THE RELATION BETWEEN THE ELECTROENCEPHALOGRAM AND MUSCLE ACTION POTENTIALS IN CERTAIN CONVULSIVE STATES

Abstract

Repeated simultaneous eeg tracings and appropriately placed electromyographic tracing in 2 patients with myoclonic epi lepsy and in 1 with mild myoclpnic twitches accompanied by almost continuous spike and wave activity are described. The recording and amplification techniques are de -scribed in detail. Ink writers at speeds up to 9 cm./sec. with some checks with cathode ray oscilloscopes for wave forms of higher frequencies were used. All 3 patients showed some form of "spike" discharge with or without a slow wave in the interseizure record. During the seizures, the patients with the severe myoclonic jerking exhibited "spikes" whose duration was 30 to 75 mille sec. and at a rate of 8-13/sec. There was an accurate correlation between the occurrence of the "spike" discharges in the eeg and action potentials of the muscular jerkings in the severe cases and a less accurate correspondence in the 3d patient with milder jerking. The muscle action potentials show recruitment and facilitation. The time course of decay is longer for flexor than extensor muscles. During interseizure periods changes in spinal reflex excitability have been demonstrated. During this period, a knee jerk will be followed after an interval of 80-180 mille sec. by a 2d jerk which may involve the antagonist as well as the muscle stimulated. The electromyograph of the 2d jerk is always more complex than that of the primary reflex. No change in theeeg tracing is produced in this stage of excitation. During the prodromata before an episode of frequent spontaneous myoclonic seizures, elicitation of tendon reflexes is followed by a generalized myoclonic jerk of the same type as those occurring spontaneously. Other sudden sensory stimuli are also effective. Here eeg changes are also elicited by the sensory stimulation. This stage is comparable to an animal in subconvulsant intoxication with a con-vulsant drug. The following differences between the myoclonic epilepsy described above and the patient with continuous spike and wave activity and mild muscular jerking are: (1) The jerking movements in the latter type are usually accompanied by more complex myographic records of longer duration; (2) the time relation between the myographic trace and eeg is more variable; and (3) the muscle action potential is about 1/50 of that seen in the first 2 cases.