Facial palsy is a devastating condition potentially amenable to rehabilitation by functional electrical stimulation. Herein, a novel paradigm for unilateral facial reanimation using an implantable neuroprosthetic device is proposed and its feasibility demonstrated in a live rodent model. The paradigm comprises use of healthy-side electromyographic activity as control inputs to a system whose outputs are neural stimuli to effect symmetric facial displacements. The vexing issue of suppressing undesirable activity resulting from aberrant neural regeneration (synkinesis) or nerve transfer procedures is addressed using proximal neural blockade.
Epimysial and nerve cuff electrode arrays were implanted in the faces of Wistar rats. Stimuli were delivered to evoke blinks and whisks of various durations and amplitudes. The dynamic relation between electromyographic signals and facial displacements was modeled, and model predictions were compared against measured displacements. Optimal parameters to achieve facial nerve blockade by means of high-frequency alternating current were determined, and the safety of continuous delivery was assessed.
Electrode implantation was well tolerated. Blinks and whisks of tunable amplitudes and durations were evoked by controlled variation of neural stimuli parameters. Facial displacements predicted from electromyographic input modelling matched those observed with a variance-accounted-for exceeding 96 percent. Effective and reversible facial nerve blockade in awake behaving animals was achieved, without detrimental effect noted from long-term continual use.
Proof-of-principle of rehabilitation of hemifacial palsy by means of a neuroprosthetic device has been demonstrated. The use of proximal neural blockade coupled with distal functional electrical stimulation may have relevance to rehabilitation of other peripheral motor nerve deficits.
Boston, Mass.; and Montreal, Quebec, Canada
From the Massachusetts Eye and Ear Infirmary, Harvard Medical School, the Department of Otolaryngology, Surgical Photonics & Engineering Laboratory; and the Department of Biomedical Engineering, McGill University.
Received for publication December 21, 2017; accepted May 3, 2018.
Presented in part at the 2016 Annual Meeting of the American Society for Peripheral Nerve, in Scottsdale, Arizona, January 15 through 17, 2016.
Disclosure: Dr. Jowett and Dr. Hadlock hold a patent on the methods and systems described herein (WO2017124019A1).
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Nate Jowett, M.D., Massachusetts Eye and Ear Infirmary and, Harvard Medical School, 243 Charles Street, Boston, Mass. 02114, firstname.lastname@example.org