Interhemispheric interaction between the hand motor areas in patients with cortical myoclonus.
OBJECTIVE
To study interhemispheric interaction between the hand motor areas of both hemispheres through the corpus callosum in myoclonus epilepsy.


METHODS
Five patients with benign myoclonus epilepsy and ten age matched normal volunteers.


METHODS
We studied effects of a medially directed conditioning stimulus over the right hand motor area on responses in the right first dorsal interosseous muscle to a posteriorly directed test stimulus over the left hand motor area.


RESULTS
In normal subjects, inhibition was evoked at interstimulus intervals (ISIs) of 8-20ms (late inhibition). In contrast, facilitation occurred in patients at ISIs of 4-6ms (early facilitation) with no late inhibition.


CONCLUSIONS
The lack of late inhibition in the patients is consistent with the idea that cortical inhibitory interneurones are affected in myoclonus epilepsy. We propose that this releases interhemispheric facilitation from powerful surround inhibition. The consequence is a predominant early facilitation between the hemispheres in patients with myoclonus epilepsy.
Department of Neurology, Division of Neuroscience, Graduate School of Medicine, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
R
R
Hanajima
Y
Y
Ugawa
S
S
Okabe
K
K
Yuasa
Y
Y
Shiio
N K
NK
Iwata
I
I
Kanazawa
D003337:Corpus Callosum / Q000503:physiopathology; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography; D004831:Epilepsies, Myoclonic / Q000503:physiopathology*; D006225:Hand / Q000294:innervation / Q000502:physiology; D006801:Humans; D008280:Magnetics / Q000295:instrumentation; D016555:Matched-Pair Analysis; D009044:Motor Cortex / Q000503:physiopathology*; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009433:Neural Inhibition; D013997:Time Factors