Reversible Splenic Lesion in a Patient with Febrile Infection-Related Epilepsy Syndrome (FIRES)

Febrile infection-related epilepsy syndrome (FIRES) is a severe epileptic syndrome that manifests with refractory seizures or status epilepticus in previously healthy children after banal febrile illness. The neuroimaging findings in the acute phase of FIRES are nonspecific or normal. We report the case of a 7-year-old boy with FIRES who presented with a reversible lesion in the splenium of the corpus callosum on brain magnetic resonance imaging (MRI). The patient developed clusters of clonic seizures with a deviation of the eyes after a 3-day history of fever. A reversible splenial lesion was observed on brain MRI and, therefore, the initial diagnosis was mild encephalitis/encephalopathy with a reversible splenial lesion (MERS). However, the intractable complex partial seizures necessitated a long-term midazolam infusion, indicating that FIRES was a more likely diagnosis than MERS. All other findings of this patient met the diagnostic criteria for FIRES. With this diagnosis, a high-dose phenobarbital was administrated, and the seizures were successfully controlled. This case indicated that FIRES should be considered even in patients with a reversible splenial lesion associated with encephalitis/encephalopathy.