Stimulation to Enhance Walking Post-SCI

The purpose of this pilot study is to investigate the effects of transcutaneous direct current stimulation (tsDCS) on locomotor function and rehabilitation outcomes in individuals with incomplete spinal cord injury (ISCI). tsDCS is a mild, non-invasive form of electrical stimulation that can alter spinal cord excitability.

Specific Aim 1: To test the hypothesis that tsDCS applied during walking will improve motor activation in adults with chronic ISCI. A random order, double blind cross-over study will be conducted across two test sessions to compare the immediate effects of two dosages of tsDCS during walking. To assess motor activation, the primary outcome measure will be lower extremity surface electromyography.

Specific Aim 2 (Interventional): To test the hypothesis that tsDCS applied during 16 sessions of locomotor training will improve functional walking outcomes. Participants will be randomized to receive 16 sessions of locomotor training with one of the two tsDCS dosages. The primary outcome is walking function as measured by standardized clinical tests of walking speed and endurance.

To address the aims of the study, the investigators will use a two-part study design. Following phone and in-person screenings and physician approval, individuals will provide informed consent to the study procedures. In the first part, participants will complete two separate testing sessions, presented in random order, that involve up to 30 minutes of tsDCS at one of two dosages levels while walking. The researchers will assess changes in motor activation before and at the end of the period of walking. For the second part, participants will be randomized to receive 16 sessions of locomotor training with one of the two dosages of tsDCS. Before and after the 16-session intervention (i.e., at baseline and post intervention), the study team will assess functional outcomes through standardized tests of walking speed and endurance.

• Soterix Medical tsDCS stimulator (Device): tsDCS will be delivered to the lumbar region of the spinal cord with electrodes placed over the low back and abdomen. The electrodes will be secured with a large elastic bandage so that stimulation can be applied for up to 30 minutes during locomotor training with a harness attached to the ceiling for safety. A physical therapist will supervise the session.
• Locomotor training (Other): Participants will complete 16 sessions of locomotor training (4 times per week for 4 weeks). This involves walking on a treadmill for up to 30 minutes with a harness attached to the ceiling for safety, followed by 10 minutes of overground walking training; with physical assistance as needed.

Primary outcomes

• Change in 10-Meter Walk Test (Interventional) [Baseline; Week 4]: Performance assessment of comfortable and fastest safe walking speed for 10 meters. A reduced time (in seconds) to complete the 10-Meter Walk Test reflects improvement in walking function.
• Change in Plantar Flexor Muscle Electromyogram Activation During Walking (Immediate Effects) [Baseline; 1 hour]: The change in normalized amplitude of muscle activation recorded from the right ankle plantar flexor muscles (soleus and gastrocnemius) will be reported. EMGs will be recorded during speed-matched trials during walking on a treadmill. The normalized mean activation during single limb stance will be quantified for each step and averaged. For each participant, the change in activation will be quantified by subtracting activation pre training from post-training activation. The mean change and standard deviation of change will be reported for each group.

Secondary outcomes

• Change in 6-Minute Walk Test (Interventional) [Baseline; Week 4]: The 6-Minute Walk Test (6 MWT) is a submaximal exercise test that entails measurement of distance walked over a span of 6 minutes. An increase in the number of meters walked during this assessment reflects an improvement in walking endurance.

Sex: All, ages: 18 Years to 65 Years

Inclusion Criteria:

* Single spinal cord injury (duration >1 year) classified as neurologic level T12 or above based on the International Standards for the Neurologic Classification of Spinal Cord Injury, and classified on the American Spinal Cord Injury Association (ASIA) Impairment Scale (AIS) as 'C' or 'D' motor incomplete
* Capable of ambulating 10 feet with or without the use of gait devices, braces, or the assistance of one person
* Medically stable with no acute illness or infection
* Able to provide informed consent

Exclusion Criteria:

* Current diagnosis of an additional neurologic condition such as multiple sclerosis, Parkinson's disease, stroke, or brain injury
* Presence of unstable or uncontrolled medical conditions such as cardiovascular disease, myocardial infarction (<1 year), pulmonary infection or illness, renal disease, autonomic dysreflexia, infections, pain, heterotopic ossification
* Cognitive or communication impairments limiting communication with study staff or ability to provide informed consent
* Lower extremity joint contractures limiting the ability to stand upright and practice walking
* Skin lesions or wounds affecting participation in walking rehabilitation
* Acute or unstable fracture, diagnosis of osteoarthritis or bone impairments affecting safe participation in walking rehabilitation
* Severe spasticity or uncontrolled movements limiting participation in walking rehabilitation
* Body weight or height that is incompatible with safe use of a support harness and body weight support system
* Pain that limits walking or participation in walking rehabilitation
* Current participation in rehabilitation to address walking function
* Botox injections in lower extremity muscles affecting walking function within 4 months of study enrollment
* Legal blindness or severe visual impairment
* Known pregnancy
* Implanted metal hardware below the level of the 8th thoracic vertebrae

Participant flow

Outcome results

• Change in 10-Meter Walk Test (Interventional) (Primary), Mean, meters/second: Interventional Effects: Higher Dosage 0.18 +/- 0.29; Interventional Effects: Lower Dosage -0.05 +/- 0.23
• Change in Plantar Flexor Muscle Electromyogram Activation During Walking (Immediate Effects) (Primary), Mean, mV: Immediate Effects: Low Dose tsDCS 0.0102 +/- 0.1091; Immediate Effects: Higher Dose tsDCS -0.0023 +/- 0.1257
• Change in 6-Minute Walk Test (Interventional) (Secondary), Mean, meters: Interventional Effects: Higher Dosage 36.4 +/- 69; Interventional Effects: Lower Dosage 4.9 +/- 56.9

Adverse events

Time frame: eight weeks

Other adverse events by term

• Study Protocol and Statistical Analysis Plan (PDF, 2019-04-25)
• Informed Consent Form (PDF, 2021-01-04)

• Emily Fox, PT, PhD, Principal investigator, University of Florida