The first pediatric case of mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) associated with Neisseria meningitidis

Background: Mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) is a clinic-radiological syndrome characterized by neurological deficiencies and reversible magnetic resonance imaging findings in the splenium of the corpus callosum. Usually, it has a good prognosis, and patients recover without any sequelae. A viral infection has caused most MERS cases, and bacterial agents have rarely been reported as a cause of MERS. Case report: A 5-month-old male was admitted to the hospital with fever, poor feeding, decreased activity and groaning. He had focal seizures and required mechanical ventilation. A lumbar puncture was performed, and nucleic acid amplification tests (NAATs) of cerebral spinal fluid was positive for non-typeable serogroup of Neisseria meningitidis. Cranial magnetic resonance imaging (MRI) performed on day 3 of admission showed T2 hyperintensity and diffusion restriction at the splenium of corpus callosum (SCC). Diffusion restriction in the occipital horn of the left ventricular compatible with empyema was also obvious. According to the findings on cranial MRI, this clinical course was diagnosed as MERS associated with meningitis. His fever resolved in one week, cefotaxime was discontinued after 14 days, and the patient completely recovered. A follow-up MRI performed after three weeks of admission showed complete resolution of the signal intensity changes in the SCC and the occipital horn of the left lateral ventricle. Conclusion: To the best of our knowledge, this is the first report of MERS associated with Neisseria meningitidis in children. Bacterial agents as a cause of MERS should be kept in mind, and we should avoid unnecessary treatment strategies due to the good prognosis of MERS in children. (C) 2021 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.