Restoration of blink in facial paralysis patients using FES

Six subjects with profound facial paralysis were tested to determine the feasibility of restoring functional blink via electrical stimulation of the orbicularis oculi muscle (OOM) without also evoking painful sensations. Stimulation of the paretic eyelid was triggered by EMG detection of blink in contralateral healthy OOM to deliver charge during inhibition of the levator palpebrae antagonist. Transcutaneous and percutaneous stimulation electrode placements were tested during multiple stimulation trials in subjects. Stimulation was delivered via two constant voltage computer controlled channels. Sensory activation thresholds were approximately an order of magnitude lower for percutaneous stimulation (0.4 V) vs. transcutaneous stimulation (3 V). Exploration of multiple possible stimulation paradigms yielded a means by which sufficient muscle activation could be recruited to evoke complete eyelid closure without producing prohibitively painful sensation. Stimulation efficacy across subjects correlated with degree of patient neuromuscular recovery following initial paresis.