Epilepsia partialis continua and defects in the mitochondrial respiratory chain

Epilepsia partialis continua (EPC) is characterized by continuous myoclonic or clonic jerks repeated at short intervals followed by a slowly progressive neurological disorder. We report three patients with EPC and a defect in the mitochondrial respiratory chain.

Clinical, neuroradiological, and biochemical data were reported.

The patients presented continuous myoclonic jerks at age of 8 months, 11 months and 6 years, respectively. Two of the three patients had a previous developmental delay. Neurological examination at first admission revealed extrapyramidal symptoms in all patients. Initial biological investigations suggested mitochondrial dysfunction. Initial EEG showed a continuous discharge of periodic spikes (0.5-1Hz). MRI studies were initially normal then progressed to cerebral hemiatrophia. EEG revealed both correlation and absence of correlation between spikes or sharp waves and myoclonic jerks. The activity of one or several complexes of the mitochondrial respiratory chain was reduced in the muscle samples of the three patients. No mutation of mtDNA was found.

Our report suggests that EPC can be due to mitochondrial respiratory chain disorders. Some clinical findings and initial investigations were indicative of a disorder of mitochondrial metabolism. Previous developmental delay, extrapyramidal symptoms and other organ involvement should suggest a possible mitochondrial etiology of EPC. In case of infant presenting EPC, mitochondrial respiratory chain disorder should be considered first.