MELAS - CLINICAL AND PATHOLOGICAL CORRELATIONS WITH MRI, XENON CT, AND MR SPECTROSCOPY/

We describe the clinical, imaging, and pathologic findings in a patien t with mitochondrial myopathy, encephalopathy, lactic acidosis, and st roke-like episodes (MELAS). The patient experienced her first stroke-l ike episode at age forty-four. Brain MRI, obtained at symptom onset, a t 3 weeks, and at 1 year, revealed migrating T-2-weighted hyperintensi ties in the temporal/parietal and occipital cortices and later reveale d atrophy. Abnormal cerebrovascular reserve was evident on xenon/CT fo ur days after the first MRI. MR spectroscopy at 1 year revealed increa sed lactate in both the occipital and the temporal lobes. Histologic s ections demonstrated spongy degeneration of the cortex that was most p rominent at the crests of the gyri. Electron microscopy of the blood v essels showed increased numbers of abnormal mitochondria within the va scular smooth muscle and in endothelial cells. We hypothesize that the stroke-like episodes in MELAS may be due to impaired autoregulation s econdary to the impaired metabolic activity of mitochondria in the end othelial and smooth muscle cells of blood vessels.