Abstracts

Rationale: The international seizure classification depends primarily on the mode of seizure onset. Partial onset seizures may become secondarily generalized, whereas generalized onset seizures remain generalized throughout their course. We report the clinical and electrographic features of six patients with generalized epilepsy who had recorded seizures with a generalized onset and subsequent evolution into a focal discharge.Methods: Patients were included if they had strong evidence for generalized epilepsy based on interictal EEG, no focal MRI or exam abnormalities, no consistent focal interictal EEG abnormalities, and recorded seizures that clearly had a generalized EEG onset with subsequent focal evolution. We reviewed these patients' medical records, video-EEG studies, imaging data, and response to treatment. IRB approval was obtained for this retrospective review.Results: Patients were aged 2.5 to 22 at the time of their study. Five were female, one male. All patients were referred for intractable seizures and were admitted for confirmation of the diagnosis and classification of seizure type. Four were thought to have complex partial seizures by history and five of the patients were treated with antiepileptic medications which were not effective against absence or myoclonic seizures. After admission all patients had strictly generalized interictal epileptiform activity. The ictal electrographic onset was with generalized spike-and-slow-wave activity in all seizures. In 4 patients the discharge started with regular three Hz spike-and-wave typical of absence. In two patients the seizures began with irregular and brief spike-and-wave activity. The ictal discharge evolved into bitemporal rhythmic delta activity in one patient, left posterior quadrant polyspike-and-slow-wave activity in two patients, and rhythmic alpha activity in the left posterior temporal area in one patient. The video recorded clinical seizures that began as generalized absence (4 patients) or generalized myoclonic (2 patients). The most common subsequent clinical pattern was prolonged behavioral arrest with mild automatisms and altered responsiveness followed by postictal confusion (5 patients). In one patient mild generalized clonic activity occurred with later focal clonic activity. The seizures tended to be prolonged (only one lasted less than 6 minutes). Of note is that one patient also had isolated typical generalized absence and another isolated typical generalized myoclonic seizures recorded. After treatment with appropriate AEDs, three patients are seizure-free, one had marked improvement, and two had a moderate decrease in seizure frequency.Conclusions: Some generalized-onset seizures can acquire clinical and electrographic focal features and be mistaken for complex partial seizures. However, these seizures can require antiepileptic medications with efficacy to control generalized seizures.