Effects of acyclovir on facial nerve paralysis induced by herpes simplex virus type 1 in mice

Objectives: Bellʹs palsy has recently been claimed to be caused by herpes simplex virus type 1 (HSV-1) infection. The anti-viral agent acyclovir is a specific inhibitor of herpesvirus replication, and the most effective agent for the treatment herpesvirus infection. The purpose of this experiment was to assess the effect of acyclovir on the facial nerve paralysis included by HSV-1 infection. Methods: We succeeded in producing an animal model of acute and transient facial nerve paralysis induced with HSV-1 neuritis simulating human Bellʹs palsy. In this study, acyclovir administration was performed before and after facial nerve paralysis, and continued for 5 days. Controls were given phosphate-buffer saline (PBS) instead of acyclovir, and the incidence and duration of facial nerve paralysis was compared in the acyclovir groups and controls. Results: The incidence of facial nerve paralysis was significantly lower in the group given acyclovir before the paralysis than in the controls, and the duration of facial nerve paralysis was shorter. Conclusions: Administration of acyclovir before the paralysis reduced the incidence and duration of facial nerve paralysis. Administration of acyclovir after the paralysis improved the duration of facial nerve paralysis.