Research Report
Population: Adult
Kate Frost, MS RCEP, PhD Graduate Student, University of Minnesota jahnk035@umn.edu
Mo Chen, PhD, Scientist, University of Minnesota mchen@umn.edu
Jessica Cassidy, PhD, DPT, Post-Doctoral Fellow, University of Minnesota krea0014@umn.edu
LeAnn Snow, MD, PhD, Assistant Professor, University of Minnesota snow0018@umn.edu
Teresa Kimberley, PhD, PT, Assistant Professor, University of Minnesota tjk@umn.edu
Keywords: Prevention
Purpose/Hypothesis: Noninvasive brain stimulation shows potential for improving post-stroke motor recovery through neuromodulation of cortical excitability. Paired associative stimulation (PAS), an emerging method of noninvasive brain stimulation, induces a long-lasting change in neuronal plasticity by pairing a peripheral nerve stimulus with a cortical stimulus. The timing of these two stimuli is critical. Yet optimal parameters for inhibitory PAS targeting the contralesional hemisphere have not been determined in people with chronic stroke. This pilot study tests the hypotheses that 1) A single individualized interstimulus interval (ISI) will significantly decrease cortical excitability in the contralesional hemisphere and 2) PAS applied to the contralesional hemisphere will not adversely affect cognitive or motor abilities.
Subjects: Three adults (2 female; average age 57.6 ± 5.3 years) with chronic stroke (average 11.6 ± 5.2 years since stroke).
Materials/Methods: In a preliminary effort to determine an ideal ISI and also to evaluate safety, we applied inhibitory PAS at three different ISIs (N20-3ms, N20-5ms, or N20-7ms) targeting the abductor pollicis brevis of the non-paretic hand in three individuals with chronic stroke. A fourth condition (N20+100ms) was used as a control. Change in corticospinal excitability was assessed by comparing the average of 30 motor evoked potentials elicited by single-pulse transcranial magnetic stimulation before PAS treatment and 0, 10, 20, 30, 40, 50 and 60 minutes following treatment. Data analysis included a two-way repeated measures ANOVA to assess differences between conditions and within conditions across time. Demonstration of safety was measured through physician assessment, questionnaire, memory test, as well as non-paretic finger tracking.
Results: Our results showed that there were no adverse events and that PAS induced significant inhibition lasting up to 60 minutes following treatment. However, the precise ISI for optimizing inhibition in the contralesional hemisphere differed between individuals.
Conclusions: PAS effectively and safely induced inhibition in the contralesional hemisphere but individual characteristics may affect optimal treatment parameters. Further investigation of PAS as a method for neuromodulation to promote motor recovery in individuals with chronic stroke is warranted.
Clinical Relevance: Following a stroke, individuals experience an abnormal balance of cortical excitability possibly resulting in maladaptive neuroplasticity. Noninvasive neuromodulation provides a rehabilitative adjunct to rebalance excitability and upregulate activity that may help to optimize subsequent behavioral training. PAS targeting the upper limb holds promise as an evidence-based translational effort to restore sensorimotor activity in the ipsilesional hemisphere and improve paretic arm function in people with chronic stroke.
Citation:
Frost, Kate , MS RCEP; Chen, Mo , PhD; Cassidy, Jessica , PhD, DPT; Snow, LeAnn , MD, PhD; Kimberley, Teresa , PhD, PT. Investigating different interstimulus intervals of paired associative stimulation in people with chronic stroke.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online. https://u.osu.edu/ivstep/poster/abstracts/039_frost-et-al/