Transient blindness associated with mild encephalitis/encephalopathy with a reversible splenial lesion (MERS): a case report and review of literature

BACKGROUND: Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is a clinical-radiological syndrome that can be related to infectious and non-infectious conditions. The most prominent neurological symptoms are disturbance of consciousness, abnormal speech, delirious behavior, seizures, muscle weakness, ophthalmoplegia, facial nerve paralysis and headache. Here we report the case of a child with MERS presenting with the unusual symptom of bilateral transient blindness. CASE PRESENTATION: A 4-year-old female patient, with a history of fever, abdominal pain, loss of appetite and cough lasted for a few days, experienced 3 episodes of transient bilateral loss of vision with difficulty in walking. Her physical examination showed absence of focal neurological and meningeal irritation signs, although responsiveness was slightly impaired. The ophthalmologic evaluation, including a fundus oculi examination, was negative. The electroencephalogram showed slow activity in the temporo-occipital regions, more evident in the right hemisphere. A lumbar puncture was performed and cerebrospinal fluid analysis revealed normal glycorrhachia, cell counts, protein levels and IgG index. Magnetic resonance imaging of the brain showed a signal alteration in the splenium of the corpus callosum, without contrast enhancement. This finding was suggestive of a reversible cytotoxic lesion. Empiric antiviral treatment with acyclovir and intravenous dexamethasone was initiated. Polymerase chain reaction search for neurotropic viral nucleic acid sequences in the cerebrospinal fluid was negative, while a low number of HHV-6 DNA copies was detected in the blood. Electroencephalograms were repeated in the following days, showing a progressive normalization of the pattern. The child was discharged without symptoms after 10 days of treatment with oral corticosteroids. After 40 days, brain magnetic resonance imaging showed a complete normalization of the signal alteration in the splenium of the corpus callosum. CONCLUSION: Transient blindness was reported as an initial symptom of MERS in a few children. To date, there is no evidence of effective treatment methods. Nonetheless, MERS diagnosis provides pediatricians with valuable prognostic information in order to reassure patients and their families about the good outcome of this disease.