Effect of electrical stimulation of receptive fields in people with lower limb amputation on variables of gait

People with amputation may perceive phantom limb sensations or pain in the amputated body part when ipsilateral body-regions are stimulated. These body-regions are called receptive fields. This study assessed whether receptive fields change in size and position over the course of one month in people with trans-tibial amputation and whether electrical stimulation of these fields in synchrony with walking affects phantom sensations and variables of gait. Thirty-one subjects participated in this study. Receptive fields were mapped seven times over a one month period. Thereafter, the effect of electrical stimulation in synchrony with walking was compared to placebo stimulation in an acute setting with a randomized, single-blind gait analysis in 18 participants. Results showed that receptive field size and position presented an adequate degree of consistency (difference in point of first response position of 4.9 ± 4.8 cm and overlap of total receptive field area of 54.3 ± 35.0 %) for future use of electrical stimulation. Gait parameters for everyday activities (speed, gait width, % stance and swing phase) as well as perception of phantom pain were not altered to a clinically relevant degree by electrical stimulation and no negative effects were reported. In conclusion: Location and size of receptive fields are consistent enough for daily electrical stimulation without laborious daily assessment. If applied acutely, no significant effect on gait or pain could be detected. However, results are promising enough to test chronic application of electrical stimulation during gait in a long-term setting.