Bell's Palsy



  • Acute, idiopathic peripheral CN VII (facial nerve) palsy
  • Complete recovery in 85% of cases without treatment
  • Degree of deficit correlates with prognosis:
    • Complete lesions have poorest prognosis
    • Partial lesions often have excellent results
  • Recovery usually begins within 2 wk (often taste returns first) and is complete by 2–3 mo:
    • Advanced age and slow recovery are poor prognosticators
  • Affects men and women equally
  • Age predominance between the third and fifth decade (may occur at any age)
  • Diabetes and pregnancy increase risk
  • Incidence: 15–40 per 100,000 per year


  • Idiopathic by definition, but viral cause (particularly herpes simplex) suspected
  • Possible infectious causes which may cause peripheral seventh nerve palsy:
    • Lyme disease
    • Infectious mononucleosis (Epstein–Barr virus [EBV] infection)
    • Varicella zoster infections
  • Mechanism: Edema and nerve degeneration within stylomastoid foramen
  • Innervation to each side of forehead is from both motor cortices:
    • Unilateral cortical processes do not completely disrupt motor activity of forehead
  • Only peripheral or brainstem lesion can interrupt motor function of just 1 side of forehead

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