American Society for Peripheral Nerve (ASPN)
Summer 2019
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What's new in nerve this month?
Tessa A. Hadlock, MD
Tessa A. Hadlock, MD
Nate Jowett, MD
Nate Jowett, MD

Highlights of an ASPN Member Publication
Compiled By Hollie Power, MD

Toward the Bionic Face: A Novel Neuroprosthetic Device Paradigm for Facial Reanimation
Consisting of Neural Blockade and Functional Electrical Stimulation.

Nate Jowett MD, Robert E. Kearney PhD, Christopher J. Knox BS, Tessa A. Hadlock MD
Plastic and Reconstructive Surgery, 2019; 143: 62eľ76e
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.

Q&A with ASPN member Nate Jowett:

1. What is the take home message from your study?
A fully-implantable neuroprosthetic device, similar to a cochlear implant, could potentially be employed for rehabilitation of facial palsy.

2. Where do you think this technique fits into the reconstructive options for facial palsy?
This approach could potentially be employed to re-establish spontaneous facial expressions while eliminating undesirable ("synkinetic") facial movements in patients with severe facial palsy following aberrant facial nerve regeneration, interposition graft repair, or nerve transfer procedures. In one iteration, this approach could be employed to add spontaneity to smile in patients who have previously undergone reanimation procedures by trigeminal motor branch neurotization, while eliminating undesirable smile activation with prandial activity.

3. What are the next steps in your research?
Demonstrate long-term efficacy and safety of this approach in small and large animal models, and secure funding and partners for device development and commercialization.

In this work, we demonstrated how high-frequency alternating current (HFAC) neural blockade by means of implanted nerve cuff electrode arrays could potentially be employed for therapeutic management of undesirable facial nerve activity. We believe use of HFAC neural blockade for management of spasticity and pain disorders warrants further investigation.

BACKGROUND: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: 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.

Press Release from the American Society for Plastic Surgeons

See more ASPN member publications on the ASPN Member Publication webpage.

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