Case Study Report
Population: Adult
Kimberly J Miller, PT, PhD, Canadian Heart and Stroke Foundation Postdoctoral Fellow, Department of Physical Therapy, The University of British Columbia kimberly.miller@ubc.ca
Lara Boyd, PT, PhD, Associate Professor, Department of Physical Therapy, The University of British Columbia lara.boyd@ubc.ca
Carlo Menon, P.Eng, PhD, Associate Professor, Engineering Science, Simon Fraser University cmenon@sfu.ca
S. Jayne Garland, PT, PhD, Department Head, Department of Physical Therapy, The University of British Columbia jayne.garland@ubc.ca
Keywords: Plasticity, Stroke, Rehabilitation Technology, Upper Extremity
Background and purpose: High-frequency repetitive transcranial magnetic stimulation (rTMS) and robotic-assisted intensive movement practice (RW) have previously been applied to improve upper extremity (UE) motor impairments following stroke. However, the effects of combining these interventions are not known. This study investigated the effects of simultaneous application of 5 Hz rTMS, over the ipsilesional primary motor cortex, with robotic-assisted active wrist extension practice (rTMS+RW) on muscle activation of the paretic wrist extensors.
Case description: Four participants with chronic stroke who had poor UE motor recovery (Fugl-Meyer UE scores 8-30) completed 30 trains of rTMS+RW.
Outcomes: Paretic extensor carpi radialis (ECR) and ulnaris (ECU) muscle activity was recorded using two high-density surface electromyography (HDsEMG) 64-channel grids during isometric handgrip contractions. Participants performed two maximal voluntary contractions (MVC) and three ramp-hold contractions to 30% MVC before (PRE) and after (POST) rTMS+RW. Changes in HDsEMG the median amplitudes across grid channels following rTMS+RW were calculated as a percentage of PRE values during the hold phase of ramp-hold contractions. Additionally, motor unit (MU) activity was analyzed to identify MUs present both PRE and POST. Recruitment thresholds (RT) (%MVC), mean firing frequency (MF) of MUs over 2 s in the hold phase and the initial firing frequency (IFF), based on the first four spikes at MU recruitment were calculated. The peak handgrip MVC values were found to increase (16-98%) following rTMS+RW, with increased median HDsEMG amplitudes (ECR 4-39%; ECU 5-24%) observed during POST ramp-hold contractions in three participants. Twenty-five wrist extensor MUs (16 ECR and 9 ECU) were identified as present both PRE and POST. The recruitment thresholds of these MUs PRE were 0.2-30 %MVC. Following rTMS+RW changes in the RT were observed in 22/25 MUs, despite comparable rates of force increase during the ramp phase of the ramp-hold contractions (PRE 3.4 %MVC/s; POST 3.6 %MVC/s, respectively). The RT decreased by a mean of 14 %MVC in 12 MUs, increased by a mean of 3 %MVC in 9 MUs and remained unchanged in 3 MUs following rTMS+RW. The MF increased by a mean of 2 Hz (MF-IFF; n = 25), with larger MF increases (3.5Hz) being observed in the 12 MUs with a lower RT following rTMS+RW. Larger modulations in firing rates (n = 25) were observed over the course of the hold phase of the ramp-hold contractions POST (mean 8.3Hz) compared to PRE (mean 4.2Hz).
Discussion: A single session of rTMS+RW was associated with changes in muscle activation, and associated MU firing behaviour, in the paretic ECR and ECU. These data suggest that improved recruitment and modulation of MU firing after rTMS+RW; however, this was not consistent across all participants. A full-scale crossover study is underway to determine the effects of rTMS+RW. Future work should address which individuals respond best to rTMS+RW after stroke.
Citation:
Miller, Kimberly J, PT, PhD; Boyd, Lara A, PT, PhD; Menon, Carlo , P.Eng, PhD; Garland, S. Jayne , PT, PhD. The effect of combining high frequency repetitive transcranial magnetic stimulation with robot-assisted movement practice on wrist muscle activation following stroke: a case series.. Poster Presentation. IV STEP Conference, American Physical Therapy Association, Columbus, OH, July 17, 2016. Online. https://u.osu.edu/ivstep/poster/abstracts/044_kimberly-et-al/