Evoking sensation in the phantom hand of amputees using invasive stimulation of peripheral nerves

Close to 3 million people suffer from upper limb amputation worldwide - the condition that dramatically de-creases the quality of life. Despite the progress in prosthetic technologies and neuroprosthetics, a fully functional bidirectional neural interface has not been developed yet for the upper limb, which prevents an amputee from fully integrating with the prosthesis - both mechanically and neurally - and hence implementation of such an interface is in high demand. A practically relevant bidirectional prosthesis of the upper limb would rely on stimulation of somatosensory pathways as the way to generate tactile and proprioceptive sensations. Moreover, such stimulation could serve to suppress phantom-limb pain, which is important because the majority of amputees suffer such pain. In this study we investigated the dynamic of tactile sense restoration and phantom limb pain suppression using stimulation of peripheral nerves with implanted electrodes. For quantitative estimation of the results, we used a survey along with images where a patient could draw a sensation field on the phantom limb. We conducted three sessions of mapping during which we matched stimulation sites with areas on the hand and levels of chronic pain. The expansion of sensation fields without dramatic increase of stimulation amplitudes and chronic pain relief during stimulation sessions were observed for all subjects.