MAGNETOENCEPHALOGRAPHIC ANALYSIS OF CORTICAL MYOCLONIC JERKS

We studied the pre-myoclonus spike using magnetoencephalography in pat ients with cortical myoclonus (6 with cortical reflex myoclonus and on e with epilepsia partialis continua), The spike was estimated as a sin gle current dipole on the pre-central gyrus in one patient with epilep sia partialis continua. In contrast, it was estimated as a single dipo le on the post-central gyrus in 5 of 6 patients with cortical reflex m yoclonus, and as two dipoles on the pre- and post-central gyrus in the remaining patient. We conclude that there are 3 physiological types o f cortical myoclonus, (1) abnormal discharges in the motor cortex prod uce the myoclonus; (2) the source of the myoclonus is mainly the senso ry cortex; (3) both the motor and sensory cortices play important role s in the production of myoclonus.