Restoration of Natural Somatic Sensations to the Amputees: Finding the Right Combination of Neurostimulation Methods

Abstract

AbstractLimb amputation results in such devastating consequences as loss of motor and sensory functions and phantom limb pain (PLP). Here we explored peripheral nerve stimulation (PNS), spinal cord stimulation (SCS) and transcutaneous electrical nerve stimulation (TENS) as the approaches to enable tactile and proprioceptive sensations in the amputees and suppress their PLP. We investigated the efficacy of these approaches in sensory discrimination tasks, namely determining object size and softness using a prosthetic hand. Two transhumeral amputees were implanted for four weeks with stimulating electrodes placed in the medial nerve and epidurally over the spinal cord. Both PNS and SCS induced sensation in different parts of the phantom hand and the corresponding electroencephalographic (EEG) responses. The sensations produced by PNS felt more natural compared to those evoked by SCS. Moreover, neurostimulation-induced sensations were felt as emerging from the prosthetic hand engaged in grasping the objects and recognizing their size. These sensations were further enhanced with dual neurostimulation that enabled appreciation of object softness. The prosthetic sensations became more natural with continued practice. We conclude that the ability to perform complex sensorimotor tasks could be restored to the amputees with an individual-based combination of neurostimulation tools. In addition to restoring sensations, neurostimulation suppresses PLP.One Sentence SummaryThe use of peripheral nerve stimulation, transcutaneous electrical nerve stimulation, and spinal cord stimulation improves and enriches prosthetic sensations in amputees by making these sensations more natural and enabling active tasks, such as discriminating object size and softness using a bionic hand.