Cranial nerves

Question 1

CN VII (7)

Answer 1

Facial nerve

Question 2

What is the pathway of CN VII (7) - facial nerve?

Answer 2

The facial nerve exits the brainstem at the cerebellopontine angle.

On its journey to the face it passes through the temporal bone and parotid gland.

It then divides into five branches that supply different areas of the face:

Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical

Question 3

Function of CNVII

Answer 3

There are three functions of the facial nerve: motor, sensory and parasympathetic.

Motor: Supplies the muscles of facial expression, the stapedius in the inner ear and the posterior digastric, stylohyoid and platysma muscles in the neck.

Sensory: carries taste from the anterior 2/3 of the tongue.

Parasympathetic: it provides the parasympathetic supply to the submandibular and sublingual salivary glands and the lacrimal gland (stimulating tear production).

Question 4

Parasympathetic function of facial nerve?

Answer 4

it provides the parasympathetic supply to the submandibular and sublingual salivary glands and the lacrimal gland (stimulating tear production).

Question 5

Sensory function of the facial nerve?

Answer 5

carries taste from the anterior 2/3 of the tongue.

Question 6

Motor function of the facial nerve?

Answer 6

Supplies the muscles of facial expression, the stapedius in the inner ear and the posterior digastric, stylohyoid and platysma muscles in the neck.

Question 7

Facial nerve palsy: UMN lesion vs LMN lesion?

Answer 7

Each side of the forehead has upper motor neurone innervation by both sides of the brain. Each side of the forehead only has lower motor neurone innervation from one side of the brain.

In an upper motor neurone lesion, the forehead will be spared and the patient can move their forehead on the affected side - SUSPECT STROKE

In a lower motor neurone lesion, the forehead will NOT be spared and the patient cannot move their forehead on the affected side - can be reassured and managed in the community.

Question 8

How might a CNVII palsy (facial nerve palsy) present?

Answer 8

Unilateral facial weakness
Forhead invovlement (LMN)
Drooping of eyelid, exposing eye
Loss of nasolabial fold

Question 9

What might cause an UMN lesion of the facial nerve?

Answer 9

Unilateral upper motor lesions occur in:

Cerebrovascular accidents (strokes)
Tumours

Bilateral upper motor neurone lesions are rare. They may occur in:

Pseudobulbar palsies
Motor neurone disease

Question 10

Bell’s Palsy, how is it managed, and what is the prognosis?

Answer 10

UNILATERAL LMN FACIAL NERVE PALSY

The majority of patients fully recover over several weeks but recovery may take up to 12 months. A third are left with some residual weakness.

If patients present within 72 hours of developing symptoms, NICE guidelines recommend considering prednisolone as treatment, either:

50mg for 10 days
60mg for 5 days followed by a 5-day reducing regime of 10mg a day

The NICE Clinical Knowledge Summaries do not recommend using antivirals but say an antiviral plus steroids may offer a “small benefit” (this should be discussed with a specialist).

Patients also require lubricating eye drops to prevent the eye on the affected drying out and being damaged. If they develop pain in the eye they need an ophthalmology review for exposure keratopathy. Tape can be used to keep the eye closed at night.

Question 11

How are Opthalmic risks managed in a CNVII nerve palsy?

Answer 11

Lubricating eye drops to prevent the eye on the affected drying out and being damaged.

If they develop pain in the eye they need an ophthalmology review for exposure keratopathy.

Tape can be used to keep the eye closed at night.

Question 12

What is Ramsey Hunt syndrome?

Answer 12

CNVII LMN PALSY

Ramsay-Hunt syndrome is caused by the varicella zoster virus (VZV)..

Patients stereotypically have a painful and tender vesicular rash in the ear canal, pinna and around the ear on the affected side.
This rash can extend to the anterior 2/3 of the tongue and hard palate.

Treatment should ideally be initiated within 72 hours. Treatment is with:

Prednisolone
Aciclovir

Patients also require lubricating eye drops.

Question 13

Causes of LMN CN VII (facial nerve) palsy?

Answer 13

Infection:
VZV (Ramsey Hunt Syndrome)
Otitis media
Malignant otitis externa
HIV
Lyme’s disease

Systemic disease:
Diabetes
Sarcoidosis
Leukaemia
Multiple sclerosis
Guillain–Barré syndrome

Tumours:
Acoustic neuroma
Parotid tumours
Cholesteatomas

Trauma:
Direct nerve trauma
Damage during surgery
Base of skull fractures

Idiopathic:
Bell’s Palsy