attention to anatomical variations and the resulting vagus nerve injury during RF ablation of bulging thyroid nodules.

Laryngeal reinnervation using ansa cervicalis for thyroid surgery-related unilateral vocal fold paralysis: a long-term outcome analysis of 237 cases

Objective

To evaluate the long-term efficacy of delayed laryngeal reinnervation using the main branch of the ansa cervicalis in treatment of unilateral vocal fold paralysis (UVFP) caused by thyroid surgery.

Summary of Background Data

UVFP remains a serious complication of thyroid surgery. Up to now, a completely satisfactory surgical treatment of UVFP has been elusive.

Methods

From Jan. 1996 to Jan. 2008, a total of 237 UVFP patients who underwent ansa cervicalis main branch-to-recurrent laryngeal nerve (RLN) anastomosis were enrolled as UVFP group; another 237 age- and gender-matched normal subjects served as control group. Videostroboscopy, vocal function assessment (acoustic analysis, perceptual evaluation and maximum phonation time), and electromyography were performed preoperatively and postoperatively. The mean follow-up period was 5.2±2.7 years, ranging from 2 to 12 years.

Results

Analysis of videostroboscopic findings indicated that the glottic closure, vocal fold edge, vocal fold position, phase symmetry and regularity were significantly improved in the UVFP group (P<0.001, postoperative vs. preoperative). The postoperative parameters of vocal function were also significantly improved in the UVFP group (P<0.001) and showed no statistical differences compared to the control group (P>0.05, respectively). Postoperative laryngeal electromyography confirmed successful reinnervation of laryngeal muscle.

Conclusions

Delayed laryngeal reinnervation with the main branch of ansa cervicalis is a feasible and effective approach for treatment of thyroid surgery-related UVFP; it can restore the physiological laryngeal phonatory function to the normal or a nearly normal voice quality.

A novel modification of the ansa to recurrent laryngeal nerve reinnervation procedure for young children

Vocal ford paralysis is a condition often seen in otolaryngologic adult and pediatric clinics. We report a case we believe to be the youngest child to undergo ansa cervicalis (ansa) to recurrent laryngeal nerve (RLN) reinnervation for unilateral vocal fold paralysis. We have included the preoperative and postoperative videostroboscopic and acoustic findings. The acoustic data shows improvement and is consistent with the patient's improved voice quality. Most notably the patient's voice quality is less raspy and his volume has improved while subjectively requiring less effort.

Unusual origin of the ansa cervicalis observed during carotid endarterectomy

The surgical approach of the carotid artery for carotid endarterectomy demands knowledge of normal anatomy and anatomic variation. During carotid endarterectomy, a rare anatomic variant of the origin of the upper root of the ansa cervicalis was found. Contrary to commonly found anatomy, no upper root of the ansa cervicalis originating from the hypoglossal nerve was found. Instead, what seemed to be the ansa cervicalis originated from the vagus nerve and passed over the carotid bifurcation, branching to the infrahyoid muscles. Transection of this ansa cervicalis, for the purpose of good exposure, had no functional or cosmetic consequences.

Changes in surgical anatomy following thyroidectomy

Thyroid reoperation is known to carry a higher risk for complications because of the increased challenge of identifying tissue planes, presence of adherent strap muscles, and generalized scarring of the thyroid bed. Consideration of postsurgical changes in the anatomy of important landmarks, such as the recurrent and superior laryngeal nerves, brachiocephalic artery, and parathyroid glands, is crucial during preoperative planning for thyroid reoperations. This article provides a review of these key changes in surgical anatomy and the implications of the anatomic changes after thyroidectomy.

