|Year : 2016 | Volume
| Issue : 1 | Page : 28-30
A rare case of tendinous clavicular insertion of the trapezius muscle: Could it be a cause for supraclavicular nerve entrapment syndrome?
Jyothsna Patil, Melanie R D'Souza, Naveen Kumar, S Swamy Ravindra, Ashwini Aithal
Department of Anatomy, Melaka Manipal Medical College (Manipal Campus), Manipal University, Manipal, Karnataka, India
|Date of Web Publication||29-Feb-2016|
Department of Anatomy, Melaka Manipal Medical College (Manipal Campus), Manipal University, Manipal - 576 104, Karnataka
Source of Support: None, Conflict of Interest: None
Supraclavicular nerve entrapment syndrome is a rare cause for anterior shoulder girdle pain. This syndrome is usually related to anatomic variants involving the bones, fibrous bands, muscles, and tendons. Here, we report a case of an unusual tendinous insertion of trapezius muscle with the possible entrapment of the supraclavicular nerves. The tendon appeared from the muscle fibers and inserted into the clavicle along the posterior boundary posterior triangle and ran forward above the clavicle and inserted into the clavicle, apart from the insertion of the sternocleidomastoid muscle, along with the few additional slips of the sternocleidomastoid muscle. The supraclavicular nerve coursed downward deep into this variant tendon and its lateral division and then passed through the gap formed between the tendon and the clavicle. In addition to this, the external jugular vein (EJV) passed through the same thin gap. Clinicians should be aware of such rare variations, which might be a possible cause for the supraclavicular nerve entrapment syndrome.
Keywords: External jugular vein (EJV), nerve entrapment, supraclavicular nerve, trapezius
|How to cite this article:|
Patil J, D'Souza MR, Kumar N, Ravindra S S, Aithal A. A rare case of tendinous clavicular insertion of the trapezius muscle: Could it be a cause for supraclavicular nerve entrapment syndrome?. Sifa Med J 2016;3:28-30
|How to cite this URL:|
Patil J, D'Souza MR, Kumar N, Ravindra S S, Aithal A. A rare case of tendinous clavicular insertion of the trapezius muscle: Could it be a cause for supraclavicular nerve entrapment syndrome?. Sifa Med J [serial online] 2016 [cited 2022 Dec 8];3:28-30. Available from: https://www.imjsu.org/text.asp?2016/3/1/28/177694
| Introduction|| |
The supraclavicular nerves arise as a common trunk formed from the cervical spinal nerve 3 (C3) and the cervical spinal nerve 4 (C4) nerves that divide into the medial, intermediate, and lateral branches just superior to the clavicle between the sternocleidomastoid and trapezius muscles. The medial branch supplies the skin as far as the midline and as low as the second rib. The intermediate branch supplies the skin over the pectoralis major and deltoid muscle and the lateral branch supplies the skin of the upper and posterior parts of the shoulder. 
The trapezius muscle forms the posterior boundary of the posterior triangle of the neck. It is a composite muscle as it is derived partly form the branchial mesoderm and partly from the adjacent myotomes.  Routinely on either side, the muscle is attached to the superior nuchal line, external occipital protuberance, Ligamentum nuchae, spinous processes and their supraspinous ligaments of thoracic vertebrae. The superior fibers, also known as occipital fibers, are attached to the clavicle; the middle and inferior fibers are attached to the scapula.  Variations of the trapezius muscle are common in its cervical, occipital, vertebral, and clavicular attachments. In the present case, an unusual tendinous insertion of the trapezius muscle is reported. The variant tendon was formed by some muscle fibers getting separated from the superior fibers of the trapezius muscle along the posterior boundary of the posterior triangle above the clavicle and getting inserted into the clavicle near its medial end, apart from the insertion of sternocleidomastoid muscle, along with the attachment of few additional slips of the sternocleidomastoid muscle.
External jugular vein (EJV) is a superficial vein of the neck formed by the union of the posterior division of the retromandibular vein and the posterior auricular vein near the angle of the mandible. In its course, it obliquely descends superficial to the sternocleidomastoid muscle and pierces the investing layer of the deep cervical fascia before it drains into the subclavian vein. In the present case, the EJV was markedly thinner and relatively deeper in its situation. Due to variant tendinous insertion of the trapezius muscle into the medial end of the clavicle, the EJV was passing through the gap between the tendon and the clavicle.
| Case Report|| |
During the routine dissection of the neck region of a 60-year-old male cadaver, we found an unusual tendinous insertion of the trapezius muscle. The upper fibers of the trapezius muscle originating from the superior nuchal line of the occipital bone were absent. The occipital artery and greater occipital nerve appeared in the scalp directly after piercing the semispinalis and splenius capitis muscles. The upper fibers arising from the external occipital protuberance and the Ligamentum nuchae proceeded downward and laterally to insert into the posterior border of the lateral third of the clavicle. A tendon that appeared from the trapezius muscle fibers ran forward above the clavicle and inserted into the clavicle 6-cm lateral to its medial end, along with the few additional slips of the sternocleidomastoid muscle. The supraclavicular nerve coursed downward deep to this variant tendon and then passed forward through the gap between the tendon and the clavicle. Here, it divided into medial, intermediate, and lateral branches and pierced the deep fascia to supply the skin of the pectoral and the shoulder regions. We also noted that the EJV was passing through the same thin gap [Figure 1].
