An Electroencephalographic Study of Nocturnal Sleep in Temporal Lobe Epilepsy

Summary A whole night EEG study was carried out on twenty temporal lobe epileptics and fourteen normal subjects. ECG, respiratory curve, GSR and horizontal eye movements were also simultaneously recorded polygraphically. Primary attention was devoted to the changes of temporal spikes in different stages of nocturnal sleep and also to the characteristics of sleep course of the patients. The electrographic depth of sleep was divided into the following five stages; A (wakefulness), B (drowsiness and light sleep), C (moderately deep sleep), D (deep sleep) and P (paradoxical phase of sleep or REM sleep). The sleep diagrams were drawn on all the patients and the rate of incidence of spike discharges throughout a whole night was demonstrated in each stage of sleep on seven patients. As to the pattern of sleep cycles during a whole night, the majority of twenty patients with temporal lobe epilepsy showed some disorganizations of the pattern of sleep cycles to more or less degree. Although there were great individual differences, the most characteristic features observed on the sleep course of the patients were prolongation and frequent appearance of C stage, shortening or poor appearance of D stage and irregular appearance of P stage. These changes were observed more remarkably in younger patients. The disorganizations of sleep cycles observed on temporal lobe epileptics seemed partly due to the dysfunctions or lesions of limbic system of the brain. Spindle‐formed rhythmical waves with frequencies ranging from 8 to 12 c/s were found during C stage of the patients. The lower voltage of delta waves during the deepest stage of sleep and the poor appearance of humps during light stage of sleep were also observed. The most frequent incidence of temporal spikes was observed during C stage on most of the patients. Only a few patients showed the most frequent incidence of spikes during B stage. No clear correlation was found between the types of the incidence of spike discharges and etiological or clinical factors. During P stage, spike discharges were generally suppressed as well as during A stage in most of the patients. On the patients with bilateral multifoci, the mode of incidence of spikes during sleep almost the same in both hemispheres. Nine clinical seizures were observed on seven patients during nocturnal recordings. Two seizures occurred during C stage, three during D stage, three during P stage and one during B stage. On a female patient, three seizures were provoked during B stage and P stage in one night. So the predilected depth of sleep for nocturnal seizures was never found in this study. After clinical seizures, the depth of sleep did not alter, the patients did not generally awake and could not remember their nocturnal fits next morning. Ictal EEG patterns were rhythmic slow waves started at the region of the EEG spike focus with a exception of a case which showed irregular spike and wave complex. The neuronal mechanisms underlying the modifications of incidence of spike discharges during sleep were discussed in terms of interrelation between the activity level of the brain and the mechanism producing seizure discharges.