Restoration of Standing and Walking With ISMS in Humans

Spinal cord neural circuitry exists in the lumbar enlargement that makes it possible to stand and create synergistic, rhythmic stepping activity in the lower limbs. In the past 20 years, clinicians have tried to reengage such these circuits for standing and walking in the lower spinal cord of paralyzed humans through novel paradigms of physical therapy, pharmacological stimulation of the spinal cord, or recently - epidural stimulation of the spinal cord. Although standing and stepping with these maneuvers are rudimentary at best, these human studies offer promise to restore controlled, lower extremity movement to the spinal cord injured (SCI) individual. Evidence from animal data suggests that more focal activation of intraspinal circuitry (IntraSpinal Micro-Stimulation - ISMS) would produce more fatigue resistant, natural standing and stepping activity in humans. To date, there has been no direct confirmation of such circuitry in the spinal cord of bipedal humans who have been paralyzed. Furthermore, mapping of such circuitry would provide the basis of a novel intraspinal neuroprosthetic that should be able to restore control of standing or walking in a manner that is much more physiologically normal and tolerable than by stimulating each individual muscle group. Proof of the existence of these spinal circuits in man, and the ability to activate and control these circuits by first mapping the spinal cord is the basis of this proposal.

Two study volunteers who are completely paralyzed (T2-8 region) to undergo an evaluation of ISMS during an otherwise normal thoracic spinal surgical procedure.

The potential volunteers will be asked to review and sign a screening consent form prior to initial screening. This is to ensure that the ideal two patients are selected for this study and that foreseeable issues are identified and risks minimized for the volunteers. The subjects must have a stable, complete spinal cord injury involving their upper thoracic spinal cord (T2-8 region), and are otherwise planning to undergo a spine surgery involving the lower thoracic spinal cord.

Subjects who have volunteered for this study will undergo their intended spinal surgery by the clinical team. The usual indications for undergoing such a surgery is either to correct a deformity involving the lower thoracic region, or stabilizing the lower thoracic region due to chronic instability from degenerative disease. The surgery intended for clinical treatment must involve exposure of the T9-T12 spinal lamina. However, exposure of the spinal cord through a dural opening would not normally be performed in this clinical scenario. The experimental portion of the surgery begins then, with a laminectomy of T9-T12 and exposure of the spinal cord through a durotomy using standard neurosurgical techniques for spinal cord exposure. The spinal cord in this region will then be mapped and stimulated using ISMS and the effects on the legs measured to determine if the circuitry exists to potentially allow standing or walking through the use of ISMS. The research requests subjects to specifically allow 2 hours of extra time during the routine spinal surgery to perform this study.

Eligibility Criteria:
Inclusion Criteria:

1. Age 18-50 years old; male or female (no preference).
2. Complete paraplegia (ASIA A classification) as a result of a spinal cord injury between the levels of T2-8.

   i. No motor or sensory function below the level of injury as determined by a physician.

   ii. No voluntary bladder function - defined as the inability to sense bladder fullness or voluntary contraction of the bladder (meets criteria for no sacral sparing).

   iii. Stable paraplegia.
3. Patients with involuntary spasms are allowed. However, spasticity must be less than Ashworth 4 or spasm rating of 3 or less.
4. History of spinal cord injury greater than 1 year.
5. Intent to undergo spine surgery involving exposure of at least T9-T12 vertebral lamina.
6. MRI studies performed within the past year showing presence of spinal cord between T8-L1 with reasonable normal anatomical shape. No chronic infections.
7. Ability to travel to Vanderbilt Medical Center.

Exclusion Criteria:

1. Acute medical conditions that are under active treatment. Examples include active urinary tract infection, respiratory illness, decubital ulcers, fractures, upper extremity injury, back pain.
2. Pregnancy.
3. Presence of a neurostimulator, bladder stimulator, cardiac stimulator or other electrical stimulator device implant.
4. Inability to transfer from wheel chair to chair or bed.
5. Inability to tolerate 1 hour of physical activity such as gait training in a harness.
6. Severe depression requiring active medical treatment or counseling.
7. Cognitive impairment that places the study volunteer under the 6th grade reading level.
8. Inability to provide consent.
9. Intradural or extradural masses compressing or displacing the spinal cord between T8-L1 region.
10. Significant change in motor or sensory function over the previous year.
11. History of spinal cord injury less than 1 year.
12. Previous laminectomy and intradural spinal cord procedure involving the region of T9-T12.
13. Patients with involuntary spasms with rigidity more than Ashworth 4 or spasm rating of 3 or more.