Terminal branches of the facial nerve (parotid plexus)
Division or branch · CN VII Motor
Inside the parotid gland the facial nerve divides into temporofacial and cervicofacial trunks and then five terminal branches, temporal, zygomatic, buccal, marginal mandibular and cervical, that fan across the face to the muscles of facial expression. The nerve is the surgical plane between the superficial and deep lobes of the parotid.
Traced from the start
- Pons
- Facial nerve (CN VII)
- Stylomastoid foramen
- Terminal branches of the facial nerve (parotid plexus)
Detail
- Motor
- Temporal → frontalis and upper orbicularis oculi; zygomatic → orbicularis oculi; buccal → buccinator, orbicularis oris and lip elevators; marginal mandibular → depressor anguli oris, depressor labii inferioris, mentalis; cervical → platysma
- Given off before the parotid
- Posterior auricular nerve (occipitalis, auricular muscles), nerve to posterior belly of digastric and to stylohyoid
- Reflex
- Efferent limb of the corneal reflex (orbicularis oculi via temporal and zygomatic branches)
- Surgical landmarks
- Tragal pointer, tympanomastoid suture and the posterior belly of digastric lead to the trunk; the marginal mandibular branch runs below the angle of the mandible over the facial vessels
When it goes wrong
Parotid malignancy (adenoid cystic or mucoepidermoid carcinoma) infiltrating the nerve within the gland
Lower motor neurone facial weakness with a parotid lump; a benign pleomorphic adenoma never causes facial palsy, so a parotid mass with facial weakness means malignancy until proved otherwise
Superficial parotidectomy or a deep laceration of the cheek
Weakness of individual branches, most often temporary neuropraxia of the marginal mandibular or temporal branch; permanent palsy if a branch is divided
Marginal mandibular branch injury during submandibular gland excision or neck dissection (the reason incisions are placed at least 2 cm below the mandible)
Asymmetric smile with drooping of the lower lip corner on that side from depressor anguli oris paralysis
Orbicularis oculi paralysis in any facial palsy
Incomplete blink and eye closure with exposure keratitis; needs lubricant drops by day, ointment and taping at night, and tarsorrhaphy if recovery is delayed
Practise this structure
2 questions in the bank tagged Facial Nerve.
A 52-year-old woman has had two months of numbness over the right forehead, the right upper eyelid and the tip of her nose, with a gritty feeling in the right e…
Foundations · middle twist
A 44-year-old man has had drooping of the right side of his face for three days. He drools from the right corner of his mouth, the right nasolabial fold is flat…
Foundations · common