Tolerability of facial electrostimulation in healthy adults and patients with facial synkinesis

PURPOSE: To evaluate optimal stimulation parameters with regard to discomfort and tolerability for transcutaneous electrostimulation of facial muscles in healthy participants and patients with postparetic facial synkinesis. METHODS: Two prospective studies were performed. First, single pulse monophasic stimulation with rectangular pulses was compared to triangular pulses in 48 healthy controls. Second, 30 healthy controls were compared to 30 patients with postparetic facial synkinesis with rectangular pulse form. Motor twitch threshold, tolerability threshold, and discomfort were assessed using a numeric rating scale at both thresholds. RESULTS: Discomfort at motor threshold was significantly lower for rectangular than for triangular pulses. Average motor and tolerability thresholds were higher for patients than for healthy participants. Discomfort at motor threshold was significantly lower for healthy controls compared to patients. Major side effects were not seen. CONCLUSIONS: Surface electrostimulation for selective functional and tolerable facial muscle contractions in patients with postparetic facial synkinesis is feasible. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s00405-020-05818-x) contains supplementary material, which is available to authorized users.