Objective: To determine whether herpes simplex virus type 1 (HSV-1) causes Bell palsy.
Design: Prospective study.
Setting: University inpatient service.
Patients: 14 patients with Bell palsy, 9 patients with the Ramsay-Hunt syndrome, and 12 other controls.
Measurements: 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.
Results: 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.
Conclusions: Herpes simplex virus type 1 is the major etiologic agent in Bell palsy.