Study of variant anatomical structures (bony canals, fibrous bands, and muscles) in relation to potential supraclavicular nerve entrapment

A Cadaveric Case of an Accessory Cleido-Occipital Muscle Over the Common Trunk of the Supraclavicular Nerves

The current study describes a case of an aberrant cleido-occipital muscle. In particular, this muscle was arising from the middle part of the clavicle, inserted into the medial part of the upper trapezius muscle, and crossed over the supraclavicular nerves with possible compression of them, especially during shoulder abduction. Knowledge of the muscular variability of the posterior cervical triangle is crucial for supraclavicular nerve entrapment syndrome diagnosis and treatment. The appearance of aberrant muscular fascicles may lead to misinterpretation of neck imaging, as well as difficulties during surgical procedures undertaken in the region.

The supraclavicular nerve

INTRODUCTION/AIMS

The aim of this study was to describe a new method for studying the supraclavicular nerve (SCN) conduction and to report four cases with SCN lesions.

METHODS

The SCN was antidromically recorded with a pair of self-adhesive electrodes located in the middle of the clavicle. Stimulation (<5 mA) was delivered 7 cm proximally with a bar electrode. To facilitate recording, it was explained to the participant that they would feel a very faint electrical sensation locally and an electrical tingle upward (ear) or downward (shoulder/clavicle). Each participant was asked to say when the tingling moved downward.

RESULTS

In normal subjects, median values were 16 μV (range: 9-33) for sensory nerve action potential (SNAP) amplitude; 1.2 ms (range: 1-1.5) for onset latency; and 1.25 (range: 1-1.7) for side-to-side amplitude ratio. In the four patients, the SCN SNAP was absent on the pathological side and normal on the healthy side. All four patients complained of unilateral neuropathic hypoesthesia on the anterior aspect of the neck, chest, and shoulder that occurred after radical neck surgery for thyroid or larynx cancer (x3) and first rib resection (x1).

DISCUSSION

A comparison with previous reports shows that this simple method provides similar or highest SNAP amplitudes. SCN lesions are rare, and rarely referred for electrodiagnosis, and often overlooked. However, the SCN conduction study, which causes very slight inconvenience (low-intensity stimulation), allows a better understanding of the origin of the complaints and permits the patient to benefit of more suitable treatment.

Fascial entrapment neuropathy

Entrapment neuropathies are debilitating clinical conditions, creating significant morbidity in the upper and lower extremities in terms of pain, sensory abnormalities, and motor weakness, becoming a challenge to diagnose and treat. Because entrapments can have multiple origins, a misinterpretation of anatomy during examination can lead to incorrect diagnosis and treatment. This review addresses understanding of the anatomy of fascia that can play an important role in this syndrome. There is a specific microenvironment around the nerve composed of connective tissues that include deep fascia, intermuscular septa, epineurium, and perineurium. The microenvironmental modifications can be translated into change in mobility with consequence decreasing of the independency of the nerve from the surrounding structures lading to entrapments and "internal stretch lesion." The entrapments reported in this article reinforce the importance of fascia tissue in generating common symptoms that pose more difficult diagnostic challenges and may often be confused with more common clinical conditions. Clin. Anat. 32:883-890, 2019. © 2019 Wiley Periodicals, Inc.

A rare anatomical variant: transosseous supraclavicular nerve identified during clavicle fracture fixation

We describe a rare case of an anatomical variant of the supraclavicular nerve in the intra-operative setting of clavicle fixation for a fracture. Intra-operatively it was noted that one of the supraclavicular nerves was passing through a foramen in the clavicle shaft. A 60-year-old gentleman presented with a displaced multifragmentary fracture of the left clavicle after a fall. Plate fixation with a pre-contoured locking plate was performed under general anaesthesia. The clavicle was exposed through an infraclavicular transverse incision. It was necessary to divide this transosseous nerve branch to permit appropriate plate positioning. Post-operatively the patient was left with some incisional chest numbness. Surgeons should aim to preserve the branches of the supraclavicular nerve although this may not always be possible as we have demonstrated. The patient should be warned about potential deficit.

Congenital Anatomical Variant of the Clavicle

The aim of this study is to present a rare abnormality of the clavicle (Code: SGS01) that was discovered in an ossuary in the Church of San Gaetano (Sulmona, central Italy; XVII-XIX centuries CE). In the middle third, the clavicle had three areas with losses of substance in the form of oval-shaped foramina with maximum diameters of 1-2 cm that were located in the anterior and superior surfaces of the diaphysis. The margins of these foramina were well defined and rounded, and the surfaces of the canal walls were smooth. Additionally, there were no zones of bony activity or reactive changes around the foramina. This new congenital anomaly of the clavicle and blood vessels is consistent with a variant that might have originated during fetal growth in which the subclavian vein or artery remained included during the process of ossification of the clavicle. Anat Rec, 300:1401-1408, 2017. © 2017 Wiley Periodicals, Inc.

Tunnels and grooves for supraclavicular nerves within the clavicle: review of the literature and clinical impact

Perforation of the clavicle by supraclavicular nerves is a common anatomical variation. This variation has been reported in several studies based on post-mortem, surgical and radiologic findings, with an overall frequency between 1 and 6.6 %. The penetrating branch passes either through a bony tunnel or a groove on the superior surface of the bone. Entrapment neuropathy of the perforating branch is a documented clinical entity reported in the literature. The intraosseous course of the supraclavicular nerves makes them vulnerable to injury in case of clavicular fractures or during surgical manipulations of these fractures. Furthermore, this variation should be taken into account during the interpretation of chest and shoulder radiographs. The purpose of the current study is to perform an extended review of the relevant literature, highlighting the clinical impact of this variation, as well as to incorporate our own findings into them.

