Functional electrical stimulation

In the health-care professions, electrical stimulation is used for three purposes: to aid diagnosis; as a therapeutic tool; and to restore lost or damaged functions. Functional electrical stimulation (FES) and functional neurostimulation (FNS) are terms which are more or less interchangeable, and which encompass the third of these purposes. FES itself can also be conveniently divided into three classes, according to purpose: the restoration of sensor functions; the restoration of skeleto-motor functions; and the restoration of autonomic functions. Potentially, a fourth class would comprise devices restoring cognitive or psychological functions, but no such devices are clinically available as yet. The methods and devices which are currently available for providing FES are reviewed, as are the sorts of result and benefit that may be expected from them. The structure and emphasis of the review is on the clinical applications and the relevant anatomical and neurophysiological considerations, and this approach is chosen for two main reasons. Firstly, the clinical, anatomical, and physiological considerations are independent of technological change and development, so they will not become quickly out of date. Secondly, the author is a clinician by profession, and an engineer only by inclination. The functional aims of FES methods will continue to develop as a result of experience gained following the introduction and use of successful devices, and these evolutionary improvements will come from within the FES programme; but the engineering embodiment of those devices may be revolutionized at any time by technological advances coming from elsewhere.