Differential diagnosis

• Bell's palsy remains a diagnosis of exclusion and 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. 2-23% of people with Bell's palsy actually have Ramsay Hunt syndrome and it should be suspected when pain is significant, especially in those aged over 60. (2)
    • sarcoidosis
      • sarcoidosis affecting the parotid gland is suggested by recurrent facial palsy
      • facial weakness is often bilateral
    • Guillain-Barré syndrome
      • facial weakness is often bilateral
    • HIV infection
      • more likely if the facial weakness is bilateral
      • look for lymphadenopathy
    • tumours
      • cholesteatoma, parotid gland tumours
  • supranuclear (central) causes (1)
    • 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 3rd nerve palsies produce a ptosis

References

• 1. Effrey D. et al. Bell's Palsy: Diagnosis and Management. Am Fam Physician 2007;76:997-1002, 1004.
• 2. Worme M, Chada R, Lavallee L. An unexpected case of Ramsay Hunt syndrome: case report and literature review. BMC Res Notes. 2013 Aug 28;6:337