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An acute, usually unilateral, peripheral facial nerve palsy of unknown etiology. Herpes-mediated viral inflammatory/immune mechanism is the likely cause of most cases, causing subsequent swelling and compression of cranial nerve VII (facial) and the associated vasa nervorum.
- Affects 0.02% of the population annually
- No race, geographic, or gender predominance
- Median age of onset is 40 years but affects all ages.
- Accounts for about half of all cases of unilateral facial paralysis
- Occurs with equal frequency on the left and right sides of the face
- Most patients recover, but as many as 30% are left with facial disfigurement and pain.
- 25 to 30 cases per 100,000 people in the United States per year
- Lowest in children ≤10 years of age; highest in adults ≥70 years of age
- Higher among pregnant women (3 times the risk)
Affects 40,000 Americans every year
Etiology and Pathophysiology
- Results from damage to the facial cranial nerve (VII)
- Exact pathogenesis is still controversial; infective, immune, and ischemic mechanisms are potential contributors.
- The most likely cause is activation of latent herpes virus (herpes simplex virus [HSV] type 1 and herpes zoster virus) in cranial nerve ganglia.
- Inflammation of cranial nerve VII causes swelling and subsequent compression and possibly demyelination of both the nerve and the associated vasa nervorum.
- Ischemia from arteriosclerosis associated with diabetes mellitus
May be associated with a genetic predisposition, but it remains unclear which factors are inherited
- Pregnancy, especially in the 3rd trimester or in the 1st postpartum week
- Immunocompromised status
- Diabetes mellitus
- Age >30 years
- Exposure to cold temperatures
- Upper respiratory infection (e.g., coryza, influenza)
- Chronic HTN
- Migraine headache
Commonly Associated Conditions
- Herpes zoster virus
- Lyme disease
- Diabetes mellitus
- Hypertension, Ramsay-Hunt syndrome
- Sjögren syndrome