Relationship of Interictal Epileptiform Discharges to Seizures during Sleep.
Abstract number :
1.091
Submission category :
Year :
2001
Submission ID :
492
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
A. Natarajan, MS, Biostatistics, University of Michigan, Ann Arbor, MI; M.L. Marzec, BS, Neurology, University of Michigan, Ann Arbor, MI; C. Milling, MD, Neurology, University of Michigan, Ann Arbor, MI; X. Lin, PhD, Biostatistics, University of Michigan
RATIONALE: Whether interictal epileptiform discharges increase, decrease, or are unchanged prior to epileptic seizures has implications for the pathophysiology of epilepsy. Although prior studies of the relationship between IEDs and seizures have not demonstrated a change in IEDs prior to seizures, they have not controlled for the depth of sleep. Our objective is to test the hypothesis that IEDs are related to seizures during sleep while adjusting for log delta power (LDP), a measure of sleep depth.
METHODS: Consecutive records were reviewed to identify 32 seizures during sleep in 18 subjects with epilepsy admitted for presurgical monitoring. The IEDs that occurred in the hour of sleep prior to each seizure were used to test the relationship between IEDs and seizure occurrence. Periods of wakefulness were excluded. Some patients were observed over two nights. Sleep depth was measured by log delta power (quantity of 1-4 Hz activity in 30-second epochs) and records were scored visually for sleep staging (MM) and for IEDs (BAM; MM confirmed IEDs in portion of recordings). Multivariate logistic regression analyses based upon generalized estimating equations (GEEs) were implemented for three groups: all seizures, all seizures excluding rapid eye movement (REM) sleep and wake periods, and a subset of 17 seizures with continuous NREM sleep the hour prior to the seizure.
RESULTS: Using all the seizures, and adjusting for log delta power, the number of seizures prior to the current seizure, which night was observed (the first or second), the quartile of the night, and the total number of IEDs that occurred during the night, IEDs did not increase or decrease prior to seizures (p=.43). Similar findings held for analyses using only NREM sleep epochs and analyses using only continuous NREM sleep prior to the seizure (p=.79 and p=.88, respectively). The rate of IEDs increased directly with LDP (p [lt] 0.0001), as shown in prior work (Malow et al., Epilepsia 1998; 39(2):1309-1316).
CONCLUSIONS: IEDs are not increased or suppressed prior to seizures during sleep, suggesting that different pathophysiological processes underlie these two phenomena. These results corroborate several past studies, while providing a more advanced analysis by adjusting for sleep depth and applying the method of generalized estimating equations.
Support: NINDS KO2 NS02099.