Five-headed superior omohyoid

Morphogenesis and functional aspects of the muscular layer of the middle deep cervical fascia in humans

BACKGROUND

In recent years, the fasciae of the human body have received significant attention because of their crucial role in the transmission of muscle force. However, studies on the development of the fasciae, particularly the cervical fascia, remain scarce.

PURPOSE

This study was performed to examine the development of the fascia of the infrahyoid strap muscles, also known as the middle layer of the deep cervical fascia (MDCF), in 17 human embryos aged 6-8 weeks and 20 human foetuses aged 9-14 weeks.

METHODS

Histological examination of serial sections was performed using conventional light microscopy.

RESULTS

Three stages in the development of the MDCF were identified: the initial, formation, and maturation stages. In the initial stage (week 6 of development, Carnegie stages 18-19), the mesenchymal primordium of the epimysium of the infrahyoid muscles was observed and found to be continuous with the mesenchymal primordium of the MDCF. The infrahyoid muscles already exhibited intramuscular fibres, the primordium of the perimysium, and the endomysium. In the formation stage (weeks 7-8 of development, Carnegie stages 20-23), fibroblast-like cells and collagen fibres appeared in the primordium of the muscle epimysium and in the MDCF. Intramuscular fibres had become very evident. In the maturation stage (from week 9 of development onward), further development and organisation of the fascial structures occurred.

CONCLUSION

Our results suggest that the MDCF of the neck develops in parallel with the mechanical activity of this region. The relationship between the MDCF and the lymphatic and venous structures of this region suggests that the MDCF may facilitate venous and lymphatic circulation.

The previously undescribed variant of the thyrohyoid muscle and its potential impact on surgical procedures

The thyrohyoid muscle belongs to the infrahyoid group located in the carotid triangle. It normally originates from thyroid cartilage and inserts into hyoid bone. Quite often, it is continuous with the sternohyoid muscle. Furthermore, there are variants that have their origin in the cricoid cartilage only, however, this occurs very rarely. During anatomical dissection, a two-headed variant of this muscle was found. One head had its origin in the cricoid cartilage and the other in the thyroid cartilage. This variant of thyrohyoid had not been previously described in the available literature. Therefore, we believe that it may be referred to as the cricothyrohyoid muscle. As the thyrohyoideus is often used as a landmark during surgical procedures in the prelaryngeal area and as a muscle graft, a thorough knowledge of its anatomy and variation is extremely important. We speculate that the two-headed version of this muscle may be problematic during surgical procedures in this region, however, it may also provide more options as a muscular graft.

Diagnostic value of high-frequency ultrasound in omohyoid muscle syndrome

PURPOSE

To investigate the diagnostic value of high-frequency ultrasound in omohyoid muscle syndrome.

MATERIAL AND METHODS

A retrospective analysis of 11 patients diagnosed with omohyoid muscle syndrome was carried out, and the characteristics of high-frequency ultrasound images were summarized.

RESULTS

Ultrasonography of the omohyoid muscle showed a narrow band of hypoechoic muscle bundle. The ultrasonographic manifestation of omohyoid muscle syndrome showed a thickening of the omohyoid muscle on the affected side. The omohyoid muscle on the affected side bulged forward during swallowing and lifted the overlying sternocleidomastoid muscle. The difference between the thickness of the omohyoid muscle intermediate tendon on the affected side and the healthy side at rest was statistically significant (t = 58.23, P < 0.001). The difference between the thickness of the affected omohyoid muscle intermediate tendon at rest and during swallowing was statistically significant (t = 14.57, P < 0.001). There was no statistically significant difference between the thickness of the omohyoid muscle intermediate tendon on the healthy side at rest and during swallowing (t = 0.56, P > 0.05).

CONCLUSION

High-frequency ultrasound is the preferred imaging method in the diagnosis of omohyoid muscle syndrome.