Bell's Palsy


Idiopathic facial nerve palsy (CN VII)


Bell’s palsy is a diagnosis by exclusion
Clinical diagnosis:

  • Unilateral Lower motor neuron pattern facial palsy (the forehead muscles are involved)
  • Bell’s phenomenon: the eyes will roll upwards and backwards when eyelid closure is attempted. This is a normal response that occurs in everyone, but it is visible to the examiner in Bell’s palsy. Patients who are not making an effort to close their eyes will not have Bell’s phenomenon.

Electrodiagnosis: nerve conduction studies, electromyography:

  • Normal for 3 days, excitation decreases for 4-10 days. Therefore is done at least 3 days after complete paralysis, best done at 14 days
  • If excitation is present, 90% recover, if abscent 20% recover
  • If less than 90% degeneration 80% recover, if 90% degeneration 50% recover


  • Edema, lymphocytic infiltrate, nerve fibre degeneration

Investigations to consider:

Consider electrodiagnosis if complete paralysis
To exclude other causes (if any atypical features):

  • Syphilis serology
  • HIV tests
  • Vasculitis screen: ESR, CRP, ANA screen, ENA panel (anti- dsDNA, anti-Sm, anti-RNP, SSA, SSB, anti-Jo-1, antitopoisomerase ‘formerly anti Scl-70’, antinucleolar, anticentromere), ANCA (c-ANCA, p-ANCA), Complement C3, C4 and CH50
  • CSF analysis

If recurrent or bilateral:

  • MRI, base of the skull
  • Borrelia serology: Lyme disease
  • Sarcoidosis tests


Protect the cornea:

  • Artificial Tears while awake every 4 hours & tape eyes closed while sleeping


  • Prednisolone orally days & taper over 7 days.

+some people consider antivirals P.O. [weak evidence] e.g. valacyclovir BD
If no recovery:

  • In 3-6 weeks: Reconsider the Dx
  • Permanent: Consider cross-facial grafting or hypoglossal facial anastomosis, consider tarsorrhaphy

Related articles:


  1. Sullivan, F.M., et al., Early treatment with prednisolone or acyclovir in Bell’s palsy. N Engl J Med, 2007. 357(16): p. 1598-607.
  2. Gilden, D.H., Clinical practice. Bell’s Palsy. N Engl J Med, 2004. 351(13): p. 1323-31.