Motoric electrical stimulation of mimic muscles: Compatibility of various surface electrical pulse forms and lengths in subjects and patients with facial palsy

Introduction:

To evaluate the applicability of facial electrostimulation (es) of the facial muscles by means of triangular pulses (tp) and rectangular pulses (rp) of different lengths in different areas of the face.

Methods:

We performed electrical stimulation with tp and rp in 48 (58% male, median age: 45 years) subjects in the area of the eye (A), cheek (W) and mouth (M) in increasing phase duration (0.1 – 500 ms) and amplitude (0.01 – 40mA), detecting the motor and discomfort thresholds. In another study 30 subjects (73% male, median age: 49 years) and 31 patients with facial palsy and synkinesia (29% male, median age: 52 years) were stimulated by rp while the discomfort threshold was detected

Results:

Rp showed a significantly lower amplitude for each electrode position with the same phase duration until triggering visible muscle contractions compared to tp (A p = 0.01, W p = 0.003, M p = 0.005). The tolerated amplitude up to the discomfort threshold was significantly higher for tp with the same phase duration than for rp (A p = 0.03, W p = 0.04, M p = 0.02). Tp was more frequently cancelled compared to rp before triggering visible contractions (4% vs. 84%). The discomfort at maximum stimulation was significantly higher in tp compared to rp only at the mouth angle (p = 0.003). There was a significantly lower pain perception in rp of patients with facial palsy and synkinesia compared to healthy subjects on the eye (p = 0.04) and on the cheek (p = 0.02).

Conclusions:

Rp are less well tolerated by volunteers with the same pulse duration than tp. Overall, patients perceived the ES as less painful than subjects. An individual adaptation of the es makes sense.

Publication History

Publication Date:
23 April 2019 (online)