  Epilepsy is recognised as a dynamic disease, where both seizure
susceptibility and seizure characteristics themselves change over time.
Specifically, we recently quantified the variable electrographic
spatio-temporal seizure evolutions that exist within individual patients. This
variability appears to follow subject-specific circadian, or longer, timescale
modulations. It is therefore important to know whether continuously-recorded
interictal iEEG features can capture signatures of these modulations over
different timescales.
  In this work, we analyse continuous intracranial electroencephalographic
(iEEG) recordings from video-telemetry units and find fluctuations in iEEG band
power over timescales ranging from minutes up to twelve days.
  As expected and in agreement with previous studies, we find that all subjects
show a circadian fluctuation in their iEEG band power. We additionally find
other fluctuations of similar magnitude on subject-specific timescales.
Importantly, we find that a combination of these fluctuations on different
timescales can explain changes in seizure evolutions in most subjects above
chance level.
  These results suggest that subject-specific fluctuations in iEEG band power
over timescales of minutes to days may serve as markers of seizure modulating
processes. We hope that future work can link these detected fluctuations to
their biological driver(s). There is a critical need to better understand
seizure modulating processes, as this will enable the development of novel
treatment strategies that could minimise the seizure spread, duration, or
severity and therefore the clinical impact of seizures.
