Abstracts

Rationale: Treatment options for intractable epilepsy are extremely limited especially when clinicians fail to identify a focal lesion. We characterized our patients with intractable epilepsy who did not have a lesion on brain magnetic resonance imaging (MRI), but received a resection. Surgical outcome was assessed.Methods: Between January 1st 2011 and December 31st 2014, 23 patients with brain MRI-negative epilepsy underwent resective surgery at Severance children’s hospital. Clinical variables and results of the diagnostic tests were assessed.Results: Among 23, 15 were female and 8 were male. Mean age of the seizure onset was 3.4 ± 3.2 years old and mean age of the operation was 9.6 ± 4.6 years old. Diagnosis of the patients was extratemporal lobe epilepsy in 12, Lennox-Gastaut syndrome in 9 and temporal lobe epilepsy in 2. Most (17/23) had an extensive surgery including lobectomy. Five patients had received a previous corpus callosotomy. Everyone received a subdural electrode implantation. Pathologically, in 60% (14/23) of the patients, focal cortical dysplasia (FCD) was confirmed. Type IIa FCD was the most common type (10, 43%). Of 23, 15 (65%) were seizure free for the initial 3 months and most of them were still seizure free at 1 year after the surgery (52%, 12/23). Seizure freedom was related to the localized positron emission tomography (PET) results (p = 0.04). In our study, we did not see any relationship between favorable seizure outcome and the localized ictal electroencephalography (EEG) discharges (p=0.4), localized interictal EEG discharges (p = 0.1), the interictal single photon emission computed tomography (SPECT) results (p = 0.5) or the ictal SPECT results (p = 0.8).Conclusions: This study shows that a favorable surgical outcome can be achieved for patients with intractable epilepsy even when there is no visible lesion on MRI. Multidisciplinary approach including the use of a PET study or corpus callosotomy can be helpful in delineating a concealed abnormality. Further investigation and implication of these findings would be warranted in a larger pediatric population.