Abstracts

Rationale: Parasagittal and mesial lobe epilepsies present diagnostic and therapeutic challenges during presurgical evaluation. This is particularly so when nonlesional, where only a single modality of investigation such as scalp electroencephalogram (EEG) or metabolic scan showed potential foci. This study evaluated the clinical semiology and EEG characteristics of epilepsies at any antero-posterior location within the mesial and or parasagittal locations. Methods: Eighty patients with parasagittal and or mesial hemispheric epilepsy confirmed by scalp and or subdural EEG and or imaging evaluated from January 1973 till December 2008 defined this cohort. Inclusion criteria : (a) Lesion on the mesial surface of cerebral hemisphere and or (b) physiological evidence of mesial epileptogenesis, (c) mesial coverage with more than 2 electrodes, (d) sagittal spikes or seizures on scalp EEG .Exclusion criteria: (a) epileptogenic lesion in other lobes,(b) seizures not of sagittal or parasagittal origin,(c) seizures of undetermined origin. Results: There were 51 males and 29 females, age range 3-57 years (SD 24.9 +/-11.6).Seizures arose exclusively from the parasagittal regions in 19/80 (23.8%) and from the mesial regions in 28/80 (25%).Over 90% had motor seizures; history and or videotelemetry disclosed asymmetrical motor features in 55/80 (68.8%). Visual phenomena heralded 15 of 20 (75%) of mesial occipital seizures, but occurred very rarely elsewhere. Seizures arose simultaneously in mesial and parasagittal regions in 33/80 (41.25%) of this series. Conclusions: As mesial hemispheric-parasagittal seizures arising anywhere from anterior frontal to occipital areas share many common features, subdural EEG and imaging are essential for precise localization of epileptogenesis.