The aim of this prospective study is to define the prognostic significance of lymphocyte subset analysis in children with Bell's palsy. Lymphocyte subgroup analysis in peripheral blood was performed in 17 children with Bell's palsy by using flow cytometry. Before a standard protocol of corticosteroid treatment, patients were categorized into two groups for facial nerve impairment on the basis of the clinical findings: Group I (mild to moderate impairment), 7 patients; and Group 2 (severe impairment), 10 patients. Outcome of the patients was evaluated at the end of 3 months follow-up and categorized as satisfactory recovery (n = 12) or unsatisfactory recovery (n = 5). Decreased percentages of B cells (CD19) and T helper/inducer (CD4) subsets were measured in patients with Bell's palsy compared with age-matched healthy control patients. Patients with severe impairment had significantly lower percentages of CD4 and CD19 subsets, whereas patients with mild to moderate impairment had only decreased percentage of CD19 subsets. There was no statistically significant difference in the percentage of lymphocyte subsets between the patients with satisfactory and unsatisfactory recovery. These results provide additional support for cell-mediated immunopathogenesis in patients with Bell's palsy, without any prognostic significance for the outcome. (C) 2004 by Elsevier Inc. All rights reserved.