[Motor cortex stimulation for Parkinson's disease and dystonia: lessons from transcranial magnetic stimulation? A review of the literature].
BACKGROUND
Over the last few years, deep brain stimulation techniques, with targets such as the subthalamic nucleus or the pallidum, have bee found to be beneficial in the treatment of Parkinson's disease and dystonia. Conversely, therapeutic strategies of cortical stimulation have not yet been validated in these diseases, although they are known to be associated with various cortical dysfunctions. Transcranial magnetic stimulation (TMS) is a valuable tool for non-invasive study of the role played by the motor cortex in the pathophysiology of movement disorders, in particular by assessing various cortical excitability determinants using single or paired pulse paradigms. In addition, repetitive TMS (rTMS) trains can be used to study the effects of transient activity changes of a targeted cortical area.


BACKGROUND
Studies with TMS revealed significant motor cortex excitability changes, particularly regarding intracortical inhibitory pathways, both in Parkinson's disease and in dystonia, and these changes can be distinguished owing to the resting state or to the phases of movement preparation or execution. However, more specific correlation between electrophysiological features and clinical symptoms remains to be established. In addition, the stimulation of various cortical targets by rTMS protocols applied at low or high frequencies have induced some clear clinical effects.


CONCLUSIONS
The TMS effects are and will remain applied in movement disorders to better understand the role played by the motor cortex, to assess various types of treatment and appraise the therapeutic potential of cortical stimulation.


CONCLUSIONS
TMS provides evidence for motor cortex dysfunction in Parkinson's disease or dystonia. Moreover, rTMS results have opened new perspectives for therapeutic strategies of implanted cortical stimulation. By these both aspects, TMS techniques show their usefulness in the assessment of movement disorders.
Lefaucheur
J-P
JP
Service de Physiologie, Explorations Fonctionnelles, Hôpital Henri Mondor, Créteil. jean-pascal.lefaucheur@hmn.ap-hop-paris.fr
D046690:Deep Brain Stimulation; D004421:Dystonia / Q000628:therapy*; D004599:Electric Stimulation Therapy; D004567:Electrodes, Implanted; D004574:Electromagnetic Fields; D006801:Humans; D009044:Motor Cortex / Q000502:physiology* / Q000503:physiopathology; D010300:Parkinson Disease / Q000503:physiopathology / Q000628:therapy*