The Cervical Branch of the Facial Nerve (CN VII)
The nerve that runs lateral and deep to the platysma is the cervical branch of the facial nerve (CN VII).
Anatomical Course and Relationship to Platysma
The cervical branch of the facial nerve consistently travels deep to the platysma muscle after exiting the parotid gland 1, 2. This anatomical relationship is critical for surgical planning and understanding the nerve's vulnerability during neck procedures.
Key Anatomical Features:
After exiting the parotid gland, the cervical branch travels beneath the investing layer of the deep cervical fascia for a brief distance, then traverses this fascia to travel within areolar connective tissue before terminating anteriorly in the platysma muscle 2
The nerve courses deep to the platysma in 100% of cases and runs inferior to the mandible 1
Branching pattern varies: Single trunk in 61.3%-80% of specimens, double branches in 20%-38.7% 1
Clinical Significance
Motor Function
The cervical branch provides the primary motor innervation to the platysma muscle 3, 4, 3, 4. The platysma contributes to lower facial animation and neck contour, making this nerve clinically important for both function and aesthetics.
Surgical Vulnerability
The nerve is particularly vulnerable during:
- Neck dissection procedures
- Rhytidectomy (facelift surgery)
- Subplatysmal dissection
The nerve lacks a protective barrier in certain areas, making it susceptible to direct trauma or thermal damage from electrocautery, especially during median surgical approaches 2.
Important Anastomoses
The cervical branch frequently communicates with other nerves, which has significant clinical implications:
- Transverse cervical nerve: 16%-100% of cases
- Great auricular nerve: 24%-38.7% of cases
- Marginal mandibular branch: 24% of cases 1
Critical caveat: Due to these anastomoses, injury to the cervical branch may indirectly affect the marginal mandibular branch, potentially resulting in lower lip paresis 1. This interconnection means that seemingly isolated cervical branch injury can produce unexpected functional deficits.
Surgical Implications
When performing subplatysmal dissection, the cervical nerve's relatively deeper position below the mandible's angle facilitates safer dissection via a lateral approach for release of cervical retaining ligaments 2. However, surgeons must exercise extreme caution with electrocautery and direct manipulation given the nerve's exposed position within areolar tissue.
The high frequency of anatomical variation (particularly in branching patterns and inter-nerve communications) necessitates meticulous dissection technique during any cervicofacial surgery 1.