Abstracts

Rationale: Some children with non-lesional intractable epilepsy undergo corpus callosotomy in the hope to achieve epileptic control through desynchronization of widespread spike discharges. Whereas this often yields significant effect, there are some patients who have very little effect. Although thalamus has been assumed to have a role in the pathogenesis of intractable seizures, the exact significance of this hypothesis has not been confirmed. We aimed in this study to elucidate this issue by analyzing the relationship between the interictal-ictal thalamic perfusion changes before callosotomy and the outcome of this surgical intervention in pediatric patients with non-lesional intractable epilepsy.Methods: A retrospective review of non-lesional intractable epilepsy patients at the National Center Hospital, National Center of Neurology and Psychiatry from January 2008 to June 2010 identified 15 pediatric patients who had undergone corpus callosotomy and had had both ictal and interictal single photon emission computed tomography (SPECT) during their pre-surgical evaluation. The patients who had only drop attack or had obvious epileptic focus were excluded. All pediatric patients were followed up for at least one year after callosotomy. The patients were divided into either seizure free (n=5) or minimally improved (<=50% reduction) (n=10) groups at the time of one year. Blood perfusion counts of thalamus and whole brain using SPECT were calculated by three-dimensional stereotaxic region of interest template (3D SRT) analysis (Fujifilm RI pharma Co., Ltd), and then we used the ratio that thalamic counts divided by whole brain to normalize the result of thalamic blood perfusion counts in each of ictal and interictal SPECT. The degree of changes in thalamic perfusion rate between interictal and ictal SPECT were compared seizure free with minimally improved group.Results: Ictal and interictal SPECT were obtained from fifteen consecutive pediatric patients (5.0 4.5 years, range 1-9 years) who was subjected to total (n=9) or partial (n=6) callosotomy. Thalamic blood perfusion showed significant ictal changes in the minimally improved group, and in contrast seizure free group showed essentially no change (p<0.001, Mann-Whitney test).Conclusions: The correlation between the ictal change in thalamic perfusion and the persistence of seizures after callosotomy suggests that thalamus is involved in the pathomechanism of intractable seizures in some cases. The 3D SRT-based assessment of change in thalamic blood perfusion using SPECT is a promising method to determine the indication of corpus callosotomy in non-lesional intractable epilepsy.