Bell's palsy

Question 1

Define Bell’s palsy.

Answer 1

Acute unilateral facial palsy of probable viral aetiology.

Clinical diagnosis of exclusion.

Deficits affect all facial zones equally and fully evolve within 72 hours.

Question 2

Describe the onset of Bell’s Palsy.

Answer 2

Abrupt onset (eg overnight or after a nap) with complete unilateral facial weakness at 24–72h

Question 3

What is the aetiology of Bell’s palsy?

Answer 3

Strong evidence that it is caused by HSV1 within geniculate ganglion

Question 4

Is it Bell’s if the facial palsy is of an otherwise known origin? What if it is waxing and waning or affects facial zones in an uneven distribution?

Answer 4

Facial palsy of an otherwise known aetiology (e.g., Lyme disease-associated facial palsy), or facial palsy that is progressive, waxing and waning, or affects facial zones in an uneven fashion, is not Bell’s palsy.

Question 5

What is the prognosis with Bell’s palsy?

Answer 5

Complete recovery to normal facial function occurs in approximately 70% of untreated cases,

with permanently impaired facial function occurring to a minor degree in 13%

and to a major degree in 16% of cases

Onset of clinical recovery within 4 to 6 months; absence of return of hemi-facial tone/movement by this time is suggestive of an alternative diagnosis.

Question 6

Describe the pathophysiology of Bell’s palsy.

Answer 6

Reactivation of HSV1 –> ganglion cell destruction and infection of Schwann cells –> demyelination and neural inflammation

Affect FACIAL NERVE (CNVII) - has four fibre types -

• somatomotor to muscles of facial expression(–>pasly), axons to stapedial muscle (–>hyperacusis),
• gustatory fibres (–>hypo or dysgeusia),
• sensory (–> otalgia and post-auricular pain),
• parasympathetic (–> lacrimal and salivary dysfunction)

Question 7

How common is Bell’s palsy?

Answer 7

Most common aetiology of unilateral facial palsy amongst those >2yrs age

Pak incidence 20-40yrs

incidence ~30/100,000/yr

Equally distributed between both sexes and sides of the face

Question 8

What are the risk factors for Bell’s palsy?

Answer 8

• Intranasal influenza vaccination (stopped now)
• Pregnancy (x3 especially in third trimester)

Other:

• URTI
• Cold climate
• HTN
• Diabetes (x5)
• FH

Question 9

What are the symptoms of Bell’s palsy?

Answer 9

• Abrupt onset unilateral facial weakness
• Ipsilateral numbness or pain around ear
• Reduced taste (ageusia)
• Hypersensitivity to sounds (from stapedius palsy)

Other:

• Unilateral sagging of mouth
• Drooling of salive
• Food trapped between gum and cheek
• Speech difficulty
• Failure of eye closure may cause watery or dry eye, ectropion (sagging and turning-out of the lower lid), injury from foreign bodies, or conjunctivitis.)

Question 10

What are the signs of Bell’s palsy on examination?

Answer 10

• Unable to wrinkle forehead (confirming LMN pathology - forehead not spared)
• Unable to whistle (tests buccinator)
• Keratoconjunctivitis sicca (dry eye)

Other:

• Synkinesis - late sequela: involuntary and abnormal synchronous movement of a facial region concomitant with reflex or voluntary movement in another facial region

Question 11

What investigations would you do for Bell’s palsy?

Answer 11

Bell’s palsy remains a clinical diagnosis of exclusion - red flags for other diagnosis*. If history and physical examination are consistent with Bell’s palsy then no further tests are required (except in those who have travelled to Lyme disease-endemic regions)

Imaging:

• Electroneuronography (ENoG) - >90% decrease in the amplitude of the compound muscle action potential (CMAP) on the affected as compared to the healthy side (–> do needle EMG)
• Needle EMG - absence of voluntary motor unit potentials
• Pure-tone audiometry - normal
• Stapedius reflex - impaired in the ipsilateral efferent limb of stapedius reflex
• MRI (gandolium enhanced fine cut of facial nerve course) - not routine unless neoplasm; neural enhancement may be seen for up to 1 year following onset.

Bloods:

• Serology for Borrelia burgdorferi - should be negative unless Lyme disease

Question 12

How do you manage Bell’s palsy?

Answer 12

Prednisolone within 72hrs - 60mg for 5 days then cut down by 10mg each day until ends.

