Paired associative stimulation improves motor function in the upper extremity in chronic incomplete spinal cord injury: a corroborative study

To corroborate findings suggesting that spinally targeted paired associative stimulation improves upper extremity motor function in chronic incomplete spinal cord injury.

Prospective interventional study.

Five adults with chronic tetraplegia.

Participants received paired associative stimulation, combining peripheral nerve stimulation and navigated transcranial magnetic stimulation towards 1 arm (16 1-h sessions during 4 consecutive weeks, targeting the 3 large nerves). Manual muscle testing (MMT) was performed in 23 muscles in each arm, at 3 time points (pre-stimulation, t0; the week following the stimulation period, t1; and 4-5 weeks post-stimulation, t2). Additionally, grip strength and changes in the Canadian Occupational Performance Measure were assessed.

The mean improvement in manual muscle testing scores in the targeted extremity was +0.49 at t1 (p = 0.078) and +0.55 at t2 (p = 0.062). Grip strength in the stimulated extremity increased by 3.2 kg at t1 and 3.4 kg at t2, and in the non-targeted extremity by 2.2 and 3.6 kg, respectively. Performance and satisfaction increased by 2.1/2.4 points at t1, and by 2.0/1.9 points at t2.

Paired associative stimulation improved motor function: at the group level, MMT of the stimulated hand (p = 0.06) and non-stimulated hand (p = 0.04). Most participants achieved clinically relevant improvement. Thus, the results corroborate prior studies. The method may complement conventional rehabilitation for improving upper extremity function in incomplete tetraplegia.