Volume 1, Issue 3 , Pages 226-229, September 2006
Rectus cervicalis—Anomalous muscle in the anterior compartment of the neck
Article Outline
Summary
We present a supernumerary muscle in the anterior compartment of the neck previously undescribed in the English electronic literature—rectus cervicalis. History: A 3-year-old boy presented with a history of recurrent infections of a mid-line neck lesion with an associated skin tag. Treatment: This was excised under general anaesthetic. An unusual mid-line lesion consisting of a skin tag and a tubular tract and muscle bands running from a notched mandible to the manubrium were noted. Discussion: The anomalous muscle seen in this patient resembled the rectus abdominis muscle. Cases of rectus sternalis have been reported. The authors propose that this is the first recoded case of rectus cervicalis.
Keywords: Thyroglossal cyst, Anterior triangle, Anatomy, Supernumerary muscle, Rectus cervicalis, Rectus sternalis
1. History
A 3-year-old boy presented to the ENT out-patients department with a mid-line neck lesion which had been present since birth. The lesion was 3
cm long and approximately 0.5cm wide with a skin tag at its upper end. The history revealed occasional discharge and inflammation. In addition there was an obvious mid-line defect in the mandible (Fig. 1). On palpation, there was a tight band of fibrous tissue running longitudinally beneath the lesion, from the notched mandible to the suprasternal notch. The lesion was unrelated to tongue protrusion and swallowing. Thyroid function tests were normal.
Fig. 1.
Patient aged 3 years.
CT scan confirmed the presence of a mid-line soft tissue mass and a bifid mandible (Figs. 2–3).
Figs. 2–3
CT and diagrammatic representation: (1) notch in mandible; (2) tissue band; (3) trachea; (4) cervical vertebra.
At operation the lesion was found to consist of two longitudinal bands of muscle and a tubular duct running from the notch in the mandible to the suprasternal notch (Figs. 4–5). The lesion lay entirely superficial to the investing layer of deep cervical fascia (Fig. 6).
Figs. 4–5
Intraoperative view and linear representation: (1) muscle and duct; (2) cyst; (3) superficial cervical fascia.
Fig. 6.
Excised specimen.
Histological examination showed that the bands of muscle were striated muscle and they were associated with a duct like structure which was lined by columnar epithelium and surrounded by lymphoid tissue (Fig. 7). This duct like structure extended from the notch in the mandible to the suprasternal notch.
Fig. 7.
Histology.
2. Discussion
Using PubMed and Google, a search using keywords supernumerary muscle, thyroglossal cyst, anomalous anatomy and pathology revealed no previous documentation of this lesion in the electronic English literature.
Thyroglossal tract remnants are the commonest cause of congenital mid-line neck lesions in children [1] and this was our first diagnosis. However, there were a number of features that made us doubt this diagnosis:
We think therefore it is much more likely that the lesion could represent a different embryological cause; At the beginning of the third week of foetal development the embryo undergoes gastrulation. This is the beginning of morphogenesis [2]. During this phase the bilaminar germ disc develops into a flat trilaminar germ disc which includes all three germ cell layers. This also establishes the cranio-caudal axis and bilateral symmetry of the future embryo. The sides of the disc then fold downwards and meet in the mid-line so that the embryo consists of a tube of endoderm surrounded by a tube of ectoderm with mesoderm between the two. Similarly the mandible develops as two mandibular processes which fuse in the mid-line [3]. Failure of these mid-line fusions could result both in a bifid mandible and in a duplication of endoderm, so forming a duct as in our patient (Fig. 8).
Fig. 8.
Embryological failure of fusion and formation of duct.
Abnormal mid-line development might also explain the appearance of the mid-line muscle bands, the skin tag and the duct. Morphologically the muscle of the body wall is arranged in three layers. In the abdomen these are the internal and external oblique muscles and the transverses abdominis muscle. These muscles fuse together in the anterior mid-line and turn to run longitudinally as rectus abdominis. In the thorax there are also three layers of muscle but these do not extend to the anterior mid-line except in 5% of cases where longitudinal muscle is found running on the outer surface of the sternum where it is known as rectus sternalis [4]. In the neck, the anterior longitudinal muscles are represented by geniohyoid and the strap muscles and these of course are deep to the investing layer of deep cervical fascia. In our case we found longitudinal muscle superficial to this fascia and perhaps this is the equivalent of rectus sternalis in the chest and might therefore be described as rectus cervicalis.
3. Conclusion
We present an anomalous neck lesion, previously undescribed in the electronic English literature and suggest a pathogenesis. The authors suggest that this could be similar to the rectus sternalis muscle and propose the name rectus cervicalis.
References
- . Investigation and treatment of thyroglossal cysts in children. J. R. Soc. Med. 2000;93(January (1)):18–21
- . The Third Week from Human Embryology. second ed.. London: Churchill Livingston; 1997;pp. 49–72 (Chapter 3)
- . The Third Week of Human Development From Before We Are Born. London: WB Saunders Company; 1998;pp. 61–80 (Chapter 5)
- R.M.H. McMinn, Upper Limb from Last's Anatomy, Tenth ed., Churchill Livingstone Inc., 650 Avenue of the Americas, New York, NY 10011, USA, 1999, pp. 54–55 (Chapter 2).
PII: S1871-4048(06)00065-7
doi:10.1016/j.pedex.2006.06.002
© 2006 Elsevier Ireland Ltd. All rights reserved.
Volume 1, Issue 3 , Pages 226-229, September 2006
