The correlation between transcranial magnetic stimulation parameters and neuromuscular properties in children with cerebral palsy

We studied the correlation between corticospinal signaling and neuromuscular properties in children with Cerebral Palsy (CP). Corticospinal signaling was evaluated using Transcranial Magnetic Stimulation (TMS). Neuromuscular properties were quantified using Hoffmann reflex (H-reflex), sonoelastography, clinical measurements, and isokinetic measures. In particular, we determined the relationship between the TMS parameters of the ankle joint and the neuromuscular features of ankle extensors and flexors as well as popular clinical measures of gait speed, endurance, balance and mobility. Seventeen CP patients and twelve healthy control subjects were evaluated. Our findings showed that the motor evoked potential (MEP) latency of TMS was significantly longer in CP than in healthy subjects. The MEP-latency was significantly correlated with the H-reflex response (r=0.71, p-value=0.04) and isokinetic features; i.e. max acceleration extension time (r=0.5, p-value=0.005), and max flexion time in the cycle (r=0.5, p-value =0.002). No significant correlation was observed between MEP-latency and clinical measurements of gait and sonoelastography of ankle muscles. The results suggest that the changes in corticospinal signaling could contribute to muscle weakness and hyperexcitability of reflexes observed in children with CP.