Functional electric stimulation for sensory and motor functions: Progress and problems

Abstract

Functional Electrical Stimulation (FES) endeavors to restore the lost functions of the nervous system by means of electrical stimulation. It is a multidisciplinary field on the interface between the neuroscience, engineering, rehabilitation and the clinic. In this review, the principal notions behind FES are outlined together with the relevant moments of its history. The specific research problems encountered in the development of FES applications are extensively covered. From an engineering perspective, special attention is dedicated to the electrodes for selective stimulation. The major clinical applications are overviewed: pacing of the heart, respiratory pacing of the diaphragm, cochlear neuroprostheses for restoration of hearing, the rehabilitation and restoration of locomotion and hand functions, and the restoration of bladder and bowel functions. An analysis of the current FES applications is performed from the perspective of the evidence-based clinical approach. Currently, FES for restoration of the lost locomotor functions is a rapidly developing area that is on the verge of broadening its acceptance in the clinic. Evidence for this is the increasing number of various neuroprosthetic devices, some of them already beyond the prototype stage, that have been developed recently. The present FES treatments combined with conventional occupational and physical therapy still remain the most promising approach in rehabilitation of the spinal cord injury patients and the stroke patients. FES in combination with neuromodulation, which is however still in a rather empirical state of operation, becomes a viable option in the treatment of various urological disorders. The analysis indicates that the pacing of the heart and cochlear neuroprostheses remain the most developed applications of FES. The presented overview of the FES applications shows that a number of fundamental scientific problems have to be solved before a comparable degree of effectiveness and penetration in the common medical practice is achieved for the locomotion neuroprostheses and the urological FES appliances. Finally, a summary is given of the major clinical and fundamental directions of research needed for further improvement of FES.