Exoskeleton Research: Myoelectric Orthosis for Rehab of Severe Chronic Arm Motor Deficits

Current rehabilitation methods fail to restore normal arm function for many stroke survivors, particularly those with severe deficits. The main objective of this study is to test efficacy and evaluate underlying neurophysiological mechanisms of a novel approach to treat persistent severe arm deficits after stroke with a combination of MyoPro and motor learning-based therapy. The investigators will also estimate cost effectiveness of this therapeutic approach. Rationale: Motor learning-based therapy is one of the most effective stroke rehabilitation methods available, however its application is challenging for individuals with severe arm impairment because of their limited ability to practice volitional arm movement effectively. The MyoPro is an exoskeletal myoelectrically controlled orthotic device that is custom fitted to an individual's paretic arm and assists the user to move the paretic arm. MyoPro can help with motor learning-based therapy for individuals with severe motor deficits as it motivates practice because even weak muscle activity is translated into patient-initiated arm movement. Preliminary results of motor-learning therapy using MyoPro in the investigators' laboratory showed an increase in Fugl-Meyer for Upper extremity score (FM) of 7.4 points following 18 weeks of training (18 in-clinic therapy sessions over 9 weeks followed by 9 weeks of home practice) for chronic stroke survivors with baseline FM 30. However, comparison of the same dose of combination therapy with motor-learning alone remains to be determined. Study Design: Using a randomized, controlled design, individuals with chronic severe stroke ( 6 months post; Fugl Meyer UE score 30;n=60) will participate in either MyoPro+motor learning (M+ML) or motor learning alone (ML-alone). The study intervention will include 9 weeks of in-clinic training (18 sessions;1.5 hours each) followed by 9 weeks of home practice and a 6-week follow-up. Aim 1 is to determine whether M+ML results in greater treatment gains compared to ML-alone. The primary outcome will be change in FM. Secondary outcome measures will assess overall paretic arm performance and will include: kinematics, muscle tone (Modified Ashworth Scale; MAS), grip/pinch/arm dynamometry, sensory function (Semmes Weinstein mono-filament test, joint proprioception), arm function (Arm Motor Ability Test (AMAT);actigraphy) and quality of life (Stroke Impact Scale (SIS)). Aim 2 is to characterize structural and functional brain changes after treatment. Outcomes include corticospinal excitability (motor evoked potential recruitment curve (MEP-rc)), and functional connectivity (resting state function Magnetic Resonance Imaging(rs-fMRI). Aim 3 is to identify baseline factors associated with greater functional improvement with treatment. Outcomes are as follows: baseline integrity of the stroke-affected corticospinal tract (lesion load, MEP-rc; Diffusion Tensor Imaging); baseline motor ability of the affected arm (FM); baseline functional connectivity (rs-fMRI); device usage and actigraphy. Aim 4 is to evaluate cost effectiveness of M+ML versus ML-alone. Outcomes include: direct/indirect costs and health related quality of life surveys (Short Form 12v.2 and SIS). Significance: This study will address an important problem for the VA patient population by testing for the first time whether MyoPro combined with motor learning-based therapy is superior to motor learning alone in the treatment of chronic, severe arm impairment in stroke. If found to be effective, the study intervention is readily deployable to the clinical setting.

Inclusion criteria

• 18-89 years of age
• Unilateral arm weakness due to stroke (6 months or more since onset)
• Adequate range of motion at the elbow, forearm, wrist, and hand to don the device
• Active shoulder flexion of at least 30 degrees and active shoulder abduction of at least 20 degrees
• Ability to generate volitional, consistent, and detectable EMG signals from the upper arm and forearm sensor sites with wrist in neutral or flexed positions as detected by the MyoPro software
• MAS score less or equal to 3 for the biceps, triceps, supinators and pronators of the impaired arm
• Able to read and comprehend the English language
• Able to follow directions
• Able to provide informed consent
• Medically and psychologically stable.
• Ability to don/doff MyoPro independently or have support as needed.
• Ability to undergo MRI
• Ability to undergo TMS procedures

Exclusion criteria

• Previous stroke(s) affecting motor function on the opposite side.
• Persistent and severe shoulder subluxation, pain or dislocation
• Shoulder passive range of motion < 45 degrees in flexion and abduction
• Fixed upper limb contractures on the impaired arm and hand
• Unable to safely support the weight of their arm plus 4 lbs (1.82 kg; the weight of the device) without pain even with arm supported.
• Skin rash or open non-healing wound on impaired arm
• Involuntary movements of the impaired arm
• Pacemaker or other implanted devices that are not compatible with testing procedures or would interfere with donning/doffing and functioning of device.
• Metal in the skull or deformity of the skull
• Claustrophobia, or inability to operate the MRI patient call button
• Contraindications for MRI (standardized screening form for MRI).
• Past history of seizures
• Family history of medication refractory epilepsy
• Pregnancy or pregnancy planning during the study period
• Currently taking medications or substances that lower the threshold for onset of seizure.