A.2 - The Facial nerve

Question 1

what is the facial nerve?

Answer 1

• The facial nerve = CN 7
• contains:
  1. mainly motor fibers supplying the muscles of facial expressio
  2. visceral efferent parasympathetic
  3. visceral afferent (taste) fibers.

Question 2

where does the facial nerve exists?

Answer 2

Both nerves leave the brainstem adjacent to the vestibular nerve, between the inferior cerebellar peduncle and the olive

Question 3

what are the facial nerve fibers?

Answer 3

Sensory
gustatory sensation
Autonomic
motor

Question 4

where is the motor nucleus of the facial nerve located?

Answer 4

lies in the lower pons,
medial to the descending nucleus and tract of the Vth cranial nerve.

Question 5

where does the facial nerve branch off?

Answer 5

The facial nerve gives off several branches before exiting from the skull through the stylomastoid
foramen.

Question 6

what is nervus intermedius?

Answer 6

The facial nerve and its visceral root

Question 7

route of nervous intermedius

Answer 7

exit from the lateral aspect of the
brainstem and cross the cerebellopontine angle immediately adjacent to the VIII cranial nerve →
internal auditory meatus → facial canal of the temporal bone (lie in close proximity to the inner ear and tympanic membrane)

Question 8

route of Visceral efferent and visceral afferent fibres

Answer 8

They run together as the nervus intermedius and accompany the facial nerve to the internal auditory meatus.

arise and terminate in the superior salivary nucleus and solitary nucleus/tract respectively

Question 9

route of facial nerve visceral efferent fibers

Answer 9

The parasympathetic fibres (visceral efferent) pass in the greater petrosal nerve
→ sphenopalatine /pterygopalatine ganglion
→ lacrimal gland (producing tears) + in the chorda tympani nerve
→ submandibular ganglion.

Question 10

what does the chorda tympani nerve contain?

Answer 10

parasympathetic efferent and visceral afferent fibres.

Question 11

what are chorda tympani parasympathetic fibers responsible for?

Answer 11

salivation.

Question 12

what sensations Visceral afferent fibres of the chorda tympani convy?

Answer 12

taste from the anterior two-thirds of the tongue.

Question 13

where are the cell bodies of the visceral afferent fibers of the chorda tympani?

Answer 13

geniculate ganglion contains the bipolar cell bodies

visceral afferent fibers = taste

Question 14

Supranuclear control of facial muscles

Answer 14

● Upper face:
both hemispheres (bilateral representation)

● Muscles of lower face:
contralateral hemisphere

● Lower motor neuron lesion → paralyses all facial muscles on that side

● Upper motor neuron (supranuclear) lesion → paralyses the muscles in the lower half of the face
on the opposite side.

Question 15

Clinical examination of the facial nerve?

Answer 15

facial weakness
taste impairment
reduced lacrimation on one side
reduced salivation on one side
hyperacusis (exaggeration of sounds -loss of the stapedius reflex-).

Question 16

Facial weakness is due to?

Answer 16

1. lesion in pons : VI nerve palsy
2. lesion at cerebellopontine angle/ IAM):
   V, VIII, (IX, X, XI) nerve palsies
3. lesion in facial canal:
   Loss of taste and salivation, hyperacusis
4. facial nerve lesions : diabetes, infectious mononucleosis
5. peripheral nerve lesion :
   Lacrimation, taste and salivation retained, weakness localized to specific muscle group

Question 17

where is the lesion localised in case of VI nerve palsy, contralateral limb weakness

-what are the causes

Answer 17

→ Pons

→ Causes:
-vascular
-demyelination
-tumor
-encephalitis
-syringobulbia
-motor neuron disease

Question 18

where is the lesion localised in case of V, VIII, (IX, X, XI) nerve palsies, where there is loss of:
- taste, salivation
- lacrimation
- and hyperacusis

Answer 18

→ Cerebellopontine angle/internal auditory meatus

Causes:
-acoustic tumors
-meningioma
-epidermoid
-glomus jugulare tumor

Question 19

where is the lesion localised in case of:
1. Loss of taste and salivation (proximal to nerve to stapedius)
2. hyperacusis
3. but retained lacrimation retained lacrimation

???

Answer 19

→ Facial canal

→ Causes: f
- racture of skull base
- spread of middle ear infection
- herpes zoster
- Ramsay-Hunt synd (geniculate ggl)
- petrous-temporal carcinoma
- Bell’s palsy
- leukemia deposits

Question 20

where is the lesion localised in case of:
Lacrimation, taste and salivation are all retained but weakness may be localized to a specific muscle group

Answer 20

→ Peripheral nerve

→ Causes: parotid gland lesion (eg. uveoparotid fever of sarcoidosis), parotid operations,
facial trauma

Question 21

what could be Other causes of facial nerve lesions?

