Motor Neuroprostheses

Abstract

Neuroprostheses (NPs) are electrical stimulators that activate nerves, either to provide sensory input to the central nervous system (sensory NPs), or to activate muscles (motor NPs: MNPs). The first MNPs were belts with inbuilt batteries and electrodes developed in the 1850s to exercise the abdominal muscles. They became enormously popular among the general public, but as a result of exaggerated therapeutic claims they were soon discredited by the medical community. In the 1950s, MNPs reemerged for the serious purpose of activating paralyzed muscles. Neuromuscular electrical stimulation (NMES), when applied in a preset sequence, is called therapeutic electrical stimulation (TES). NMES timed so that it enhances muscle contraction in intended voluntary movements is called functional electrical stimulation (FES) or functional neuromuscular stimulation (FNS). It has been 50 years since the first FES device, a foot‐drop stimulator, was described and 40 years since the first implantable version was tested in humans. A commercial foot‐drop stimulator became available in the 1970s, but for various reasons, it failed to achieve widespread use. With advances in technology, such devices are now more convenient and reliable. Enhancing upper limb function is a more difficult task, but grasp‐release stimulators have been shown to provide significant benefits. This chapter deals with the technical aspects of NMES, the therapeutic and functional benefits of TES and FES, delayed‐onset and carryover effects attributable to “neuromodulation” and the barriers and opportunities in this rapidly developing field. © 2019 American Physiological Society. Compr Physiol 9:127‐148, 2019.

Why brain-controlled neuroprosthetics matter: mechanisms underlying electrical stimulation of muscles and nerves in rehabilitation

“…Transcutaneous systems, which will be the focus of this article, are most frequently used for NMES, FES, and FEST to activate the motor system [ 119 ]. Electrical stimulators create a potential difference between two electrodes, a positive anode and a negative cathode, using surface (transcutaneous) stimulation electrodes [ 118 ].…”

“…When electrical stimulation is patterned and temporally sequenced to generate coordinated limb movements, this is referred to as functional electrical stimulation (FES). Overall, FES systems fall into the category of motor neuroprostheses [ 119 ], which are devices that use electrical stimulation to activate paralyzed muscles in a functional manner to generate limb movements [ 118 ]. While motor neuroprosthesis could include spinal cord stimulation and deep brain stimulation systems, this review will primarily focus on FES devices for stimulation of muscles and nerves.…”

“…While motor neuroprosthesis could include spinal cord stimulation and deep brain stimulation systems, this review will primarily focus on FES devices for stimulation of muscles and nerves. Clinical use of FES neuroprostheses includes, but is not limited to, restoration of upper and lower extremity functions, bladder and bowel functions, and respiratory function [ 108 , 119 ]. Typically, FES neuroprostheses were designed to be worn as permanent assistive devices, which an individual can use to perform otherwise impaired functional movements.…”

Neuromuscular electrical stimulation‐promoted plasticity of the human brain

“…This form of stimulation is deemed to be adaptive, as it provides direct compensation for the motor disability. In the period since Liberson and colleagues (1961) demonstrated that stimulation delivered to the common peroneal nerve reduced the degree of foot-drop during the swing phase of gait, numerous applications of FES have been developed successfully to assist movement of the upper and lower extremities (Prochazka, 2018). Yet NMES may also be used restoratively, with a view to promoting neural changes that lead ultimately to increased (intrinsic) functional capacity.…”

Neuroprosthetics: from sensorimotor to cognitive disorders

“…Motor neuroprostheses refer to a particular type of neuroprostheses that aim at restoring motor function by electrical stimulation of the structures involved in the generation of movement (muscles, peripheral nerves, spinal cord, or brain), after neuromotor disorders such as stroke or SCI 16 . The very first motor neuroprosthesis was a peroneal nerve stimulator invented in 1961 by Liberson and colleagues to treat foot drop after hemiplegia 17 .…”