Vol. 94 No. 10 October　2001

Bell’s Palsy and Herpes Simplex Virus

   Bell’s palsy is the most common cause of facial paralysis ; it has an incidence of 20 to 30 per 100,000 people. Many events such as viral infection, ischemia and autoimmune reaction have been proposed as causes of Bell’s palsy. However, to date there have been no reports of conclusive evidence of the etiological agent responsible for Bell’s palsy since Sir Charles Bell described the disease in 1830. Because the etiological agent remains unknown, treatment of this condition is empiric, varying from observation alone to the use of steroids and surgical decompression.
   Recent advancements in the molecular methods of in situ hybridization and polymerase chain reaction have revealed the existence of HSV-1 genomes in the involved facial nerve as well as the geniculate ganglion. In addition, animal experiments have shown that HSV-1 may induce facial paralysis and the beneficial effect of the antiviral agent of acyclovir for facial function has also been demonstrated. These findings provide the evidence that latently infected HSV-1 causes Bell’s palsy when it reactivates and it is controversial whether we should continue using the term “Bell’s palsy” to mean “idiopathic facial paralysis” or whether we should now recognize Bell’s palsy as “herpetic facial paralysis”. However, currently, we have no reliable, widely available clinical test for the early identification of HSV-1 infection in Bell’s patients. Methodological break-through will resolve this problem and data accumulation will datermine the percentage of patients with Bell’s palsy in whom HSV-1 is the etiological agent.

Key words : Bell’s palsy, herpes simplex virus, polymerase chain reaction