Epilepsy Characteristics and Clinical Outcome in Patients With Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes (MELAS).

BACKGROUND: Epileptic seizures in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) are heterogeneous with no pathognomonic features. We reviewed epilepsy characteristics and clinical outcome exclusively in a pediatric population.

METHODS: Twenty-two children and adolescents (13 males) with confirmed mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes due to mitochondrial DNA A3243G mutation and epilepsy were recruited. Clinical data including seizure semiology, treatment response, neuroimaging findings, and electroencephalography were analyzed. We also examined the effect of the age at seizure onset and initial symptoms on the clinical variables.

RESULTS: Seizure semiology and electroencephalography abnormalities showed no syndrome-specific findings. Focal seizures occurred in 21 of 22 subjects (95.5%), whereas generalized seizures developed in seven of 22 subjects (31.8%). Twenty of 22 subjects (90.9%) achieved partial to complete reduction of clinical seizures for more than one year with a combination of more than two antiepileptic drugs. The subgroup with earlier seizure onset presented significantly earlier and showed significantly higher rates of drug-resistant epilepsy compared with the late onset group, although there were no significant differences in the initial symptoms. The subjects with severe epileptic conditions tended to have more severe clinical dysfunction and more severe organ involvement.

CONCLUSIONS: Both focal and generalized seizures occurred in patients with MELAS. Epilepsy in this population is drug resistant, but a certain degree of clinical seizure reduction was achievable with antiepileptic drugs, with more favorable outcomes than historically expected. Close observation and active epilepsy treatment of individuals with MELAS episodes and earlier seizure onset might improve the prognosis.