Mitochondrial encephalopathies.

Although no single neurological manifestation is specific of mitochondrial encephalopathies, several neurological syndromes are clearly suggestive of the diagnosis. Muscle biopsy for histochemicals, biochemical, and mitochondrial DNA studies is frequently necessary to establish diagnosis of mitochondrial encephalopathy presenting with such neurological syndromes. Mitochondrial encephalopathies most frequently result from nuclear gene defects and biochemical studies are frequently helpful in reaching a specific diagnosis. Various therapeutic interventions are beneficial in selected cases.