Answer 21

diabetes
infectious mononucleosis

Question 22

what is Bell’s palsy

Answer 22

Acute idiopathic peripheral facial palsy is also known as Bell palsy

Acute paralysis of the face related to inflammation and swelling
of the facial nerve within the facial canal or at the stylomastoid
foramen.

It is usually unilateral and may occur repetitively.

A family history can sometimes be found.

Question 23

what is the etiology for Bells palsy?

Answer 23

Etiology:
* primary: idiopathic

Secondary:
* Trauma (e.g., temporal bone fracture)
* Infection:
*Herpes zoster (Ramsay Hunt syndrome)
*Borreliosis (Lyme disease)
*HSV reactivation
*HIV
*Malignant otitis externa
* Tumors (parotid gland tumors, acoustic neuroma)
* Pregnancy
* Diabetes mellitus
* Guillain-Barré syndrome
* Sarcoidosis (Heerfordt syndrome)
* Amyloidosis
* Stroke

• epidemics of Bell’s palsy occur sporadically

-borellia can cause bilateral bells palsy

Question 24

Symptoms of bells palsy?

Answer 24

● Pain of variable intensity over the ipsilateral mastoid
precedes weakness, which develops over a 48h period

● Impairment of taste, hyperacusis and salivation depend
on the extent of inflammation and will be lost in more severe cases

● Lacrimation is rarely affected

● Bell´s phenomenon : attempt to close eyes and show teeth → one eye unable to close, eyeball rotates upward and outwards

Question 25

what does bells palsy diagnosis depends on?

Answer 25

on typical presentation and exclusion of:
- middle ear disease
- diabetes
- sarcoidosis
- Lyme disease

Question 26

bells palsy th

Answer 26

● Acute stage: Protect exposed eye during sleep

● High dose prednisolone for 10 days has shown improved recovery

● Role of antiviral therapy less clear

● Eye care (shielding and artificial tears) is important in preventing corneal abrasion.

Question 27

bells palsy prognosis?

Answer 27

● Most patients (70%) recover in 4-8 weeks w/o treatment

● Residual facial asymmetry may require corrective surgery in the remaining 30%

● Incomplete paralysis → good prognosis

● In patients with complete paralysis → electrical absence of denervation on electromyography is
an optimistic sign

Question 28

what is Ramsay Hunt syndrome?

Answer 28

Herpes zoster infection of the geniculate (facial) ggl

Question 29

the symp’s of Ramsay Hunt syndrome?

Answer 29

○ Sudden severe facial weakness with a typical zoster vesicular eruption within the external auditory meatus

○ Pain is a major feature and may precede the facial weakness

○ Serosanguinous fluid may discharge from the ear

Question 30

complications of Ramsay Hunt syndrome?

Answer 30

Deafness may result from VIII involvement, occasionally other cranial nerves from V-XII are
affected

Question 31

Treatment of Ramsay Hunt syndrome?

Answer 31

Acyclovir may help

Question 32

what are Hemifacial spasm?

Answer 32

unilateral clonic spasms beginning in the orbicularis oculi and spreading to
involve other facial muscles.

Contractions are irregular, intermittent and worsened by emotional stress and fatigue

Question 33

what happens if stapedius m is affecred in hemifacial spasm?

Answer 33

subjective ipsilateral
clicking sound

Question 34

Onset of Hemifacial spasm?

Answer 34

middle to old age, more common in females

Question 35

Cause of hemifacial spasms

Answer 35

usually vascular compression of the facial n. at the root entry zone.

Sometimes caused by tumor compressing the nerve.

Question 36

Diagnosis of hemifacial spasms?

Answer 36

exclude tics, and “focal” seizures selectively affecting the face.

MRI of posterior fossa excludes the presence of cerebellar pontine angle lesion and may show a dilation of the basilar artery

Question 37

Treatment of hemifacial spasms

Answer 37

○ Drugs:
local injection of botulinum toxin of involved muscles.
Effect only last 3 months

○ Surgery:
Post. fossa exploration and microvascular decompression (cure rate 80%), carries the risk of producing deafness and rarely brain stem damage

Question 38

mention some other facial nerve lesions?

Answer 38

• Tonic facial spasm
• Facial myokymia
• Myoclonus
• Blepharospasm

Question 39

what is Tonic facial spasm?

Answer 39

Less common than hemifacial spasm.

Occurs with cerebellar pontine angle
lesions.

It produces tonic elevation of the corner of the mouth with narrowing of the eye.

The diagnosis is confirmed by CT/MR scanning and treatment is surgical.

Question 40

what is Facial myokymia?

Answer 40

• rare condition seen most often in multiple sclerosis.
• Flickering of facial muscles results from spontaneous discharge in the facial motor nucleus.
• Other brainstem signs
  are present.
• The facial movements respond to carbamazepine.

Question 41

what is Myoclonus?

Answer 41

Rhythmic facial movement associated with similar palatal movements and
characteristic of dentate or olivary nucleus disease

Question 42

what is Blepharospasm?

Answer 42

Spasmodic closing or screwing up of eyes