Stroke can lead to significant impairment of upper limb function which affects performance of activities of daily living (ADL). Functional electrical stimulation (FES) involves electrical stimulation of motor neurons such that muscle groups contract and create or augment a moment about a joint. Whilst lower limb FES was established in post-stroke rehabilitation, there is a lack of clarity on the effectiveness of upper limb FES. This systematic review aims to evaluate the effectiveness of post-stroke upper limb FES on ADL and motor outcomes.
Systematic review of randomised controlled trials from MEDLINE, PsychINFO, EMBASE, CENTRAL, ISRCTN, ICTRP and ClinicalTrials.gov. Citation checking of included studies and systematic reviews. Eligibility criteria: participants > 18 years with haemorrhagic/ischaemic stroke, intervention group received upper limb FES plus standard care, control group received standard care. Outcomes were ADL (primary), functional motor ability (secondary) and other motor outcomes (tertiary). Quality assessment using GRADE (Grading of Recommendations Assessment, Development and Evaluation) criteria.
Twenty studies were included. No significant benefit of FES was found for objective ADL measures reported in six studies (standardised mean difference (SMD) 0.64; 95% Confidence Interval (CI) [−0.02, 1.30]; total participants in FES group (n) = 67); combination of all ADL measures was not possible. Analysis of three studies where FES was initiated on average within 2 months post-stroke showed a significant benefit of FES on ADL (SMD 1.24; CI [0.46, 2.03]; n = 32). In three studies where FES was initiated more than 1 year after stroke, no significant ADL improvements were seen (SMD −0.10; CI [−0.59, 0.38], n = 35).
Quality assessment using GRADE found very low quality evidence in all analyses due to heterogeneity, low participant numbers and lack of blinding.
FES is a promising therapy which could play a part in future stroke rehabilitation. This review found a statistically significant benefit from FES applied within 2 months of stroke on the primary outcome of ADL. However, due to the very low (GRADE) quality evidence of these analyses, firm conclusions cannot be drawn about the effectiveness of FES or its optimum therapeutic window. Hence, there is a need for high quality large-scale randomised controlled trials of upper limb FES after stroke.
Stroke is defined as a clinical syndrome characterised by rapidly developing focal or global disturbance in cerebral function lasting more than 24 h or leading to death due to a presumed vascular cause . Globally, approximately 16 million people have a stroke each year  and in the UK, first-ever stroke affects about 230 people per 100,000 population each year . Stroke represents a cost to the UK economy of approximately £9 billion annually, of which £1.33 billion results from productivity losses .
Stroke often leads to significant impairment of upper limb function and is associated with decreased quality of life in all domains except for mobility . Few patients attain complete functional recovery ; this deficit impairs performance of activities of daily living (ADL), including self-care and social activities [7, 8]. ADL reflect the level of functional impairment in daily life and are therefore the most clinically relevant outcome measures in assessing recovery after stroke .
Functional electrical stimulation (FES) was well established as an intervention for motor rehabilitation. FES is the electrical stimulation of motor neurons such that muscle groups are stimulated to contract and create/augment a moment about a joint . Transcutaneous electrodes offer the most immediate and clinically viable treatment option as they are non-invasive and may permit home-based treatment.
There are various terms used in the literature to describe different forms of electrical stimulation, often inconsistently. Some authors define FES as electrical stimulation applied to a subject which causes muscle contraction. This passive modality is also referred to as neuromuscular electrical stimulation . Others define FES as electrical stimulation applied during a voluntary movement . This definition acknowledges the volitional component of physical rehabilitation and was used in this systematic review. The distinction is important because neuroimaging studies have identified different cortical mechanisms according to stimulation type [11, 12, 13]. Indeed, perfusion to the ipsilesional sensory-motor cortex and cortical excitability were increased with FES when compared to passive modalities of electrical stimulation [12, 13, 14]. These findings could indicate greater potential for volitional FES to induce neuroplasticity. This is believed to play an important role in neurorehabilitation  and is a key objective of post-stroke functional recovery .
FES has been widely researched for post-stroke lower limb rehabilitation; several systematic reviews [17, 18, 19] and national guidelines [20, 21] exist. Improvement in upper limb function is central to post-stroke rehabilitation as it positively affects ADL and quality of life . Yet, there is still a lack of clarity on the effectiveness of FES in post-stroke upper limb rehabilitation  despite systematic reviews having been undertaken [24, 25, 26, 27, 28]. In part, this is due to methodological limitations [27, 28] or the outdated nature of some existing reviews [24, 25, 26]. The latter was highlighted by a recent Cochrane overview of reviews calling for an up-to-date review and meta-analysis of randomised controlled trials (RCTs) related to electrical stimulation . A more recent systematic review found a significant improvement in motor outcomes with upper limb FES . However, this was based on a single meta-analysis that combined ADLs with upper limb-specific measures of functional motor ability, including studies where results were at risk of performance bias (intervention groups receiving greater duration of treatment than control groups) . Another found no improvement in motor function when FES was applied within 6 months of stroke . However, this predominantly included studies that applied electrical stimulation in the absence of volitional muscle contraction, confounding interpretation of the results. This inconsistency is reflected in the 2016 guidelines set by the Royal College of Physicians which recommends FES only in the context of clinical trials as an adjunct to conventional therapy .
This systematic review aims to elucidate the effectiveness of upper limb FES compared to standard therapy in improving ADL, in addition to motor outcomes, post-stroke. It represents an important addition to the literature that focuses on the use of volitional FES and, for the first time, distinguishes its effect on clinically relevant patient outcomes from surrogate markers of patient rehabilitation. This includes analyses based on patient sub-groups defined by the time after stroke at which FES was initiated.
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