Anatomy of the ansa cervicalis: nerve fiber analysis

Ansa cervicalis complex, which innervates the infrahyoid muscles, is formed by the union of two roots derived from the anterior primary rami of the first three or four cervical spinal nerves. According to its relationship with the internal jugular vein, there are three ansa types: medial, lateral, or mixed. Nerve fiber microscopy was carried out in 18 ansa cervicalis complexes after staining with Sudan Black, in order to study composition and structural arrangement in detail. Fibers from both first and second cervical nerves (C1, C2) joined the hypoglossal nerve and later left it partially in the superior root of the ansa, which also contained ascending fibers derived from the inferior root components; usually the second and third cervical nerves. Those ascending fibers, together with the C1 and C2 fibers remaining in the hypoglossal nerve, innervate thyrohyoid and geniohyoid muscles. Cervical nerve fibers could be observed within the hypoglossal nerve even after the ramification of those branches. Further, cervical nerve fibers were continuously issued to the peripheral layers of the hypoglossal nerve where the fibers of the two nerves intermingled, forming a complex structure. The general arrangement of the ansa did not change according to its type or segmental composition. Although the hypoglossal nerve does not make any significant contribution to the formation of the ansa, the close relationship between the two nerves observed in the present study calls for the use of a more descriptive term such as ansa hypoglosso-cervicalis. The pattern of innervation of the infrahyoid muscles is also discussed.

Ansa Cervicalis-to-Recurrent Laryngeal Nerve Anastomosis for Unilateral Vocal Fold Paralysis: Experience of a Single Institution

Objectives:

One treatment option for unilateral vocal fold paralysis (UVFP) is ansa cervicalis-to-recurrent laryngeal nerve (ansa-RLN) anastomosis to provide reinnervation to the affected vocal fold. The advantages of this treatment approach are that it 1) provides vocal fold tone, bulk, and tension, 2) is technically simple, and 3) does not preclude other medialization procedures. We present all patients who have undergone ansa-RLN anastomosis for UVFP at our institution.

Methods:

An Institutional Review Board-approved retrospective chart review was performed to include all patients who had undergone an ansa-RLN anastomosis procedure for UVFP at our institution. Data from clinical and endoscopic laryngoscopy with stroboscopy were recorded. Statistical analysis was performed on visual and perceptual vocal data.

Results:

A total of 46 patients were included in the study. Stroboscopic analysis and perceptual vocal evaluation was performed in a blinded fashion on the 21 patients who had preoperative and postoperative stroboscopy. Severity, roughness, breathiness, and strain all improved significantly over time. Glottic closure, vocal fold edge, and supraglottic effort all significantly improved after operation. Of the 38 patients with at least 3 months of follow-up, all except 1 demonstrated evidence of reinnervation.

Conclusions:

This technique for treating UVFP results in significant improvements in patients' voice and on visual examination.

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.

Microsurgical anatomy of the hypoglossal nerve

The aim of the present study was to review the surgical anatomy of the hypoglossal nerve (HN), to reveal its relationships on its course and to provide some landmarks to its identification. Ten cadaveric head dissections (20 sides) were performed using microsurgical techniques. The anatomical relationships between the HN and other nerves, muscles, arteries and veins were carefully recorded, and some measurements were made between the HN and related structures. Thus, various landmarks were determined for the easy identification of the HN. In addition, the hypoglossal triangle, which containes major vascular structures, is described. The HN is divided into three main parts: cisternal, intracanalicular and extracranial. The HN arises from the medulla as a line of rootlets situated along the anterior margin of the lower two-thirds of the olive in the preolivary sulcus. It is the newly described 'hypoglossal' triangle in the anterior neck that is bordered by the descending hypoglossus laterally, transverse hypoglossus inferiorly and inferior border of the stylohyoid muscle superiorly. In our specimens, we determined that the HN was 3-7 mm (mean 5 mm) inferior to the digastric tendon, as well as mostly superficial. The occipital artery arose from the posterior surface of the external carotid artery (ECA) 6-9 mm (mean 7 mm) above the carotid bifurcation. There is also an important 'cross' between the occipital artery and the HN. In all cadavers, this crossing point was 7-9 mm (mean 8 mm) superior to the emergence of the occipital artery from the ECA. In conclusion, understanding the detailed anatomy of the HN and using landmarks to identify the nerve are crucial for surgery in the region.

