Herpes simplex virus type 1 and Bell's palsy-a current assessment of the controversy

Abstract

Bell's palsy causes about two thirds of cases of acute peripheral facial weakness. Although the majority of cases completely recover spontaneously, about 30% of cases do not and are at risk from persisting severe facial paralysis and pain. It has been suggested that herpes simplex virus type 1 (HSV-1) may be the etiological agent that causes Bell's palsy. Although corticosteroid therapy is now universally recognized as improving the outcome of Bell's palsy, the question as to whether or not a combination of antiviral agents and corticosteroids result in a better rate of complete facial recovery compared with corticosteroids alone is now a highly contentious issue. The evidence obtained from laboratory studies of animals and humans that HSV-1 may be linked to facial nerve paralysis is first outlined. The discussion then focuses on the results of different clinical trials of the efficacy of antiviral agents combined with corticosteroids in increasing the rate of complete recovery in Bell's palsy. These have often given different results leading to opposite conclusions as to the efficacy of antivirals. Of three recent meta-analyses of previous trials, two concluded that antivirals produce no added benefit to corticosteroids alone in producing complete facial recovery, and one concluded that such combined therapy may be associated with additional benefit. Although it is probably not justified at the present time to treat patients with Bell's palsy with antiviral agents in addition to corticosteroids, it remains to be shown whether antivirals may be beneficial in treating patients who present with severe or complete facial paralysis.