Feasibility of Surface Stimulation to Alleviate Phantom Limb Pain
Dr. Katharine Polasek
Phantom Limb Pain, a pain or discomfort in the missing limb, is experienced by 50-80% of amputees. A leading hypothesis suggests phantom limb pain is due to reorganization of the somotosensory cortex of the brain. Our working hypothesis states that by eliciting a “real” sensation in the phantom limb, the progression of cortical reorganization may be reduced or even reversed to decrease or eliminate phantom limb pain.
To obtain distal sensation in able-bodied subjects, the median and ulnar nerves were stimulated at the elbow using surface electrodes. A non-symmetric rectangular voltage controlled pulse train was created using optically isolated biostimulators and MATLAB software. The adaptive procedure Parameter Estimation by Sequential Testing (PEST) was used to determine threshold values for sensation in the hand. A strength-duration curve was found for both electrode positions to relate pulse width and threshold values for hand sensation. Stimulation was then sent at 25% and 75% of the subject’s voltage range at pulse widths of 50, 100, and 500µs. Data was collected on the magnitude, position, and type of sensation (prickly/buzzing/tapping…). Results showed that changing the amplitude and pulse width changed the magnitude of sensation, but did not change the position or type of sensation. Future work will include using different waveforms in order to vary the sensation. In addition, the effect of using an array of electrodes in order to vary the location of sensation in the hand will be investigated.
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