Long-Term Follow-Up Results of Selective Laryngeal Adductor Denervation-Reinnervation Surgery for Adductor Spasmodic Dysphonia

Selective laryngeal adductor denervation-reinnervation surgery for the treatment of adductor spasmodic dysphonia was reported in 1999 in 21 patients with encouraging results. Here, we report long-term results of this procedure. Surgical outcome was evaluated using patient surveys and perceptual voice assessment. Measured outcomes included Voice Handicap Index (VHI)-10 scores, patient questionnaire, and perceptual evaluation for voice breaks and breathiness. Patient survey was obtained from 83 patients, and perceptual voice evaluation was performed in voice samples from 46 patients. Average follow-up interval was 49 months. Mean VHI-10 scores improved from a mean of 35.6 to 12.7. Eighty-three percent showed significantly improved VHI-10 scores, representing improved physical, social, and emotional well-being. There was a high degree of patient satisfaction, with 91% agreeing that their voice is more fluent after the surgery. Perceptual evaluation of postoperative voice samples revealed voice breaks in 26% (15% mild, 4% moderate, 7% severe) and breathiness in 30% (11% mild, 13% moderate, 6% severe). A majority of patients had stable, long-lasting resolution of spasmodic voice breaks.

Laryngeal reinnervation

Laryngeal reinnervation refers to any of a number of surgical procedures intended to restore neural connections to the larynx, which have usually been lost from some type of trauma (eg, surgical). The nerve function(s) to be restored may be those of the recurrent laryngeal nerve or its subdivisions, those of the superior laryngeal nerve, or both, and they may be motor or sensory. Several different donor nerves are available and have been described. The technique used may be direct end-to-end anastomosis (neurorrhaphy), direct implantation of a nerve ending into a muscle, the nerve-muscle pedicle technique, or muscle-nerve-muscle methods. These nerves and techniques may be combined in many ways. A number of new techniques have been reported in animal studies; however, the animal studies do not always predict the results of analogous surgeries in human patients. The historical and current perspectives on these techniques are discussed in this article.

Electromyographic findings in recurrent laryngeal nerve reinnervation

Abductor, adductor, and combined reinnervation procedures have been explored with variable success rates. We describe the experience of a tertiary care center with adductor reinnervation procedures, including preoperative and postoperative videostroboscopy and electromyography (EMG) findings. A retrospective chart review was performed from 1997 to 2001 that included 9 patients. Preoperative and postoperative voice comparison was performed by 3 blinded speech pathologists. Clinical comparisons of videostroboscopy findings for vocal fold bulk, tone, position, presence of gap, and movement are elucidated. The preoperative and postoperative EMG findings are described. In all patients, preoperative EMG revealed a dense, complete denervation of the affected recurrent laryngeal nerve. No movement was noted on videostroboscopy with persistent glottic gap. Reinnervation involved a nerve-muscle pedicle or a direct neurorrhaphy of the ansa cervicalis to the recurrent laryngeal nerve. Voice improvement was noted between 60 days and 3 months after reinnervation. Four postoperative EMG studies were performed. An early postoperative EMG study at 5 months revealed activation of the lateral cricoarytenoid muscle and thyroarytenoid muscle with head-lift. Videostroboscopy showed excellent near-midline static positioning of the vocal fold. Late EMG studies, performed 12 to 16 months after reinnervation, revealed "learning" of these muscles, with new activation on "eee" phonation. We conclude that recurrent laryngeal nerve reinnervation procedures belong in the armamentarium of the laryngologist for the treatment of vocal fold paralysis. The EMG findings reported in this study suggest that ongoing reinnervation allows for activation with phonation in matured neuronal anastomoses. Overall, this procedure results in excellent patient acceptance and near-normal vocal quality.

Vagal origin of the ANSA cervicalis nerve - report of two cases

Ansa cervicalis is a loop of nervers usually by C1, C2 and C3 fibres in the lateral aspect of the neck, Occasionally the superior root of the ansa (derived from C1) may original from the vagus either party or entirely, but the fibres can be traced back to their true cases of ansa cervicalis arising from the nagal trunk observed in dissection room cadavers is described here. Since the ansa cervicalis is frequently used in reinnervation of the paralyzed larynx, awareness of such a variation will be of use to the surgeon during a surgical procedure.

Bilateral oblique approach to parathyroid glands

OBJECTIVE

To propose a simple and minimally invasive approach for parathyroid surgery.

SUMMARY BACKGROUND DATA

Minimally invasive approaches to the parathyroid glands may involve preoperative morphologic explorations, perioperative biologic controls, or videocervicoscopy, a new method.

