MELAS syndrome (Mitochondrial encephalomyopathy, lactic acidosis, stroke-like episodes), is considered a mitochondrial encephalopathy, a group of diseases which have in common biochemical defects in cell mitochondrial respiratory chain. Sometimes it is difficult to reach a diagnosis due to the possibility of normalbiochemical and genetic studies, and absent ultrastructural alterations in muscle biopsy. Neuroimaging (CT, MRI and MR spectroscopy) provides useful information that helps us suggest the diagnosis of this disease. Learning objectives of our work is to describe the most common manifestations encountered with neuroimaging...

MELAS syndrome (Mitochondrial encephalomyopathy, lactic acidosis, stroke-like episodes) was first described by Pavlakis in 1984. It is characterized by errors in cell metabolism caused by mutations in nuclear genes, as well as a defective mitochondrial oxidative phosphorylation. The pathophysiology of the disease is uncertain although have been proposed several hypotheses regarding the stroke-like episodes: Vascular ischemia mechanism hypothesis: supports the theory of mitochondrial angiopathy. Generalized cytopathic neurovascular mechanism and nonischemic cellular mechanism hypothesis: support the theory of mitochondrial cytopathy. MELAS's clinical presentation is highly variable...

Diagnosis of MELAS syndromeis based on the demonstration of mitochondrial dysfunction and clinical symptoms. Biochemical examination of blood and CSF shows high concentrations of lactate. Genetic studies: mitochondrial DNA mutation A3243G (80% aprox)Fig. 1 . Muscle biopsy: presence of ragged-red fibers which are characterized by abnormal proliferation of mitochondriaFig. 2 . Neuroimaging studies (CT, MRI, MR spectroscopy): The images used to illustrate the findings described below belong to two studies of two different patients with first degree consanguinity (mother and son) both with neurosensorial hearing...

MELAS syndrome is a poor prognosis disease, sometimes difficult to diagnose. The knowledge of neuroimaging characteristic findings on MRI, MR spectroscopy and MR DWI allows us to suggest and support this diagnosis if clinically suspected but without histologic, biochemical or genetic confirmation. Since biochemical determinations and histological findings are not always conclusive for the diagnosis of MELAS, the diagnose should be considered if neuroimaging and clinical findings described are present in a young patient.

1. Lorenzoni PJ, Scola RH, Kamoi Kay CS, Arndt RC, Freund AA, Bruck I, et al. MELAS clinical features, muscle biopsy and molecular genetics. Arq Neuropsiquiatr. 2009;67:668-676. 2. Hiromichi Ito, Kenji Mori, Shoji Kagami. Neuroimaging of stroke-like episodes in MELAS. Brain Dev. 2011;33:283-288. 3. Friedman SD, Shawn DWW, Ishak G, Gropman AL, Saneto RP. The use of neuroimaging in the diagnosis of mitochondrial disease. Dev Disabil Res Rev. 2010;16:129-135. 4. Cano A, Romero AI, Bravo F, Vida JM, Espejo S. Sindrome de MELAS: hallazgos neurorradiológicos....