Is motor neuroprosthesis (MN) effective for improving activities and participation of people in their natural environment after stroke?
Stroke survivors usually face long-term impairment, activity limitation, and reduced participation. MN consists of electronic devices that electrically stimulate a nervous system structure to help the performance of daily activities in the natural environment in which people live, as an orthosis (a device applied to a body segment to optimize position, or to limit or assist movement). However, the role of MN for improving activities and participation after stroke is unclear.
We found four studies of MN involving a total of 831 participants who more than three months poststroke, with mean ages from 53 to 64 years. All participants were able to walk from less than 0.5 m/s to more than 0.7 or even 0.9 m/s. The included studies were published between 2007 and 2015 in the USA and the Netherlands. All included studies applied MN directed to a nerve in the leg (peroneal nerve) to promote the contraction of a muscle at the front of the leg, thus preventing the foot 'dropping' as the leg was swung forward while the participant walked. MN was used from up to eight hours per day to all-day use for walking about in the natural environment in which people live. Three studies used an MN device that interfaces with the nervous system through electrodes positioned over the skin in the projection of the peroneal nerve in the leg. Only one study used a implantable device whose electrical stimulus is released directly on the nerve by electrodes placed under the layer that surrounds the nerve. All studies compared MN versus ankle-foot orthosis (AFO), that is an assistive device usually made of a rigid material and placed externally on the lower leg to hold the foot and ankle to prevent the foot dropping.
There is limited evidence that people after stroke who receive MN as an orthosis for walking in the home or community context may not improve activities involving limbs such as walking speed between 6 and 12 months of device use (low-certainty evidence), Timed Up and Go (moderate-certainty evidence), and modified Emory Functional Ambulation Profile (low-certainty evidence); as well as participation scale of health-related quality of life (very low-certainty evidence), exercise capacity (low-certainty evidence), and balance (moderate-certainty evidence), compared with people after stroke who receive AFO. There was evidence of an effect that the control intervention (AFO) attained a higher walking speed after six months of device use (low-certainty evidence), but this evidence showed that the improvements were too small to indicate a meaningful change to patients, and when we excluded the study in which the people that assessed the outcomes were aware of the intervention details, this effect was no longer found. There was no difference in effects on walking speed between MN with surface versus MN with implantable electrodes. No study reported outcomes related to independence in activities of daily living.
The majority of studies reported adverse events such as falls and serious adverse events related to device use, which were found to be similar for MN and AFO use (moderate- and low-certainty evidence, respectively). One study considered serious adverse events related to device use as serious falls. More people who received MN withdrew from the studies than did people who received AFO (low-certainty evidence). The results of this review indicate that little is known about the effects of MN and that further information is required.
It is unknown if people less than three months poststroke could benefit from MN use as an assistive device to perform activities in daily life. The impact of MN applied to the upper limb or MN that uses brain or muscle signals to trigger the stimulation is unknown in people with stroke. We found no evidence evaluating the costs of delivering MN.
Certainty of the evidence
The certainty of the evidence ranged from moderate to very low.
Current evidence indicates that MN is no more beneficial than another assistive technology device for improving activities involving limbs measured by Timed Up and Go, balance (moderate-certainty evidence), activities involving limbs measured by walking speed and modified Emory Functional Ambulation Profile, exercise capacity (low-certainty evidence), and participation scale of HRQoL (very low-certainty evidence). Evidence was insufficient to estimate the effect of MN on independence in ADL. In comparison to other assistive devices, MN does not appear to increase the number of falls (moderate-certainty evidence) or serious adverse events (low-certainty evidence), but may result in a higher number of dropouts during intervention period (low-certainty evidence).
Motor neuroprosthesis (MN) involves electrical stimulation of neural structures by miniaturized devices to allow the performance of tasks in the natural environment in which people live (home and community context), as an orthosis. In this way, daily use of these devices could act as an environmental facilitator for increasing the activities and participation of people with stroke.
To assess the effects of MN for improving independence in activities of daily living (ADL), activities involving limbs, participation scales of health-related quality of life (HRQoL), exercise capacity, balance, and adverse events in people after stroke.
