Bell's palsy and herpes viruses: To (acyclo)vir or not to (acyclo)vir?

The majority of peripheral seventh cranial nerve palsy cases remain without an identified etiology and will eventually be diagnosed as idiopathic or Bell's palsy. Some features of this condition may be characteristic of a viral infection. Indeed, several herpes viruses have been implicated as potential causative pathogens. Besides varicella-zoster virus, shown to cause Bell's palsy under the Ramsay-Hunt syndrome, recent years have seen an increased interest and focus on the possible herpes simplex virus type 1 (HSV-1) etiology in idiopathic facial paralysis. We review the clinical, biological and virological basis for the potential herpetic cause of Bell's palsy and the rational for antiviral therapy in this condition.