Temporal Distribution Of Focal Seizures Arising From Different Brain Regions

ObjectiveThis study aims to determine whether temporal distribution of seizure occurrence in focal epilepsy is random or not. If it does, we would further investigate the temporal distribution of focal seizures in frontal, temporal or posterior quadrant epilepsy, respectively.MethodsRetrospective analysis was made on 167 consecutive patients with focal epilepsy admitted in the Epilepsy Center, Department of Neurology, Second Affiliated Hospital of Zhejiang University. We recorded the time of onset of epileptic seizures and the state of sleep or wake at that time. Classification of Seizure localization was made based on the findings of patient history, video-encephalography, MRI and PET, and intracranial EEG monitoring if necessary. We set 3 hours for one time epoch; and one day is divided into 8 time epochs. By comparing the number of seizures in each time epoch, we assessed the temporal distribution of epileptic seizures arising from different regions. SPSS 19.0 software was used for statistical analysis. The chi square test was used to test each group of seizures heterogeneity, and the sleep wake state heterogeneity. P<0.05 was set as statistically significant difference.ResultsThis study included frontal lobe epilepsy (56 cases,273 seizures), temporal lobe epilepsy (100 cases,377 seizures) and posterior quadrant epilepsy (11 cases,59 seizures). Non-uniform seizure distributions were observed in the frontal lobes (P<0.01) and temporal lobes (P<0.05). Frontal lobe seizures followed a unimodal distribution, peaking between 4:00 and 10:00 am. Temporal lobe seizures were distributed bi-modally, with the peak in the late afternoon between 16:00 and 19:00; and they more often occurred in awake. Temporal distribution of the seizure arising from posterior quadrant in each time epoch was not statistical different, which is probably due to the smaller sample size.ConclusionFocal seizure occurrence was not random. Frontal lobe seizures more likely occur in the dawn; whereas temporal lobe seizures more likely occurred in the afternoon and in awake.