Facial nerve Flashcards
What is the special sensory of the facial nerve?
Via Chorda Tympani → Taste to Ant. 2/3rds Tongue
What is the Parasympathetic innervation of the facial nerve?
Submandibular and sublingual Salivary and Lacrimal Glands
What is the sensory innervation of the facial nerve?
Posterior Auricular Branch → External Auditory Meatus and Ear
State ALL motor branches of the facial nerve (7)
1) Branch to stapedius (in middle ear)
2) Motor branches to the posterior belly of digastric and stylohyoid muscles (after exiting stylomastoid foramen)
5) terminal motor branches (T,Z,B,M,C) (inside the parotid gland)
PNS pre-ganglionic fibres from the glossopharyngeal synaps on the _______ ganglion.
Here post-ganglionic fibres hitchhike with a branch of _______ known as the _______ nerve to reach the parotid gland for salivary production
otic, V3, auriculotemporal
With what other CN does the facial nerve exit the brainstem?
Where exactly do these exit?
CN VIII (vestibulocochlear) via the internal auditory meatus at the cerebellopontine angle
PNS pre-ganglionic fibres from the facial nerve travel via the _______ nerve to synaps on the _______ ganglion.
Here post-ganglionic fibres travel directly to lacrimal gland and glands of _______ and _______ to stimulate tears and _______ production
greater petrosal, pterygopalatine, nose, palate, mucus
PNS pre-ganglionic fibres from the facial nerve travel via the _______ nerve (hitchikes with lingual nerve- V3) to synaps onto the _______ ganglion.
Here post-ganglionic fibres travel directly to _______ and _______ glands to stimulate salivary production
chorda tympani, submandibular, sublingual
What 2 ganglion are associated with the facial nerve?
Pterygopalatine ganglion: supplies lacrimal, nasal and mucous glands
Submandibular ganglion: supplies salivary glands
Sensory and motor fibers of CN VII travel through the _______, then enter the facial canal.
Here it turns sharply at the _______ where pre-ganglionic PNS fibres leave for the _______ via the _______ nerve
CN VII continues into the middle ear within the facial canal where it gives off the nerve to _______ (M) and _______ (SS) nerve
The main nerve then exits skull via the _______
IAM, geniculate ganglion (bulge in middle ear), lacrimal gland, greater petrosal, stapedius, chorda tympani, stylomastoid foramen
What are the 3 branches of the facial nerve given of in the middle ear?
1) Greater Petrosal Nerve (PNS)
2) Nerve to Stapedius (M)
3) Chorda Tympani (SS)
What nerve does the Chorda Tympani join with, and where do these travel to?
The lingual nerve (branch of V3)
Togther these travel to the tongue where the:
- lingual nerve provides general sensation to ant 2/3rds
- chorda tympani provides taste to the ant 2/3rds
Where exactly in the middle ear is the chorda tympni given off?
Between Incus and Malleus
What are the PNS fibres that supply the salivary glands termed?
Secretomotor fibres
How do the PNS fibres of the facial nerve reach the sublingual and submandibular gland?
1) preganglionic fibres travel via chorda tympani AND hitchhikes with lingual nerve (V3)
2) synaps onto submandibular ganglion
3) post-ganglionic fibres travel to submandibular and sublingual glands top stimulate salivation
What 2 fibres of the facial nerve are carried with the lingual nerve (V3)?
Chorda Tympani and PNS fibres
After the facial nerve exits the stylomastoid foramen it gives off 3 branches; motor to the _______ and _______ muscles and sensory branch that is the _______ nerve.
