Bell’s Palsy

Basics

Description

  • 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 3rd and 5th decade (may occur at any age)
  • Diabetes and pregnancy increase risk
  • Incidence: 15–40 per 100,000 per year

Etiology

  • Idiopathic, but viral cause (particularly herpes simplex) suspected
  • Possible infectious causes which may cause peripheral seventh nerve palsy:
    • Varicella zoster infections
    • Infectious mononucleosis (Epstein–Barr virus [EBV] infection)
    • Lyme disease
  • 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

There's more to see -- the rest of this topic is available only to subscribers.