Abstracts

Rationale: We report on a patient with right sided Sturge Weber Syndrome (SWS), who underwent hemispherotomy but had recurrent seizures with left sided seizure pattern in ictal EEG. Ictal single photon emission computed tomography (SPECT) revealed seizure onset in the previously operated right hemisphere and allowed for a second resection, leading to seizure freedom.Methods: Case report.Results: We examined a boy with right sided SWS, suffering from pharmacoresistant seizures since eight months old. At age of 3 years, partial right sided hemispherectomy and hemispherotomy was performed, rendering the patient seizure free for two years. However, seizures recurred. At the time of admission, the patient had an average of 5 left sided or bilateral tonic seizures and hypermotor seizures per day. He was mentally retarded and showed left sided hemiparesis. Interictal EEG showed right temporoparietal and right frontal spikes, whereas ictal EEG demonstrated only left hemispheric seizure pattern. Ictal SPECT was performed, using a technetium 99m labeled perfusion marker (ethylcysteinate dimer, ECD). The scan revealed a well circumscribed right frontoorbital hyperperfusion of 65%, compared to the interictal SPECT scan. This result verified the hypothesis of a right sided seizure onset. We assume that after the previous resection a too small volume of cortex was involved in the right hemisphere to generate a seizure pattern visible in non invasive ictal EEG. Repeated high resolution MRI with diffusion tensor imaging showed an incomplete hemispherotomy, leaving a tiny transcallosal connection between the remaining right frontal lobe and the left hemisphere, providing a pathway for fast seizure spread to the left side. Three dimensional image fusion of SPECT and MRI was performed for precise localization and a second operation was performed with resection of the right frontoorbital cortex and disconnection from the corpus callosum. The patient is now seizure free for more than one year, his mental and physical development improved. Conclusions: This patient illustrates the value of ictal perfusion SPECT in previously resected epilepsy patients and the limitations of non invasive ictal EEG. Therefore we encourage the use of ictal SPECT in those cases, where ictal EEG findings are not consistent with the hypothesized seizure onset zone.