Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes with special reference to the mechanism of cerebral manifestations.

A 29-year-old man with mitochondrial encephalomyopathy caused by partial deficiency of mitochondrial NADH-ubiquinone oxidoreductase (Complex I) is described. Clinical manifestations were characterized by generalized convulsion, dementia and stroke-like episodes consisting of hemianopsia, Gerstmann's syndrome and visual hallucination. Blood and cerebrospinal fluid lactate and pyruvate levels were elevated. Biochemical studies on a muscle biopsy specimen revealed partial deficiency of Complex I activity, and decreases in the 75-kDa and the 20-kDa subunits of Complex I by immunoblotting analysis. Serial brain CT scans revealed multiple low-density areas with fluctuating densities. Single photon emission tomographic study revealed preservation of blood circulation where CT scans showed diminished density in acute stage, suggesting the presence of abnormal cellular metabolism rather than vascular occlusion as the basic mechanism of his stroke-like episodes. Pathogenesis of neurological manifestations in MELAS is discussed with reference to the possible involvement of free radicals in inducing brain damage.