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.