Duplicate Omohyoid Muscle Causing Progressive Dysphagia and Dyspnea: A Case Report

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Rijul Kshirsagar, MD¹; Jason Gilde, MD¹; Raul Cruz, MD¹

Perm J 2019;23:18.316 [Full Citation]

https://doi.org/10.7812/TPP/18.316

E-pub: 09/12/2019

Abstract

Introduction: Duplicate omohyoid muscles are uncommon anomalies and exceedingly rare causes of progressive clinical symptoms. The goals of this case report are to describe the clinical characteristics, cross-sectional imaging, intraoperative findings, and curative treatment of our patient, to develop a differential diagnosis for this condition, and to review the pertinent literature regarding this particular type of anomalous omohyoid muscle as one among many variations.
Case Presentation: A 20 year-old man presented with progressive limited neck range of motion followed by dysphagia and then dyspnea caused by his duplicate omohyoid muscle. He underwent curative surgery in 2015 at our tertiary care center.
Discussion: Although rare, a duplicate omohyoid muscle should be considered in the differential diagnosis of dysphagia and dyspnea with concurrent central neck deformity. We report the first case, to our knowledge, of an anomalous omohyoid that caused significant progressive clinical symptoms. Direct excision of the restrictive anomalous tissue proved curative.

Introduction

Anatomic variations of the omohyoid muscle occur with relatively high frequency likely because of the complicated embryologic and anatomic features. The omohyoid is an infrahyoid strap muscle that consists of a superior and inferior belly separated by an intermediate tendon. The muscle originates from the upper border of the scapula and inserts at the lower border of the body of the hyoid bone. Numerous anomalous variations of the omohyoid have been previously described. However, few of these deformities cause clinical symptoms. We report the first case, to our knowledge, of a duplicate omohyoid-causing neck deformity, specifically laryngeal-hyoid complex torsion with limited neck motion, followed by progressive dysphagia and dyspnea. The study is a retrospective medical record review, including clinical evaluation, imaging studies, and preoperative, intraoperative, and postoperative photographs. The goals of the present study are to describe the clinical characteristics, cross-sectional imaging, intraoperative findings, and curative treatment for our patient, to develop a differential diagnosis, and to describe pertinent variations in the anomalous omohyoid muscle based on the published literature.

This article was originally presented as a poster at the American Academy of Otolaryngology—Head and Neck Surgery Annual Meeting; September 18, 2016 to September 21, 2016; San Diego, CA.

CASE PRESENTATION

Presenting Concerns

A 20-year-old man first presented to our institution for evaluation of progressive neck distortion, limited range of motion in the left side of the neck, and positional dysphagia. The patient was born via a normal atraumatic vaginal delivery and had no early torticollis. His clinical examination revealed neck distortion with prominent right-sided laryngeal complex rotation and inferior displacement. A tense subcutaneous band could be palpated in the right side of the neck between the hyoid and clavicle, which was especially pronounced with left-sided head rotation. Results of a modified barium swallow study revealed normal swallowing without aspiration. Physical therapy yielded no benefit. He declined steroid injection and opted for observation.

At 23 years of age, he was reevaluated after developing mild dyspnea. Subsequent physical examination (Figures 1A and 1B), distal chip camera laryngoscopy (Figure 2), and magnetic resonance imaging of the neck (Figures 3A and 3B) were performed. After reviewing the results, we suspected the patient to have a muscular anomaly, and surgery was planned for exploration and possible excision of abnormal tissue.

Therapeutic Intervention and Treatment

Despite a preoperative endoscopy that revealed a rotated but patent, unobstructed airway, intubation of the patient proved difficult. Even with an easily visible laryngeal introitus, the endotracheal tube would not pass the subglottic level on 2 routine intubation attempts. With video laryngoscope used for visualization, a tube-changer stylet was passed beyond the subglottis after several attempts, and the patient was intubated by sliding the endotracheal tube over the stylet (modified Seldinger technique). We retrospectively hypothesized that the endotracheal tube was lodging in the prominent anterior cricoid shelf. This hypothesis was confirmed on preoperative endoscopy and revealed to be caused by laryngeal distortion associated with this deformity.

During the procedure, after the subplatysmal flaps were raised, a normal-appearing lateral omohyoid and an accompanying medial duplicate omohyoid muscle were identified (Figures 4A and 4B). The duplicate omohyoid muscle at the hyoid bone was divided, resulting in an immediate 3-cm shift of the laryngeal-hyoid complex back toward the midline (Figure 4C). The normal-appearing omohyoid muscle was also divided at its hyoid attachment at this time. Pathologic analysis of the duplicate omohyoid revealed fibrous tissue and skeletal muscle.

Follow-up and Outcome

At 4 weeks after surgery, external (Figure 1B) and endoscopic examination revealed an improved appearance in the patient. At final follow-up 6 weeks after surgery, the patient reported complete resolution of his symptoms.

