Seizure Occurrence and Interspike Interval

Abstract

The distribution of interictal spikes and the frequency and time of occurrence of seizures were examined from twenty 17 to 72-hour continuous electroencephalograms recorded by radiotelemetry from five patients with epilepsy and behavior disorders. Power spectral analysis of spike incidence over time indicates that there is waxing and waning of interictal spike or spike-wave activity both day and night at periods harmonically related to 90 minutes. Seizure occurrence was noted to be systematically related to this spike cycle. Spontaneous and induced decrements in the mean interictal spike rate were followed by rebound in the abundance and duration of spike bursts. The time of occurrence of clinical seizures appears to be determined by the interaction of interictal spike rate, a 90-minute cyclic suppression of same and sensory, including affective, stimuli.