|Figure 1: Showing tendinous (TTM) insertion of the trapezius muscle (TM) into clavicle close to the insertion of the sternocleidomastoid (SCM) muscle and its accessory slip (ASCM), EJV = External jugular vein, SCN = Supraclavicular nerve with its medial (M), intermediate (IM), and lateral (L) divisions. OH = Inferior belly of the omohyoid muscle. GAN = Great auricular nerve, PG = Parotid gland, SSG = Submandibular gland|
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| Discussion|| |
The trapezius muscle extends as a flat triangular muscle over the dorsum of the neck and the upper thorax and converges on the outer part of the pectoral girdle. The muscle consists of superior, middle, and inferior fibers that have been referred as cleido-occipitalis, dorso-scapularis superior, and dorso-scapularis inferior, respectively. 
Variations of the muscle have been described, which is mainly concerned with its morphological attachments. Absence of the superior portion,  inferior portion,  and sometimes the whole of the muscle has been reported previously. 
In the present case, we found a tendon arising from the clavicular fibers of the trapezius muscle that was then inserted into the clavicle blending with a slip from the sternocleidomastoid muscle. Kwak et al. christened this type of variant muscle as cleido-occipitalis cervicis muscle.  However, these types of variant muscular slips have also been identified by different names in the literature. Variant muscular slips arising from the trapezius muscle termed cleido-occipitalis and cleidocervicalis muscles have been reported by Nagashima et al.  and variant muscular slip in the neck region has been referred as celido-occipitalis reported by Tomo et al. 
Rahman and Yamadori  and Kwak et al.  reported such cases and proposed the embryological basis of the existence of such a variation stating that the cleido-occipitalis muscle results from an anlage degeneration and abnormal segregation of a part of the trapezius muscle. This portion of the variant muscle probably got isolated during the separation of the trapezius muscle and the sternocleidomastoid muscle anlagen and remained separated instead of joining with the main muscle mass of the trapezius.
Interestingly, in both the reports of homologous muscular variations, the authors did not report on the possible compression of any vascular or nervous structures. Rahman and Yamadori  reported not in the text but in the figure legend that the tendinous portion of the aberrant muscle is crossed by the supraclavicular nerves.
The supraclavicular nerve branches pierce the deep fascia to supply the skin over the front of the chest and the shoulder. Shoulder pain can be caused due to rotator cuff injuries, frozen shoulder, thoracic outlet syndrome, tendonitis, fibromyalgia, etc. Since the supraclavicular nerve lies in close proximity to the clavicle, it is vulnerable to injury in cases of clavicle fracture and in the surgical treatment of these fractures. Entrapment of the supraclavicular nerve with the bony canal of the clavicle has already been recognized as a cause for nerve entrapment neuropathy. The development of painful neuromas after iatrogenic transection and symptomatic nerve entrapment in fracture callus after healing has also been described. 
Our finding unveils the possibility of entrapment of nerve due to variant muscle attachments as we observed the supraclavicular nerve passing through the space formed by the insertion of the variant tendon to the clavicle. Due to this, during slight abduction of the ipsilateral arm the fibrous arch can compress the underlying supraclavicular nerves.
Hence, the existence of a cleidocervicalis muscle should be considered in cases of shoulder pain consistent with supraclavicular nerve entrapment or compression.
We also found the EJV passing through the space beneath the tendinous arch. Here, the caliber of the vein was much reduced. Such findings were also reported by Ravindra et al.  This unique anatomical position of the EJV may lead to its impingement during certain actions of the trapezius muscle. EJV is often used for catheterization and also as venous manometers. Their ligation is a prerequisite during radical neck dissection surgeries.  Possible entrapment of the EJV in the spaces created by the persistence of anomalous structures in the neck could mislead these approaches and might pose severe clinical complications.
Awareness of the variant attachment of the muscle is important as it can be mistaken as pathologically enlarged lymph nodes, cysts, or thrombosed veins.  It is also vital for the surgeon in order to gain a better examination of the region and for the anesthesiologist in order to execute with more accuracy and safety. Also, such a variant could result in difficulties during the procedure of vein catheterization.
| Conclusion|| |
Knowledge of unexpected passage of supraclavicular nerves and EJV through the abnormal passage created by the presence of tendinous muscle slips is clinically important, particularly in the management of supraclavicular nerve entrapment syndrome and in various therapeutic approaches involving EJV.
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Conflicts of interest
There are no conflicts of interest.
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