Shigella-associated mild encephalitis with reversible splenial lesion in Hospital Center Delafontaine, Saint-Denis, France: a case report

Background Mild encephalitis with reversible splenial lesion of the corpus callosum (MERS) is a clinical/radiological syndrome characterized by hyperintense signal changes in the splenium of the corpus callosum visible on diffusion weighted imaging (DWI) in the brain Magnetic Resonance Imaging (MRI) associated with various neurological symptoms. Progression is usually favorable with disappearance of the MRI brain lesion and regression of clinical symptoms over a few days to a few weeks. The exact pathophysiology remains unclear. MERS can be associated with various pathogens. Case presentation We report here a paediatric case of MERS associated with Shigella flexneri infection. A five-year-old boy with no relevant past medical history presented with symptoms such as headache, fever, profuse diarrhea and hallucinations. A brain Magnetic Resonance Imaging performed on Day 2 of the symptoms revealed hyperintense signal changes of the splenium of the corpus callosum in T2 FLAIR sequence. This infection had a favorable outcome after antibiotic therapy. No further recurrence of symptoms was observed and a follow-up clinical examination eight weeks later was normal. A follow-up brain Magnetic Resonance Imaging three months after discharge was also normal and the hyperintense signal changes of the splenium of the corpus callosum had disappeared completely. Conclusions MERS is a clinical/radiological syndrome with a generally good prognosis. We believe that this is the first description of a case of Shigella-associated MERS. It is useful to know about this condition to help distinguish it from acute disseminated encephalomyelitis.