[Mitochondrial encephalopathy affecting only the central nervous system]

A 32 year-old diabetic woman presented with an acute coma followed by epileptic seizures, aphasia and constructive apraxia. No ischemic lesion was demonstrated by CT scan and carotid angiograms. The other investigations showed sensorineural hearing loss, retinal degeneration, calcifications of the basal ganglia and lactic acidosis. The follow-up was marked by pseudo-dementia with personality disorders, memory deficits, behavioural changes, migrainous and epileptic features. Although there was no sign of muscular deficiency, a muscular biopsy showed characteristic ragged-red fibers and mitochondrial abnormalities at electron microscopy. The muscular biopsy enables us to classify this case as a mitochondrial encephalopathy similar to the MELAS syndrome. The stroke-like episodes are probably caused by a specific angiopathy involving the mitochondria of brain vessels.