Will Rising Tides Improve Outcomes in Multiple Sclerosis Patients?
December 2017 Issue
The phrase "a rising tide raises all boats," with economic implications, was first introduced to the nation by President John F. Kennedy, and made even more popular by President Ronald Reagan. However, the implicit message of the phrase resonates in other spaces as well. The rising tide can also refer to technological advancements developed in one area that are transferred to other domains where they provide still more benefits.
Technology transfer frequently occurs in healthcare, where good ideas find broader applications. This article speaks to two novel advancements in lower-limb orthotic technologies that, while not initially developed with the multiple sclerosis (MS) community in mind, may ultimately find their place as treatment modalities for this population. Powered exoskeletons initially developed for those with paraplegia due to spinal cord injury have now been trialed in patients with MS.1 Similarly, functional electrical stimulation (FES) that was developed for the stroke community has found increasing application among the MS population.2-3 This article reviews the extent to which these two modalities may improve outcomes in individuals with MS.
The premise of this article, examining the transferability of technologies designed for the complex challenges of complete paraplegia and the comparatively simpler presentation of unilateral foot drop to a single patient population, underscores the variability encountered under the broad umbrella of MS. The extent of these variations was studied in an aggressive survey effort that ultimately aggregated the experiences of more than 1,000 individuals with MS and more than 300 of their caregivers.4
The patient cohort was unquestionably negatively affected by their diagnoses, with the majority of the queried subjects and their caregivers reporting negative impacts in their abilities to perform activities of daily living (70 percent), shop (61 percent), and engage in physical activities or exercise (60 percent).4
While walking compromise was frequently reported, it was not the most prevalent limitation. Fatigue (76 percent), abnormal sensations (60 percent), and balance compromise (54 percent) were all reported with greater frequency than walking difficulty. Yet among the 41 percent of those individuals who reported difficulty walking, 70 percent reported this limitation to be the most challenging aspect of their MS.4 Among this same cohort (those reporting either difficulty with or an inability to ambulate), additional adverse events that were frequently reported included a compromised ability to perform daily tasks (91 percent), detrimental effects on self-esteem (84 percent), and injurious impacts on work life (83 percent). Additional limitations identified by subjects who reported walking compromise included a reduced ability to socialize outside the home (82 percent), negatively impacted relationships with friends (67 percent), and family (65 percent), the need for occasional assistance from family members, friends, and work colleagues (83 percent), and interference with one's ability to work (79 percent).4
Thus, among those with MS, walking compromise is common and disruptive, and often further aggravated by the compounding concerns of fatigue and balance compromise.
The recent approvals from the U.S. Food and Drug Administration for the ReWalk, Indego, and Ekso exoskeletal orthoses in individuals with spinal cord injury has ushered in the next stage of growth for the technology. Developed for and largely tested among individuals with paraplegia secondary to complete spinal cord injury, the decision to evaluate the mobility among individuals affected by MS represented a novel application of this emerging modality.
Thirteen subjects were initially recruited for this pilot feasibility and safety trial that ultimately entailed eight weeks of data collection with the intervention. Predetermined inclusion criteria required that the subjects present with Expanded Disability Status Scale (EDSS) scores between 5.0 (Disability severe enough to preclude full daily activities; able to walk without aid or rest for 100m) and 7.5 (Unable to take more than a few steps; restricted to wheelchair and may need aid in transferring; can wheel self but cannot carry on in standard wheelchair for a full day and may require a motorized wheelchair).1
Of these original 13 subjects, two failed the initial screening process because of prohibitive joint contractures at the hip and/or ankles and were subsequently excluded. Of the remaining 11 subjects, six voluntarily withdrew from the study, citing either transportation concerns or walking-related pain. Thus, only five of the original cohort completed more than 20 walking sessions with the exoskeleton, satisfying the protocols of the study.1
The exoskeleton orthoses were only used at the hosting clinic during 30- to 90-minute sessions, up to three times per week over the eight-week trial period. These sessions were devoted to progressive instruction on the use of the device, beginning with establishing an initial fit and learning to sit and stand with appropriate forearm crutch placement. This was followed by the progressive introduction of weight shifting, assisted steps, pivot turns, assisted walking over short distances, and reduced assistance, with a goal of walking with no assistance for 30 minutes.1
The five individuals who completed the study protocols were extremely compromised in their baseline ambulatory abilities. Two of the five were unable to complete the baseline walking tests of 25 meters and six minutes. The remaining subjects required 20, 37, and 95 seconds respectively to complete the 25-meter walk test. Six-minute walk test (6MWT) values were equally compromised at only 30, 37, and 85 meters.1
Of the five individuals who completed the study protocols, three reported reasonably high satisfaction with the exoskeletal device using the Quebec User Evaluation of Satisfaction with Assistive Technology, a validated measure of the satisfaction experienced with such elements as the dimensions, weight, security, durability, ease of use, comfort, and efficacy of the device. Not surprisingly, these three individuals also experienced the greatest success with the exoskeleton, with peak performances of 351, 373, and 602 meters as their longest walks within the device, facilitating 821, 1,086, and 1,388 steps respectively.1
Reflecting upon their prior experience with this technology in patients with spinal cord injury, the authors observe that the patients with MS "showed more variability and did not progress as far or quickly…." Suggested reasons for these differences hearken back to the multidimensional challenges associated with MS, including fatigue, balance compromise, declines in coordination, and insufficient upper-extremity strength.1 Thus the transferability of exoskeletons to this population appears to be limited to a small subset of individuals with extreme mobility compromise who are able to successfully master the skills associated with their use.
