Bell's Palsy
Basics
Basics
Basics
Description
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 third and fifth decade (may occur at any age)
- Diabetes and pregnancy increase risk
- Incidence: 15–40 per 100,000 per year
Etiology
Etiology
- 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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