The impact of sleep characteristics and epilepsy variables on memory performance in patients with focal seizures

Abstract

Disturbed sleep can negatively affect overnight memory retention as well as new learning the subsequent day. In healthy participants, positive associations between memory performance and sleep characteristics (e.g., time spent in slow-wave sleep [SWS]) have been detected. In a previous study, we found that SWS was much reduced in patients with focal seizures, but when correlations between memory complaints and various sleep characteristics were considered, the only significant relationship was with the time to onset of rapid eye movement (REM) sleep (i.e., REM latency). In this study, we investigated the relationships between sleep, epilepsy, and objective memory performance variables. Twenty-five patients with focal seizures had their memory tested while undergoing a two-day ambulatory electroencephalography (EEG). The sleep variables of interest were the percentage of time spent in SWS (%SWS) and REM latency. Epilepsy variables included the presence of (1) seizures, (2) interictal epileptiform discharges, and/or (3) hippocampal lesions as well as site of seizure origin (temporal vs extratemporal). Overnight retention (of autobiographical events, a story, and a complex geometric figure) and the ability to learn a word list on day 2 were the measures of memory. A significant positive correlation was found between word-list learning and %SWS during the previous night. A significant negative correlation was observed between REM latency and overnight retention of autobiographical events. Overnight retention scores for the story and geometric figure were not related to sleep characteristics but were negatively affected by the presence of epileptiform activity. Story retention was also worse for temporal lobe epilepsy (TLE) than for patients with extratemporal epilepsy (ETE). Those with hippocampal lesions were more impaired than those without lesions on word-list learning, autobiographical events' retention, and story retention. When multiple contributing factors were entered into regression analyses, %SWS was found to be the best predictor of subsequent word-list learning, whereas the presence of a hippocampal lesion was the best predictor of overnight retention of autobiographical events and a story. These findings provide further evidence of the ways in which particular sleep characteristics are associated with memory and suggest that treatment of sleep disturbances in patients with epilepsy might be helpful for improving their performance.

Quantitative spatio-temporal characterization of epileptic spikes using high density EEG: Differences between NREM sleep and REM sleep

“…The majority of mortality and morbidity occurs in 30-40% of patients with medication refractory epilepsy 2 . The presence of epileptic spikes has also been correlated with negative cognitive consequences 3,4 . Epilepsy surgery has been shown to be an effective treatment for medication refractory patients, if the epileptogenic zone (EZ) can be correctly identified 5 .…”

Effects of Antiepileptic Drug Tapering on Episodic Memory as Measured by Virtual Reality Tests

“…In patients with epilepsy, many factors may have a negative influence on memory performance (39). There is evidence for the negative influence of pathological changes in the brain (40), genetic background (41,42), age at onset (43), duration of epilepsy (44,45), epilepsy-specific disturbances of sleep (46), psychosocial consequences of the disorder, including lower levels of education and poor social integration (47,48), and seizures (6). Our results suggest that the effect of drugs should be taken into account when examining the influence of other factors.…”

Accelerated long‐term forgetting in focal epilepsy: Do interictal spikes during sleep matter?

“…Even in patients with ALF, a beneficial effect of sleep on memory performance has been observed. [77][78][79][80] Comparing verbal memory performance after either 12 h of wakefulness or 12 h of sleep in controls and patients with epilepsy-related ALF, Atherton et al 77 showed a significant interaction between sleep condition and performance in both patients and controls (F =20.15, p < .001). In addition, they found a significant interaction in the group of patients (F =7.73, p = .019) independently from the controls.…”