Intermediate
Technical
IVT
marginal mandibular nerve
Branch of facial nerve controlling lower lip movement; injury causes asymmetric smile and lip incompetence.
Full Definition
The marginal mandibular nerve is the most inferior branch of the facial nerve, providing motor innervation to the muscles of the lower lip including the depressor labii inferioris and depressor anguli oris. In head and neck oncology, this nerve is at risk during submandibular gland excision, neck dissections involving level I, and mandibular procedures. Injury results in an asymmetric smile with inability to depress the ipsilateral lower lip, creating both functional and cosmetic deficits.
Usage
Usage note: Often abbreviated as MMN in surgical documentation.
In Context
- "The marginal mandibular nerve was identified and preserved during submandibular gland excision." — Operative note
- "Post-operative facial nerve assessment revealed marginal mandibular nerve weakness." — Clinical examination
Also known as
MMN
lower division of facial nerve
Don't confuse with
buccal branch
cervical branch of facial nerve