Abstracts

Rationale: Evolution of seizures from focal spikes to generalized 3 Hz spike-wave complexes (SWC) is an uncommon electrophysiological pattern; reported, for example, in 3 patients with Gastaut type childhood occipital lobe epilepsy by Caraballo (2005). While assessing the origin of this phenomonon in a patient, it is important to distinguish secondary bilateral synchrony vs two separate epilepsy syndromes in the same patient, since the therapeutic stragegy often hinges on this distinction. We present two pediatric patients who showed electrophysiological seizure propagation patterns that included 1) symmetrical, or bilaterally synchronous from onset SWCs, 2) focal activity which progressed to generalized 3 Hz SWC seizures. These cases illustrate the sometimes close relationship in children between a focal epileptogenic area and generalized discharges. Methods: Case 1: A 10-year-old boy, whose seizures started at the age of 6. Seizure frequency was about 5 per day and semiology consisted of either dialeptic (absence-like) seizures or abdominal aura evolving to automotor seizures. MRI showed a small mass in the left medial temporal structures, which was subsequently resected (see Figure). Case 2: A 9 year-old girl, whose seizures started at the age of 5, and became intractable by the age of 7 years. The patient had a history of very frequent dialeptic seizures ranging from 5 to 100 per day. Development and neuropsychological function were within the expected range for the patient s age. MRI was normal, but ictal SPECT scan showed areas of hyperperfusion in the left superior and middle temporal gyrus. Results: In both of these cases, the EEG showed 1) synchronous generalized 3Hz SWC, characteristic of typical absence seizures, and 2) unusual secondarily generalized 3 Hz SWC seizure patterns, which initially arose from the left temporal region. In addition both patients showed focal spikes in the left temporal region, and at times both temporal regions. Patient 1 was rendered seizure-free (follow-up period of 29 months) following resection of the mass lesion, pathologically-confirmed as a ganglioglioma. Postoperative EEGs no longer showed focal or generalized epileptiform abnormalities. In case 2, magnetoencephalopgraphy (MEG) localized the spikes to the left superior and mid-temporal gyrus. This patient was not offered resective epilepsy surgery due to proximity of the putative epileptogenic area to eloquent (language) cortex. Conclusions: The disappearance of SWC and the corresponding dialeptic seizures after a small resection in case 1 confirms that the unusual evolution of this patient s seizures was indeed secondary bilateral synchrony. MEG results in case 2 also render support to the hypothesis of a focal onset with secondarily generalized SWC. These cases illustrate the complex and sometimes surprising interactions between generalized and focal epileptogenic tendencies. Employing multiple modalities to sort out these interactions can produce a successful therapeutic strategy.