Week 18 - Clinical Lecture: Facial Nerve Flashcards
What is the seventh paired cranial nerve?
The facial nerve (CN VII)
What are the primary functions of the facial nerve?
- Motor: muscles of facial expression, posterior belly of the digastric, stylohyoid, and stapedius muscles
- Sensory: small area around the concha of the external ear
- Special Sensory: taste sensation to the anterior 2/3 of the tongue
- Parasympathetic: supplies glands in the head and neck
What are the glands supplied by the parasympathetic fibers of the facial nerve?
- Submandibular salivary gland
- Sublingual salivary gland
- Nasal mucous glands
- Palatine mucous glands
- Pharyngeal mucous glands
- Lacrimal glands
What are the two main parts of the facial nerve’s anatomical course?
- Intracranial
- Extracranial
Where does the facial nerve arise?
In the pons of the brainstem
What are the two roots of the facial nerve?
- Large motor root
- Small sensory root (intermediate nerve)
What important events occur within the facial canal of the facial nerve?
- The two roots fuse to form the facial nerve
- Formation of the geniculate ganglion
- Giving rise to the greater petrosal nerve, nerve to stapedius, and chorda tympani
Through which foramen does the facial nerve exit the skull?
The stylomastoid foramen
What is the first extracranial branch of the facial nerve?
The posterior auricular nerve
What are the five terminal branches of the facial nerve within the parotid gland?
- Temporal branch
- Zygomatic branch
- Buccal branch
- Marginal mandibular branch
- Cervical branch
What is the function of the chorda tympani branch of the facial nerve?
Innervates the anterior 2/3 of the tongue with the special sense of taste
Fill in the blank: The _______ nerve carries parasympathetic fibers to the mucous glands and lacrimal gland.
Greater petrosal
What is the clinical relevance of damage to the facial nerve?
Can produce varied symptoms depending on the site of the lesion
What are the symptoms of intracranial lesions of the facial nerve?
- Paralysis or severe weakness of facial expression muscles
- Reduced salivation and loss of taste on ipsilateral 2/3 of tongue
- Ipsilateral hyperacusis
- Ipsilateral reduced lacrimal fluid production
What is a common cause of intracranial lesions of the facial nerve?
Infection related to the external or middle ear
What are the causes of extracranial lesions of the facial nerve?
- Parotid gland pathology
- Infection by herpes virus
- Compression during forceps delivery
- Idiopathic causes (Bell’s palsy)
True or False: The facial nerve contributes to the innervation of the parotid gland.
False
What are the two types of sensory functions of the facial nerve?
Special sensory (taste) and somatic (general) sensory
What types of motor functions does the facial nerve carry?
Somatic (branchial) motor and visceral (parasympathetic) motor
What type of fibers does the facial nerve carry from the muscles it innervates?
Proprioceptive fibers
Where is the motor nucleus of the facial nerve located?
In the ventrolateral part of the pons of the brainstem
Where are the cell bodies of the primary sensory neurons of the facial nerve located?
In the geniculate ganglion
The central processes of taste sensory neurons end in which nuclei?
The nuclei of the solitary tract in the medulla
The processes of general sensation sensory neurons from the external ear end in which nucleus?
The spinal nucleus of the trigeminal nerve
What are the two divisions in which the facial nerve (CN VII) emerges?
The primary root and the intermediate nerve
What does the larger primary root of the facial nerve innervate?
The muscles of facial expression
What types of fibers does the smaller intermediate nerve carry?
Taste, presynaptic parasympathetic, and somatic sensory fibers
List the structures CN VII traverses during its course.
- Posterior cranial fossa
- Internal acoustic meatus
- Facial canal
- Stylomastoid foramen
- Parotid gland
What is the sharp bend in the course of the facial nerve called?
Geniculum of the facial nerve
What is the site of the geniculate ganglion?
The geniculum of the facial nerve
What are the three branches CN VII gives rise to while traversing the temporal bone?
- Greater petrosal nerve
- Nerve to the stapedius
- Chorda tympani nerve
What are the five terminal motor branches of the parotid plexus formed by CN VII?
- Temporal
- Zygomatic
- Buccal
- Marginal mandibular
- Cervical
Which embryonic structure does the facial nerve supply?
The 2nd pharyngeal arch
What muscles are mainly supplied by the facial nerve?
- Muscles of facial expression
- Auricular muscles
- Posterior belly of the digastric
- Stylohyoid
- Stapedius
What does the facial nerve provide presynaptic parasympathetic fibers to?
- Pterygopalatine ganglion
- Submandibular ganglion
What glands are innervated by the pterygopalatine ganglion?
- Lacrimal
- Nasal
- Palatine
- Pharyngeal
What glands are innervated by the submandibular ganglion?
- Sublingual salivary gland
- Submandibular salivary gland
True or False: The pterygopalatine ganglion is associated with the maxillary nerve (CN V2).
True
What type of sensory fibers accompany the auricular branch of the vagus nerve?
Some fibers from the geniculate ganglion
Fill in the blank: Peripheral fibers of sensory neurons of the geniculate ganglion are carried by the _______.
Chorda tympani
Which nerve does the chorda tympani join to supply taste buds?
Lingual nerve of CN V3
What regions do the taste fibers supplied by the chorda tympani serve?
Taste buds of the anterior two thirds of the tongue and soft palate
Where do central fibers of taste neurons pass to after leaving the geniculate ganglion?
To the brainstem via the intermediate nerve
Which cranial nerve is the most frequently paralyzed among motor nerves?
CN VII
CN VII is also known as the facial nerve.
What functions may be lost with a lesion of CN VII near its origin or the geniculate ganglion?
Loss of motor, gustatory (taste), and autonomic functions
This includes paralysis of facial muscles and altered secretion of glands.
What type of paralysis occurs with a central lesion of CN VII?
Paralysis of muscles in the inferior face on the contralateral side
Forehead wrinkling remains unaffected due to bilateral innervation.
What is the effect of lesions between the geniculate ganglion and the origin of the chorda tympani?
Produces the same effects as lesions near the ganglion, except lacrimal secretion is not affected
This indicates that some autonomic functions may remain intact.
How is CN VII vulnerable to injury?
It is vulnerable to compression from viral infections and inflammation
This often occurs just before the nerve emerges from the stylomastoid foramen.
What types of injuries are common to CN VII?
Knife and gunshot wounds, cuts, birth injury, and temporal bone fractures
Damage is usually detectable immediately after the injury.
What conditions can affect CN VII?
Tumors, aneurysms, meningeal infections, herpes viruses
These conditions can lead to paralysis of facial muscles.
Is sensory loss common with injuries to CN VII?
No, sensory loss in the skin on the posteromedial surface of the auricle is rare
Hearing is usually not impaired, but sensitivity to low tones may increase.
What is Bell palsy?
A unilateral facial paralysis of sudden onset resulting from a lesion of CN VII
It is a specific condition that affects facial muscle control.
