Anatomic landmarks for nerves of the neck: a vade mecum for neurosurgeons

Horner syndrome immediately after deep dissection of upper thyroid pole: a case report and review of the literature

Objectives

Horner syndrome (HS) is a rare complication of thyroid surgery. However, the relationship between the occurrence of HS and thyroid upper pole injury is still not completely clear, and there are only few reports.

Case presentation

A 24-year-old female underwent endoscopic thyroidectomy for thyroid papillary carcinoma. The intraoperative examination found that the upper pole of the thyroid was bleeding. During hemostasis, the ultrasonic knife consciously peeled too deep and stopped. The patient developed HS immediately after operation. We analyzed the association between deep dissection of the upper thyroid pole and an increase in the HS incidence rate through literature searches and anatomical relationships.

Conclusions

Our case report discussed the potential relationship between the degree of thyroid upper pole dissection and the occurrence of HS in routine thyroid surgery, and provided a warning for the degree of thyroid upper pole dissection in the clinic to avoid HS.

Anatomic Variability of the Accessory Nerve: Implications for Dissection of Level IIB

OBJECTIVES

During neck dissection, level IIB lymphadenectomy necessitates manipulation of the spinal accessory nerve that might be avoided and might cause postoperative disability. Current literature does not describe the effect of variation in the spinal accessory nerve in the upper neck. We sought to measure the effect of the dimensions of level IIB on nodal yield in level IIB and on patient reported neck symptoms.

METHODS

We measured the boundaries of level IIB of 150 patients undergoing neck dissection. Level II was dissected and separated into levels IIA and IIB intraoperatively. Patient-reported symptoms were assessed in 50 patients using the Neck Dissection Impairment Inventory. We computed descriptive statistics, and sought to identify correlation with the number and proportion of level IIB nodes and the number of metastatic nodes. Level IIB dimensions were analyzed as predictors of postoperative symptoms.

RESULTS

We measured 184 sides, with 37.7% of level II nodes found in level IIB. Mean accessory nerve length across level II was 2.5 cm. Every additional 1 cm in accessory nerve length was associated with two more level IIB nodes. At all accessory nerve lengths, meaningful numbers of nodes were present in level IIB. Accessory nerve length and other factors did not correlate with NDII scores.

CONCLUSIONS

Longer lengths of accessory nerve across level IIB correlated with greater nodal yield. However, data did not point to an accessory nerve length cutoff below which level IIB dissection could be avoided. In addition, the dimensions of level IIB did not correlate with postoperative neck symptoms.

LEVEL OF EVIDENCE

2 Laryngoscope, 134:154-159, 2024.

Horner syndrome after thyroid-related surgery: a review

BACKGROUND

Horner syndrome (HS) is caused by damage to the cervical sympathetic nerve. HS is a rare complication after thyroidectomy. The main manifestations of HS include miosis and ptosis of the eyelids, which seriously affect esthetics and quality of life. At present, there is a lack of research on HS after thyroidectomy, and its etiology is not completely clear. This review aimed to evaluate how to reduce the incidence of HS and promote the recovery from HS as well as to provide a reference for the protection of cervical sympathetic nerves during surgery.

RESULTS

HS caused by thyroid surgery is not particularly common, but it is still worthy of our attention. After searching with "Horner Syndrome," "Thyroid" as keywords, a total of 22 related cases were screened in PubMed. The results showed that open surgery, endoscopy, microwave ablation, and other surgical methods may have HS after operation. In addition, the statistics of 1213 thyroid surgeries in our hospital showed that the incidence of HS after endoscopic surgery (0.39%) was slightly higher than that after open surgery (0.29%). Further, this review analyzed potential causes of HS after thyroidectomy, so as to provide a theoretical basis for reducing its incidence.

CONCLUSION

Preventing HS during thyroidectomy is a difficult problem. The close and highly variable anatomical relationship between the thyroid and cervical sympathetic nerves increases the risk of sympathetic nerve damage during thyroidectomy. Surgery and the use of energy equipment are also closely related to the occurrence of HS.

Radiological evaluation of the localization of sympathetic ganglia in the cervical region

PURPOSE

To determine local variations of cervical sympathetic ganglia (CSG) according to vertebral levels on preoperative neck magnetic resonance imaging (MRI) by designating carotid artery (CA) as the standard landmark at the center, in attempts to prevent injury to CSG in the anterior-anterolateral approaches performed in the cervical spinal region.

MATERIALS AND METHODS

The retrospective study reviewed neck MRI images of 281 patients, of which the images of 231 patients were excluded from the study based on the exclusion criteria. As a result, the MRI images of the remaining 50 patients were included in the study. The circumference of carotid artery (CA) was divided into eight equal zones with CA defined as the standard landmark at the center. High-risk zones were determined based on the anterior-anterolateral approaches.

RESULTS

At C1 level, a superior ganglion was located on the right side in 32 (64%) and on the left side in 30 (60%) patients. At this level, it was most commonly located in Zone 6. Middle ganglion was observed most frequently at C3 level, which was detected on the right side in 17 (34%) and on the left side in 17 (34%) patients. At this level, it was most commonly located in Zone 2.