In sharp contrast to the individuals just described are those who are reasonably ambulatory with a comparatively straightforward, often unilateral foot drop as their primary limitation. FES, initially developed for application among individuals who have experienced a stroke, has found increasing application for this second group of individuals with MS, summarized in two recent literature reviews.2-3
The first of these examines a range of considerations in a narrative format, including gait speed, energy costs and efficiency, gait kinematics, user satisfaction, and perceived benefits. The authors summarize their findings as follows: "Overall, the growing body of evidence reported above suggests that FES for foot drop has beneficial orthotic and training effects on various quantitative measures of gait and walking in patients with MS." The strength of this statement is found in the wealth of information from which it was ultimately derived; the authors having aggregated the observations of 408 patients with MS taken from 18 clinical trials.2
The subsequent systematic review on this topic includes a more detailed meta-analysis on the impacts of FES on the various considerations of gait speed.3 Among those with MS, the initial orthotic effect (benefits observed while actively using FES) during short-distance walking tests increased by an average of .05 m/s, or roughly 7 percent.3 These figures represent the aggregate observations from 11 studies with 353 patients in which the average gait speed improved from .69 m/s to .74 m/s with the introduction of FES.3
Ongoing orthotic benefits of FES were observed at .08 m/s, or roughly 11 percent. These were derived from the cumulative observations of eight trials with 255 participants in which the average gait speed increased from .74 m/s to .82 m/s with and without the active use of an FES system that had been worn on an ongoing basis.3
The therapeutic effects of FES, meaning the benefits experienced by the individual who has been using FES but is not actively using the device at the time of the assessment, was less pronounced. Average gait velocities without the active use of FES were no different between baseline assessments and assessments performed after the extended use of an FES system. This statement was supported by the observations of 244 patients taken from six clinical trials with an average performance speed of .74 m/s that remained unchanged.3
The impact of FES on this population during longer walking tests such as the 6MWT was still positive, but failed to reach statistical significance. For example, among the 89 patients in five studies examining the initial orthotic effect over longer walking distances, gait speed demonstrated a modest improvement from .61 m/s to .63 m/s. Similarly, among 81 individuals in four studies examining the ongoing benefits of FES over longer walking distances, gait speed again demonstrated a modest improvement, this time from .64 m/s to .68 m/s.3 The therapeutic benefit of FES over longer walking distances was also assessed. Limited to only 61 patients from three studies, the average gait speed once more demonstrated a modest, non-significant benefit from .58 m/s to .64 m/s.3
FES Caveats and the Road Ahead
After summarizing the general benefits of FES among those with MS, the authors of the earlier narrative review continue, "However, not all studies report statistically significant changes, and the clinical significance of the benefits observed is not consistently ascertained. Patient-reported data also suggest perceived benefits from FES, although these effects are not always reflected on standardized measures of symptom severity and functional studtus"2
The inconsistency of both observed and perceived benefits with FES among individuals with MS is likely a reflection of the tremendous variability observed in this population and their capacity to improve with this modality. This position is found in the authors' assertion that mobility devices, "must be tailored to the individual's characteristics and needs," with the application of FES being "no exception to this general rule."2
This being the case, the field is now faced with the need to mimic efforts undertaken within the stroke population to identify likely "FES responders" in the MS community.2 A number of factors may contribute to such questions of candidacy. Foremost among these is the disease course. In contrast to those populations like stroke and spinal cord injury, where deficits are the product of a single event with subsequent extended recovery and rehabilitation, MS is a progressive disorder characterized by tremendous variability in the rate of decline.
Thus, the cumulative benefits that can occur with ongoing use of FES must exceed the progressive declines in performance frequently seen in this population. Indeed, given the progressive nature of MS, simply maintaining gait speed with FES may be sufficient to justify its use in this population.
Additional observations include the prevalence of fatigue within the MS population and its potential counter effects to the positive impact of FES, and those presentations where foot drop is coupled with other gait disturbances such as hip and knee flexor weakness, where single-channel FES of the dorsiflexors cannot address the full complement of functional gait deficits.2
Given the high prevalence of MS, the frequency with which gait is compromised within this population, and the extent to which gait preservation is valued, it is little wonder that clinical research is seeking solutions from those initially developed for other populations. While the application of exoskeletons is in the early stages, data suggests that there may be at least some individuals with MS who may benefit from this rather extreme solution. By contrast, the MS population now has an established record of benefits with the use of FES, especially regarding its orthotic benefits. Additional work will be required with both modalities to better isolate which patients will prove to be better responders to these technological advancements.
Phil Stevens, MEd, CPO, FAAOP, is in clinical practice with Hanger Clinic, Salt Lake City. He can be contacted at firstname.lastname@example.org.
1. Kozlowski, A. J., M. Fabian, D. Lad, and A. D. Delgado. 2017. Feasibility and safety of a powered exoskeleton for assisted walking for persons with multiple sclerosis: A single-group preliminary study. Archives of Physical Medicine and Rehabilitation 98:1300-7.
2. Dapul, G. and F. Bethous. 2015. Functional electrical stimulation for foot drop in multiple sclerosis. US Neurology 11:10-8.
3. Miller, L., et al. 2017. Functional electrical stimulation for foot drop in multiple sclerosis: A systematic review and meta-analysis of the effect on gait speed. Archives of Physical Medicine and Rehabilitation 98:1435-52.
4. LaRocca, N. 2011. Impact of walking impairment in multiple sclerosis. Patient 4(3):189-201.