Marginal mandibular branch of the facial nerve

Branch of the facial nerve

The marginal mandibular branch of the facial nerve is a critical component of the facial nerve (cranial nerve VII) that plays a significant role in the innervation of the muscles responsible for facial expression, particularly those around the lower lip and chin.

Anatomy

The marginal mandibular branch arises from the lower division of the facial nerve, which exits the stylomastoid foramen of the temporal bone. It travels forward beneath the platysma muscle and the deep cervical fascia, coursing along the lower border of the mandible.

Lateral view of head anatomy showing the course of the facial nerve

This nerve branch is responsible for innervating the muscles of the lower lip, including the depressor anguli oris, depressor labii inferioris, and the mentalis muscle. These muscles are essential for movements such as frowning, pouting, and other expressions involving the lower lip.

Clinical Significance

The marginal mandibular branch is of particular interest in surgical procedures involving the lower face and neck, such as parotidectomy, submandibular gland excision, and facelift surgeries. Due to its superficial course, it is susceptible to injury, which can result in asymmetry of the lower lip and compromised facial expressions.

Injury to this nerve can lead to a condition known as "marginal mandibular nerve palsy," characterized by drooping of the lower lip on the affected side, difficulty in expressing emotions, and challenges in speech articulation.

Surgical Considerations

Surgeons must exercise caution to avoid damaging the marginal mandibular branch during procedures. Techniques such as identifying anatomical landmarks, using nerve monitoring, and employing meticulous dissection methods are crucial to preserving nerve function.

Illustration showing the branches of the facial nerve

Related Pages

• Facial nerve
• Cranial nerves
• Facial expression
• Parotid gland