Bell's Palsy

Question 1

Definition

Answer 1

Idiopathic lower motor neurone facial nerve palsy

Question 2

Aetiology/Risk factors

Answer 2

· IDIOPATHIC

· 60% are preceded by an upper respiratory tract infection

· This suggests that it has a viral or post-viral aetiology

Question 3

Epidemiology

Answer 3

Most cases: 20-50 yrs

Question 4

Presenting symptoms

Answer 4

· Prodrome of pre-auricular pain (in some cases)

· This is followed by unilateral facial weakness and droop

· Maximum severity: 1-2 days

· 50% experience facial, neck or ear pain or numbness

· Hyperacuisis
o This is due to stapedius paralysis

· Loss of taste (uncommon)

· Tearing or drying of exposed eye
o Because it may be difficult to close the eye fully

Question 5

Signs on physical examination

Answer 5

· Lower motor neurone weakness of facial muscles
o Affects ipsilateral muscles of facial expression
o Does NOT spare the muscles of the upper part of the face (unlike upper motor neurone facial nerve palsy)

· Bell’s Phenomenon
o 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)

Question 6

Investigations

Answer 6

· Usually unnecessary (except for excluding other causes)

· EMG - may show local axonal conduction block

Question 7

Management plan

Answer 7

· Protection of cornea with protective glasses/patches or artificial tears

· High-dose corticosteroids is useful within 72 hrs
o Only given if Ramsey-Hunt Syndrome is excluded

· Surgery - lateral tarsorrhaphy (suturing the lateral parts of the eyelids together)
o Performed if imminent or established corneal damage

Question 8

Possible complications

Answer 8

· Corneal ulcers

· Eye infection

· Aberrant reinnervation
o E.g. Blinking may cause contraction of the angle of the mouth due to aberrant sympathetic innervation of orbicularis oculi and oris
o Crocodile Tears Syndrome - parasympathetic fibres may aberrantly reinnervate the lacrimal glands causing tearing whilst salivating

Question 9

Prognosis

Answer 9

85-90% recover function within 2-12 weeks with or without treatment