Bell's palsy Flashcards
Define
Idiopathic lower motor neurone facial nerve palsy
What’s the aetiology?
IDIOPATHIC
60% are preceded by an upper respiratory tract infection
This suggests that it has a viral or post-viral aetiology
Strong evidence points to reactication of HSV-1 within the geniculate ganglion which results in destruction and infection of Schwann cells leading to demyelination and inflammation.
What are the risk factors?
Black or hispanic
Hypertension
Diabetes
Pregnancy (strong factor, rest are weak)
Positive family history
Epidemiology
Most cases: 15-45 yrs
What are the presenting symptoms?
Prodrome of pre-auricular pain (in some cases)
Single episode (recurrence in rare and prompts further diagnosis)
This is followed by unilateral facial weakness and droop
Maximum severity: 1-2 days
50% experience facial, neck or ear pain or numbness
Keratoconjuctivitis sicca (dry eye, may lead to ulcerative keratitis and blindness)
Hyperacuisis
This is due to stapedius paralysis
Loss of taste (uncommon)
Tearing or drying of exposed eye
Because it may be difficult to close the eye fully
What are the signs?
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 appropriate investigations?
Usually unnecessary (e.g. MRI or CT scan, only for excluding other causes)
Clinical diagnosis
EMG - may show local axonal conduction block
What’s the management plan?
Protection of cornea with protective glasses/patches or artificial tears
High-dose corticosteroids (prednisolone) is useful within 72 hrs
Only given if Ramsey-Hunt Syndrome is excluded
Surgery - lateral tarsorrhaphy (suturing the lateral parts of the eyelids together)
Performed if imminent or established corneal damage
What are the possible complications?
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
What’s the prognosis?
85-90% recover function within 2-12 weeks with or without treatment
Extent of facial palsy – most predictive parameter of ultimate recovery outcome
