Abstracts

RATIONALE: How timing information is transferred from the suprachiasmatic nucleus to other regions of the brain to mediate neuronal activity, whether physiologic or pathologic, is largely unclear. Epileptic seizures in animal models and in groups of patients occur in daily patterns, but evidence from individuals is rare. A 57 y.o woman with intractable epilepsy and a well-documented, long term seizure diary provided a unique means to demonstrate how susceptibility to chronobiological modulation varies with brain region. METHODS: Evaluation for epilepsy surgery required intracranial EEG with bilateral intrahippocampal and subdural electrodes. Two independent epileptic foci were revealed, one right hippocampal causing complex, partial seizures, and the other right parietal causing ictal pain of the left hand. Five years of an hour-by-hour seizure diary maintained by the patient and her husband yielded 1009 seizures identified by major symptoms corresponding to those confirmed by EEG. Nonparametric analyses were performed to evaluate the degree of randomness and possible daily patterns of each seizure type. RESULTS: Seizure rate was stationary as determined by simple regression of seizure number and interseizure interval. Approximate entropy analysis determined data were highly ordered by time of day. Seizures from both foci occurred periodically with a dominant period of 24 hours but were out of phase with each other (clock time of phase peak by FFT- nonlinear least squares with 95%CI: temporal 12:10 (10:59 - 14:19), parietal 02:50 (00:28 - 05:12). 573/694 (83%) of temporal lobe seizures compared to 133/315 (36%) parietal seizures occurred between 0700-1900. Beyond ultradian periods most likely from harmonic artifacts of FFT analysis, an infradian rhythm of 18.2 days was resolved in temporal seizures. CONCLUSIONS: These data suggest that neuronal excitation and inhibition, depending on the anatomical system involved in epilepsy, may be differently affected by circadian modulation and confirms daily distributions of seizures demonstrated in groups of patients with limbic and nonlimbic partial epilepsy.