A single session of motor imagery paired with spinal stimulation improves manual dexterity and increases cortical excitability after spinal cord injury

Objective Non-invasive stimulation of the spinal cord at the cervical level (TSCS) can induce neural plasticity and improve upper limb function in people living with cervical spinal cord injury (SCI) when paired with task practice. The aim of this study was to investigate the effects of a session of motor imagery (MI) paired with TSCS on manual dexterity, corticospinal and spinal excitability in people living with cervical SCI. Methods Eight participants (4 females, mean age 46yrs ± 17) completed three sessions of: 1) MI; 2) TSCS at C5–C6 level; 3) MI + TSCS, listening to the MI script while receiving TSCS. Manual dexterity was assessed with the Purdue Pegboard Test (PPT), corticospinal excitability was assessed with Transcranial Magnetic Stimulation (TMS) delivered at motor threshold and suprathreshold (120 % intensities, and spinal excitability delivered at motor threshold and suprathreshold (110 %, 120 %) intensities was assessed with single pulses of TSCS. Results Manual dexterity increased from baseline after all three conditions (p = 0.016). Corticospinal excitability increased from baseline after MI (p = 0.002] and MI + TSCS (p = 0.031], but not TSCS (p = 0.343). Spinal excitability was not affected by any of the conditions (p = 0.425). Conclusions These findings demonstrate that a single session of MI and TSCS, either alone or in combination, can increase manual dexterity in people living with cervical SCI. The increase in dexterity was paralleled by increases in corticospinal excitability for the MI and MI + TSCS conditions. Significance Our findings indicate that MI and TSCS improve manual dexterity and increase corticospinal excitability in people living with cervical SCI when employed in isolation or in combination.