Drowsiness

Patients with epilepsy are probably more susceptible to the cognitive and functional consequences of sleep disruption than the general population. The most common consequence of sleep disruption in patients with epilepsy is drowsiness. While most often a nuisance, drowsiness can potentially have life threatening ramifications as it increases the likelihood of accidents, especially motor vehicle related accidents. Therefore, it is essential that patients with epilepsy who are legally able to drive understand the impact that sleep disruption can have on daytime drowsiness and the potential dangers that can result. It is also important to note that patients with fully controlled seizures can still have disrupted sleep due to coincident sleep disorders or seizure medications (discussed below).

Memory

Besides adversely affecting attention, sleep disruption can have an effect on memory. Although the exact function of sleep remains unclear, there is growing evidence that sleep, and REM and/or slow wave sleep in particular, are required for optimal cognitive function. Sleep loss has been clearly documented to affect both cognitive and procedural skills, particularly when chronic. There are recent studies showing that chronic sleep restriction by as little as 2 hours per night can severely impair neurobehavioral functions in normal individuals over a one-to two-week period of time. This makes sense as most of us are able to function relatively well after one or two nights of disrupted sleep. We then feel the need to “catch up” and sleep longer for one or more nights. If sleep disruption continues for many nights, however, we can feel our abilities diminishing.

It may be that specific stages of sleep are more important than others. Both REM and slow wave sleep are considered to be “essential sleep”, and subjects who are deprived of sleep (at least in the short term) will “rebound” or make up most of the REM and slow wave sleep that are lost. Very little stage 1 or 2 sleep is regained. Although the function of REM sleep remains speculative, there is considerable information suggesting that increased REM is correlated with enhanced learning of certain tasks. Additionally, enhancement of REM sleep occurs with drugs useful in Alzheimer’s disease. Increased slow wave sleep has also been correlated with certain types of learning in one human study.

Patients with epilepsy frequently have problems with memory and other aspects of cognitive functioning. While there may be multiple reasons for these problems, sleep disruption could be a potentially correctable cause, and therefore medical evaluation for a possible sleep disorder should be considered under these circumstances.

Topic Editor: Carl Bazil, M.D.
Last Reviewed:10/01/05