Selective Stimulation of Facial Muscles Following Chronic Intraneural Electrode Array Implantation and Facial Nerve Injury in the Feline Model

Abstract

Background Our group has previously shown that activation of specific facial nerve (FN) fiber populations and selective contraction of facial musculature can be achieved through acute intraneural multi-channel microelectrode array (MEA) implantation in the feline model. Hypothesis Selective stimulation of facial muscles will be maintained in the setting of (1) chronic and (2) acute MEA implantation following FN injury and subsequent recovery. Methods This study included seven cats. In three cats with normal facial function, 4-channel penetrating MEAs were implanted chronically and tested biweekly for six-months. Electrical current pulses were delivered to each channel individually, and elicited electromyographic (EMG) voltage outputs were recorded for each of several facial muscles. For FN injury experiments, two cats received a standardized hemostat-crush injury, and two cats received a transection-reapproximation injury to the FN main trunk. These four underwent acute implantation of MEA and EMG recording in terminal experiments four months post-injury. Results Stimulation through individual channels selectively activated restricted nerve populations, resulting in contraction of individual muscles in cats with chronic MEA implantation and following nerve injury. Increasing stimulation current levels resulted in increasing EMG voltage responses in all cases. Nerve histology showed only minor neural tissue reaction to the implant. Conclusion We have established in the animal model the ability of a chronically implanted MEA to selectively stimulate restricted FN fiber populations and elicit contractions in specific facial muscles. Likewise, following FN injury, selective stimulation of restricted FN fiber populations and subsequent contraction of discrete facial muscles can be achieved following acute MEA implantation.

Selective Neural Electrical Stimulation of an Injured Facial Nerve Using Chronically Implanted Dual Cuff Electrodes

“…This may have been due to variations in the study environment, including EMG electrode placement, prior stimulations, and level of animal sedation. Nevertheless, the effective selectivity of the MCE, as demonstrated in this and previous works [ 20 , 23 , 24 ], is encouraging for future investigations and an eventual human implantation trial.…”

Interfacing with the nervous system: a review of current bioelectric technologies

“…Increases in stimulation current levels resulted in corresponding increases in EMG voltage response. Moreover, long-term presence of the microelectrode array in the facial nerve confirmed the efficacy and stability of this intraneural stimulation approach [131]. Intraneural stimulation of restricted neural populations with one or more multichannel arrays may play a role in reanimating the face for patients with permanent facial paralysis and may also help rehabilitate other motor and sensory functions throughout the central and peripheral nervous systems [129].…”

Selective Facial Muscle Activation with Acute and Chronic Multichannel Cuff Electrode Implantation in a Feline Model

“…Previous work has demonstrated the utility of a penetrating microelectrode array (MEA), when inserted into the FN, to stimulate movement and contraction in specific muscles in a feline model. 9,10,13 However, the histological reaction and electrode migration that ensued following chronic implantation warranted the investigation of alternative electrodes that would mitigate the fibrotic response and have enhanced stimulation characteristics when chronically implanted. These results have led to the exploration of the ability of a MCE to selectively activate facial muscles.…”

“…7,8 Previous works have suggested that neuroprosthetic technologies may be efficacious in the treatment of FP in animal models. [9][10][11] Functional restoration of paretic or paralyzed FN activity (in the case of intact and still functional FN and distal musculature) requires selective stimulation of the fascicle, which then subsequently activates specific muscles. Here, we test the ability of a multichannel cuff electrode (MCE) to selectively activate feline facial muscles in both acute and chronic settings, and in both uninjured and injured FN.…”