Conditioning Neural Circuits to Improve Upper Extremity Function

Transcranial direct current stimulation (tDCS) is a technique in which low intensity electrical current is applied over the skull in order to excite the underlying brain tissue. It has been studied in many populations (stroke, spinal cord injury, learning disability, migraine, memory) and may be a useful counterpart to traditional rehabilitation of neurological injuries. Preliminary studies from members of the investigator's lab group have indicated beneficial, single-session effects of tDCS on hand function in people with spinal cord injury. Longer-term, multi-session trials are now warranted.

Another approach that has research support for augmenting the effects of hand function training is peripheral nerve somatosensory stimulation (PNSS). Unlike tDCS, which excites brain tissue directly, PNSS excites the brain via an indirect approach. Members of the investigators' lab have found the combination of PNSS and fine motor training to be more effective in improving hand function than either intervention alone. Multi-session trials of PNSS have been conducted; however it has not yet been compared with another clinically accessible adjunctive therapy, like tDCS, in a multi-session trial.

The investigators plan to study the comparative effects of tDCS and hand function training to PNSS and hand function training and hand function training alone in people with neck-level spinal cord injuries. People with both acute/subacute (<6 months post-injury) and chronic (>1 year post-injury) injuries will be enrolled, in order to look at responses to tDCS at different stages of recovery.

Before beginning training, participants will complete approximately three hours of testing of their arm/hand function and self-reported perception of their overall function. Participants will then be randomly assigned to receive either tDCS, PNSS, or sham tDCS in combination with personalized fine motor training. This training will take place 3 times/week, for a total of 3 hours of training/week, for 4 weeks. Fine motor training will be based on principles that have been shown to optimize neuroplasticity (changes in the brain and/or spinal cord), yet customized, in order to allow participants to work towards individualized goals. At the end of 4 weeks, participants will complete a three-hour post-test using the same measures as before to examine any changes in arm and hand function. Participants will be asked to return to Shepherd Center 4 - 6 weeks following the post-intervention assessment to complete the post-intervention assessment.

Inclusion criteria

• Be 18-65 years of age
• Have a cervical (neurological level C1-C8) SCI that occurred either <6 months ago (subacute) or >1 year (chronic) prior to the time of enrollment
• For subjects with acute/subacute SCI: the injury must be a traumatic injury (i.e. not the result of illness or a condition within the body)
• Have ISNCSCI severity classification (A, B, C or D)
• Have self-reported limitations in arm and hand function in at least one upper limb (a GRASSP quantitative score of no more than 26/30 in the hand that is the focus of treatment)
• Have the ability to pick up objects with at least one hand without using assistive devices (a GRASSP quantitative score of at least 4/30 in the hand that is the focus of treatment)
• Have shoulder strength lift an arm up to chest level
• Have the ability to sit for at least one hour at a time (e.g. good skin integrity, stable blood pressure)
• For subjects with acute/subacute SCI: adequate time remaining in their treatment at Shepherd Center to allow 5 weeks of participation
• For subjects with chronic SCI: active hand function is required (see Pre-intervention assessment) reliable transportation in order to complete the intervention in its entirety
• Ability and willingness to consent and authorize use of personal health information

Exclusion criteria

• Pacemaker or a metal implant in the head
• Current pregnancy
• Severe shoulder weakness, injury, or pain that contraindicates repetitive fine motor training
• Lower motor neuron damage (as documented in medical record, per participant report, or as noted by in-person screening)
• Severe hypersensitivity or pain of the arm/hand
• Severe contractures of the arm/hand that would limit participation in fine motor training
• Prior tendon or nerve transfer surgery
• Have a history of seizures
• Have a history of frequent or severe headaches