Bell's palsy (N) Flashcards
Define Bell’s palsy.
Acute, unilateral, idiopathic, peripheral facial nerve palsy (paralysis) in patients for whom physical examination and history are otherwise unremarkable
Deficits in Bell’s palsy affect which facial zones?
Affects all facial zones equally - no forehead sparing
How long does it take for deficits in Bell’s palsy to fully evolve?
Deficits affecting all facial zones equally fully evolve within 72 hours
Is Bell’s palsy an UMN or LMN condition?
LMN condition - unlike UMN conditions of the face, LMN conditions affect the entire side of the face - in this case ipsilateral CN VII affected
Which demographics is Bell’s palsy most common in? (2)
- 15-45y/o
- pregnant women
What condition are most cases of Bell’s palsy preceded by?
URTI - suggests viral or post-viral aetiology
Which virus has a strong correlation with Bell’s palsy?
Herpes simplex virus type 1 (HSV-1) - affects the geniculate ganglion
Describe the aetiology of Bell’s palsy.
- reactivation of HSV-1 within the geniculate ganglion
- infection of Schwann cells –> demyelination and neural inflammation
How can you tell whether a lesion is UMN or LMN?
- assess for forehead sparing on affected side
- if no forehead sparing: LMN lesion
- if forehead sparing: UMN (i.e. stroke) - because forehead innervated by both sides of cerebral cortex, so a unilateral stroke will not paralyse the forehead as ipsilateral UMN still functions
- forehead sparing = can wrinkle forehead, raise eyebrow and close eye on affected side, but cheeks and mouth still affected
What are the clinical features of Bell’s palsy? (11)
- single episode
- unilateral acute facial weakness and droop
- absence of constitutional symptoms (fever, malaise, myalgia, arthralgia, headache, rash)
- non-forehead sparing = ipsilateral LMN lesion
- forehead sparing = contralateral UMN lesion
- all branches of facial nerve involved
- keratoconjunctivitis sicca (dry eyes and mouth) - lack of adequate blink function + parasympathetic dysfunction of lacrimal gland
- may later progress to epiphora and gustatory hyperlacrimation
- hyperacusis - hypersensitivity to loud noises
- dysgeusia - loss of taste in anterior 2/3 of tongue
- synkinesis - involuntary and abnormal movements of face
- speech impairment
- pain - post-auricular pain and mild-mod otalgia
What might you see on examination of Bell’s palsy? (3)
- involvement of all facial nerve branches - equal distribution of facial weakness
- hyperacusis - hypersensitivity to loud noises
- dysgeusia - taste disturbance anterior 2/3 of tongue
What might the face of a patient with Bell’s palsy look like? (7)
- inability to wrinkle forehead
- inability to raise brow
- droopy eyelid + inability to close eye (–> irritation)
- inability to puff cheek
- asymmetrical smile
- asymmetrical facial muscle tone
- ‘sagging’ face
Describe the Bell phenomenon seen in patients with Bell’s palsy.
When asked to close eyes, unaffected eye closes but affected side does not, with eyeball rolling upwards
What are some risk factors for Bell’s palsy? (10)
- intranasal influenza vaccination
- pregnancy (3x risk)
- HSV exposure (infection or vaccination)
- URTI
- arid/cold climate
- hypertension
- diabetes
- Fx
- Black/Hispanic ancestry
- dental procedures
What is the main method of diagnosis of Bell’s palsy?
Clinical diagnosis of exclusion - acute unilateral facial palsy with otherwise normal physical examination
What other investigations can be done for Bell’s palsy? (3)
- electroneuronography (ENoG AKA evoked EMG) - if near-complete/complete facial paralysis o/e, should be done 72h-14d after onset
- needle electromyography (EMG) - used to confirm absence of voluntary motor unit potentials in facial musculature of one side
- serology for Borrelia burgdorferi - indicated in all patients with recent travel to Lyme disease-endemic area
When can Bell’s palsy NOT be diagnosed? (3)
- facial palsy of an otherwise known aetiology (e.g. Lyme disease-associated facial palsy)
- facial palsy that is progressive, waxing and waning
- affects facial zones in an uneven fashion / forehead sparing
What are some differential diagnoses for Bell’s palsy? (8)
- Herpes Zoster oticus (Ramsay Hunt Syndrome)
- stroke - sparing of upper 1/3 of face, presence of other neurological deficits if cortical
- Lyme disease - skin rash, frontal headache, bilateral
- facial nerve tumour - progressive
- chronic otitis media or cholesteatoma
- necrotising otitis media
- idiopathic orofacial granulomatosis
- uveoparotid fever
What scale is used to measure the severity of facial nerve damage or paralysis in Bell’s palsy?
House-Brackmann score:
- grade I - normal
- grade II - slight weakness/asymmetry
- grade III - obvious weakness with movement but absence of disfigurement at rest; intact ability to close the eye
- grade IV - obvious weakness with movement and disfigurement at rest; inability to fully close the eye
- grade V - barely perceptible movement
- grade VI - no movement
What is the 1st-line management for acute Bell’s palsy?
Corticosteroid (prednisolone PO) within 72hrs (careful in patients with DM, immunodeficiency, poorly controlled hypertension, Hx psychosis)
PLUS eye protection (glasses, artificial tears, ophthalmic lubricant, eye taping at night) - eye will dry out –> corneal damage
How do we manage severe palsy/complete palsy on presentation of Bell’s palsy? (3)
- corticosteroid (prednisolone) + eye protection
- concurrent antiviral therapy (valaciclovir, acyclovir)
- surgical decompression:
- clinical undetectable unilateral facial movement
- facial palsy onset within 14d
- ENoG performed 72h-14d
- needle EMG confirms absence of voluntary motor unit potentials in facial musculature
What do you do if no signs of improvement after 3 weeks of Bell’s palsy?
Immediate urgent ENT referral
What are some complications of Bell’s palsy? (6)
- keratoconjunctivitis sicca
- exposure keratopathy
- ulcerative keratitis (eye ulcers)
- ectropion (sagging eyelid)
- contracture and synkinesis
- gustatory hyperlacrimation
Describe the prognosis of Bell’s palsy.
85-90% recover function with 2-12 weeks with/without treatment
Some develop permanent weakness/paralysis
