Eye movement enhancement in Parkinson's disease as a result of CN-NINM intervention: a case study.

Abstract

Purpose: The neurorehabilitation of sensory and motor functions in Parkinson's disease (PD) patients is undeveloped, and recovery of eye-movement control is largely unexplored. There are very few methods that show the possibility of rehabilitation of eye movements affected by PD. The goal of this research was to investigate how well cranial-nerve non-invasive neuromodulation (CN-NINM) can reduce the effects of PD-induced impairments of oculomotor function and help to recover eye movement control.

Methods: We completed a 4-month intervention with a 66-year-old male 6 years after he was diagnosed with PD symptoms. This individual demonstrated abnormal gait, poor posture and balance, occasional tremor and noticeable impairment of oculomotor function. The CN-NINM intervention used a combination of both physical and cognitive exercises with electrotactile stimulation to the tongue using a Portable Neuromodulation Stimulator (PoNS^tm). Assessment of oculomotor function was performed before and after the CN-NINM intervention using special 4-channel binocular eye tracking goggles (VisualEyes, Micromedical Inc). To evaluate the state of subject’s eye movements we used three static nystagmus tests (vertical and horizontal gaze, and spontaneous nystagmus) and three dynamic tests (random saccade, smooth pursuit and optokinetic). All of the tests were performed without tongue stimulation.

Results: The CN-NINM intervention resulted in the gradual enhancement of patient eye movement control in all 6 tests. We observed improvement of eye fixation, accuracy and stability in nystagmus and gaze tests, increased eye movement accuracy and precision, improved gain and velocity of target tracking, and changes in both smoothness and synchronization of binocular movement control in oculomotor tests. The most significant improvements in eye movement control were found during performance of smooth pursuit and random saccade testing. We also observed improvement in his gait, posture and balance.

Conclusions: Our study establishes a proof of concept and effectiveness of a new non-invasive neuromodulation therapy. The improvements of eye movement control demonstrated by this individual suggest that rehabilitation using a combination of exercise and tongue-based neurostimulation may benefit people affected by PD and would offer a novel treatment option for this disease.