Favorable outcomes and FDG-PET changes following tocilizumab treatment for febrile infection-related epilepsy syndrome in a child.

Febrile Infection-Related Epilepsy Syndrome (FIRES) is an infrequent yet severe form of epilepsy that rapidly evolves into status epilepticus following a febrile episode. Prompt diagnosis coupled with effective treatment strategies is critical for improving patient outcomes. Herein, we describe the case of an 11-year-old male with FIRES who was successfully treated with tocilizumab, resulting in no further seizures or residual disability. The patient initially did not respond to antiseizure medications and first-line immunomodulatory therapy. Characteristic EEG patterns and elevated interleukin 6 levels in the cerebrospinal fluid contributed to an early presumptive diagnosis of FIRES. Tocilizumab was administered on day 10 after the seizure onset, leading to seizure cessation within 24 h, with no subsequent episodes. Serial cranial MRI imaging studies demonstrated transient abnormalities that resolved over time. Notably, on day 9, the patient exhibited bilateral frontal lobe hypermetabolism on FDG-PET, with EEG showing global slow waves predominantly in the bilateral frontal regions. As seizure control was achieved and encephalopathy symptoms improved, a follow-up EEG on day 25 revealed persistent slow waves in the bilateral frontal regions, with FDG-PET hypermetabolism present only in the left frontal lobe. By day 88, both EEG and FDG-PET had returned to normal. These findings suggest tocilizumab may play a role in the management of FIRES, though further studies are required to substantiate its therapeutic efficacy. Additionally, early bilateral frontal FDG-PET hypermetabolism and EEG slow-wave activity, may serve as an early biomarker in FIRES patients. However, more research is necessary to establish its validity.