P019 Ipsilesional and contralesional cortical silent period in pediatric stroke: Preliminary reports

Abstract

Question The cortical silent period (CSP) is a transient supression of electromyographic (EMG) activity in a pre-activated muscle after a transcranial magnetic stimulation (TMS) pulse. CSP duration reflects intracortical inhibitory mechanisms. Prolonged lesional and shortened non-lesional CSP durations have been associated with poor functional recovery after adult stroke. However, there are few reports regarding CSP duration in children. Our aims is to characterize ipsilesional and contralesional CSP duration in pediatric stroke. Methods Eight children with congenital hemiparesis due to stroke (4 male, age = 11.75 ± 3.26 years) participated. Surface bipolar electrodes were placed over the affected and non-affected first dorsal interosseous (FDI) muscles. TMS single-pulses were delivered using a Magstin 200 stimulator connected to a 70-mm figure of eight coil over the primary motor cortex, bilaterally. Resting motor threshold (RMT) was determined for the FDI. CSP was assessed at 120% RMT during 20% of FDI maximal voluntary contraction. Results Three children presented without an ipsilesional MEP. Ipsilesional RMT average was 64.8% of maximum stimulator output (MSO) (SD = 9.3; range = 53–75) and 56.7% of MSO (SD = 11.6; range = 38–71) for the contralesional hemisphere. Ipsilesional CSP duration was analyzable in one child, x ¯ = 170.5 ms (SD = 11.4; range = 155.5–196.1) and contralesional CSP duration was found in all 8 children, x ¯ = 118.0 ms (SD = 47.3; range = 62.8–174.9) (Fig. 1 Download : Download high-res image (250KB) Download : Download full-size image ). Conclusion Absence of ipsilesional MEPs has been reported in pediatric hemiparesis and could reflect a persistent or enlarged ipsilateral corticospinal tract projections after stroke. Ipsilesional CSP data was largely unanalyzable (no noticeable CSP) with challenges surrounding the ability of the children to sustain paretic FDI contraction, poor motor control (Fig. 2A) and hand spasticity (Fig. 2B Download : Download high-res image (200KB) Download : Download full-size image ). Reports in typically developing children present with shorter CSP duration (25.5–53.8 ms) than adults (150–300 ms). Our results are similar to previous study with pediatric hemiparesis which showed longer CSP duration in ipsilesional and contralesional hemisphere (Mackey et al., 2014). Longer CSP duration could be related to increased activity of inhibitory interneurons in the motor cortex after a perinatal stroke.