OBJECTIVE: Details regarding the molecular biological features of Bell’s palsy have not been widely reported in textbooks. We genetically analyzed facial muscles and clarified these points. MATERIALS and METHODS: We performed genetic analysis of facial muscle specimens from Japanese patients with severe (House-Brackmann facial nerve grading system V) and moderate (House-Brackmann facial nerve grading system III) dysfunction due to Bell’s palsy. Microarray analysis of gene expression was performed using specimens from the healthy and affected sides, and gene expression was compared. Changes in gene expression were defined as an affected side/healthy side ratio of &gt
1.5 or &lt
0.5. RESULTS: We observed that the gene expression in Bell’s palsy changes with the degree of facial nerve palsy. Especially, muscle, neuron, and energy category genes tended to fluctuate with the degree of facial nerve palsy. CONCLUSION: It is expected that this study will aid in the development of new treatments and diagnostic/prognostic markers based on the severity of facial nerve palsy.