[Transcranial magnetic stimulation (TMS) in movement disorders].
Transcranial magnetic stimulation (TMS) has been used to study several aspects of movement disorders: central motor conduction time (CMCT), electromyographic (EMG) silence evoked by TMS, reset of tremor rhythm by TMS, GABAergic inhibitory interneuronal function of the motor cortex studied with paired-pulse TMS. In this communication, We briefly summarize results of paired-pulse TMS in movement disorders.
A subthreshold conditioning stimulus over the motor cortex reduced the size of EMG responses to a succeeding suprathreshold test stimulus given to the same motor cortex. This inhibition is considered to be an inhibitory effect on the motor cortex because the same conditioning stimulus has no influence on H-reflexes or electrical cortical responses. Pharmacological effects on this inhibition suggested that it is mediated by GABAergic inhibitory systems in the motor cortex.


METHODS
The cortical inhibition was reduced in cortical myoclonus, which is consistent with the notion that the studied effect is mediated by GABAergic systems. The inhibition was disturbed in focal dystonia, whereas normal inhibition was elicited in Segawa's disease. Reduced inhibition was seen in Parkinson's disease (PD), whereas normal inhibition in essential tremor. Normal inhibition was evoked in all patients with chorea. Abnormal inhibition in basal ganglia disorders must reflect damaged movement selection in the motor cortex secondary to the primary lesion in the basal ganglia. This abnormality occurs in some movement disorders and does not occur in the others, which indicates different pathomechanisms for involuntary movements. It is conspicuous that normal inhibition was evoked in Segawa's disease even though the patients had dystonia.
Ugawa
Y
Y
Department of Neurology, Tokyo University School of Medicine.
Hanajima
R
R
D001479:Basal Ganglia / Q000503:physiopathology; D006801:Humans; D009044:Motor Cortex / Q000503:physiopathology*; D009069:Movement Disorders / Q000209:etiology / Q000503:physiopathology*; D009433:Neural Inhibition; D009474:Neurons / Q000502:physiology; D010812:Physical Stimulation / Q000379:methods; D050781:Transcranial Magnetic Stimulation; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D005680:gamma-Aminobutyric Acid