Abstract
Facial paralysis can be a devastating condition, causing disfiguring facial droop, slurred speech, eye dryness, scarring and blindness. This study investigated the utility of closed-loop functional electric stimulation (FES) for reanimating paralyzed facial muscles in a quantitative rodent model. The right buccal and marginal mandibular branches of the rat facial nerve were transected for selective, unilateral paralysis of whisker muscles. Microwire electrodes were implanted bilaterally into the facial musculature for FES and electromyographic (EMG) recording. With the rats awake and head-fixed, whisker trajectories were tracked bilaterally with optical micrometers. First, the relationship between EMG and volitional whisker movement was quantified on the intact side of the face. Second, the effect of FES on whisker trajectories was quantified on the paralyzed side. Third, closed-loop experiments were performed in which the EMG signal on the intact side triggered FES on the paralyzed side to restore symmetric whisking. The results demonstrate a novel in vivo platform for developing control strategies for neuromuscular facial prostheses.
Highlights
Facial paralysis is a disfiguring condition affecting 127,000 individuals annually (Bleicher et al, 1996)
We developed a rodent model for studying functional electric stimulation (FES)-based facial reanimation
The facial musculature of the rats was implanted with microwires to allow both EMG recording and FES of facial muscles (Figure 1D)
Summary
Facial paralysis is a disfiguring condition affecting 127,000 individuals annually (Bleicher et al, 1996). The ultimate goal of facial reanimation is to enable independent control of paralyzed facial muscles. Development of effective treatment options is confounded by the wide range of causes that result in a shared facial palsy phenotype, namely, trauma, infection, neoplasm, iatrogenic insults and idiopathic etiologies (Melvin and Limb, 2008). Current treatments palliate the condition by partially restoring muscle tone or by attempting to prevent catastrophic consequences, like blindness. Dynamic procedures routinely take 9–18 months to become effective and require rigorous rehabilitation (Spector et al, 1991; Robey and Snyder, 2011)
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