Corticospinal disinhibition in paroxysmal kinesigenic dyskinesia

Objective To investigate the underlying mechanism responsible for paroxysmal kinesigenic dyskinesia (PKD). Methods We performed a transcranial magnetic stimulation (TMS) study in 12 drug-naïve patients with PKD and 10 healthy volunteers. TMS parameters included resting motor threshold, recruitment curve of motor evoked potential amplitudes, short intracortical inhibition and facilitation, long intracortical inhibition (LICI), and silent period. We also measured compound muscle action potential. Results LICI, representing GABA-mediated inhibition, was significantly reduced in the patients (P=0.033), while results for all other TMS parameters tested were comparable between the two groups. Conclusions and significance These results suggest that a specific type of corticospinal inhibitory mechanism is impaired in patients with PKD.