This diffusion-weighted MR image shows cortical ribbon-like high signal consistent with diffusion restriction in a patient with known MELAS and an acute presentation with confusion and focal neurological deficit.
Mitochondrial myopathy, lactic acidosis and stroke (MELAS) is a genetic mitochondrial disorder. It may be sporadic or familial via the maternal line. Patients often present with sudden-onset global or focal neurological deficits. Other presentations include migraines and seizures. There is typically an associated proximal myopathy.
During attacks restricted diffusion may be present in cortex, subcortical white matter, and basal ganglia. High T2 signal may also be present in these locations, and there may be nonspecific periventricular and deep white matter high signal in addition. T2 signal changes may persist, and encephalomalacia can be seen in previously affected areas. Proton MR spectroscopy will often demonstrate elevated lacate in apparently unaffected brain, and in CSF.
Reference: Lin DDM, Crawford TO and Barker PB. Proton MR spectroscopy in the diagnostic evaluation of suspected mitochondrial disease. AJNR 2003;24:33-41

Credit: Dr Laughlin Dawes