A magnetoencephalographic study of negative myoclonus in a patient with atypical benign partial epilepsy.
OBJECTIVE
To clarify the neurophysiological mechanism of epileptic negative myoclonus (NM) of a patient with atypical benign partial epilepsy whose NM was completely suppressed with ethosuximide.


METHODS
Polygraphic recordings of whole-head type magnetoencephalography (MEG), EEG and electromyography were made during NM of the bilateral hands. The silent period of 200-400 ms duration in the bilateral biceps muscles was associated with paroxysmal spikes on EEG and MEG. Single equivalent current dipoles (ECD) were calculated for each spike component associated with NM and the estimated generator sources of spikes were superimposed on the patient's head MRI.


RESULTS
The magnetic fields of each peak associated with NM showed clear single dipole pattern and ECDs of each peak were located in the neck and orofacial division of the primary motor cortex.


CONCLUSIONS
Abnormal firing of the neck and orofacial division of the primary motor cortex was associated with NM generation. Taking the beneficial effect of ethosuximide (a T-type Ca2+ channel blocker in thalamic neurons and the corresponding cortex) and the MEG result together, it is suggested that abnormal interaction of the thalamo-cortical network might be closely related to the pathogenesis of NM.
Kubota
Masaya
M
Department of Pediatrics, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. mkmegped@opal.plala.or.jp
Nakura
Michiaki
M
Hirose
Hiroyuki
H
Kimura
Ikumi
I
Sakakihara
Yoichi
Y
D000927:Anticonvulsants / Q000627:therapeutic use; D002648:Child; D004292:Dominance, Cerebral / Q000502:physiology; D004569:Electroencephalography / Q000187:drug effects; D004831:Epilepsies, Myoclonic / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D004828:Epilepsies, Partial / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D005013:Ethosuximide / Q000627:therapeutic use; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015225:Magnetoencephalography; D009044:Motor Cortex / Q000187:drug effects / Q000503:physiopathology; D009415:Nerve Net / Q000187:drug effects / Q000503:physiopathology; D013788:Thalamus / Q000187:drug effects / Q000503:physiopathology
D000927:Anticonvulsants; D005013:Ethosuximide