Advancing Education, Research, and Quality of Care for the Head and Neck oncology patient.
Introduction: Facial nerve paralysis significantly impacts patients' quality of life by impairing essential functions such as facial expression, speech, and swallowing, often leading to severe psychological and social consequences. Current treatments, including nerve transfers and reconstructive surgeries, are often inadequate, with unpredictable outcomes. We present an innovative approach involving a rat model of facial nerve injury to investigate the feasibility of bionic nerve stimulation for restoring symmetrical facial movement.
Objective: This study aims to demonstrate the potential of a bionic device in reanimating facial movement following nerve injury and repair. Specifically, we are investigating the effectiveness of VII-to-XII hypoglossal-facial nerve transfer in rats, combined with an external stimulation device, to achieve synchronous and symmetrical whisker movement.
Methods: In the first series of experiments, survival surgeries are performed on rats to create a VII-to-XII nerve transfer model for chronic unilateral facial paralysis. The left facial nerve is transected and anastomosed to the ipsilateral hypoglossal nerve. After allowing sufficient time for reinnervation, electrical stimulation is applied to the distal facial nerve segment on the injured left side as well as on the uninjured right side to induce whisking. In the second series of experiments, only the left facial nerve is transected to cause an acute VII nerve injury. Immediately thereafter, spontaneous electrical activity in the right, uninjured facial nerve is detected with an electronic discriminator and used instantaneously to trigger electrical stimulation of the distal segment of the left, transected facial nerve to induce whisking. In both series, parameters of whisker movements are measured in high-speed video recordings by neural-network-based markerless pose estimation.
Results: In the first series of experiments of this ongoing study, the two out of seven rats tested so far exhibited stimulated whisking on the injured left side that was indistinguishable from the uninjured right side with respect to time course, amplitude, and stimulation-current threshold, indicating successful reinnervation of distal VII by proximal XII. In the second series of experiments, the rats tested exhibited stimulated whisking on the injured left side that was indistinguishable from the spontaneous whisking on the uninjured right side with respect to time course, amplitude, and synchrony, indicating successful generation of symmetric movement.
Conclusion: This preclinical study demonstrates the potential of combining VII-to-XII nerve transfer with bionic stimulation for effective facial reanimation. Our findings so far support the feasibility of using a bionic device to provide real-time stimulation to the reconstructed facial nerve, achieving meaningful functional outcomes in a rat model of facial paralysis. The promising results in rats lay the foundation for future development of a clinically viable device aimed at restoring symmetrical facial movement in patients suffering from chronic facial paralysis. Continued exploration of this approach is warranted, with further refinement of the stimulation parameters and histological analyses to confirm reinnervation quality.