Bell's palsy Flashcards
define bell’s palsy?
Idiopathic lower motor neurone facial nerve palsy
Physical examination and history are otherwise unremarkable (no fever, malaise, headache to suggest alternative diagnosis)
outline the aetiology of bell’s palsy?
IDIOPAHTIC
strong evidence points towards reactivation of HSV-1 type 1
Possible mechanism is that reactivation causes destruction of ganglion cells and infection of schwann cells leads to demyelination and neural inflammation
summarise the epidemiology of bell’s palsy?
most cases 20-50 years
3 x more common in pregnancy
what are the presenting symptoms of bell’s palsy?
unilateral facial weakness and droop
abscence of constitutional symptoms-> fever, malaise
Maximum severity: 1-2 days
involves all nerve branches
50% experience facial, neck or ear pain or numbness
Hyperacuisis (uncommon) - this is due to stapedius paralysis
Loss of taste (uncommon)
Keratoconjuctivitis sicca ( dry eye)->difficult to close the eye fully and parasympathetic dysfunction to the lacrimal gland as a contributing factor (can lead to ulcerative keratitis and subsequent blindness)
Late stages of Bell’s palsy, facial synkinesis may occur (involuntary + abnormal synchronous movement of a facial region)-> However if the facial synkinesis occurs with facial weakness acutely it may be something neoplastic
explain why bell’s involves all nerve branches?
Facial nerve conduction blockade in Bell’s palsy originates proximal to the geniculate ganglion, prior to any branching; hence, all branches are affected in equal fashion. Unequal distribution of facial weakness across facial zones on examination in the acute setting rules out Bell’s palsy.
explain the pain caused by bell’s palsy?
Post-auricular pain and mild-to-moderate otalgia often occurs, as the facial nerve carries general somatic sensory axons that relay cutaneous sensation from the posterior external auditory canal, concha, and post-auricular region (the cell bodies of which are located in the geniculate ganglion).
Sensory disturbances range from absent, to a dull ache or feeling of heaviness, to mild-to-moderate pain.
Severe pain suggests zoster sine herpete of the facial nerve
what are the signs of bell’s palsy on physical examination?
Lower motor neurone weakness of facial muscles
- Affects ipsilateral muscles of facial expression
- Does NOT spare the muscles of the upper part of the face (unlike upper motor neurone facial nerve palsy)
Bell’s Phenomenon
- Eyeball rolls up but the eye remains open when trying to close their eyes
- Despite reporting unilateral facial numbness, clinical testing of sensation is normal
Examine the ears to check for other causes of facial nerve palsy (e.g. otitis media, herpes zoster infection)
what are the investigations for bell’s palsy?
history and physical examination-> acute, unilateral facial palsy, with an otherwise normal physical examination
ENoG - 90%+ decrease in amplitude of muscle action on affected side compared to healthy side
EMG - may show local axonal conduction block (absence of voluntary motor unit potentials)
Check for Lyme disease (another differential for facial weakness)-> serology for Borrelia Burgodorferi in all patients with recent travel to lyme disease endemic area
outline a management plan for bell’s palsy?
Protection of cornea with protective glasses and artificial tears; overnight ophthalmic lubricant should be applied with the eyelid taped close (AVOID EYEPATCHING)
High-dose corticosteroids (prednicsolone) is useful within 72 hrs
- Start with 60mg for 5 days then slowly reduce dose by 10mg for the next 5 days
- Only given if Ramsey-Hunt Syndrome is excluded
Surgical decompression if there is clinically undetectable unilateral facial movement and onset within 14 days
Antivirals (valaciclovir – give aciclovir if this doesn’t work) reduce long-term sequelae of Bell’s compared to corticosteroids alone – but giving antvirals is controversial
what are the possibel complication of Bell’s palsy?
Corneal ulcers
Eye infection
Aberrant reinnervation
- E.g. Blinking may cause contraction of the angle of the mouth due to aberrant sympathetic innervation of orbicularis oculi and oris
- Crocodile Tears Syndrome - parasympathetic fibres may aberrantly reinnervate the lacrimal glands causing tearing whilst salivating
summarise the prognosis of bell’s palsy?
85-90% recover function within 2-12 weeks with or without treatment
what are the risk factors for bell’s palsy?
intranasal influenza vaccination
pregnancy
What is a key differential for bell’s palsy and what are it’s features?
Ramsay Hunt differential:
LMN facial nerve palsy due to varicella zoster
- Pain often a prominent feature
- other cranial nerves can be affected
- vesicles in the ipsilateral ear, hard palate or the anterior two thirds of the tongue
- can include deafness and vertigo
- It should be suspected when pain is significant, especially in those aged over 6
