[Idiopathic facial palsy].

Idiopathic facial palsy (IFP), or Bell's palsy, is an acute peripheral unilateral paresis of the facial nerve with an abrupt onset of unknown origin. Primary infection or reactivation of the Herpes simplex virus is suggested as a possible mechanism in some but not all patients. Since IFP is a diagnosis of exclusion, all other causes, especially other neurological diseases or Herpes zoster reactivation need to be excluded, as does Lyme disease in children and endemic areas. If recovery or defective healing has not taken place within 6-12 months, it is mandatory to exclude malignant disease. Severity of the paresis and electromyography are to date the best prognostic markers for defective healing. Steroid application is the only evidence-based therapy to date with recovery rates >90%. The spontaneous recovery rate is about 80%. There is a lack of well defined diagnostic procedures to detect those patients who will recover spontaneously. On the other hand, patients with severe complete paresis might profit from additional antiviral drugs. There is an urgent need for further clinical trials in patients with severe IFP.