Bipartite clavicular attachment of the sternocleidomastoid muscle: a case report

Sternocleidomastoid Muscle in Fetuses: Classification, Morphometric Analysis, and Clinical Significance

PURPOSE

This study aimed to examine variations and morphometric properties of the sternocleidomastoid muscle (SCM) in fetuses in terms of infancy and early childhood surgeries.

MATERIALS AND METHODS

Neck regions of 27 fetuses (mean age: 23.30±3.40 wk, sex: 11 boys and 16 girls) fixed with 10% formalin were dissected bilaterally. Photographs of the dissected fetuses were taken in the standard position. Morphometric measurements, such as length, width, and angle, were performed on the photographs using the ImageJ software. In addition, the origin and insertion of SCM were detected. Taking into account the studies in the literature, a classification consisting of 10 types associated with the origin of SCM was carried out.

RESULTS

No statistically significant difference was observed in the parameters in terms of side and sex (P>0.05), except from the linear distance between the clavicle and motor point where the accessory nerve enters SCM (20.10±3.76 for male, 17.53±4.05 for female, P=0.022). Two-headed SCM (Type 1) was detected in 42 out of 54 sides. Two-headed clavicular head (Type 2a) was detected on 9 sides, and 3-headed (Type 2b) on 1 side. A 2-headed sternal head (Type 3) was detected on 1 side. A single-headed SCM (Type 5) was also detected on 1 side.

CONCLUSION

Knowledge related to variations of the origin and insertion of fetal SCM may be helpful in preventing complications during treatments of pathologies such as congenital muscular torticollis in early period of life. Moreover, the calculated formulas may be useful to estimate the size of SCM in newborns.

Variation of the sternocleidomastoid muscle: a case report of three heads and an accessory head

PURPOSE

Anatomical variations of the sternocleidomastoid muscle (SCM) have been observed to occupy multiple origins and insertion points and have supernumerary heads, sometimes varying in thickness.

METHODS

An 85-year-old Korean male cadaver was dissected and a SMC with unilateral supernumerary heads was identified.

RESULTS

Three heads and an accessory belly of the sternal head were recorded on the left side. There were two clavicular heads, one lateral and one medial. The sternal head originated inferior to the manubrium of the sternum. A small belly arose from the sternal head and merged to the lateral clavicular head on the C5 vertebrae level. These bellies inserted into the mastoid process of the temporal bone.

CONCLUSIONS

These variants may be problematic during surgical approaches to the upper neck and occipital, and should thus be appreciated by the clinician.

Bilateral sternocleidomastoid variant with six distinct insertions along the superior nuchal line

Anatomical variations of the sternocleidomastoid muscle (SCM) have been observed to occupy multiple origins and insertion points and have supernumerary heads, sometimes varying in thickness. During routine dissection, a SCM was observed to have six distinct insertions that interface with the course of the superior nuchal line, ending at the midline, bilaterally. This variation was also seen to receive innervation from the accessory nerve as well as the great auricular nerve. To our knowledge, this variant of supernumerary insertions and nerve innervations has not yet been reported. These variants may pose as problematic during surgical approaches to the upper neck and occiput, and should thus be appreciated by the clinician. Herein we discuss the case report, possible embryological origins, and the clinical significance of the observed variant SCM.

Accessory Clavicular Sternocleidomastoid Causing Torticollis in an Adult

Background

Sternocleidomastoid anomalies are mostly discovered in cadavers during routine dissection. Such anomalies causing torticollis are rare in adults. We report a case of accessory mid-clavicular head of the sternocleidomastoid causing torticollis in an adult.

Case

A previously healthy 27-year-old man presented with neck and shoulder pain following heavy manual work. On examination, he had mild restriction of left tilt of the head and right rotation of the neck. Palpation revealed a bipartite right sternocleidomastoid. There was no abnormal posturing of other body parts. The range of motion of the cervical spine was limited to rotation of 70° and tilt of 38° on the left side and rotation of 65°and tilt of 46° on the right side. Neck extension was 40°. The accessory sternocleidomastoid muscle belly was visible and inserted at the middle of the clavicle. Musculoskeletal ultrasound imaging confirmed the diagnosis. Radiological images of the cervical spine and electromyography were normal. Myectomy of the lateral accessory clavicular belly of the sternocleidomastoid was planned, but the patient declined this treatment. Currently, he uses oral analgesics and participates in occasional sessions of physical therapy.

Discussion

An accessory sternocleidomastoid can result in torticollis because it causes a physical restriction preventing the neck from tilting and rotating to the opposite side. In mild cases, the anomaly may remain undiagnosed until adulthood and can be confused with cervical dystonia and fibromatosis colli. Knowledge of the anatomy and possible variants of the sternocleidomastoid muscle is of the utmost importance to medical practitioners involved in the diagnosis and management of problems in the neck area. Variants of the sternocleidomastoid can be a concern for surgeons, physicians, and anesthetists performing interventional procedures on the neck because of possible confusion of anatomical landmarks.

Absence of Posterior Triangle: Clinical and Embryological Perspective

Sternocleidomastoid (SCM) and Trapezius (TM) muscle present in the cervical region serves as an important landmark in forming boundaries of posterior triangle of neck. This case reports a continuous muscle sheet obscuring the left posterior triangle in the neck of a 60-year-old Indian male cadaver. An unfamiliar oval gap was observed in its posterosuperior portion. Description of such a variant in anatomical literature is rare and is scarcely reported. An attempt has been made to portray its embryological and phylogenetic basis. In addition authors have endeavoured to discuss its clinical implications. Awareness of such anatomical variations is relevant for the operating surgeons in their endeavour to perform various reconstruction surgeries of head and neck, radiologists while concluding various levels in Computed Tomography (CT) and Magnetic Resonance Images (MRI) of the region and to the anaesthetists in their search for nerves and vessels while attempting various anaesthetic procedures.

Dorsoscapularis triangularis: embryological and phylogenetic characterization of a rare variation of trapezius

The muscle trapezius shows considerable morphological diversity. Variations include an anomalous origin and complete or partial absence of the muscle. The present study reported, a hitherto undocumented complete bilateral absence of the cervical part of trapezius. Based on its peculiar origin and insertion, it was named dorsoscapularis triangularis. The embryological, phylogenetic and molecular basis of the anomaly was elucidated. Failure of cranial migration of the trapezius component of the branchial musculature anlage to gain attachment on the occipital bone, cervical spinous processes, ligamentum nuchae between 11 mm and 16 mm stage of the embryo, resulted in this anomaly. A surgeon operating on the head and neck region or a radiologist analyzing a magnetic resonance imaging of the cervical region would find the knowledge of this morphological variation of trapezius useful in making clinical decisions.

Resection of Primary Brachial Plexus Tumor via a Modified Supraclavicular Approach

Benign peripheral nerve sheath tumors are generally considered curable lesions, and surgical resection is recommended as the primary line of treatment. When these tumors occur in the brachial plexus, they are most frequently accessed via the supraclavicular approach. Traditional descriptions of this approach have included either transection of sternocleidomastoid (SCM) muscle fibers or disarticulation of the clavicular head of the SCM muscle. This report presents a simple and easy-to-adapt modification of the supraclavicular approach that offers greater preservation of the SCM muscle. The modification primarily consists of the creation of an intramuscular window between the sternal and clavicular heads of the SCM via the splitting and dilation SCM muscle fibers. This technique minimizes the disruption of SCM muscle tissue compared with previous descriptions and may be associated with improved postoperative pain and return to function.