Mitochondrial encephalomyopathies: CT and MRI findings and correlations with clinical features.

Seven patients (3 men, 4 women; age 15-48 years) from 6 families with mitochondrial encephalomyopathies were studied. There were 4 patients with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and 3 patients with myoclonus epilepsy and ragged-red fibers (MERRF). The clinical course was variable in both MELAS and MERRF patients. Interestingly, one MERRF patient had putaminal hemorrhage with left hemiplegia. In MELAS patients, brain computed tomography (CT) revealed cerebral hypodensity lesions affecting all four lobes and relative sparing of the basal ganglia and the thalamus. The CT of MERRF patients showed cerebral and cerebellar cortical atrophies in two and ventricular dilatation in one. During the recovery stages, magnetic resonance images (MRI) revealed subcortical white matter lesions in two MELAS patients and one MERRF patient. These subcortical white matter lesions were most prominent in the paraventricular areas. The present data indicate that in MELAS the hypodense lesions tend to affect the cerebral hemisphere and to spare the subcortical gray matter. Furthermore, the involvement of the paraventricular white matter may occur in both MELAS and MERRF.