Stylohyoid Muscle Anatomy

The stylohyoid muscle is a slender, ribbon-like muscle that extends from the temporal bone to the hyoid bone, it’s paired and narrow muscle in close proximity to the digastric muscle. It has various physiological functions such as chewing, swallowing, and phonetics when working with the other suprahyoid muscles (stylohyoid, digastric, mylohyoid, and geniohyoid). 

Stylohyoid Muscle Anatomy

The stylohyoid muscle originates from the posterior surface of the styloid process of the temporal bone, specifically from its lateral aspect. The muscle courses anteroinferiorly, parallel to the posterior belly of the digastric muscle, before inserting into the lateral aspect of the body of the hyoid bone at its junction with the greater cornu. A notable anatomical feature is the perforation of the muscle by the intermediate tendon of the digastric muscle near its insertion point.

The stylohyoid muscle typically measures between 2-3 cm in length and demonstrates a fusiform shape. The muscle maintains important anatomical relationships with several neighboring structures. Laterally, it relates to the external carotid artery and the posterior auricular artery. Medially, it borders the internal carotid artery, internal jugular vein, and cranial nerves IX through XII. The muscle’s course is closely associated with the stylohyoid ligament, which often serves as a guide for surgical identification.

The facial nerve (CN VII) provides motor innervation to the stylohyoid muscle via its stylohyoid branch, which typically emerges from the nerve’s main trunk near the stylomastoid foramen. The arterial supply primarily derives from branches of the external carotid artery, specifically the stylomastoid artery and occasional contributions from the occipital artery. Venous drainage follows the typical pattern of the region, ultimately emptying into the internal jugular vein.

See Also: Sternocleidomastoid Muscle Anatomy

Functional Significance

The stylohyoid muscle serves several critical functions in the complex mechanism of deglutition and phonation. During swallowing, it works synergistically with other suprahyoid muscles to elevate and draw the hyoid bone posterosuperiorly. This action is fundamental in the elevation of the larynx and the subsequent protection of the airway during deglutition. The muscle also contributes to the stabilization of the hyoid bone during speech and other phonatory activities.

Embryology

The stylohyoid muscle develops from the second pharyngeal arch, sharing its embryological origin with other structures derived from Reichert’s cartilage. This developmental history explains its innervation pattern by the facial nerve and provides context for understanding various congenital anomalies affecting this region.

Clinical Considerations

Understanding the stylohyoid muscle’s anatomy becomes particularly relevant in several clinical scenarios. Eagle syndrome, characterized by elongation of the styloid process or calcification of the stylohyoid ligament, can directly affect the muscle’s function and cause significant symptomatology. Additionally, the muscle serves as an important surgical landmark during procedures in the lateral neck region, particularly during selective neck dissection and approaches to the parapharyngeal space.

Dysfunction of the stylohyoid muscle, whether due to denervation or mechanical factors, can contribute to dysphagia and altered laryngeal mechanics. Careful evaluation of the muscle’s integrity and function is essential in patients presenting with unexplained swallowing difficulties or cervical pain syndromes.

References & More

1. Gray’s Anatomy: The Anatomical Basis of Clinical Practice
2. Clinically Oriented Anatomy – 8th Edition
3. Rathee M, Jain P. Anatomy, Head and Neck, Stylohyoid Muscle. [Updated 2023 Jan 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed