Abstracts

Rationale: Many types of clinically confirmed mitochondrial diseases have been identified as being associated with epileptic conditions resulting from mitochondrial dysfunction. The seizures have been reported to occur in 35-60% of patients with mitochondrial diseases. The primary objective of this study was to review the clinical features and evaluate long-term developmental trends of pediatric patients with epilepsy in mitochondrial diseases (MDs). Methods: Of 300 pediatric patients with MDs, 69% of the patients have been diagnosed with epilepsy. Disease-related clinical variables of 207 patients with epilepsy (95 males, 46%) were reviewed from hospital records and the results of developmental evaluations. Results: he age at onset of symptoms for MDs was 1.7±2.7 years (0–16.8 years) and the nature of the initial symptoms varied, with seizures (113 patients, 55%) being the most frequent and followed by developmental delay (75 patients, 36%). In terms of epilepsy type, partial epilepsy was most common as being 28%, and then generalized epilepsy as 15.9%, infantile spasm 15.2%, and Lennox-Gastaut syndrome 9.3%. Of 207 patients with epilepsy, non-specific MDs (60.9%) were the most common type of syndrome, followed by 17.9% of Leigh syndrome and 3.9% of MELAS. The mean age at the first symptom was 1.7±2.7 years (0–16.8 years) and the lead time from the first clinical presentation until the confirmative diagnosis of MDs was 2.6±2.6 years (0.03–16.9 years). In terms of severity of the clinical manifestations, all patients had involvement of the central nervous system, and 46.7% were included in severe level of clinical severity, followed by 31.5% in moderate level. MRI studies of 69% patients (142 of 206) were abnormal and showed a variety of findings including atrophy or abnormal signals in different areas of the brain. Long-term follow-up over the course of 7.7 years showed declining trends over all periods, which revealed consistent patterns of significant developmental deterioration during lead time, whereas no significant differences after diagnosis were observed. Conclusions: In terms of epilepsy, the patients who have diagnosed with epilepsy showed significantly delayed development compared to those without epilepsy and drug-resistant epilepsy patients showed significantly delayed development than drug-responsive epilepsy patients. Age at the first symptom onset showed positive correlation with the level of DQs, while lead time to diagnosis was negatively associated with DQ at all-time points. Funding: This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2016R1A2B4011052).