Illustrate the imaging findings of our case series of MERS. Discuss the possibles etiologies and physiopathological mechanisms. Display differential diagnosis of lesions of the splenium of the corpus callosum.

MERS is a clinical-radiological entity, characterized by mild encephalitis or encephalopathy associated with reversible lesion of the corpus callosum, which commonly involves the splenium. Epidemiology Affects mainly young patients and children, being reported mostly in oriental population, with more tan 50 published cases. Its precise frequency is unknown, but it is likely underreported, since magnetic resonance imaging examination is not routinely performed in the responsible disorders. [1] Clinical presentation Clinically its present with nonspecific prodromal symptoms including cough, rhinorrhea, vomiting, headache, and sore throat. Later...

Classification Recently, reversible lesions with transiently reduced DWI have also been reported with lateral extension from the splenium into the frontoparietal subcortical white matter, and with anterior extension to involve the entire corpus callosum. Then, MERS is classified into types 1 which exhibits only splenial corpus callosum lesions, and type 2 that shows white matter lesions in addition to lesions of the entire corpus callosum; however, the splenial lesion is always the last to disappear. In general, patients with MERS type 2 lesions have also...

This lesion itself seems to be a nonspecific phenomenon. Per definition, all patients had symptoms suggestives for encephalitis/encephalopathy and showed the typical lesions on MRI the corpus callosum and/or on the center semiovale bilaterally. The more frequent use of MRI allows more patients to be examined, resulting in detection of the lesion. It is important to consider this entity and be differentiated from other diseases affecting the corpus callosum. Moreover, it is expected that the variety of pathogens in patients with MERS type 2 lesions...

1. Garcia-Monco JC, Martinez A, Brochado AP, Saralegui I, Cabrera A, Beldarrain MG. Isolated and Reversible Lesions of the Corpus Callosum: A Distinct Entity. Journal of Neuroimaging. 2010;20(1):1–2. 2. MD AN, MD JW, MSc LC, Van Coster PhD R, MD HV. Expanding the Spectrum of MERS Type 2 Lesions, a Particular Form of Encephalitis. Pediatric Neurology. 2013;48(2):135–138. 3. Hara M, Mizuochi T, Kawano G, et al. A case of clinically mild encephalitis with a reversible splenial lesion (MERS) after mumps vaccination. Brain and Development. 2011;33(10):842–844....