Facial Electromyography Mapping in Healthy and Bell's Palsy Subjects: A High-Density Surface EMG Study

Bell's palsy impairs the symmetry of facial appearance and movement. Detailed examination of facial muscle activities should be important for the diagnosis and treatment of the Bell's palsy. In this study, facial muscle activities in normal and Bell's palsy conditions were measured using a high-density (HD) electromyography (EMG) technique. The EMG signals during active tasks (four different facial expressions) and resting task were collected with a HD array of EMG electrodes from forehead and cheek muscles. To visualize facial EMG activities, the EMG maps were reconstructed from the HD-EMG recordings. The two-dimension (2D) correlation coefficients between right and left sides of facial EMG maps were calculated to evaluate the symmetry of facial muscle activities during these tasks. Our experimental results showed that the 2D correlation coefficients during active tasks were different significantly (P<0.01) between the healthy group(n=4) and Bell's palsy group(n=3). These results demonstrated that the synchronism of facial muscle activities during active tasks in healthy subjects is greater than that in the Bell's palsy subjects. This pilot study suggested that HD-EMG would be a potential technique to assess abnormal asymmetric activities of facial muscles for Bell's palsy.