Dual epileptic foci in a single patient express distinct temporal patterns dependent on limbic versus nonlimbic brain location.

How timing information is transferred from the suprachiasmatic nucleus to other regions of the brain to mediate activity, either physiological or pathological, is largely unclear. A patient with medically refractory epilepsy and a well-documented, long-term seizure diary provided a unique means to demonstrate how susceptibility to chronobiological modulation varies with brain region. Evaluation for epilepsy surgery disclosed two independent epileptic foci, one limbic and the other nonlimbic. Seizures from both foci occurred periodically with a dominant period of 24 hours but were out of phase with each other. Temporal lobe seizures occurred maximally in the light portion of the daily light-dark cycle, and parietal lobe seizures occurred nocturnally and out of phase with limbic seizures. These data suggest that neuronal excitation and inhibition, depending on the anatomical system involved in epilepsy, may be differently affected by circadian modulation.