CEREBRAL METABOLISM OF OXYGEN AND GLUCOSE IN A PATIENT WITH MELAS SYNDROME

We studied cerebral oxygen and glucose metabolism as well, as cerebral blood flow using positron emission tomography (PET) in a case with ME LAS showing dementia, diabetes mellitus, ataxia and lactic acidosis wi thout any signs of stroke. This case, confirmed to have a point mutati on at position 3243 in the transfer RNA gene of mitochondrial DNA, dev eloped a stroke-like episode 8 months after the PET study. Uncoupling was observed between cerebral oxygen metabolism and cerebral blood flo w with reduced fractional oxygen extraction ratio, indicating ''hypere mia'', not ischemia, The ''hyperemia'' may be closely related to the m alfunction of mitochondria in aerobic energy production. A drastic dec rease in cerebral oxygen metabolism (CMRO(2)) was found globally in co ntrast to preserved cerebral glucose metabolism (CMR(glu)), resulting in a remarkable decrease in the metabolic ratio (CMRO(2)/CMR(glu)). Th e dissociation between cerebral glucose and oxygen metabolism may be c haracteristic of MELAS.