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Multiple Sclerosis Functional Electrical Stimulation for Foot Drop in Multiple Sclerosis Geraldine P Dapul, MD and Francois Bethoux, MD Mellen Center for Multiple Sclerosis Treatment and Research, Neurological Institute, Cleveland Clinic, Cleveland, Ohio, US Abstract Functional electrical stimulation is an effective treatment strategy for the management of foot drop in various neurologic conditions, as demonstrated in improvements in gait performance, mobility, physiologic cost, perceived walking ability, balance, fall frequency, and quality of life. In this article, we review the current literature on the effects of functional electrical stimulation for foot drop in persons with multiple sclerosis. Keywords Multiple sclerosis, gait, foot drop, functional electrical stimulation, review Disclosure: Geraldine P Dapul, MD, has no conflicts of interest to declare. Francois Bethoux, MD, served as site principal investigator and national principal investigator for a randomized clinical trial of the WalkAide ® FES device in stroke patients (INSTRIDE trial), sponsored by Innovative Neurotronics, Inc. Money was paid to his institution for his contribution to this study. No funding was received for the publication of this article. Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any noncommercial use, distribution, adaptation, and reproduction provided the original author(s) and source are given appropriate credit. Received: January 15, 2015 Accepted: February 9, 2015 Citation: US Neurology, 2015;11(1):10–8 Corresponding author: Geraldine P Dapul, MD, Mellen Center U-10, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH, 44195, US. E: dapulg@ccf.org Multiple sclerosis (MS) is a chronic, progressive disease of the central nervous system, believed to be caused by an autoimmune process, and resulting in demyelination and axonal loss in the brain, spinal cord, and optic nerves. MS affects approximately 400,000 individuals in the US alone and 2.5 million people worldwide. A decline in neurologic function, most notably in coordination, strength, tone, cognition, vision, sensation, and volitional control of bowel/bladder are hallmark characteristics of the disease, leading to reduced quality of life (QoL) and decreased participation in activities. Of primary concern to the MS population is impaired mobility, as it is the most visible disability and because of its profound impact on daily life. 1,2 Gait disturbance is present in a large number of persons with MS (pwMS) and has been identified as one of the most disabling features of this neurologic disease. Compared with healthy controls, pwMS demonstrate decreased walking speed, decreased stride length, increased cadence, reduced active lower extremity range of motion (ROM), and increased variability in gait parameters. 3–9 One of the more common gait pattern abnormalities demonstrated by pwMS is foot drop, caused by weakness of muscles responsible for ankle dorsiflexion and spasticity of the ankle plantarflexors. The ability to clear the foot by maintaining active dorsiflexion during the swing phase of the gait cycle is compromised in individuals with foot drop. Therefore, foot drop causes decreased gait efficiency and gait instability, leading to unwanted stumbles and falls. As a result, pwMS develop compensatory strategies including pelvic obliquity, hip hiking, and hip abduction with circumducted gait pattern to preserve foot clearance. 10 Treatment modalities to address foot drop include stretching, exercise, rehabilitation, orthotics, and assistive devices. The goals of treatment regardless of the intervention are to improve gait efficiency and safety, and overall improve the gait pattern to reduce musculoskeletal stress from altered biomechanics. The standard of care for foot drop has been the use of an ankle–foot orthosis (AFO). A more recently developed alternative to the AFO is functional electrical stimulation (FES). Functional Electrical Stimulation for Foot Drop The term FES refers to applying electrical current to a peripheral nerve via transcutaneous, percutaneous, or implanted electrodes, which in turn triggers muscles contractions with the goal of improving balance and gait. In the case of the FES application to foot drop, the electrical stimulation is applied to the common peroneal nerve, recruiting muscles controlled by both the deep and superficial peroneal nerves, and resulting in dorsiflexion and eversion of the ankle. The stimulation is synchronized with the gait cycle, so that it occurs during the swing phase of gait, and stops during the stance phase. FES devices generally include a power source (usually batteries), a stimulation unit, electrodes, and a mechanism to turn the stimulation on and off depending on the phase of the gait cycle. Various designs have been developed: wired versus wireless; tilt sensor on the leg versus heel switch. Commercially available FES systems for foot drop include the Odstock Dropped Foot Stimulator (ODFS ® , Odstock Medical Limited, Salisbury, UK), the WalkAide ® system (Innovative Neurotronics Inc., Austin, TX, US), the Bioness NESS L300 ® Foot Drop System (Bioness Inc., Valencia, CA, US), and the MyGait ® system (Ottobock, Duderstadt, Germany). A majority of the published research in MS has focused on the ODFS and WalkAide devices. To date, only one head-to-head trial of Touch ME d ica l ME d ia