Abstracts

Rationale: Seizures are classified into focal and generalized seizures with absence epilepsy as the prototype for the genetic epilepsies with generalized seizures. Focal seizures often evolve to convulsions. Generalized seizures commonly display lateralizing semiologies however generalized seizures that undergo focal evolution are rare. We report 2 patients with typical absence seizures that evolved to focal temporal seizures. Methods: We retrospectively identified 1 adult and 1 pediatric patient following retrospective review of 2 large databases at 2 academic medical centers obtained from elective video-EEG monitoring. Patients were admitted for uncontrolled seizures and evaluated over 1-3 days to classify the mechanism for recurrent staring that was unresponsive to AEDs. Interictal and ictal recordings were obtained using continuous video-EEG monitoring. Clinical, neuroimaging, EEG, and treatment was analyzed.Results: The two patients had typical absence seizures suggested by their history and later confirmed by vEEG. Seizure onset occurred at 7 and 9 years of age with multiple brief daily episodes of staring leading to the diagnosis of childhood absence epilepsy. A delayed onset of a 2nd type of staring episode was noted prompting vEEG for classification. Each had staring episodes that became prolonged lasting 30 seconds to 1 minute associated with oral automatisms and post-ictal confusion and lethargy. Patient 1 also had grand mal seizures that began after puberty. Both patients had normal general and neurological examinations. No family history of epilepsy was present and no risk factor for focal seizures was noted in either case. Brain MRIs with an epilepsy protocol were normal without focal lesions. Absence seizures were the primary seizure type in both cases though patient 1 was taking OXC and patient 2 CBZ. Frequent interictal bursts of generalized bifrontally predominant regular 3-3.5 Hz generalized spike-and-waves were noted that were state independent. The electrocerebral background activity was normal without focal or lateralizing features on interictal EEG. Recurrent electroclinical absence seizures lasting 5-10 seconds were characterized as brief staring associated with sustained bursts of 3-3.5 Hz generalized bifrontally predominant spike-and-waves during impaired responsiveness. Clinical features were typical absence without aura or post-ictal state. Focal seizures were noted to evolve from a typical absence in each case. One patient evolved into a convulsive seizure. Patient 1 was drug-resistant to broad spectrum AEDs and became nearly seizure free with Phenobarbital. Patient 2 became seizure free when VPA was substituted for CBZ. Conclusions: Absence seizures may undergo ictal transformation to focal temporal seizures. Misclassification may result in mistreatment with an inappropriate use of narrow-spectrum AEDs which may aggravate seizures. The intrinsic epileptogenicity of the temporal lobe may predispose thalamic synchronization of ictal discharges to focal temporal evolution of absence seizures in the presence of CBZ products to function as a default brain region.