Thyroid crisis mimicking clinically mild encephalitis/encephalopathy with a reversible splenial lesion: A pediatric case report

Background: Reversible lesions in the splenium of the corpus callosum (SCC) with viral infections are associated mainly with clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS). We report a pediatric patient in thyroid crisis with reversible SCC lesions. Case description: We diagnosed a 9-year-old girl with thyroid crisis. She had presented with fever, tachycardia, and impaired consciousness. Magnetic resonance imaging revealed hyperintense signals in the splenium and genu of the corpus callosum and a white matter lesion of the left hemisphere in diffusion-weighted imaging. The initial, tentative diagnosis was clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS). We initiated intravenous methylprednisolone pulse therapy; thereafter, her level of consciousness rapidly improved. On admission, thyroid function studies revealed elevation of free thyroxine and a low level of thyroid stimulating hormone with thyroid-related autoantibodies. She was begun on thiamazole and was discharged without neurological sequelae. Conclusion: Thyroid crisis is similar to acute encephalitis or encephalopathy associated with viral infection, especially with MERS, because the clinical and radiological features resemble those of thyroid crisis; therefore, thyroid diseases should be considered as a possible cause of reversible lesions in the splenium of the corpus callosum. (c) 2020 The Japanese Society of Child Neurology Published by Elsevier B.V. All rights reserved.