Bell Palsy
Basics
Description
An acute, unilateral, self-limiting facial nerve (cranial nerve VII) palsy; Bell palsy is often idiopathic, resulting in the inability to voluntarily move the facial muscles of the affected side. It is associated with edema and compression of cranial nerve VII (CN VII).
Epidemiology
- No race, geographic or gender predominance
- Affects all ages, with the highest incidence being in patient ages 15 to 45 years
- Occurs with equal frequency on the left and right sides of the face
Incidence
- Global studies have demonstrated annual incidence of up to 53 per 100,000.
- Lifetime risk is 1 in 60.
Etiology and Pathophysiology
- The etiology of Bell palsy remains unclear.
- Inflammation of CN VII causes edema, subsequent compression, and possible degeneration of both the nerve and the associated vasculature.
- Activation of a latent herpes virus (herpes simplex type 1 [HSV-1] or herpes zoster) in cranial nerve ganglia is thought to account for many cases.
Risk Factors
- Pregnancy, with increased risk seen in patients with chronic hypertension, maternal obesity, and severe preeclampsia
- Immunosuppression
- Diabetes mellitus
- Viral upper respiratory infection
- Chronic hypertension
- Obesity
- Extremes of temperature
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