The timing of epileptic seizures may be linked to natural circadian rhythms, which may help to guide future treatment options, new research suggests. In what is believed to be the largest study of individual patients' seizure cycles, researchers found that most seizures followed a circadian rhythm.
Some patients experienced weekly and 3-weekly seizure cycles, and some had a combination of daily, weekly, or longer cycles associated with their seizures. This will help guide therapy, and may ultimately allow more tailored therapies to be provided," Cook said. The study was published in Lancet Neurology.
It has long been suspected that patterns of epileptic seizures exist, but these patterns have been poorly defined, chiefly because no accurate databases of seizure activity over sufficiently long time frames were available.
Our results suggest that seizure cycles are robust, patient specific, and more widespread than previously understood. For the study, the investigators used data from two unique databases of seizure activity. The NeuroVista study captured continuous EEG recordings from intracranial electrodes for up to 3 years in 12 patients.
Seizure cycles occurred in more than 80% of all patients; for 891 of 1118 people using SeizureTracker (80%) and for 11 of 12 of those with EEG recordings (92%), seizures followed a circadian rhythm.
In the SeizureTracker cohort, between 77 (7%) and 233 (21%) of the 1118 patients experienced seizures that followed strong weekly rhythms, with a clear 7-day period. Between 151 (14%) and 247 (22%) patients experienced significant seizure cycles that were longer than 3 weeks.
Seizure cycles were equally common in men and women, and peak seizure rates were evenly distributed across all days of the week. In addition, for about two thirds (64%) of the SeizureTracker study cohort, seizures were associated with more than one type of cycle.
For those whose seizures followed a circadian cycle, peak time of seizures varied as per time of day, but more seizures occurred in the morning (8:00 AM) and evening (8:00 PM). Weekly cycles did not favor any day of the week, but for slightly more patients, seizure rates were higher on Tuesdays and Wednesdays.
Cycling Alterations In Seizure
There is evidence emerging that such slow cycles below well-known circadian rhythms influence both physiological functioning and disease states. It is remarkable that the group of Mark Cook found such long-lasting cycling alterations in seizure propensity over several weeks, which have also been reported in chronic psychiatric diseases," he writes.
Seizure rhythms can vary between individuals, and "identification of this can be a step towards individualized adaptations of treatmet. As present-day state-of-the-art documentation of seizures suffers from problems of correct memorizing by patients, objective means of seizure documentation are presently an object of research.
Some but not all seizure types can already be detected by devices during the night, but major effort is yet needed to provide a complete and reliable seizure documentation. This certainly would have major implications for the steering of treatment.