RELATIONSHIP OF INTERICTAL EPILEPTIFORM DISCHARGES TO SLEEP DEPTH IN PARTIAL EPILEPSY

Non-rapid eye movement (NREM) sleep activates interictal epileptiform discharges (spikes) in many epileptic syndromes. To define this phenom enon more precisely, we studied the relationship of spikes to absolute log delta power (LDP), a continuous measure of sleep depth, in 8 pati ents with partial epilepsy. LDP differed significantly across visually scored sleep stages. Logistic regression analyses of spike occurrence in relation to LDP were carried out on the central-occipital channel contralateral to the dominant spike focus (C4-O2 for left and C3-O1 fo r right temporal focus). Within NREM sleep, spikes were more likely to occur: (1) at higher levels of LDP, (2) on the ascending limb of LDP, and (3) with more rapid rises in LDP. Spike frequency per minute was 4.6 times higher in NREM than in rapid-eye movement (REM) sleep and di minished with time from sleep onset. When the effect of LDP was contro lled for in the analysis, however, there was no significant effect of REM sleep stage or time on spike occurrence. Only 1% of spikes occurre d within 10 a of an arousal. These findings suggest that processes und erlying the deepening of NREM sleep may contribute to spike activation in partial epilepsy. (C) 1997 Elsevier Science Ireland Ltd.