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

STUDY in man of the relation between the occurrences in the electroencephalogram (EEG) and the muscular jerkings in convulsive states has been limited. Possibly this has been due to the difficulty of anticipating the time of onset of seizures sufficiently often, and with sufficient accuracy. In two types of case this difficulty may be overcome. The first is that in which myoclonic jerkings occur over a period of one or two hours as a prodrome of a major convulsive seizure and the second that in which a wave and spike discharge in the EEG lasts for 24 to 48 hours and is accompanied by muscular jerkings. It is the purpose of this paper to describe the results of repeated examinations of patients with these conditions. Gibbs, Davis and Lennox (1935) showed that in those patients with epilepsy in whom a discharge of wave and spike form appeared in the EEG during a seizure, minor muscular jerkings might occur at the same rate as that of the repetition of the wave and spike complex. They also reported that in the clonic stage of a major convulsive seizure the jerkings of the muscles occurred in time either with slow waves or groups of spikes in the EEG. In neither case was fuller analysis of the temporal relations of the EEG waves and the muscular movements described. Jasper and Andrews (1938) by recording the EEG, muscle action potentials and movements studied the relations between wave and spike discharges in the EEG and the muscular jerkings during minor epileptic seizures. They found that when wave and spike discharges in the EEG were provoked by overbreathing, a burst of muscle action potentials was often associated with each wave and spike complex. In some subjects this correspondence did not occur and from this they concluded that in certain circumstances the control of the motor functions concerned might be taken over by subcortical centres. Recording of the EEG and muscle action potentials has been used by Strauss and Landis (1938) to compare the features of spontaneous convulsions and those produced by cardiazol. They used the method to time the contractions of flexor and extensor muscle groups but they give few details of their results in this connection. During the severe muscular jerkings which occur in myoclonic epilepsy Grinker, Serota and Stein (1938), who studied a group of patients with a hereditary form of this complaint, were able to show that a close correspondence existed during the jerkings between groups of spikelike discharges in the EEG and the muscle action potentials. They recorded the muscle action potentials only from the biceps muscle of the arm and no simultaneous recordings from antagonistic muscle groups were reported. Their records would not allow accurate measurements of the time relations of the individual spikes of a group and any particular phase of the muscular jerkings. Confirmation of the findings of Grinker et al. is given by Jasper (1941) and Gibbs and Gibbs (1941) who also describe groups of spike-like discharges in the EEG in time with the myoclonic jerkings, but in neither case are any facts added about the time relations of the spikes and the jerks. The present investigations have been made on two types of case with myoclonic symptoms during epileptic states. The results of simultaneous recordings during myoclonic attacks of the EEG and muscle action potentials in flexor and extensor muscle groups of the limbs will be described.