Bell Palsy



An acute, usually unilateral, self-limiting peripheral (lower motor neuron) facial nerve (cranial nerve VII) palsy; Bell Palsy is largely idiopathic. It results in the inability to voluntarily move the facial muscles of the affected side. It is associated with edema and compression of CN VII.


  • No race, geographic, or gender predominance
  • Affects all ages, with the highest incidence being in patients aged 15 to 45 years
  • Occurs with equal frequency on the left and right sides of the face

Global studies have demonstrated annual incidence of up to 53 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.
  • Activation of latent herpesvirus (herpes simplex virus type 1 and herpes zoster virus) in cranial nerve ganglia thought to account for many cases of Bell palsy.

Risk Factors

  • Pregnancy, with increased risk seen in patients with chronic hypertension, maternal obesity, and severe preeclampsia
  • Immunosuppression
  • Diabetes mellitus
  • Upper respiratory infection with viruses such as influenza A
  • Chronic hypertension
  • Obesity
  • Extremes of temperature (1)

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