Electrical Stimulation for Recovery of Ankle Dorsiflexion in Chronic Stroke Survivors

Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), Case Western Reserve University

Ankle dorsiflexor weakness (paresis) is one of the most frequently persisting consequences of stroke. The purpose of this exploratory study is to compare two different treatments -- Contralaterally Controlled Neuromuscular Electrical Stimulation (CCNMES) and Cyclic Neuromuscular Electrical Stimulation (cNMES) -- for improved recovery of ankle movement and better walking after stroke.

Ankle dorsiflexor weakness results in inefficient and unstable gait. While routine physical therapy is beneficial, for many individuals it remains limited in its effectiveness, and consequently many stroke survivors have difficulty walking safely or remain non-ambulatory. Ankle-foot-orthoses (AFOs) are often prescribed to provide ankle stability, but because they limit ankle mobility they may actually inhibit recovery of dorsiflexion. Advanced rehabilitation techniques that emphasize active, repetitive, goal-oriented movement of the impaired limb have produced measurable functional improvements, yet a significant degree of lower extremity disability often remains. In addition, some of these emerging therapies are difficult to administer and are applicable only to patients who retain at least some degree of ambulation. Thus, there is a need for alternative treatments. This is an exploratory study of an innovative neuromuscular electrical stimulation (NMES) treatment for restoring lower extremity motor control following stroke. We will investigate whether stroke survivors with chronic footdrop recover voluntary ankle dorsiflexion after a novel treatment of NMES. Surface electrodes will deliver stimulation to dorsiflex the ankle with an intensity that is proportional to the amount of dorsiflexion of the other unimpaired ankle. Thus, voluntary dorsiflexion of the unaffected ankle produces stimulated dorsiflexion of the affected ankle. We refer to this stimulation paradigm as Contralaterally Controlled Neuromuscular Electrical Stimulation (CCNMES). In contrast to existing peroneal nerve stimulators, CCNMES is not intended to be used to assist ambulation; rather it is intended as solely a motor retraining paradigm that may reduce lower extremity impairment and improve ambulation. The primary objective of the proposed study is to obtain pilot data so that an estimate can be made of the efficacy of CCNMES in reducing lower extremity impairment and improving ambulation. Twenty-six chronic stroke survivors (>6 months post-stroke) will be randomized to either CCNMES or cyclic NMES, an intervention that provides electrical stimulation of the ankle dorsiflexors, but with preprogrammed timing and intensity. For both groups, the treatment will last 6 weeks. Assessments of ankle impairment and ambulation will be made at baseline and at end of treatment. This study is the first randomized controlled trial of CCNMES for restoring ankle dorsiflexion in patients with chronic hemiplegia.

6-week intervention 15 minutes of therapist-guided stimulated ankle exercise + 30 minutes of physical therapy in the laboratory twice a week. Self-administered active repetitive ankle dorsiflexion exercise performed twice a day, 6 days a week at home using the device.

The Lower Extremity Fugl-Meyer (LEFM) Assessment is a measure of lower limb motor impairment. Participants are asked to attempt to perform a list of isolated and simultaneous movements of the hip, knee, and ankle that take into account synergy patterns, isolated strength, coordination, and hypertonia. Each movement attempt is graded on a 3-point ordinal scale (0, cannot perform; 1, perform partially; and 2, perform fully) and these subscores are summed to provide a maximum score of 34, minimum score of 0. Higher scores are considered to be a better outcome. For each individual, the score prior to treatment was subtracted from the score at end of the 6-week treatment. Then for each treatment group, these change scores were averaged.

Gait velocity was assessed using a motion capture and analysis system which collected spatio-temporal data as the participant walked 5-meters 10 times at a self-selected comfortable speed within the field of view of the motion capture system. A higher gait velocity is considered to be a better outcome. For each individual, the gait velocity prior to treatment was subtracted from the gait velocity at end of the 6-week treatment. Then for each treatment group, these change values were averaged.

The MEFAP is a measure of functional ambulation, measuring the time to ambulate through 5 common environmental terrains: 1) 5-meter walk on a hard floor, 2) 5-meter walk on a carpeted floor, 3) rise from a chair, 3-meter walk, return to seated position, 4) standardized obstacle course (bricks to step over), 5) stair ascent and descent. The five times subscores were added to derive a total time. Lower times are considered to be a better outcome. For each individual, the MEFAP completion time prior to treatment was subtracted from the MEFAP completion time at end of the 6-week treatment. Then for each treatment group, these change values were averaged.

Inclusion Criteria: Age 21 to 80 years >6 months from a first clinical non-hemorrhagic or hemorrhagic stroke Medically stable Unilateral lower extremity hemiparesis Ankle dorsiflexor strength of ≤4/5 on the Medical Research Council (MRC) scale, while seated Able to ambulate 16 feet (5 meters) continuously with minimal assistance or less, without the use of an ankle-foot orthosis (AFO). AFO is clinically indicated (footdrop during ambulation or inefficient gait patterns) Neuromuscular electrical stimulation (NMES) of the paretic ankle dorsiflexors produces ankle dorsiflexion to neutral without pain. Full voluntary dorsiflexion of the contralateral ankle Skin intact on hemiparetic lower extremity Able to don the NMES system or caregiver available to assist with device if needed. Able to hear and respond to stimulator auditory cues Able to follow 3-stage commands Able to recall 2 of 3 items after 30 minutes Exclusion Criteria: Brainstem stroke Severely impaired cognition and communication History of peroneal nerve injury History of Parkinson's, spinal cord injury, traumatic brain injury, or multiple sclerosis Uncontrolled seizure disorder Uncompensated hemi-neglect (extinguishing to double simultaneous stimulation) Edema of the affected lower extremity Absent sensation of lower leg and foot Evidence of deep venous thrombosis or thromboembolism History of cardiac arrhythmias with hemodynamic instability Cardiac pacemaker or other implanted electronic system Botulinum toxin injections to any lower extremity muscle in the last 3 months Pregnancy Currently receiving Physical Therapy for the lower extremity

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