Bell's palsy

Bell's palsy is a facial paralysis, usually unilateral, and of sudden onset.

It is a lower motor neurone palsy usually diagnosed by exclusion. Typically, presentation is with facial distortion, loss of taste, hyperacusis and a watery eye.

• Bell's palsy was previously considered as an idiopathic lower motor neurone nerve palsy but there has been increasing evidence to suggest that the main cause of Bell's palsy is latent herpes viruses (herpes simplex virus type 1 and herpes zoster virus), which are reactivated from cranial nerve ganglia
  • polymerase chain reaction techniques have isolated herpes virus DNA from the facial nerve during acute palsy
• inflammation of the nerve initially results in a reversible neurapraxia - however ultimately Wallerian degeneration ensues
• herpes zoster virus appears to exhibit more aggressive biological behaviour than herpes simplex virus type 1 - this is because it spreads transversely through the nerve by way of satellite cells

Note that a fifth of cases of acute facial palsy have an alternative cause that should be managed appropriately.

Key points:

• facial palsy improves after treatment with oral prednisolone:
  
  
  • for people presenting within 72 hours of the onset of symptoms, consider prescribing prednisolone
    • no consensus regarding the optimum dosing regimen, but options include (2):
      • prednislone 25 mg twice daily for 10 days, or
      • prednisolone 60 mg daily for five days followed by a daily reduction in dose of 10 mg (for a total treatment time of 10 days) if a reducing dose is preferred
        
        
    • early treatment with prednisolone increases the chance of complete recovery of facial function to 82% (3)
      • eleven people need to be treated for one extra complete recovery at six months
        
        
  • around a fifth of patients will progress from partial palsy, so these patients should also be treated
    
    
  • Bell's palsy - left untreated, 70-75% of patients make a full recovery
    
    
  • no supportive evidence has been found for use of steroids or antivirals in children with Bell's palsy
    
    
• with respect to combined oral antiviral therapy and prednisolone in adults
  • seek expert advice
    
    
• treatment of partial Bell's palsy is controversial; a few patients don't recover if left untreated
  
  
• treatment is probably more effective before 72 hours and less effective after seven days
  
  
• inability to close the eye on the affected side, can lead to irritation and corneal ulceration
  • requires urgent consultation with an ophthalmologist
  • the inability to close the eye on the affected side can, if ignored, lead to irritation and even corneal ulceration
    • can be avoided if good advice on eye care is offered at the outset
    • eye care focuses on lubricating the eye regularly, taping the eye closed overnight and manual blink and eyelid stretching

Reference:

Glass GE, Tzafetta K. Bell's palsy: a summary of current evidence and referral algorithm. Fam Pract. 2014 Dec;31(6):631-42