[Cerebral circulation and metabolism in patients with mitochondrial myopathies]

In order to study the cerebral circulation and metabolism in 6 patients with mitochondrial myopathies and 6 normal control subjects, positron emission tomography with oxygen-15 labelled tracers was performed. Four patients had predominantly central nervous system involvement, whereas 2 had myopathy alone. In comparison with normal control subjects, patients with mitochondrial myopathies showed decreased cerebral blood flow (CBF), decreased cerebral oxygen metabolic rate (CMRO2), and low oxygen extraction fraction (OEF) value due to an uncoupling of CBF and CMRO2. The reduction of OEF was remarkable in the 2 patients having predominantly central nervous disease and 1 having myopathy alone. We suppose that these findings are greatly related to mitochondrial myopathies and that they reflect the disturbance of mitochondrial oxidative metabolism in the brain. The patients whose central nervous symptoms progressed rapidly tended to show the reduction of OEF, but the degree of the reduction of OEF was not necessarily related to the severity of the central nervous symptoms. These findings suggest that the disturbance of cerebral metabolism is not uniform in patients with the same central nervous disease.