CONCLUSION

Variations in the localizations of superior and middle cervical ganglia should be taken into consideration prior to surgical procedures planned for this region. This study sheds light on high-risk zones in the surgical site and could guide surgeons to better understand the location of cervical sympathetic ganglia before surgical planning.

Concerning Auricular Vagal Nerve Stimulation: Occult Neural Networks

Auricular vagal nerve stimulation (AVNS) is an evolving neuromodulation technology that has a wide range of therapeutic applications across multiple disciplines of medical science. To date, AVNS results had been interpreted in the context of a monolog concept of the auricular branch of the vagus nerve (ABVN): that this is the sole network of the mechanism of action and/or structure in the auricular area of the stimulation in the context of activations in the brainstem nuclei, including the nucleus tractus solitarius (NTS), locus coeruleus (LC), trigeminal brainstem nuclei, and the nucleus cuneatus. This review considers the overlooked aspects of neural networks, connections, hijacking axons from cranial nerves and cervical sympathetic ganglions, the inhomogeneous distribution of perivascular sympathetic nerves, and intrinsic/extrinsic auricular muscles in the auricular zone that can explain the vagal and non-vagal nucleus activations in AVNS. In addition, the unique cortical representation of the human ear and interspecies differences in the auricula are discussed. The detailed auricular anatomy of the AVNS zone explored in the present study references structural and functional neural network information to overcome default designs and misinterpretations of existing research on AVNS to provide a better foundation for future investigations that use this modality.

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.

Triangles of the neck: a review with clinical/surgical applications

The neck is a geometric region that can be studied and operated using anatomical triangles. There are many triangles of the neck, which can be useful landmarks for the surgeon. A better understanding of these triangles make surgery more efficient and avoid intraoperative complications. Herein, we provide a comprehensive review of the triangles of the neck and their clinical and surgical applications.

An Unusual Superior Root of the Ansa Cervicalis

The ansa cervicalis is located around the carotid sheath and forms a neural loop, which consists of superior and inferior roots. It innervates the infrahyoid muscles. Anatomical variations of the superior root of the ansa cervicalis are uncommon. Herein, we present an extremely rare case of the superior root of the ansa cervicalis arising both from the hypoglossal and vagus nerves.

Anatomic study of the musculus longus capitis flap

PURPOSE

To clearly delineate the anatomy of the musculus longus capitis, determine its clinical applications for reconstruction surgery, and provide a safer surgical method of developing the longus capitis muscle flap.

METHODS

Anatomical investigations were performed in seven adult cadavers (five cadavers for gross anatomy and two for transparent specimen preparation) with respect to the location, morphology, arterial supply, and innervation of the musculus longus capitis, as well as its spatial relationship with the cervical sympathetic trunk, superior cervical ganglion, carotid sheath, and other surrounding structures.

RESULTS

The musculus longus capitis is located anterior to the C1-6 vertebrae, segmentally supplied by branches of the ascending cervical artery, innervated by the C1-5 nerve, and spatially close to the cervical sympathetic trunk, superior cervical ganglion, and carotid sheath. These anatomic findings indicate that the development of a cranial or caudal pedicled longus capitis muscle flap is feasible.

CONCLUSION

The musculus longus capitis can be developed into a cranial or caudal pedicled flap for repair of head and neck defects with negligible morbidity of the donor site.

Neuroanatomy and clinical analysis of the cervical sympathetic trunk and longus colli

Anterior cervical surgery is commonly used for cervical vertebral body lesions. However, the structure of blood vessels and nerve tissues along the route of anterior cervical surgery is complex. We aimed to measure the data of the longus colli, the sympathetic trunk and the cervical sympathetic trunk (CST) ganglia in Chinese cadaver specimens. A total of 32 adult cadavers were studied. We delineated the surgical anatomy of the CST. The superior and inferior/cervicothoracic ganglia of the sympathetic trunk consistently appeared. The middle ganglion was observed in 28.1% of the specimens and there were 2 cases of unilateral double middle cervical ganglia. The inferior ganglion was observed in 25.0% of the specimens and the cervicothoracic ganglion was observed in the remaining specimens. The distance between the CST gradually decreased from the top to the bottom, and the distance between the medial edges of the longus colli gradually broadened from the top down. The average angle between the bilateral CST and the midline of the vertebra was 11.2°±1.8° on the left side and 10.3°±1.4° on the right side. The average angle between the medial margins of longus colli of both sides was 11.1°±1.9°. The CST is at high risk when LC muscle is cut transversely or is dragged heavily, especially at the levels of C6 and C7. Awareness of the regional anatomy of the CST could help surgeons to identify and preserve it during anterior cervical surgeries.

