Describe the sensory nerve supply to the face.
"
The trigeminal nerve (CN V) provides sensory innervation to the face. It is divided into three groups (which are then further subdivided):
- CN V1 – Ophthalmic nerve – sensory.
- CN V2 – Maxillary nerve – sensory.
- CN V3 – Mandibular nerve – mixed (motor component mainly supplies muscles of mastication).
Note: Cutaneous innervation of the scalp and face anterior to the pinna is by branches of CN V. However, spinal cutaneous nerves C2 & C3 (greater & lesser occipital nerves) and the greater auricular nerve provide sensory supply posterior to the pinna.
"
Name the branches of the ophthalmic division of the trigeminal nerve.
The three main branches of the ophthalmic division are: i) lacrimal; ii) nasociliary (including infratrochlear and posterior ethmoidal) and; iii) frontal (including supraorbital and supratrochlear).
Name the branches of the maxillary division of the trigeminal nerve.
The main branches of the maxillary division are: i) infraorbital; ii) zygomatic (which is further divided into zygomaticotemporal and zygomaticofacial); iii) superior alveolar; iv) palatine; v) pharyngeal, and; vi) superior labial.
Name the main divisions of the mandibular division of the trigeminal nerve.
"
The mandibular division of the trigeminal nerve, after exiting the foramen ovale, gives off the nerves to medial pterygoid, tensor tympani and tensor veli palatini. It then subdivides into an anterior and posterior branch. The anterior division is mainly a motor root with one sensory nerve while the posterior division is mainly a sensory root with one motor nerve.
- Anterior division:
- Motor nerves - masseteric, deep temporal, lateral pterygoid
- Sensory nerve - buccal
- Posterior division:
- Motor nerve - inferior alveolar nerve
(a mixed nerve that gives off the nerve to mylohyoid)
- Sensory nerves - inferior alveolar,
auriculotemporal, lingual
"
Name the sensory branches of the mandibular division of the trigeminal nerve.
Name the branches of the facial nerve within the substance of the parotid gland.
Name the structures that attach to the styloid process.
"
- Stylohyoid muscle and ligament
- Styloglossus
- Stylopharyngeus
- Stylomandibular ligament
"
Name the muscles that attach to the mastoid process.
"
- Sternocleidomastoid
- Splenius capitis
- Posterior belly of digastric
- Longissimus capitis
What does the marginal mandibular branch of the facial nerve supply?
"
The marginal mandibular branch supplies depressor labii inferioris, depressor anguli oris and mentalis.
Note: The nerve runs inferior to the mandible putting it at risk of injury during surgeries such as submandibular gland excision or carotid endarterectomy.
"
Describe the course of the facial nerve.
"
- The facial nerve is a mixed nerve comprising of a large motor and smaller sensory component.
- The motor component arises from the facial nerve nucleus in the pons, the sensory component arises from the nervus intermedius.
- Enters the petrous temporal bone via the internal auditory meatus.
- Runs a tortuous course through the facial canal.
- Exits the skull through the stylomastoid foramen.
- Enters the parotid gland between the superficial and deep lobes.
- Within the substance of the parotid gland divides into its five main branches.
Name the branches of the facial nerve before it exits the stylomastoid foramen.
"
- Nerve to stapedius.
- Chorda tympani.
- Greater petrosal nerve.
- Communicating branch to the otic ganglion.
Name the extracranial branches of the facial nerve before it enters the parotid gland.
"
- Posterior auricular nerve.
- Branch to the posterior belly of digastric muscle.
- Branch to stylohyoid muscle.
Describe the clinical significance of the course of the facial nerve?
The branches of the facial nerve lie between the superficial and deep lobe of the parotid making them vulnerable to injury during during surgery to this region (such as superficial parotidectomy). In addition, malignant tumours of the parotid gland
can present with facial weakness due to direct involvement of one or more of the facial nerve branches.