A novel variant of the cleidocervicalis muscle with clinical implications for nerve compression/entrapment

PURPOSE

The cleidocervicalis muscle occurs in approximately 1-3 % of the population that may be confused with pathological neck masses. We describe a novel variant of the muscle and its clinical implications.

METHODS

This is a case report of a cleidocervicalis muscle variant identified during routine cadaveric dissection.

RESULTS

The muscle identified originated on the C5 vertebra and inserted on the clavicle medial to the trapezius muscle. Innervation was provided by a C6 spinal nerve branch. Notably, a branch of the supraclavicular nerve was closely associated with the muscle, raising the possibility of compression of this nerve.

CONCLUSIONS

Presence of a cleidocervicalis muscle should be considered in cases of shoulder pain consistent with supraclavicular nerve entrapment or compression.

Clavicle fractures - incidence of supraclavicular nerve injury

Objective

To analyze retrospectively 309 fractures in the clavicle and the relation with injury of the supraclavicular nerve after trauma.

Methods

It was analyzed 309 patients with 312 clavicle fractures. The Edinburgh classification was used. Four patients had fractures in the medial aspect of the clavicle, 33 in the lateral aspect and 272 in the diaphyseal aspect and three bilateral fractures.

Results

255 patients were analyzed and five had paresthesia in the anterior aspect of the thorax. Four patients had type 2 B2 fracture and one type 2 B1 fracture. All patients showed spontaneous improvement, in the mean average of 3 months after the trauma.

Conclusion

Clavicle fractures and/or shoulder surgeries can injure the lateral, intermediary or medial branches of the supraclavicular nerve and cause alteration of sensibility in the anterior aspect of the thorax. Knowledge of the anatomy of the nerve branches helps avoid problems in this region.

Supraclavicular nerve entrapment syndrome

Supraclavicular nerve entrapment syndrome, although rare, should be considered among the causes of anterior shoulder girdle pain. This syndrome is usually related to anatomic variants (involving the bone structures, fibrous bands, or muscles and tendons). Computed tomography is the most useful investigation. Medications used to treat neuropathic pain may provide relief. Otherwise, a local glucocorticoid injection or even surgical decompression should be considered.

The anatomy of the supraclavicular nerve during surgical approach to the clavicular shaft

BACKGROUND

Surgery for clavicular shaft fractures is becoming more common but incisional and chest wall numbness reportedly occurs in 10% to 29% of patients. This may be the result of iatrogenic injury to the supraclavicular nerve branches.

QUESTIONS/PURPOSES

We determined if there was a predictable branching pattern of the supraclavicular nerve at the anterior clavicular border and determined the distances to these nerves from clavicular landmarks.

METHODS

We performed an anatomic dissection along the anterior border of the long axis of the clavicle in 37 cadavers. The branches of the supraclavicular nerve were identified at the anterosuperior clavicular border and the distances from these nerves to palpable bony landmarks were measured.

RESULTS

Ninety-seven percent of specimens had a medial and a lateral branch of the supraclavicular nerve. Nearly half (49%) possessed an additional intermediate branch. No branch was found within 2.7 cm of the sternoclavicular joint or within 1.9 cm of the acromioclavicular joint. Between these two positions, there was wide variability in nerve branch location.

CONCLUSIONS

There were two or three branches of the supraclavicular nerve crossing the clavicle 97% of the time and a wide variability of the location of these branches outside the safe zones.

CLINICAL RELEVANCE

There are safe zones within 2.7 cm of the sternoclavicular joint and 1.9 cm of the acromioclavicular joint. Between these safe zones, the location of the nerve branches is variable and the surgeon must use meticulous dissection if he or she wishes to prevent transection.

Morphometric study of the shoulder and subclavicular innervation by the intermediate and lateral branches of supraclavicular nerves

BACKGROUND

The supraclavicular (intermediate) and supra-acromial (lateral) branches of supraclavicular nerves contribute to the innervation of the thorax, shoulder, and neck. Despite their clinical and surgical interest, they are not often considered for descriptive anatomy. The goal of this work was to clarify the morphometric knowledge of these two branches and to discuss the clinical relevance of the anatomical features.

METHODS

Intermediate and lateral branches of supraclavicular nerves of 14 necks (8 embalmed cadavers) were dissected using magnifying glasses. Macroscopic parameters were measured and nerve relationships were recorded.

RESULTS

In 12 cases, the intermediate and lateral branches arose from a common trunk behind the posterior border of the sternocleidomastoideus muscle, at a mean distance of 96 mm (70-137) from the sternal angle. The intermediate branch divided into two or three secondary rami. Its most internal ramus crossed the middle third of the clavicle and its most external ramus crossed the second lateral quarter of the bone. The distance between the two farthest nerve endings of this branch was at mean of 98 mm (85-125). The mean distance of the most distal nerve ending from the clavicle was 46 mm (30-63). The lateral branch divided into two or three rami in eight cases and did not divide in six cases. Its most anterior rami crossed the trapezius muscle at a mean distance from the clavicular insertion of 17 mm (12-24). In 13 cases, these rami ended posteriorly or at the level of the anterior border of the acromion process and in 12 cases, they ended laterally or at the level of the acromion process with a mean distance 10.4 mm (0-24).

CONCLUSION

In case of deficiency of these nerves, pain or sensitive deficit can occur without motor trouble. The factors of acute or chronic injury are direct compression, nerve stretching, repetitive stresses, and direct wound. Moreover, several neck or shoulder surgical approaches are dangerous for these nerves.