We searched the Cochrane Stroke Group Trials Register (searched 19 August 2019), the Cochrane Central Register of Controlled Trials (CENTRAL) (August 2019), MEDLINE (1946 to 16 August 2019), Embase (1980 to 19 August 2019), and five additional databases. We also searched trial registries, databases, and websites to identify additional relevant published, unpublished, and ongoing trials.
Randomized controlled trials (RCTs) and randomized controlled cross-over trials comparing MN for improving activities and participation versus other assistive technology device or MN without electrical stimulus (stimulator is turned off), or no treatment, for people after stroke.
Two review authors independently selected trials, extracted data, and assessed risk of bias of the included studies. Any disagreements were resolved through discussion with a third review author. We contacted trialists for additional information when necessary and performed all analyses using Review Manager 5. We used GRADE to assess the certainty of the evidence.
We included four RCTs involving a total of 831 participants who were more than three months poststroke. All RCTs were of MN that applied electrical stimuli to the peroneal nerve. All studies included conditioning protocols to adapt participants to MN use, after which participants used MN from up to eight hours per day to all-day use for ambulation in daily activities performed in the home or community context. All studies compared the use of MN versus another assistive device (ankle-foot orthosis [AFO]). There was a high risk of bias for at least one assessed domain in three of the four included studies.
No studies reported outcomes related to independence in ADL. There was low-certainty evidence that AFO was more beneficial than MN on activities involving limbs such as walking speed until six months of device use (mean difference (MD) −0.05 m/s, 95% confidence interval (CI) −0.10 to −0.00; P = 0.03; 605 participants; 2 studies; I2 = 0%; low-certainty evidence); however, this difference was no longer present in our sensitivity analysis (MD −0.07 m/s, 95% CI −0.16 to 0.02; P = 0.13; 110 participants; 1 study; I2 = 0%). There was low to moderate certainty that MN was no more beneficial than AFO on activities involving limbs such as walking speed between 6 and 12 months of device use (MD 0.00 m/s, 95% CI −0.05 to 0.05; P = 0.93; 713 participants; 3 studies; I2 = 17%; low-certainty evidence), Timed Up and Go (MD 0.51 s, 95% CI −4.41 to 5.43; P = 0.84; 692 participants; 2 studies; I2 = 0%; moderate-certainty evidence), and modified Emory Functional Ambulation Profile (MD 14.77 s, 95% CI −12.52 to 42.06; P = 0.29; 605 participants; 2 studies; I2 = 0%; low-certainty evidence). There was no significant difference in walking speed when MN was delivered with surface or implantable electrodes (test for subgroup differences P = 0.09; I2 = 65.1%).
For our secondary outcomes, there was very low to moderate certainty that MN was no more beneficial than another assistive device for participation scales of HRQoL (standardized mean difference 0.26, 95% CI −0.22 to 0.74; P = 0.28; 632 participants; 3 studies; I2 = 77%; very low-certainty evidence), exercise capacity (MD −9.03 m, 95% CI −26.87 to 8.81; P = 0.32; 692 participants; 2 studies; I2 = 0%; low-certainty evidence), and balance (MD −0.34, 95% CI −1.96 to 1.28; P = 0.68; 692 participants; 2 studies; I2 = 0%; moderate-certainty evidence). Although there was low- to moderate-certainty evidence that the use of MN did not increase the number of serious adverse events related to intervention (risk ratio (RR) 0.35, 95% CI 0.04 to 3.33; P = 0.36; 692 participants; 2 studies; I2 = 0%; low-certainty evidence) or number of falls (RR 1.20, 95% CI 0.92 to 1.55; P = 0.08; 802 participants; 3 studies; I2 = 33%; moderate-certainty evidence), there was low-certainty evidence that the use of MN in people after stroke may increase the risk of participants dropping out during the intervention (RR 1.48, 95% CI 1.11 to 1.97; P = 0.007; 829 participants; 4 studies; I2 = 0%).