Abstracts

Rationale: Previous studies of the temporal distribution of seizures in women with localization-related epilepsy have determined that seizures occur periodically according to a menstrual “clock” with the peak phase of occurrence corresponding to menstrual onset. In the present study, we determined whether certain epilepsy characteristics including the lobar location and laterality of the epilepsy impact the periodicity. Methods: Baseline, pretreatment data from seizure and menstrual diaries of ~ 3 months duration were obtained from women enrolled in a trial of hormonal therapy for localization-related epilepsy. To group seizure data, durations of individual cycles were normalized to a common menstrual phase and period. The start for each cycle was identified as the onset on menstrual bleeding (day 0). Intervening days were then converted to 28 normalized cycle days. Normalized time series were then combined to create mean seizures per menstrual day evaluated by localization (lobar: temporal (TL), extratemporal(XL), multifocal(MF), unknown) and lateralization (left, right, bilateral, unknown). Nonrandom temporal distributions (evaluated with ANOVA) were curve-fitted with nonlinear least squares cosinor analysis. Results: Of 100 patients, 71 had TL (left=25, right=29, bilateral=17), 10 XL, 14 MF, and 5 unknown seizure foci. XL and MF seizures occurred randomly across the 28 day cycle. TL seizures (left=875, right 706) occurred nonrandomly (ANOVA p=0.0003) and cyclically with peak occurrence near onset of menses ((value±standard deviation) peak=1.6±2.3 days, period=27.0 days). Whereas left-side TL seizures occurred maximally and cyclically at onset of menses (ANOVA p=0.04, peak=0.0±3.0 days, period=30 days), right side TL seizures occurred randomly. Conclusions: This study determined that the circalunar rhythms of seizures in women vary with the neuroanatomic substrate of the seizure focus. Temporal lobe seizures, especially left-sided foci, are more susceptible to circalunar rhythmic occurrence than those arising from XT or MF foci.