Fascia of infrahyoid muscles

The fascia of the infrahyoid muscles—also known as the muscular division of the pretracheal layer of the deep cervical fascia—forms a distinct fascial envelope around the strap muscles of the anterior neck, including the sternohyoid, sternothyroid, omohyoid, and thyrohyoid. In some descriptions, it may also enclose the geniohyoid and mylohyoid superiorly.

It lies deep (or posterior) to the investing layer of deep cervical fascia and superficial (or anterior) to the visceral division of the pretracheal fascia,

• Note: Other fascial specializations of the deep cervical fascia include the investing layer (or superficial layer), visceral division of pretracheal layer (pretracheal is the middle layer), the prevertebral fascia (or deep layer), and the carotid sheath.

Attachments

• Superiorly, the fascia of infrahyoid muscles attaches to the hyoid bone and the thyroid cartilage, enclosing the infrahyoid muscles as it passes downward along the anterior aspect of the neck.

• Inferiorly, it extends to the posterior surface of the manubrium and the clavicles, where it becomes continuous with the clavipectoral fascia.

• Laterally, it blends with the carotid sheath.

Functions

This layer provides an independent compartment for the infrahyoid (strap) muscles, allowing them to glide smoothly during movements of swallowing and phonation. By anchoring to the hyoid bone superiorly and the thoracic fascia inferiorly, it also contributes to coordinated laryngeal and hyoid motion.

Clinical correlate

Clinically, this fascial layer (i.e. the fascia of infrahyoid muscles) is important in limiting the spread of infections within the anterior cervical region. Infections deep to the infrahyoid fascia may remain confined to the muscular compartment, whereas those deep to the visceral pretracheal fascia may extend into the superior mediastinum. The continuity of this fascial plane with the clavipectoral fascia provides a potential pathway for infection spread between the neck and the upper thorax.