METHODS

The authors describe 597 patients who underwent parathyroidectomy through an original bilateral oblique approach between 1976 and 1997. None underwent morphologic exploration or biologic perioperative monitoring. In primary hyperparathyroidism, the four glands are controlled and it is possible to check their abnormalities of location or number. In secondary hyperparathyroidism and multiple endocrine neoplasia (MEN), a total or subtotal parathyroidectomy is performed.

RESULTS

The results and vocal morbidity are the same as that from authors using transverse cervicotomy, but this approach is more comfortable for the patient and allows total exploration of the location through short incisions without bleeding, visceral contusions, or muscle lesion.

CONCLUSIONS

This cervicotomy is easy and secure even if the surgeon is not trained in this approach because it uses and respects the anatomy of the cervical fasciae. It can be used without preoperative localization, intraoperative monitoring, or specialized material. But this approach could be also proposed for unilateral exploration guided by these methods and for surgical treatment of recurrent hyperparathyroidism after a transverse cervicotomy.

Combined arytenoid adduction and laryngeal reinnervation in the treatment of vocal fold paralysis

OBJECTIVE/HYPOTHESIS

Glottal closure and symmetrical thyroarytenoid stiffness are two important functional characteristics of normal phonatory posture. In the treatment of unilateral vocal cord paralysis, vocal fold medialization improves closure, facilitating entrainment of both vocal folds for improved phonation, and reinnervation is purported to maintain vocal fold bulk and stiffness. A combination of medialization and reinnervation would be expected to further improve vocal quality over medialization alone.

STUDY DESIGN

A retrospective review of preoperative and postoperative voice analysis on all patients who underwent arytenoid adduction alone (adduction group) or combined arytenoid adduction and ansa cervicalis to recurrent laryngeal nerve anastomosis (combined group) between 1989 and 1995 for the treatment of unilateral vocal cord paralysis. Patients without postoperative voice analysis were invited back for its completion. A perceptual analysis was designed and completed.

METHODS

Videostroboscopic measures of glottal closure, mucosal wave, and symmetry were rated. Aerodynamic parameters of laryngeal airflow and subglottic pressure were measured. A 2-second segment of sustained vowel was used for perceptual analysis by means of a panel of voice professionals and a rating system. Statistical calculations were performed at a significance level of P = .05.

RESULTS

There were 9 patients in the adduction group and 10 patients in the combined group. Closure and mucosal wave improved significantly in both groups. Airflow decreased in both groups, but the decrease reached statistical significance only in the adduction group. Subglottic pressure remained unchanged in both groups. Both groups had significant perceptual improvement of voice quality. In all tested parameters the extent of improvement was similar in both groups.

CONCLUSION

The role of laryngeal reinnervation in the treatment of unilateral vocal cord paralysis remains to be established.

Strap muscle neurovascular supply

OBJECTIVES/HYPOTHESIS

Knowledge and preservation of the neurovascular supply to strap muscles, such as the sternohyoid (SH) muscle, used in laryngotracheal reconstruction are important in preventing loss of tissue and bulk from ischemia and/or denervation.

STUDY DESIGN

Arteriovenous and neural supply variations to the strap muscles were examined in cadaver specimens.

METHODS

Strap muscle neurovascular supply was studied in 16 cadavers, including one transparent corrosion cast specimen with injected vessels.

RESULTS

For the upper SH and upper belly of the omohyoid (OMO), the arterial supply consistently arose from a branch of the superior thyroid artery (STA) most commonly terminating at the cricothyroid membrane. The inferior SH was supplied by the inferior thyroid artery. The ansa cervicalis innervated the SH inferiorly with a branch below the loop. Each arterial branch to the muscles had an accompanying venous tributary. The corrosion cast specimen demonstrated that the arterial lumen diameters were almost threefold larger in branches entering the upper SH, compared with the lower SH or OMO. Small intramuscular arteries without axial supply were found within the middle third of the upper SH, the lower SH, and the upper OMO.

CONCLUSIONS

It is possible to preserve neurovascular integrity in an inferiorly based SH flap. The superior and medial borders are released, with dissection of vascular supply laterally and deep to the muscle, and preservation of the inferior terminal ansa branch.