Comparison of Transcutaneous and Epidural Spinal Stimulation for Improving Function

Incomplete spinal cord injuries (SCI) are the most frequent neurologic category, comprising 66.7% of all SCI cases. People with incomplete SCI may retain some ability to move the legs and therefore the capacity to regain walking. Studies that show functional improvement in locomotion via electrical stimulation of lumbosacral circuits suggest that the underlying mechanisms are neuromodulation of lumbosacral spinal cord automaticity and sensory feedback.

Both epidural and transcutaneous spinal stimulation are demonstrating exciting potential to improve limb function for people after chronic SCI. Available treatment options for SCI are less than satisfactory and most often do not achieve full restoration of function. Recent experimental results suggest an exciting new approach of using electrical spinal stimulation to enable users to regain control of their weak or paralyzed muscles. Using surgically-implanted electrodes, epidural stimulation results in remarkable improvements of lower extremity function as well as autonomic functions such as bladder function and sexual function.

In addition to epidural stimulation, over only the last few years a novel strategy of skin surface electrical spinal stimulation has also demonstrated exciting potential for improving walking function. Using a high-frequency stimulation pulse, current can pass through the skin without discomfort and activate the spinal cord; this results in patterned stepping movements for people without SCI and improved lower extremity function following SCI. This study will directly compare skin-surface transcutaneous stimulation with implanted epidural stimulation for improving lower extremity function.

The purpose of this study is to determine the optimal method for delivering spinal stimulation to improve walking in people with incomplete spinal cord injury. By directly comparing non-invasive transcutaneous (TransQ) stimulation with implanted epidural stimulation, investigators hope to guide the field toward the most beneficial method for restoration of lower extremity function. In addition, the investigators may identify subgroups of people that respond better to each type of stimulation, informing personalized treatment for people with different types of spinal cord injury. The research team will explore the following specific aims:

Aim 1: Evaluate the improvements in lower extremity and autonomic function via transcutaneous spinal stimulation and intensive physical therapy for people with chronic SCI.

Aim 2: Quantify additional improvements in lower extremity and autonomic function via epidural spinal stimulation and intensive physical therapy for people with chronic SCI.

The investigators will test the hypothesis that epidural stimulation leads to greater improvements than an equal dose of transcutaneous stimulation. To compare these 2 stimulation methods the study team will evaluate voluntary control of muscle activity via EMG and kinematic parameters of locomotion, as well as improvements in bladder and other autonomic functions and overall quality of life.

Eligibility Criteria:
Inclusion Criteria:

1. have a spinal cord injury at least one-year duration;
2. are between 21 and 70 years of age;
3. have difficulty with leg functions and mobility in activities of daily living (e.g. walking, transferring surface to surface, standing);
4. are candidates for an implanted stimulator;
5. are willing and able to have surgical implantation of the epidural stimulator for the treatment of pain according to the study timeline;
6. experience chronic pain;
7. are in stable medical condition without cardiopulmonary disease or frequent autonomic dysreflexia that would contraindicate participation in lower extremity rehabilitation or testing activities;
8. are capable of performing simple cued motor tasks;
9. have the ability to attend 3-5 sessions per week physical therapy sessions and testing activities over three months;
10. have adequate social support to be able to participate in assessment sessions occurring between once per week to once per month for up to 9 months;
11. are volunteering to be involved in this study;
12. are cleared for gait training by primary physician of the subject;
13. and have ability to read and speak English

Exclusion Criteria:

1. have autoimmune etiology of spinal cord dysfunction/injury;
2. have a history of additional neurologic disease, such as stroke, MS, traumatic brain injury, etc.;
3. have peripheral neuropathy (diabetic polyneuropathy, entrapment neuropathy, etc.);
4. have rheumatic diseases (rheumatoid arthritis, systemic lupus erythematosus, etc.);
5. have significant medical disease; including uncontrolled systemic hypertension with values above 170/100 mmHg; cardiac or pulmonary disease; uncorrected coagulation abnormalities or need for therapeutic anticoagulation;
6. have active cancer;
7. have cardiovascular or musculoskeletal disease or injury that would prevent full participation in physical therapy intervention;
8. have unhealed fracture, contracture, pressure sore, or urinary tract infection or other illnesses that might interfere with lower extremity rehabilitation or testing activities;
9. have any condition that would render the patient unable to safely cooperate with the study tests as judged by the screening physician;
10. are pregnant;
11. are dependent on ventilation support;
12. have implanted stimulator (e.g. epidural stimulator, vagus nerve stimulator, pacemaker, cochlear implant, etc.);
13. have depression or anxiety based on the Center for Epidemiologic Studies Depression Scale (CESD) (score \>16/60) and General Anxiety Disorder-7 item Questionnaire (score \>9/21), respectively.
14. have alcohol and/or drug abuse;
15. have cognitive impairment based on Short Portable Mental Status Questionnaire (SPMSQ) (score \>2/10);
16. are unable to read and/or comprehend the consent form;
17. are unable to understand the instructions given as part of the study;
18. have established osteoporosis and are taking medication for osteoporosis treatment;
19. have bone mineral density T scores ≤ -2.0 in anteroposterior lumbar spine and/or proximal femur measured by DEXA (if participants are clear for other criteria and have not been examined by DEXA at the screening, we will ask participants to undergo DEXA to reveal any risk of weight bearing activity);
20. have a low-energy fracture history before or after spinal cord injury;
21. have a history of orthopedic surgery in lower extremities that may be a confounding factor for interpretation of the results (such as tendon transfer, tendon or muscle lengthening for spasticity management, etc.);
22. have fixed lower extremity joint contractures;
23. are taller than 80 inches and/or weighs more than 350 pounds (due to the limitation of the experimental equipment such as the body weight support system);
24. lack the ability to fully comprehend and/or perform study procedures in the investigator's opinion/judgement