Differential diagnosis

• Bell's palsy must be distinguished from other causes of facial palsy - see facial palsy for more information
• the differential diagnosis includes:
  • nuclear (peripheral) causes (1)
    • lyme disease
      • this is more likely if the facial weakness is bilateral
      • history of tick exposure, and arthralgias
      • look for a rash
    • otitis media
      • suppurative otitis is excluded by examining the ear
      • there is gradual onset ear pain, fever, and conductive hearing loss
    • Ramsay Hunt syndrome
      • herpes zoster may produce an acute facial weakness but is accompanied by a rash within the auricle - geniculate herpes - or on the palate, pharynx, face, neck or trunk
      • there may be a pronounced prodrome of pain
    • sarcoidosis
      • sarcoidosis affecting the parotid gland is suggested by recurrent facial palsy
      • facial weekness is often bilateral
    • Guillain-Barré syndrome
      • facial weekness is often bilateral
    • HIV infection
      • more likely if the facial weakness is bilateral
      • look for lymphadenopathy
    • tumours
      • cholesteatoma, parotid gland tumours
  • supranuclear (central) causes (2)
    • multiple sclerosis
      • multiple sclerosis should be considered if the palsy is unilateral, in a young adult, is painless, and resolves in 2-3 weeks
    • stroke
    • tumours
      • metastases or primary brain tumours
      • history of cancer
      • look for mental status changes
• Horner's syndrome and IIIrd nerve palsies produce a ptosis

Reference:

• (1) Effrey D. et al. Bell's Palsy: Diagnosis and Management. Am Fam Physician 2007;76:997-1002, 1004.