Eye protection - overnight, ophthalmic lubricant should be applied and the eyelid taped closed; sunglasses during the day

If severe paralysis on presentation: give antiviral (e.g. aciclovir) +/- surgical decompression if no facial movement.

Question 13

What are the complications of Bell’s palsy?

Answer 13

• Keratoconjunctivitis sicca, exposure keratopathy, ulcerative keratitis
• Ectropion (sagging eyelid)
• Contracture and synkinesis
• Gustatory hyperlacrimation (crocodile tears or Bogorad’s syndrome) - give botulinum toxin to lacrimal glands.

Question 14

If there is no improvement in Bell’s within 3 weeks, what should be done?

Answer 14

Referral to ENT urgently

If long standing weakness is present, a referral to plastic surgery may also be done.

Question 15

Which cranial nerve has been affected in this patient?

Answer 15

Facial

Question 16

What can a facial nerve palsy cause?

• Paralysis of stapedius muscle and hyperacusis
• Taste impairment posterior part of tongue
• Taste impairment anterior part of tongue
• Increased production of saliva
• Speech impairment
• Dysphagia

Answer 16

Pooling and dribbling of saliva may occur but there is not increased production. The glossopharyngeal nerve is responsible for taste on the posterior third of the tongue. Speech impairment occurs, but not dysphagia (occurs with bulbar palsy).

• Taste impairment anterior part of tongue
• Paralysis of stapedius muscle and hyperacusis
• Speech impairment

Question 17

This patient has a probable Bell’s palsy. What further initial investigations are indicated?

• Lumbar puncture
• Magnetic resonance imaging brain
• Computed tomography brain/mastoid bone
• Viral serology
• Nerve conduction studies if palsy persists

Answer 17

• Viral serology
• Nerve conduction studies if palsy persists

There is no suggestion of cerebral tumour or demyelination in the history and cranial imaging is not needed at this stage. Viral serology may be helpful and nerve conduction studies can be performed if there is no recovery after a few weeks to assess for the presence of axonal degeneration.

Question 18

What treatments would you consider?

• Short course of oral Prednisolone
• No medication indicated
• Consider antiviral agent orally
• Encourage eyelid closure either by hand or using tape at night
• Eye protection (dark glasses)
• Anticoagulation
• Short-course antibiotics

Answer 18

• Short course of oral Prednisolone
• Consider antiviral agent orally
• Encourage eyelid closure either by hand or using tape at night
• Eye protection (dark glasses)

Short courses of oral steroid are used if patients present early to reduce nerve oedema and some physicians also use antiviral medications. Eye protection is important. Partial lidsuturing can be used in cases with severe associated ectropion.

Question 19

Which of the following statements regarding Bell’s palsy are true?

• Most patients with partial paralysis recover completely
• Most patients with complete paralysis recover completely
• Axonal degeneration is a recognised complication
• A viral neuropathy is the most likely cause
• Reconstructive surgical intervention should be considered if recovery has not occurred by 3 months
• There is an increased incidence in pregnancy
• There is an increased incidence in diabetics

Answer 19

Most patients with partial paralysis recover completely and rapidly, although in those with complete paralysis recovery may not occur until after 3 months. Recovery may be incomplete and in some patients with axonal degeneration abnormal reconnections may occur e.g. production of tears on eating. Surgery should not be considered until time for recovery (> 3 months) has been allowed.

• Most patients with partial paralysis recover completely
• Most patients with complete paralysis recover completely
• Axonal degeneration is a recognised complication
• A viral neuropathy is the most likely cause
• There is an increased incidence in pregnancy
• There is an increased incidence in diabetics

Question 20

Which condition may be the result of facial nerve palsy?

• Ramsay-Hunt syndrome
• Demyelination
• Bell’s palsy
• Cerebello-pontine angle tumour
• Cerebrovascular accident
• Meningo-encephalitis

Answer 20

Bell’s palsy

Bell’s palsy is on idiopathic facial nerve palsy and is essentially a diagnosis if exclusion once other causes are ruled out. A viral aetiology is likely with herpes simplex virus implicated. Preceding ear pain and rapid onset are typical features. Ramsay-Hunt syndrome is due to herpes zoster and is associated with a vesicular rash on the ear. The other conditions mentioned may all cause facial palsy but would not present in this manner.

Question 21

What is the role of antivirals in Bell’s palsy?

Answer 21

NICE: ‘Antiviral treatments alone are not recommended. Antiviral treatment in combination with a corticosteroid may be of small benefit, but seek specialist advice if this is being considered.’

UpToDate recommends the addition of antivirals for severe facial palsy