Improving upper limb movement after spinal cord injury with a wearable device

INTERVENTION: Subjects fulfilling the selection criteria will be randomized (via computer generated code) to one of the two equal size parallel arms of the study. Group A: Will first receive the wearable device (electrical stimulation of triceps 10 ms before auditory click) and then spend 4 weeks without the device (control). Group B: Will first spend 4 weeks without the device (control) and then 4 weeks with the stimulation device. The study device is comprised of a plastic box about the size of a smart phone, containing an electrical stimulator and audio amplifier, powered by an internal battery which can be recharged via a standard microUSB port. The wearable device generates constant‐current electrical stimulation to the target muscle through surface electrodes (220 V compliance, 150 µs pulse width). A knob on the device allows adjustment of the stimulus intensity, which is set to be just below the motor threshold (defined as a visible muscle twitch). Adequate care will be taken to prevent accidental increment of stimulus strength. Auditory stimuli are generated by delivering a 0.1 ms wide, 12 V square excitation pulse into a miniature earpiece; this produces a brief click with an intensity of 110 dB SPL. The earpiece is placed in the contralateral ear. An internal flash memory with plasticity stimulus protocol will be inserted under the cover. The back side of the device will be custom made according to participants’ preference of carrying the device during his/ her awake hours. They can either clip it on their belt/ keep it on a specialized arm pouch or just keep inside the pocket of their trousers. The correct length of the wire will be chosen and the backside of the device will be custom made (fitted with a loo CONDITION: Chronic spinal cord injury ; Injury, Occupational Diseases, Poisoning ; Injury of spinal cord, level unspecified PRIMARY OUTCOME: ; Measured at baseline, after 4 and 8 weeks:; 1. Electrophysiological changes in triceps muscle are measured using EMG; 2. Motor evoked potential (MEP) size measured using transcranial magnetic brain stimulation; 3. Maximal voluntary contraction measured using a force transducer and EMG; 4. Reaction time measured using a StartReact paradigm; 5. Reaching parameters such as speed and trajectory accuracy measured using a custom built planar reaching task; 6. Upper extremity function measured using CUE questionnaire; INCLUSION CRITERIA: 1. Chronic (>1 year) cervical injury (C2‐C7) 2. Male or female at least 18 years of age 3. Detectable EMG activity in triceps 4. Without upper limb fracture or subluxation/ dislocation of joints within last six months. 5. Be able to follow study instructions and perform study tasks. 6. Willing to provide written informed consent; if necessary through an independent witness should the subject be unable to write themselves due to their injury. SECONDARY OUTCOME: ; 1. Compliance (how long subjects use the device each day) using the device clock data and participants’ filled‐up diary.; 2. Adverse event profile among participants using our intervention device.; 3. Range, speed and accuracy of upper limb movement (reaching task with Polhemus motion tracking system) before and after intervention; 4. Maximum voluntary contraction force of elbow flexion and extension before and after intervention; 5. Auditory startle response (StartReact paradigm) of triceps before and after intervention. This assay will examine the change of reticulospinal tract activity by the intervention (if any).; 6. Auditory startle response (startle + TMS paradigm) of triceps before and after intervention. This assay will examine the change of reticulospinal tract activity by the intervention (if any).; 7. Motor evoked potentials by transcranial magnetic stimulation (TMS with 2 different coil orientations) before and after intervention. This assay will examine the change of corticospinal tract activity by the intervention (if any).;