Functional and corticomotor changes in individuals with tetraplegia following unimanual or bimanual massed practice training with somatosensory stimulation: a pilot study

Abstract

Background and purpose: In individuals with cervical spinal cord injury (SCI), damage to spinal pathways results in deficits of hand function; maladaptive cortical changes further impair function. Unimanual massed practice (MP) training with somatosensory stimulation (SS) has been shown to improve hand function and increase corticomotor excitability after SCI. However, bimanual training may be more beneficial as these individuals have bilateral impairment. We compared clinical and corticomotor changes associated with unimanual versus bimanual MP training, each combined with SS.

Methods: Participants were 13 individuals with chronic tetraplegia who had at least minimal voluntary control of the thenar muscles of 1 hand. The participants were randomly assigned to unimanual MP + SS or bimanual MP + SS. Clinical outcome measures included tests of unimanual (Jebsen Taylor Hand Function Test; JTT) and bimanual hand function (Chedoke Arm and Hand Activity Inventory; CAHAI), sensory function (monofilament test), and pinch grip strength. Neurophysiological outcome measures were corticomotor map area, center of gravity (COG), of the corticomotor map and corticomotor threshold as assessed by transcranial magnetic stimulation.

Results: There were no significant differences in outcomes between the unimanual MP + SS versus bimanual MP + SS groups, both groups showed significant improvements in the JTT, CAHAI, and monofilament test. However, trends suggest that the unimanual MP + SS group had greater improvement in the JTT whereas the bimanual MP + SS group had greater improvement on the CAHAI. Functional changes were accompanied by a strong trend toward increased corticomotor map area.

Discussion and conclusion: When combined with SS, both unimanual and bimanual MP training improve hand function and sensation in individuals with tetraplegia. Changes in hand function seem to be associated with increased corticomotor map area.