Multichannel surface EMG of the facial muscles during a 10-day biofeedback training of patients with synkinetic reinnervated facial nerve palsy

Introduction

In 2012, a 10-day biofeedback training (BT) as a day hospital treatment in the Department of Otorhinolaryngology has been established to mitigate synkinesis and asymmetries in patients with chronic facial paresis (FP) with postparalytic synkinesis. The investigation aims to track sEMG changes during the program and to assess the efficacy of the intervention.

Material and methods

36 patients with FP and synkinesis were studied. Overall sEMG signals of 56 electrodes were derived by combining two electrode schemes (bipolar Fridlund and monopolar Kuramoto scheme) covering all facial muscles during a standardized execution of facial movements. sEMG measurements were recorded before the initiation of the BT (T0) and after nine days of BT (T9). The analysis included a mixed linear model for both the absolute and the normalized sEMG amplitude values across the intervals T0 and T9 to compare the modifications in muscular activity.

Results

There was an amplitude decrease of the mean sEMG values between T0 and T9 (Fridlund scheme: T0: 7.75 µV, T9: 6.36 µV (95% confidence interval (CI) = 1.289-1.492; p<0.001), Kuramoto scheme: T0: 8.29 µV, T9: 6.62 µV (95% CI = 1.556-1.768; p<0.001)). When examining the sides of the face independently, the amplitude reduction detected by the Kuramoto scheme was more marked on the synkinetic side. Additionally, whether deploying the Fridlund or the Kuramoto scheme, each configuration independently offered the capability to distinguish facial expressions with clarity.

Conclusion

The observed reduction in sEMG activity suggests that the targeted retraining of muscle coordination may account for improved facial symmetry. Consequently, the BT regimen under study appears to be a beneficial contributor to the rehabilitation process.

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