T126. Mapping contralesional motor cortex using robotic transcranial magnetic stimulation in children with perinatal stroke

Abstract

Introduction Children with perinatal stroke have motor deficits lateralized to one side of the body (hemiparetic cerebral palsy, HCP). Motor control of the affected limb often resides in the contralesional hemisphere with preservation of ipsilateral corticospinal connections. Intensive therapies can improve hand function but mechanisms and predictors of response are unknown. Individualized maps of the motor cortex may provide insight but only two studies have examined this where manual motor mapping was tedious and potentially insensitive. This study aimed to determine the feasibility of using robotic transcranial magnetic stimulation (TMS) motor mapping to better characterize integrated motor maps of the contralesional hemisphere and their association with clinical function. Methods Ten children with unilateral perinatal stroke and HCP (aged 8–19 years) participated in a randomized controlled, double-blinded clinical trial. Children were engaged in a 2-week, goal-directed, child-friendly intensive intervention (constraint and bimanual therapies). Children were randomized to receive 20 min/day of contralesional motor cortex (M1) transcranial direct current stimulation (tDCS) or sham (1:1). Robotic TMS (Axilum Robotics) applied 4 single-pulses to each target on a custom map (12 × 12, 7 mm spacing) over the motor cortex at baseline and within one-week after intervention. Surface electromyography was recorded in bilateral first dorsal interosseous (FDI). Primary neurophysiological measures included the percentage overlap (sites inducing a motor evoked potential (MEP) in both FDI/sites inducing an MEP in the affected FDI), and area of bilateral FDI maps. Clinical outcome was assessed with the Jebsen-Taylor Test of Hand Function (JTTHF). Paired t-tests were performed to examine therapy-associated changes in all measures. Results All children completed the intervention. Two children with incomplete clinical assessments were excluded. Contralesional motor maps were successfully probed by using TMS robot. Motor map parameters did not correlate with clinical scores at baseline (p > 0.1). Percentage overlap of bilateral FDI in the contralesional M1 did not change (n = 7, baseline = 74.5 ± 29.5%, post = 71.7 ± 27.1%, p = 0.86). Averaged motor map areas of unaffected FDI may have increased from 1245 ± 854 mm2 at baseline to 1583 ± 981 mm2 after intervention (n = 10, p = 0.21). Motor map areas of the affected FDI did not change after intervention (n = 7, baseline = 1365 ± 951 mm2, post = 1358 ± 844 mm2,p = 0.98). On average, children moved 23.5 ± 20.8 s faster (12.6 ± 9.6%) with the more-affected hand in JTTHF after intervention (p = 0.02). Change in performance was not associated with change in motor map parameters. Conclusion Our preliminary findings demonstrated that it is feasible to study motor map characteristics using a TMS robot in children with HCP. The utility of using such motor maps as biomarkers to understand and predict treatment outcome will become clearer with completion of larger samples within this and other trials.