Epi Stim to Facilitate Standing and Stepping

The overall aim is to assess whether task specific locomotor training and spinal cord electrical stimulation (SCES) can induce neural reorganization of the functionally isolated human spinal cord to improve standing and stepping in individuals with functionally complete SCI. The investigators propose that locomotor training will result in generation of more effective standing and stepping efferent patterns by restoring phase dependent modulation of reflexes and reciprocal inhibition, reducing clonus and mediating interlimb coordination. The investigators propose that the SCES will optimize the physiological state of the spinal cord interneuronal circuitry compromised by compensating for loss of supraspinal input for the retraining of these tasks.

Participants will be screened for eligibility and then participate in pre-training motor, bladder and cardiovascular experiments, followed by 80 sessions of locomotor training. Participants will repeat experiments after the 80 training sessions to quantify that no motor pattern changes are achievable with locomotor training alone and will be evaluated for appropriate candidacy for surgery and epidural stimulation. Participants will be surgically implanted with an epidural stimulator and experiments will be conducted with and without stimulation. Investigators will identify appropriate stimulation parameters for inducing stepping and standing in combination with manual assistance using body weight support on a treadmill and/or overground. Participants will undergo 80-200 training sessions of locomotor training with epidural stimulation. Experiments will be repeated mid and post-training interventions.

Eligibility Criteria:
Inclusion Criteria:

* All research participants, irrespective of age or sex, will meet the following criteria:

  * stable medical condition without cardiopulmonary disease or dysautonomia that would contraindicate standing or stepping with BWST;
  * no painful musculoskeletal dysfunction, unhealed fracture, contracture, pressure sore, or urinary tract infection that might interfere with stand or step training;
  * no clinically significant depression or ongoing drug abuse;
  * no current anti-spasticity medication regimen;
  * non-progressive SCI above T10;
  * must not have received botox injections in the prior six months;
  * be unable to stand or step independently;
  * at least one-year post injury; and
  * must be at least 18 years of age.

In addition, all subjects must satisfy each of the three conditions of the functional neurophysiological assessment described below.

Functional Neurophysiological Assessment (FNPA). We will use FNPA to screen potential research participants based on specific neurophysiological inclusion criteria. Participants must have no volitional control of movement below the level of the lesion, but must retain some brain influence on spinal reflexes. Our target population, which will be identified by FNPA, cannot be identified reliable using traditional assessments: hence individual subjects may be classified widely as Class A, B, or C on the ASIA SCI scale. We will include only subjects who fulfill the following three requirements:

* There is no descending volitional control of movement below the lesion
* Segmental reflexes remain functional below the lesion
* Brain influence on spinal reflexes is retained

Exclusion Criteria:

* Ventilatory dependent
* painful musculoskeletal function, unhealed fracture, contracture, or pressure sore that might interfere with training;
* clinically significant depression or ongoing drug abuse;
* cardiovascular, respiratory, bladder or renal disease unrelated to SCI;
* severe anemia (Hgb\<8 g/dL) or hypovolemia; and
* HIV or AIDS related illness.