Impaired activation of oxygen consumption and blood flow in visual cortex of patients with mitochondrial encephalomyopathy

A current hypothesis claims that an increase of blood now is required for o xygen consumption to rise during neuronal excitation (activation). Chronic progressive external ophthalmoplegia is a mitochondrial disease associated with deletions of mtDNA or by point mutation of tRNA genes. We tested the h ypothesis that the cerebral metabolic rate of oxygen (CMRO2) may not rise i n this disorder if the accompanying cerebral blood flow increase is insuffi cient. Two patients with progressive external ophthalmoplegia were visually stimulated with a colored checkerboard pattern reversing as different freq uencies. When stimulated, Patient 1 had a small increase of cerebral blood flow, while Patient 2 had no cerebral blood flow increase. In the visually active state, the patients had no significant change of CMRO2, while health y subjects had a pronounced increase of CMRO2 in the pericalcarine visual c ortex at 4 Hz and a further slight increase at 8 Hz during activation.