Facial palsy and infection: the unfolding story.

While it is now universally accepted that Ramsay Hunt syndrome is caused by varicella-zoster virus, Bell's palsy continues to be labeled "idiopathic." We review the literature associating Bell's palsy with various infectious agents as well as with Kawasaki disease, a condition in which an infectious etiology is suspected. Good evidence--mostly serological--exists for an etiologic role for the herpes group of viruses, mumps virus, and rubella virus. In addition, recent evidence has focused on Bell's palsy in human immunodeficiency virus infection and Lyme borreliosis. In view of the multiplicity of implicated agents, it is likely that the immunologic response associated with infection triggers a cranial or generalized polyneuropathy culminating in facial nerve compression, degeneration, and paralysis. The mounting interest in Bell's palsy, coupled with the increasing availability of more sensitive and specific tests, is likely to augment the available evidence for an infectious etiology and to clarify the role of other, previously unsuspected infectious agents.