Using Non-invasive Brain and Spinal Cord Stimulation to Improve Arm and Hand Function After Spinal Cord Injury

Cervical spinal cord injury (SCI) disrupts communication between the brain and spinal circuits, affecting voluntary movement control and contributing to arm and hand impairments, the top recovery priority for people with tetraplegia. Although rehabilitation and emerging neuromodulation approaches can support meaningful gains, many individuals experience persistent limitations in reaching and grasping. Current noninvasive stimulation strategies typically target the brain OR the spinal cord alone, despite strong reciprocal interactions between these structures. Cervical transcutaneous spinal cord stimulation (tSCS) can enhance upper limb function. Cerebellar stimulation, given its key role in sensorimotor integration and modulation of corticospinal excitability, represents a promising but underexplored therapeutic target. Theta burst stimulation (TBS), a rapid form of repetitive transcranial magnetic stimulation (TMS), induces lasting changes in cortical excitability and may promote associative plasticity when paired with spinal cord stimulation. This double-blind, randomized, sham-controlled pilot trial (n=24) will evaluate the feasibility, preliminary efficacy, and mechanisms of combined cerebellar TBS + cervical tSCS in people with chronic cervical SCI (AIS B, C or D). Participants will either receive cerebellar TBS + cervical tSCS, tSCS only, or sham stimulation while engaging in functional task practice such as pinching and grasping 3x/week for 8 weeks. Feasibility outcomes include adherence, retention, and safety. Efficacy will be assessed using the GRASSP strength sub-score and KINARM-based measures of sensorimotor control. Mechanistic outcomes will assess changes in cortical and spinal cord functional connectivity using resting state fMRI, corticospinal excitability using motor evoked potentials, and spinal excitability using the H reflex. Findings will establish whether combined cerebellar TBS and cervical tSCS is feasible, safe, and capable of enhancing upper limb recovery.