Abstract
PurposeTo 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.MethodsTwo 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.ResultsDiscomfort 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.ConclusionsSurface electrostimulation for selective functional and tolerable facial muscle contractions in patients with postparetic facial synkinesis is feasible.
Highlights
In severe facial nerve paralysis with degeneration of nerve fibers, spontaneous regeneration or regeneration after nerve reconstruction typically is disordered and leads in the chronic phase to altered patterns of muscle contraction and postparetic synkinesis
Up to a pulse duration of 10 ms, the tolerability threshold was always higher than the motor threshold for rectangular and for triangular pulses
The visual impression of the results was confirmed statistically: a rmANOVA was performed for each of the four primary outcome factors and revealed the following: The amplitude at motor threshold was significantly lower for positions (Supplemental Fig. 1): (P1) than for P2 and P3, decreased with longer pulse duration, and was higher for triangular than for rectangular pulses
Summary
In severe facial nerve paralysis with degeneration of nerve fibers (axonotmesis or neurotmesis), spontaneous regeneration or regeneration after nerve reconstruction typically is disordered and leads in the chronic phase to altered patterns of muscle contraction and postparetic synkinesis. This situation has to be distinguished from the much rarer situation of a patient without any regeneration and chronic muscle. A defined set of pulse durations and positions in the face were analyzed in healthy participants in comparison to patients with postparetic facial synkinesis
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