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Yakov Verbny, Kimberly Skinner, Mitchell Tyler, Kurt Kaczmarek, Yuri Danilov; Eye movement rehabilitation by CN-NINM intervention in chronic stroke.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2568.
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The neurorehabilitation of sensory and motor functions in chronic stroke patients is undeveloped, and recovery of eye-movement control is largely unexplored. The goal of this research was to investigate how well CN-NINM (Cranial-Nerve Non-Invasive Neuromodulation) can reduce the effects of stroke induced impairments of oculomotor functions and help to recover eye movement control. There are very few results that show such possibility for eye movement rehabilitation.
We completed a 13-month intervention for 5 adult individuals 2-15 years after stroke. All demonstrated one or more of the following: abnormal gait, balance, cognition, and noticeable impairment of oculomotor functions. The CN-NINM intervention used a combination of both physical and cognitive exercises with electrotactile stimulation to the tongue with a portable neuromodulation stimulator (PoNSTM). After 6 months of intervention, there was a 30-day withdrawal period, followed by an additional 6 months continuing the exercises and device use. Assessment of oculomotor functions was perfomed before and after CN-NINM intervention using special 4-channel binocular eye tracking goggles (VisualEyes, Micromedical Inc). To evaluate the state of subjects’ eye movements we used three static nystagmus tests (vertical and horizontal gaze, and spontaneous nystagmus) and three different dynamic tests (random saccade, smooth pursuit and optokinetic).
The CN-NINM intervention resulted in the gradual enhancement of patient eye movement control in all 6 tests. We observed improved eye fixation and stability in nystagmus tests, increased eye movement accuracy and precision, improved gain (up to 30% in pursuit test) and velocity of target tracking, decreased latency (approximately 10%), 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 gaze fixation, smooth pursuit and random saccade testing.
Our study establishes a proof of concept and effectiveness of a new non-invasive neuromodulation therapy. The improvements of eye movement control demonstrated by individuals with this intervention suggest that rehabilitation using a combination of exercise and tongue-based neurostimulation may benefit people affected by stroke symptoms beyond the period previously believed that recovery was possible.
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