A Scoping Review of Neuromuscular Electrical Stimulation to Improve Gait in Cerebral Palsy: The Arc of Progress and Future Strategies

Abstract

Background: Neuromuscular deficits of children with spastic cerebral palsy (CP) limits mobility, due to muscle weakness, short muscle-tendon unit, spasticity, and impaired selective motor control. Surgical and pharmaceutical strategies have been partially effective but often cause further weakness. Neuromuscular electrical stimulation (NMES) is an evolving technology that can improve neuromuscular physiology, strength, and mobility. This review aims to identify gaps in knowledge to motivate future NMES research. Methods: Research publications from 1990- July 20th 2019 that investigated gait-specific NMES in CP were reviewed using the PubMed and Google Scholar databases. Results were filtered by the National Institute of Neurological Disorder and Stroke common data elements guidelines for CP. The Oxford Centre for Evidence Based Medicine guidelines were used to determine levels of evidence for each outcome. Gait-specific NMES research protocols and trends are described, with implications for future research. Results: Eighteen studies met inclusion criteria, reporting on 212 participants, 162 of whom received NMES while walking, average age of 9.8 years, GMFCS levels I–III. Studies included 4 randomized control trials, 9 cohort studies and 5 case studies. A historical trend emerged that began with experimental multi-channel NMES device development, followed by the commercial development of single-channel devices with inertial sensor-based gait event detection to facilitate ankle dorsiflexion in swing phase. This research reported strong evidence demonstrating improved ankle dorsiflexion kinematics in swing and at initial contact. Improved walking speed, step length, and muscle volume were also reported. However, improvements in global walking scores were not consistently found, motivating a recent return to investigating multi-channel gait-specific NMES applications. Conclusions: Research on single-channel gait-specific NMES found that it improved ankle motion in swing but was insufficient to address more complex gait abnormalities common in CP, such as flexed-knee and stiff-knee gait. Early evidence indicates that multi-channel gait-specific NMES may improve gait patterns in CP, however significantly more research is needed. The conclusions of this review are highly limited by the low level of evidence of the studies available. This review provides a historical record of past work and a technical context, with implications for future research on gait-specific NMES to improve walking patterns and mobility in CP.

Clinical Relevance of State-of-the-Art Analysis of Surface Electromyography in Cerebral Palsy

“…Neuromuscular or functional electrical stimulation (FES) is an example of the appropriate usage of temporal characteristics of sEMG recordings for determining the application of multichannel electrical stimuli to superficial skeletal muscles in order to control, compensate and/or correct their contractions (80)(81)(82)(83)(84)(85). In addition to a physiotherapy programme, it emphasizes task specificity, motor learning, and positive effects (86).…”

Evaluation of Individualized Functional Electrical Stimulation-Induced Acute Changes during Walking: A Case Series in Children with Cerebral Palsy

“…Targeting multiple joints with stimulation to multiple muscle groups has an additive effect on gait improvements [ 40 ] compared to varying results found in studies that target a single joint with stimulation to multiple muscle groups [ 31 , 41 , 42 ]. For example, stimulation of both rectus femoris and vastus lateralis were more effective in improving posture than stimulation of each muscle alone during walking in one child with CP [ 43 ].…”

“…Similar results were shown by Rose et al in three participants using a multi-channel FES system [ 45 ]. Although case studies have recently demonstrated the potential of improving gait when targeting multiple joints with multi-channel FES systems [ 44 , 45 ], evidence is limited [ 40 ]. Advancement in FES technology resulting in improved stimulation timing may contribute to differences between older and more recent multi-channel FES studies [ 40 ].…”

“…Although case studies have recently demonstrated the potential of improving gait when targeting multiple joints with multi-channel FES systems [ 44 , 45 ], evidence is limited [ 40 ]. Advancement in FES technology resulting in improved stimulation timing may contribute to differences between older and more recent multi-channel FES studies [ 40 ]. More importantly, older FES walking studies lacked subject-specific FES programs that limited the flexibility of an intervention needed for a heterogeneous population with heterogeneous gait deviations.…”

Toward a hybrid exoskeleton for crouch gait in children with cerebral palsy: neuromuscular electrical stimulation for improved knee extension

“…We propose that incorporation of NMES with motorized assistance is integral to achieving optimal long-term outcomes for those with crouch gait. NMES has the unique capability to increase muscle strength and size [21], inhibit or reduce spasticity [22,23], and enhance motor performance during specific tasks through precisely timed muscle activation or sensory cues [24]. Furthermore, peripheral muscle stimulation may stimulate greater neuroplastic changes in sensorimotor brain regions during gait training [25].…”