Anatomical study of phrenic nerve course in relation to neck dissection

The present study sought to clarify the course of the phrenic nerve and its correlation with anatomical landmarks in the neck region. We examined 17 cadavers (30 sides). In each, the phrenic nerves was dissected from the lateral side of the neck, and its position within the triangle formed by the mastoid process and sternal and acromial ends of the clavicle was determined. The point where the phrenic nerve arises in the posterior triangle was found to be similar to the point where the cutaneous blanches of the cervical plexus emerge at the middle of the posterior border of the sternocleidomastoid muscle. In the supraclavian triangle, the phrenic nerve crosses the anterior border of the anterior scalene muscle near Erb's point where the superficial point is 2-3 cm superior from the clavicle and posterior border of the sternocleidomastoid muscle. The phrenic nerve arises in the posterior triangle near the nerve point, then descends to the anterior surface of the anterior scalene muscle in the supraclavian triangle. It is necessary to be aware of the supraclavian triangle below Erb's point during neck dissection procedures.

Imaging characteristics of schwannoma of the cervical sympathetic chain: a review of 12 cases

BACKGROUND AND PURPOSE

SCSCs are rare. This study reviews our experience with CT and MR imaging of SCSCs.

MATERIALS AND METHODS

We retrospectively reviewed the CT and MR imaging studies as well as clinical data of 12 patients (6 men, 6 women; mean age, 41 years; range, 27-55 years) with surgicopathologic evidence of SCSC, referred to our institution between January 1999 to October 2008. Images were evaluated with respect to the location, number, morphology, attenuation/signal intensity, enhancement characteristics, and patterns of mass effect of the schwannomas.

RESULTS

The schwannomas were solitary, well-circumscribed, and medial to the carotid sheath. Seven were hypoattenuated to skeletal muscle on CT with poor postcontrast enhancement, 4 were isoattenuated, and a single lesion showed intense heterogeneous enhancement. At MR imaging, they were heterogeneously bright on T2WI with intense inhomogeneous postgadolinium enhancement. The ICA was displaced anteriorly in 9 patients with a component of lateral displacement in 8 of these patients. The ICA was in a neutral position in 2 patients and posterolaterally displaced in 1 patient. A single patient demonstrated separation of the ICA and IJV. There was splaying of the carotid bifurcation in 4 patients.

CONCLUSIONS

We present the patterns of mass effect and the spectrum of CT and MR imaging characteristics of SCSC, including certain observations that are infrequently described in the published literature.

Surgical anatomy of the cervical sympathetic trunk during anterolateral approach to cervical spine

The sympathetic trunk is sometimes damaged during the anterior and anterolateral approach to the cervical spine, resulting in Horner's syndrome. No quantitative regional anatomy in fresh human cadavers describing the course and location of the cervical sympathetic trunk (CST) and its relation to the longus colli muscle (LCM) is available in the literature. The aims of this study are to clearly delineate the surgical anatomy and the anatomical variations of CST with respect to the structures around it and to develop a safer surgical method that will diminish the potential risk of CST injury. In this study, 30 cadavers from the Department of Forensic Medicine were dissected to observe the surgical anatomy of the CST. The cadavers used in this study were fresh cadavers chosen at 12-24 h postmortem. The levels of superior and intermediate ganglions of cervical sympathetic chain were determined. The distance of the sympathetic trunk from the medial border of LCM at C6, the diameter of the CST at C6 and the length and width of the superior and intermediate (middle) cervical ganglion were measured. Cervical sympathetic chain is located posteromedial to carotid sheath and just anterior to the longus muscles. It extends longitudinally from the longus capitis to the longus colli over the muscles and under the prevertebral fascia. The average distance between the CST and medial border of the LCM at C6 is 11.6 +/- 1.6 mm. The average diameter of the CST at C6 is 3.3 +/- 0.6 mm. Superior ganglion of CSC in all dissections was located at the level of C4 vertebra. The length and width of the superior cervical ganglion were 12.5 +/- 1.5 and 5.3 +/- 0.6 mm, respectively. The location of the intermediate (middle) ganglion of CST showed some variations. The length and width of the middle cervical ganglion were 10.5 +/- 1.3 and 6.3 +/- 0.6 mm, respectively. The CST's are at high risk when the LC muscle is cut transversely, or when dissection of the prevertebral fascia is performed. Awareness of the CST's regional anatomy may help the surgeon to identify and preserve it during anterior cervical surgeries.

Wilhelm Erb and Erb's point

Wilhelm Erb is well known for his early contributions to the field of neurology and was an eminent physician of his time. One area described by him and that still bears his name is Erb's point. This point located just superior to the clavicle was used by Erb to transcutaneously elicit contractions of various proximal arm muscles with electrical stimulation. Many have mistakenly interchanged the terms "Erb's point" and "nerve point" when describing the point of emergence of the cutaneous branches of the cervical plexus near the posterior border of the sternocleidomastoid muscle. We present a brief history of Erb's adult life and review his original description of his supraclavicular point and contrast this to the so called nerve point of the posterior cervical triangle. Clinicians and anatomists should be aware of the discrepancy often found in the literature between these two terms.