This is an idiopathic palsy of the facial nerve (VII) resulting in a unilateral facial weakness or paralysis. Important to exclude other causes before diagnosing Bell’s Palsy. It is suspected that Bell’s Palsy may be a viral neuropathy (HSV-1).

Other Causes of Facial Nerve Palsy (Upper and Lower Motor Neuron):

• Infections:

• Ramsey Hunt syndrome (cephalic herpes zoster)
• Lyme disease
• HIV
• Meningitis/Chronic meningitis (fungal)
• Polio
• TB
• Mumps?

• Brainstem Lesions
• Brainstem tumour
• Stroke
• MS
• Cerebello-pontine angle lesions
  • Acoustic neuroma
  • Meningioma
• Diabetes
• Sarcoidosis
• Parotid tumour
• Cholesteatoma
• Trauma to skull base
  
  

Clinical Picture

Presentation:

• Facial Weakness: rapid onset, worsens for 1-2 days then stable
• Pain: below the ear (may be present), resolves within a few days
• Unilateral symptoms (otherwise other causes e.g. sarcoidosis should be suspected)
  
  

Clinical Features:

• Mouth sags
• Food gets trapped between gum & cheek
• Dribbling
• Dysarthria
• Taste impairment
• Hyperacusis: intolerant to high pitched sounds: stapedius paralysis
• Excessive watery/dry eye: fail to close eye
• Ectropion: sagging and turning out of the lower eyelid
• Conjunctivitis/Injury from foreign bodies
  
  

 Signs:

• Unable to wrinkle up the forehead = LMN lesion (no forehead sparring as occurs in upper motor neuron injuries affecting the facial nerve)
• Unable to whistle or blow out the cheeks (CN VII)
• Wide palpable fissure
  
  

Natural History & Progress:

• Incomplete Paralysis & No axonal degeneration: recover completely within weeks.
• Complete Paralysis: almost all recover but 15% have axonal degeneration

Axonal degeneration:

recovery begins after 3 months: May be:

Incomplete/No recovery/Complicated by aberrant reconnections

Management:

• Presentation within few days:

High dose prednisolone (0.5mg/kg/12h PO for 5 days)

• Electrodiagnostic studies

Help to identify axonal degeneration but doesn’t influence management

• Protect the eye with dark glasses & installation of artificial tears (eye drops)
• Aciclovir (Antiviral): as cause may be herpes virus

This is a chronic relapsing condition of unknown cause. Plaques of demyelination (and axon loss) take place at sites throughout the CNS (not peripheral nerves). Pathogenesis involves focal disruption of the blood brain barrier and associated immune response and myelin damage. 

Prevalence
England: 40/100 000
Orkney and Shetland 120/100 000 (area of highest worlwide incidence)
Rare in Black Africans & Asians

Age
Mean age of onset: ~30 yrs

Sex
M<F

Geography
Commoner in temperate areas

Incidence increases with distance from the equator

Spread

• Early Picture: Relapses followed by remissions with full functional recovery.
• Late Picture: Remissions become incomplete causing accumulation of progressive disability.

Clinical picture (+investigations)
Presentation:

• 1st Presentations: monosymptomatic

• Unilateral optic neuritis: pain on eye movement & rapid loss of central vision
• Numbness or tingling in the limbs
• Leg weakness
• Brainstem or Cerebellar symptoms; diplopia or ataxia

• Clinical Features:

• Fatigue
• Motor weakness/spasticity
• Altered sensation: numbness, pins & needles
• Pain: trigeminal neuralgia, dysaesthesia
• Bladder: frequency, urgency, incontinence
• Bowel: constipation
• Sexual dysfunction: impotence
• Swallowing disorders
• Eyes: visual defects on exercise, optic neuritis, diplopia, nystagmus
• Cerebellum: ataxia, intention tremor
• Cognition: memory, dementia
• Vertigo
• Depression
• Rarely: epilepsy, aphasia

Investigations:

• CSF:

• ↔ or <50 lymphocytes/mm3,
• increased protein
• +/- oligoclonal bands of Ig G on electrophoresis

•  Delayed visual, auditory and somatosensory evoked potentials.
• MRI: sensitive but not specific for plaque detection.

Diagnosis:

• This is clinical, requiring demonstration of lesions disseminated in time and space, unattributable to other cause.
• Isolated neurological deficits are never diagnostic but can become so if history reveals previous episodes (e.g. unexplained blindness for 1-2 weeks).

  
Prognosis (+complications, treatment)
Complications

• At 5 yrs: 70% are still employed (35% at 20 yrs)
• Poor Prognosis Factors:
• Male sex
• Older age at onset
• Motor signs at onset
• Shorter interval between 1st and 2nd attack
• Many relapses in early years
• Early disability
• Many lesions seen on MRI

Treatment:

• There is no cure.
• Dietary Polysaturated fats: may help
• Methylprednisolone: 1g/24h IV for 3 days shortens relapses. But use <2/yr
• Beta-interferon 1b: can reduce relapse rate by 1/3
• Palliation:
• Spasticity: baclfen 15-100mg/day PO or Diazepam 2-15mg/24h PO
• Urgency: oxybutynin
• Retention: intermitted clean self-catheterization
• Check benefits eligibility