Neuroprosthetic Approaches to Selective Facial Nerve Stimulation
Neuroprosthetic devices have become increasingly important in the treatment of clinical pathologies. In particular, the application of neuroprosthetic devices to restore function following damage to peripheral and cranial nerves has been demonstrated to be efficacious, safe, and has been readily adopted in the clinic to treat a wide range of pathologies. Neuroprosthetic devices have been successfully deployed in numerous cranial nerves, including the hypoglossal nerve to treat obstructive sleep apnea and the vagus nerve to treat epilepsy, heart failure, and manage blood pressure. However, the application of neuroprosthetic devices to the facial nerve (FN) for purposes of facial reanimation has not been explored.
FN injury can cause debilitating and permanent damage with oftentimes limited treatment options. In cases of FN injury, patients may develop permanent facial paralysis (FP), which can cause facial muscles to lose tone, and over time, atrophy and convert into scar tissue. FP arises from a variety of causes, including tumor, surgery, trauma or infection, and results in problems with eye irritation, visual impairment, drooling, intraoral food retention, and demoralizing cosmetic deformities.
In recent decades, considerable efforts have been undertaken to care for patients with permanent FP. Several surgical interventions, including static and dynamic options, have been described for patients with unilateral FP. However, these interventions only address specific parts of the face, have a 10-15% failure rate, and require multiple procedures involving multiple surgical sites to accomplish functional goals. An alternative approach to facial reanimation is the utilization of neuroprosthetic technologies to deliver exogenous current to the partially recovered FN in order to provide both facial tone and selective activation of individual muscles.
We demonstrate the ability of both multichannel microelectrode arrays and multichannel cuff electrodes to selectively stimulate the feline FN in both acute and chronic settings, and couple this technology with closed loop circuitry to develop a putative approach to volitional and graded hemifacial animation. We also present data from clinical investigations on human FN selectivity, and investigate the application of these technologies in the recurrent laryngeal nerve.