[Mitochondrial encephalopathies with late disclosure and predominant involvement of central nervous system].

We report three cases of mitochondrial encephalomyopathy affecting predominantly the central nervous system; two patients had the MELAS syndrome and one had "ophthalmoplegia plus". Histoenzymatic analysis of muscle biopsy and biochemical studies of muscle mitochondria demonstrated myopathy associated with partial deficiency of complex I of the electron transfer chain in three cases, complex IV in two cases and complex III in one case. Molecular analysis of mtDNA in the first case did not revealed any abnormality. Coenzyme Q10 therapy improved exercise tolerance but not the central nervous signs.