Sensory feedback prosthesis reduces phantom limb pain: proof of a principle.

BACKGROUND: Constrained functionality and phantom limb pain (PLP) are major concerns for forearm amputees. Neuroscientific investigations of PLP suggest that behaviorally relevant stimulation of the stump can decrease PLP. Furthermore the prosthesis user could use feedback information of the prosthesis hand for optimizing prosthesis motor control when handling soft and fragile objects. Somatosensory feedback information from a prosthetic hand may therefore help to improve prosthesis functionality and reduce phantom limb pain. OBJECTIVES: We wanted to find out whether a two weeks training on a hand prosthesis that provides somatosensory feedback may help to improve prosthesis functionality and reduce phantom limb pain. METHODS: Eight forearm amputees with phantom limb pain were trained for two weeks to use a hand prosthesis with somatosensory feedback on grip strength. RESULTS: The current study demonstrates a significant increase of functionality of the prosthesis in everyday tasks. Furthermore, the study shows that usage of a prosthesis that provides somatosensory feedback on the grip strength is effective to reduce phantom limb pain. CONCLUSIONS: A prosthesis with a feedback function appears to be a promising therapeutic tool to reduce phantom limb pain and to increase functionality in everyday tasks. Future studies should further investigate the scope of application of that principle.

Spatial discrimination learning of electrocutaneous stimuli is influenced by the type of stimulation.

Although spatial discrimination of electrocutaneous stimuli can be improved by training, we do not know whether the improvement of spatial discrimination varies as a function of the type of stimulus presentation. In the present study, two groups of healthy human volunteers were trained over a period of 5 days to discriminate 23 patterns of one, two, three, or four simultaneously stimulated electrodes on the upper arm. In group one, two or three simultaneously stimulated electrodes were applied at different skin areas with an anchor electrode. This type of stimulation was hypothesised to facilitate discrimination performance by providing a cue about stimulus patterns applied. In group two, two or three simultaneously stimulated electrodes were applied at different skin areas with electrodes arranged as adjacent electrodes like a zoned field. Double and triple stimulus patterns presented with an anchor electrode were discriminated significantly better than double and triple patterns presented as zoned fields. This improvement in stimulus discrimination resulted primarily from a better discrimination of double stimulation patterns. However, there was a clear influence of spatial distance between simultaneously activated electrodes on the results. Thus, both spatial distances between stimulated electrodes and, to a minor extent, the anchor stimulation per se influenced this result. Furthermore, results revealed an overall significant improvement of stimulus discrimination in both groups and an improvement varying as a function of the number of stimulated electrodes. Overall, results indicate that the improvement of spatial discrimination of electrocutaneous stimuli varies as a function of the type of stimulus presentation.