Bell's Palsy Flashcards
What is Bell’s palsy?
An acute, unilateral peripheral facial nerve palsy
What are the key features of Bell’s palsy?
- Otherwise unremarkable examination and history
- Deficit affects all zones equally
- Fully evolves within 72 hours
What features make the palsy NOT Bell’s palsy?
- Known aetiology
- Progressive palsy
- Waxing and waning
- Affect’s facial zones unequally
What is the main function of the facial nerve?
Motor innervation to the muscles of facial expression
What are the additional functions of the facial nerve?
- Sensory fibres from external auditory meatus
- Taste fibres from the anterior 2/3 tongue
- Control of salivation
- Motor fibres to the stapedius
What cranial nerve is the facial nerve?
CN VII
Where is the facial nerve nucleus situated?
The brainstem
What course does the facial nerve take when leaving the brainstem?
Fibres loop around CN VI nucleus and leave the pons medial to CN VIII
After leaving the brainstem what does the facial nerve pass through?
The internal acoustic meatus
After passing through the internal acoustic meatus what bone does the facial nerve enter?
Petrous temporal bone via the facial canal
What happens to the facial nerve within the facial canal?
It widens to form the geniculate ganglion
What is the geniculate ganglion responsible for?
Taste and salivation
Where is the geniculate ganglion situated?
The medial side of the middle ear
What happens to the facial nerve after the geniculate ganglion
It turns sharply and gives off the chorda tympani before emerging through the stylomastoid foramen to supply the muscles of facial expression
What is the cause of Bell’s palsy?
Unknown - usually occurs after a viral infection
What are the risk factors for Bell’s palsy?
- Pregnancy
- Diabetes
- Recent URTI
- Family history
What characterises Bell’s palsy?
A one-sided facial droop that comes on within 72 hours
What functions of the facial nerve may be affected?
- Blinking and closing eyes
- Smiling and frowning
- Lacrimation
- Salivation
- Flaring nostrils
- Raising eyebrows
- Taste sensation of anterior 2/3 tongue
- Innervation of stapedius muscle
What branch of the facial nerve supplies the anterior 2/3 of the tongue?
Chorda tympani
What branch of the facial nerve supplies the stapedius muscle?
Tympanic branch
What can happen as a result of impairment to stapedius innervation?
Sound sensitivity
How common is sound sensitivity in Bell’s palsy?
Rare
How is Bell’s palsy diagnosed?
By excluding other causes i.e. diagnosis of exclusion
What are the differentials for Bell’s palsy?
- Ramsay Hunt syndrome
- Lyme disease
- Benign facial nerve tumour
- Malignant facial nerve tumour
- Blunt force trauma to face or temporal bone
- Stroke
