Early ictal and interictal patterns in FIRES: The sparks before the blaze

Objective: Febrile infection-related epilepsy syndrome (FIRES) is a catastrophic epileptic encephalopathy described as explosive onset of super refractory status epilepticus (SRSE) in previously healthy children. We describe electroencephalography (EEG) abnormalities in the hyperacute phase of FIRES, with the aim of contributing to the diagnostic characterization of a syndrome otherwise lacking specific biomarkers.

Methods: This is a retrospective single-center, case series of seven children with FIRES. Cases were identified from a Neurocritical Care database. Patient characteristics and clinical course were obtained from electronic medical records. Electroencephalography recordings were reviewed in two segments: the initial 12 h of recording and the 12 h prior to initiation of a medically induced burst suppression (BS).

Results: Fourteen 12-h segments of video-electroencephalography (EEG) recordings were analyzed for commonalities. A beta-delta complex resembling extreme delta brush (EDB) occurred in at least one 12-h segment for all patients. In six patients, seizures were brief and relatively infrequent during the first recording, with a gradual evolution to status epilepticus by the second. We observed a characteristic electrographic seizure pattern in six of seven patients with prolonged focal fast activity at onset. Shifting seizures were seen in four of seven patients.

Significance: The diagnosis of FIRES is typically assigned late in a patient's clinical course, which has broad implications for clinical care and research. We retrospectively analyzed acute EEG features in seven patients with FIRES and discovered three common features: gradual increase in seizure burden, presence of a recurrent EDB, and a typical seizure pattern. Recognition of this pattern may facilitate early diagnosis and treatment.