It then enters the _______ gland where it divides into 5 Terminal MOTOR Branches that supply the muscles of facial expression
stylohyoid, posterior belly of digastric, posterior auricular, parotid
What are the 5 terminal motor branches of the facial nerve? (control muscles of facial expression)
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
Label the muscles and state where their motor innervation comes from`
Post belly of digastric and Stylohyoid: CN VII
Ant belly of digastric and Mylohyoid: branch of the Inferior alveolar nerve of V3 (CN V)
Describe the pathway of the facial nerve MOTOR branches only
1) CN VII motor nucleus is located in the pons
2) through IAM with VIII
3) bends sharply at geniculate ganglion
4) through middle ear where it gives of the nerve to the stapedius
4) exits skull at stylomastoid foramen where it gives off 2 small branches to digastric and stylohyoid
5) continues to the parotid gland where it gives of 5 terminal branches which supply muscles of facial expression
Describe the pathway of the facial nerve SENSORY/SS branches only
1) CN VII special sensory nucleus starts are the pons and is termed the nucleus of fasciculus solitarius
2) through IAM with VIII
3) bends sharply at geniculate ganglion
4) travels to back of middle ear
5) a small part exits at the stylomastoid foramen (small sensory area to pinna)
6) Most carries on with the chorda tympani (hitchhikes)
Describe the pathway of the facial nerve PNS branches only
1) CN VII special sensory nucleus starts are the pons and is termed the superior salivatory nucleus
2) through IAM with VIII
3) bends sharply at geniculate ganglion where it splits into 2
4) first is the greater petrosal nerve which branches of and travels through the pterygopalatine ganglion and supplied the nasal, lacrimal and mucous glands
5) second carries on straight through the ear and branches off (carried on) the chorda tympani to supply the submandibular and sublingual glands
What is the motor, SS and PNS nuclus of the facial nerve termed within the Pons
Motor = CNVII motor nucleus
SS = nucleus of fasciculus solitarius
PNS = superior salivatory nucleus
Compare gland innervation of the facial nerve above vs below the oral fissure
Above: all glands innervated by the greater petrosal nerve
Below: all glands innervated by the chorda tympani
What are we ‘observing’ when examining the facial nerve
Loss of facial symmetry?
List 4 things we may ask in a facial nerve examination
1) change to taste?
2) change in hearing (Hyperacusis)?
3) dry eye / unable to cry (Reduced lacrimation)?
4) dry mouth (Reduced salivation)?
List 4 ways we can test the muscles of facial expression
1) raise eye brows
2) ‘scrunch up’ (tightly close)
3) ‘puff out’ cheeks
4) show teeth
Explain what would be seen in a lesion of the facial nerve at the internal auditory meatus (and why)
- Reduced lacrimation (No GPN)
- Hyperacousis (damage to stapedius),
- Reduced salivation and taste (No chorda tympani)
- Reduced facial expression (no innervation to muscles of facial expression)
Explain what would be seen in a lesion or problem with the middle ear concerning the facial nerve
Lacrimation is NORMAL because greater petrosal nerve is given off before middle ear (at geniculate ganglion).
We may or may not get Hyperacousis depending on where the lesion is (before or after nerve to stapedius is given off)
Reduced salivation and taste (No chorda tympani)
Reduced facial expression (no innervation to muscles of facial expression)
Explain what would be seen in a lesion at the sylomastoid foramen
Lacrimation, hearing and taste all NORMAL
ONLY the muscles of facial expression will be affected (facial palsy)
Give 4 causes of facial nerve damage with examples
1) Trauma ( temporal fractures, stabbing, gunshots, child birth)
2) Iatrogenic (surgery to the parotid)
3) Non-traumatic (malignant otitis externa, parotid tumour, viral)
4) Idiopathic (Bell’s Palsy)
What 2 places MUST we look before concluding Bell’s Palsy
ALWAYS, ALWAYS Look in the ear and feel the parotid
What is the onset of Bell’s palsy?
Rapid onset
Describe the distribution of Bell’s plasy and state 4 associated symptoms
Usually unilateral and associated with:
- otalgia (ear pain)
- altered face sensation
- altered taste
- hyperacusis
Although Bell’s Palsy is idiopathic, what is thought to cause it?
virally induced immune response → inflammation and swelling of facial nerve
What is the treatment and recovery of Bell’s Palsy?
Treatment:
- steroids within 72 hours and potentially antivirals
- EYE CARE
Recovery: most recover fully in 2-3 months
What is the key distingusing feature of a stroke from Bell’s Palsy?
“Frontal Sparing” (upper spares upper) → meaning the forehead is spared
Due to the fact that the occipitalfrontalis and orbicularis oculi are BILATERALLY innervated, they are spared if damage is up in cortex
Describe the appearance of someone having a stroke/UMN lesion vs Bell’s palsy/ LMN lesion
Bell’s/LMN lesion: paralysis of ipsilateral upper and lower facial musculature (unable to raise eyebrows or smile on affected side)
Stroke/UMN lesion: paralysis of contralateral side lower facial musculature (unable to smile on affected side but can raise both eyebrows)