Discussion

Although many muscles of the neck develop embryologically from the branchial arch mesenchyme, the infrahyoid muscles form from myoblasts from the cervical myotomes.¹ Omohyoid anomalies have been suggested to occur because of pertubations in this development process.²  In addition, it has long been proposed that the superior and inferior bellies of the omohyoid develop from different muscle precursors.³ Superior muscle belly abnormalities are more commonly reported.⁴ Thus, although abnormalities of the omohyoid muscle are rarely encountered in clinical practice, they may occur relatively commonly because of the complex embryologic and anatomical structure of this muscle.

Multiple omohyoid anomalies are described according to the origin, insertion, course, number of bellies, and contribution of surrounding muscles.  In fact, in 1931, Loth⁵ attempted to develop a classification scheme for the various subtypes. However, exceptions to his classification scheme have subsequently been identified.⁴ In the more recent 2008 anatomical study by Rai et al,² among the 35 cadavers dissected, a double omohyoid was present in 1 cadaver, the inferior belly originated from the clavicle in 3 cadavers, the superior belly merged with the sternohyoid in 2 cadavers, and the omohyoid received additional muscle fibers from the sternum in 1 cadaver. Standard attachments and position of the omohyoid were observed in the remaining 28 cadavers (85%).   Indeed, the number of variations in the development and position of the muscle have caused the muscle to be questioned as a reliable surgical landmark. Mizen and Mitchell⁶ attempted to define the reproducibility of the position of the omohyoid muscle through a study of 30 cadavers and 88 patients undergoing neck dissections and found the position of the omohyoid muscle in relation to the clavicle and internal jugular vein to vary considerably. The authors suggest that the omohyoid is an unreliable surgical landmark during neck dissection and its use should be abandoned.

Descriptions of a duplicated omohyoid muscle are exceedingly rare. We found 4 cadaveric and 1 incidental description during a neck dissection of this duplicate muscle.  None of these presented with clinical symptoms.^1,7-10  Two of the reports^9,10 described a duplicate muscle that exactly matched our intraoperative findings (ie, a cleidohyoideus muscle between the hyoid and clavicle without an intermediate tendon running medial and separate from a normal omohyoid muscle).

Cadaveric studies or reports based on incidental findings during neck surgery comprise the largest volume of reports of omohyoid anomalies, certainly suggesting that clinically symptomatic variations are exceptional. In fact, reports of anomalous omohyoid varieties causing clinical symptoms are rare. Several studies^11,12 have described omohyoid muscle syndrome, also known as omohyoid sling syndrome, in which the omohyoid causes protrusion of the lower neck during swallowing. In a separate case report,¹³ fibrosis of the omohyoid was described as the cause of dysphagia and acquired torticollis.

The differential diagnosis for this type of lesion is relatively limited. Torticollis typically involves the sternocleidomastoid muscle and may be associated with delivery trauma (and thus is evident early in life). the area of neck fibrosis is recognizably different from our case. Other central neck pathologic findings that could occur would typically have an inflammatory component that contributes to scar band formation. For example, a recurrently or chronically infected thyroglossal duct cyst, laryngocele, sclerosing cervical lymphadenopathy, or upper-pole inflamed thyroid neoplasm might present similarly. A form of autoimmune thyroiditis unilaterally could also present in this manner. However, the patient’s lesion never showed evidence of an acute inflammatory stage.

We report the first case, to our knowledge, of an anomalous omohyoid that caused significantly progressive clinical symptoms and difficult intubation. In our case, direct excision and release of the anomalous tissue via an open surgical approach were curative. Zhu et al¹⁴ describe the use of an endoscope via a transaxillary approach for simple surgical transection of the omohyoid muscle in a patient with omohyoid muscle syndrome. In both of these cases, the variant muscle required surgical treatment and failed nonsurgical options.

Conclusion

The omohyoid muscle may demonstrate a variety of anomalies. the muscle may rarely be duplicated. The exact frequency of omohyoid variations is unknown, but these variations perhaps are more common than reported because of the complex embryologic and anatomic features of the muscle. However, few of these anomalies will present clinically. Ours is an extremely rare and interesting case of a duplicate omohyoid that caused progressive symptoms, produced a challenging intubation, and was cured through surgical excision. Omohyoid muscle anatomy should be relied on cautiously during neck dissection, and anomalies should be considered in the differential diagnosis of symptomatic central neck deformities.

Disclosure Statement

The author(s) have no conflicts of interest to disclose.

Acknowledgments

Laura King, ELS, performed a primary copy edit.

How to Cite this Article

Kshirsagar R, Gilde J, Cruz R. Duplicate omohyoid muscle causing progressive dysphagia and dyspnea: A case report. Perm J 2019;23:18.316. DOI: https://doi.org/10.7812/TPP/18.316

Author Affiliations

¹ Department of Head and Neck Surgery, Oakland Medical Center, CA

Corresponding Author

Rijul Kshirsagar, MD (rijul.s.kshirsagar@kp.org)

References

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Keywords: anomalous omohyoid, duplicate omohyoid, dysphagia, neck dissection