The relationship between focal seizures and sleep: An analysis of the cyclic alternating pattern

Purpose:: The aim of this study was to examine the relationship between focal epileptic seizures and sleep through analysis of the cyclic alternating pattern (CAP). Methods:: We analyzed the recordings of a total of 56 nocturnal partial seizures (13 occurring as isolated events and 43 "in clusters" during a full-night ambulatory polysomnography) in 12 adult patients affected by localization-related focal epilepsy (7 males, 5 females; mean age 35 + 12.8 years; range 25-71). Results:: On exact binomial distribution analysis, seizures were more frequent in CAP than in non-CAP sleep, and in CAP phase A than in CAP phase B (p < 0.001). Seizures occurring in clusters were more frequently associated with CAP sleep (p < 0.05) than isolated seizures and first seizures of seizure clusters. Increase of CAP rate during the 30-min of sleep period after the occurrence of a seizure was documented in both cluster and isolated seizures. Conclusions:: Our data indicate that an intra-sleep condition of highly fluctuating vigilance constitutes the real substrate for the occurrence of epileptic seizures regardless of the NREM stage in which they occur. The occurrence of partial seizures during sleep appears to induce sleep instability, which may in turn result in the facilitation of clusters of seizures. Together, these data highlight the potential of sleep fragmentation to modulate intra-sleep seizure occurrence. (c) 2005 Elsevier B.V. All rights reserved.