[Bell's palsy: from viral aetiology to diagnostic reality]

Peripheral injury of the facial nerve is a frequent disorder. It is a stressful situation for the patient and it is functionally hazardous for the cornea. Facial palsy is due to a lesion involving the facial pontine nucleus or the nerve trunk in its route from the pontocerebellar angle to the parotid. The idiopathic facial paralysis or Bell's palsy (BP) is the most common cause but acute facial palsy can also be due to tumors. A rigorous clinical history and examination must be performed to guide the additional biological, radiological and cochleovestibular investigations in order to reach the diagnosis. The pathophysiology of BP remains unclear, but seems to be due to the reactivation of Herpes simplex virus type 1 within the intrapetrous pathway of facial nerve. The treatment remains controversial but, for most of the authors, consists of early administration of corticosteroids with or without antiviral agents. Ninety percent of the patients recover normal facial function with this treatment. The severe BP resulting in hemifacial spasm must be quickly identified by electrophysiological testing. They need appropriate rehabilitation and for some authors facial nerve surgical decompression in emergency.