Abstracts

Rationale: According to Palmini classification, the observation of ‘excess’ heterotopic neurons in layer 1 and the white matter is classified as mild malformation of cortical development (mMCD) type I and II, respectively. mMCD is a matter of clinical and scientific debate, due to lack of clinical and research data and exact threshold for the diagnostic confirmation. Over the last decade, we have observed severe drug resistant early onset seizures which showed very mild neuropathological spectrum, thus analysed the clinical feature and treatment for this group. Methods: We identified 40 children and adolescents pathologically confirmed as mMCD at Severance Children’s Hospital from September 2003 and to September 2015, and this study aimed to show the clinical feature, surgical outcome, and seizure control pattern associated with pathological finding, mMCD. Results: Twenty-eight cases (70.0%) presented as childhood onset epileptic encephalopathy, further divided by 22 Lennox-Gastaut syndrome and 6 West syndrome, while 12 cases (30.0%) presented as focal epilepsy (9 cases, extratemporal lesion; 3 cases, temporal lesion). The median of seizure onset age was 1.2 year, 19 cases (47.5%) had started seizures before the age of 1 year, and 23 cases (57.5%) had seizures before the age of 2 years. Patients had median number of 3 antiepileptic drugs (AEDs), 2 to 4 AEDs trials before surgery, and ketogenic diet was tried in 14 cases (35.0%).Sixteen cases (40.0%) had nonfocal MRI abnormalities for cortical dysplasia. The most frequent surgical procedure was 18 cases (45.0%) of multilobar resections, followed by 12 cases (30.0%) of unilobar resection, 4 cases (10.0%) of posterior quadrantectomy along with frontal resection, and 1 case (2.5%) of posterior quadrantectomy. The median postoperative follow-up duration was 7.0 years. The final surgical outcome counting reoperations include 25 cases (62.5 %) which brought ILAE I-II epilepsy surgery outcome, and 4 (20.0%) out of 20 ILAE I cases that were off all the AEDs. For understanding the pattern of seizure control, seizure control for each patient was categorized into one of 5 distinct patterns. Fifteen cases (37.5%) did not have any postoperative seizures, while there were 8 cases who did not become seizure free but 7 of them consistently showed lateralized post operative EEG abnormalities in operated lesion. Conclusions: This study identified mMCD as an important pathologic finding related to comparable degree of epileptogenicity, and could be successfully treated by resective surgery. Funding: No funding to declare.