Dynamic course of intracortical TMS paired-pulse responses during recovery of motor function after

Background. Recovery of motor function after stroke may be associated with changes in inhibitory and facilitatory circuits within the motor cortex. Objective. We explored such changes longitudinally after stroke, using transcranial magnetic stimu-lation (TMS). Methods. Subjects (N = 27) with a single cere-bral infarction affecting movement of either hand were studied at <10 days poststroke, 1 month, and 6 months. Age-matched control subjects (N = 9) were studied at 2 times. Results. In contrast to previous studies, paired-pulse inhibition was increased in patients with a subcortical stroke compared to control subjects. After a cortical stroke, paired-pulse facili-tation was also increased. Stroke location affected the time course of inhibition. Subcortical stroke resulted in increased inhibition initially that decreased over time, whereas cortical stroke had no significant effect on inhibition and a more immediate and lasting effect on facilitation. Conclusions. The time course of a decline in inhibition based on TMS after sub-cortical stroke followed the gain in motor recovery. Increased facilitation in cortical stroke patients is more likely to repre-sent the effect of early cortical circuit disruption and may not play a role in subacute changes in motor function. Key Words: Motor recovery—Transcranial magnetic stimula-tion—Human—Stroke