Bell's palsy

Question 1

Define Bell’s Palsy

Answer 1

Acute unilateral LMN facial nerve palsy

Question 2

Aetiology of Bell’s palsy

Answer 2

Idiopathic, Strong evidence towards reactivation of Herpes Simplex Virus Type 1 (HSV-1) within the geniculate ganglion
Inflammatory oedema from entrapment of CNVII in narrow facial canal
60% preceded by an URTI

Facial nerve conduction blockade in Bell’s palsy originates proximal to the geniculate ganglion, prior to any branching so all branches are affected in equal fashion.
Unequal distribution of facial weakness across facial zones on exam rules out Bell’s

Question 3

Risk factors for Bell’s palsy

Answer 3

Intranasal influenza vaccination
Pregnancy
URTI
Cold climate
HTN, DM
FHx

Question 4

Symptoms of bell’s palsy

Answer 4

Preceded by Pain, post-auricular + otalgia
Single episode (ipsilateral or contralateral recurrence is unusual so recurrence should prompt further investigations)
Unilateral facial weakness and droop
50% - facial, neck or ear pain or numbness
Severe pain = zoster sine herpete of the facial nerve
Hyperacusis (sensitivity to sound ipsilateral to palsy due to impairment of stapedius reflex)
Dysgeusia (taste disturbance)
Otalgia

Question 5

Signs of Bell’s palsy on examination

Answer 5

Unilateral LMN weakness of facial muscles (no forehead sparing)
Bell’s phenomenon: eyeball rolls up but the eye remains open when trying to close eyes
Clinical sensation is normal despite reported numbness
Absence of constitutional symptoms
Involvement of all nerve branches
Keratoconjunctivitis sicca (dry eye) → epiphora and hyperlacrimation
Synkinesis

Question 6

Investigations for Bell’s palsy

Answer 6

Bell’s Palsy is a clinical diagnosis, based on history and physical examination alone

Serology for borrelia burgdorferi: ?Lyme disease (for all those with recent ravel to endemic area)
Electroneuronography (ENoG): >90% decrease in amplitude of compound muscle action potential (CMAP)
EMG: absence of voluntary motor unit potentials
MRI: exclude stroke

Question 7

Management for Bell’s palsy

Answer 7

Acute
1. Corticosteroid e.g. prednisolone 60mg for 5 days, then reduce dose by 10mg each day
2. Eye protection (glasses + artificial tears)

Severe palsy/complete paralysis on presentation
1. Concurrent antiviral therapy e.g. valaciclovir or aciclovir
2. Surgical decompression
3. Lateral tarsorrhaphy (suturing lateral parts of eyelids together) if corneal damage

Question 8

Complications of Bell’s palsy

Answer 8

Keratoconjunctivitis sicca
Exposure keratopathy
Ulcerative keratitis
Ectropion (sagging eyelid)
Contracture and synkinesis
Gustatory hyperlacrimation
Corneal ulcers

Question 9

Prognosis for Bell’s palsy

Answer 9

The extent of palsy following complete evolution of Bell’s palsy is most predictive of recovery outcome
Incomplete paralysis on clinical examination, 94% will fully recover
Complete paralysis, 61% will fully recover
Spontaneous return of normal or near-normal facial function following Bell’s is reduced by 50% when EN0G reveals a 95% difference between sides
Pregnancy-associated Bell’s may be associated with worse long-term outcomes