A study conducted at Hope College investigated surface electrical stimulation (SES) to determine whether noninvasive SES at the elbow can produce referred sensation in the hand without causing discomfort elsewhere. The results of the research suggest that, in the future, SES may provide an alternative method to deliver sensory feedback, provide natural sensation in areas of the body that are distant from the stimulation, and improve treatment for phantom limb pain.
For the study, the median and/or ulnar nerves of 35 subjects over 46 testing sessions were stimulated at the elbow using surface electrodes. The mean age of subjects in the main study was 24, and 25 in the repetitions. Strength-duration curves, a measurement of hand sensation, were found for each subject. All subjects experienced sensation in their hand, which was mostly described as a paresthesia-like sensation, varying “from tingling to itchiness to pressing. Natural sensations were reported, but the vast majority of subjects experienced tingling or prickling sensations,” according to Katharine H. Polasek, PhD, assistant professor of engineering at Hope College and lead author. Sensation in the hand was evoked through use of both current-controlled and voltage-controlled stimulation.
Measured values were found to be lower for the median nerve than the ulnar nerve, with no significant difference between genders. Repeated sessions with the same subject resulted in sufficient variability to suggest that recalculating the strength-duration curve for each electrode placement is necessary, according to the authors. Future studies will focus on obtaining different sensations using SES with the strength-duration curve defining the threshold of the effective parameter space.
Polasek said there is some indication that small modulation of the amplitude or width of the electronic pulses provides a more natural sensation, which will be explored in future experiments. “The goal of our research is to develop a noninvasive, home-based therapy for treating phantom limb pain,” she said.
The study was published in Volume 52 Number 4, 2015, of the Journal of Rehabilitation Research & Development.
Editor’s note: This story was adapted from materials provided by Hope College to Newswise.
