Implantable Closed-Loop System for Restoration of Blinking in Case of Unilateral Facial Nerve Paralysis

BACKGROUND: In facial nerve (FN) paralysis, a critical task is to restore the orbicularis oculi muscle (OOM) function to prevent corneal atrophy and vision deterioration. In this study, we present the application of a fully implantable bioelectrical closed-loop system for the restoration of blinking in a rabbit model of unilateral FN paralysis. We test the hypothesis that blinking events on the healthy side of a face could be used to trigger an electrical stimulation of eyelid muscles on the impaired side of the face resulting in functional simultaneous blinking. METHODS: We developed and tested in an animal model a functional prototype of a fully implantable closed-loop device for the restoration of blinking in patients with unilateral FN paralysis. The study was performed on 14 rabbits after complete transection of the FN on 1 side. The animals were divided into 2 groups. In the first group, the subcutaneous electrodes were implanted for functional electrical stimulation of the upper eyelid on the side of the damaged OOM, and the electromyographic signals (EMG) from the healthy OOM were recorded. Two-phase stimulation pulses with adjustable parameters were delivered between electrodes in the medial and lateral corners of a palpebral fissure. Animals from the second group had not received any treatment and were used as a control for facial paralysis. RESULTS: Stimulation parameters that were sufficient to cause complete eyelid closure were estimated. These parameters included pulse current amplitude, pulse width, and stimulation frequency. We also report the modulation of stimulation parameters during the stimulation period (days 8-30 post transection of the FN). The absence of the eyelid closure in the control group after 1 month of denervation was confirmed. CONCLUSION: Our study confirmed the possibility of restoration of simultaneous complete eyelid closure by a pre-pain threshold electrical stimulation using a fully implantable closed-loop device in animals with unilateral FN paralysis.