Bell palsy and herpes simplex virus: identification of viral DNA in endoneurial fluid and muscle.

To determine whether herpes simplex virus type 1 (HSV-1) causes Bell palsy. Prospective study. University inpatient service. 14 patients with Bell palsy, 9 patients with the Ramsay-Hunt syndrome, and 12 other controls. Viral genomes of HSV-1, varicella-zoster virus, and Epstein-Barr virus were analyzed in clinical samples of facial nerve endoneurial fluid and posterior auricular muscle using polymerase chain reaction (PCR) followed by hybridization with Southern blot analysis. Herpes simplex virus type 1 genomes were detected in 11 of 14 patients (79%) with Bell palsy but not in patients with the Ramsay-Hunt syndrome or in other controls. The nucleotide sequences of the PCR fragments were identical to those of the HSV-1 genome. Herpes simplex virus type 1 is the major etiologic agent in Bell palsy.