The application of neuroprosthesis in restoration of unilateral facial nerve paralysis: A scoping review.

Facial nerve palsy can pose functional, psychosocial, and cosmetic issues for patients. Although various surgical techniques can improve facial functions and appearance for patients who do not fully recover following conservative management, they can be extensively invasive with limited restoration of facial movement and symmetry. Functional electrical stimulation (FES) is a technology that has been developed to stimulate paralyzed nerves or muscles and has 2 different applications in facial nerve palsy treatment: facial rehabilitation and neuroprosthesis. Our study focuses specifically on the neuroprosthesis application of FES, which uses signals from the healthy side of the face to stimulate the paralyzed side. This emerging neuroprosthetic technology is less invasive and holds promise in synchronizing facial movements. The purpose of our scoping review was to understand the landscape of the models that have been developed, as well as the outcomes of these studies in leading to facial movement on the paralyzed side. We found 22 studies in our review that each used varying methods for detecting facial movement from the healthy side and differing stimulation types and parameters, with each study describing successful stimulation of facial movement on the paralyzed side using healthy hemiface input.