Bell Palsy
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Basics
Description
An acute, usually unilateral peripheral facial nerve palsy. The etiology is largely idiopathic; however, many cases have been attributable to herpes simplex virus (HSV) type 1. An ischemic process involving the facial nerve has also been posited as a likely cause for Bell palsy.
Epidemiology
- Affects 0.002% of the population annually
- No geographic or gender predominance
- Affects all ages with a median age of onset of 40 years but with highest incidence in persons over 70 years
- Occurs with equal frequency on the left and right sides of the face
Incidence
Most population studies have shown an annual incidence of 15–30 per 100,000.
Etiology and Pathophysiology
- Inflammation of cranial nerve VII causes edema of perineurium and subsequent compression and possibly degeneration of both the nerve and the associated vasa nervorum.
- Infectious, immune, and ischemic mechanisms suggested, with activation of latent herpes virus (HSV type 1 and herpes zoster virus) in cranial nerve ganglia as the most likely infectious etiology.
Risk Factors
- Pregnancy, with increased risk seen in patients with chronic hypertension, maternal obesity, and severe preeclampsia
- Immunocompromised status
- Diabetes mellitus
- Age >30 years
- Upper respiratory infection
- Chronic hypertension
- Obesity
-- To view the remaining sections of this topic, please log in or purchase a subscription --
Basics
Description
An acute, usually unilateral peripheral facial nerve palsy. The etiology is largely idiopathic; however, many cases have been attributable to herpes simplex virus (HSV) type 1. An ischemic process involving the facial nerve has also been posited as a likely cause for Bell palsy.
Epidemiology
- Affects 0.002% of the population annually
- No geographic or gender predominance
- Affects all ages with a median age of onset of 40 years but with highest incidence in persons over 70 years
- Occurs with equal frequency on the left and right sides of the face
Incidence
Most population studies have shown an annual incidence of 15–30 per 100,000.
Etiology and Pathophysiology
- Inflammation of cranial nerve VII causes edema of perineurium and subsequent compression and possibly degeneration of both the nerve and the associated vasa nervorum.
- Infectious, immune, and ischemic mechanisms suggested, with activation of latent herpes virus (HSV type 1 and herpes zoster virus) in cranial nerve ganglia as the most likely infectious etiology.
Risk Factors
- Pregnancy, with increased risk seen in patients with chronic hypertension, maternal obesity, and severe preeclampsia
- Immunocompromised status
- Diabetes mellitus
- Age >30 years
- Upper respiratory infection
- Chronic hypertension
- Obesity
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