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Studies on the effects of the pulse waveform used in electrical muscle stimulation on the activations and perceived discomfort of the waveform have been mainly executed on limb muscles with variable results, however, knowledge of these effects on facial muscles is currently lacking. We studied two waveforms, square wave and sinusoidal wavelet, for the activation of the frontalis muscle in 9 individuals with unresolved facial nerve palsy. Both waveforms produced a movement that was greater in amplitude compared with the maximal voluntary movement of the affected side in 8 participants and at least as great as the healthy side's maximal voluntary movement in 4 participants. Both waveforms were equally successful in producing movements, and there was no significant difference in perceived discomfort ratings between the two waveforms. These findings will be useful for the future development of neuroprosthetic applications for reanimating facial muscles using electrical stimulation. Trial registration: ClinicalTrials.gov NCT03496025, registration date March 19, 2018.

Objectives : Facial nerve palsy causes blurred vision and ocular discomfort due to deficits in blinking and eye closure. The objective of this study was to determine whether eye-blinks could be elicited by electrical stimulation and whether electrically induced blink would have an effect on the visual acuity and ocular symptoms in patients with acute facial nerve palsy. Methods : The zygomatic branch of the facial nerve of fifteen participants with acute facial nerve palsy was electrically stimulated in order to elicit a blink. In successful cases, the participant proceeded with a two-hour TV watching session in which an electrically induced blink was delivered every 5 seconds. The control condition consisted of an otherwise similar TV watching session without electrically induced blinking. Subjective ocular symptoms were evaluated with a Dry Eye Questionnaire and visual acuity was assessed with a Logarithm of the Minimum Angle of Resolution (LogMAR) chart before and after both sessions. Results : The stimulation produced a blink in 8 participants (53%). The visual acuity in the affected eye decreased during the control session, whereas no significant change occurred during the stimulation session. The ocular symptoms were significantly reduced during the stimulation session. Conclusions : Electrically elicited blink is a promising method for reducing the eye symptoms in individuals with acute facial nerve palsy. [ABSTRACT FROM AUTHOR]

Reanimation of paralysed facial muscles by electrical stimulation has been studied extensively in animal models, but human studies in this field are largely lacking. Twenty-four subjects with a peripheral facial nerve palsy with a median duration of three years were enrolled. We studied activations of four facial muscles with electrical stimulation using surface electrodes. In subjects whose voluntary movement was severely impaired or completely absent, the electrical stimulation produced a movement that was greater in amplitude compared with the voluntary effort in 10 out of 18 subjects in the frontalis muscle, in 5 out of 14 subjects in the zygomaticus major muscle, and in 3 out of 8 subjects in the orbicularis oris muscle. The electrical stimulation produced a stronger blink in 8 subjects out of 22 compared with their spontaneous blinks. The stimulation could produce a better movement even in cases where the muscles were clinically completely paretic, sometimes also in palsies that were several years old, provided that the muscle was not totally denervated. Restoring the function of paralysed facial muscles by electrical stimulation has potential as a therapeutic option in cases where the muscle is clinically paretic but has reinnervation. [ABSTRACT FROM AUTHOR]