Long-term follow-up of febrile infection-related epilepsy syndrome.

Purpose: Febrile infection-related epilepsy syndrome (FIRES) is an increasingly recognized epileptic syndrome that presents with multifocal refractory status epilepticus in previously normal children and evolves into a chronic, refractory, focal epilepsy with associated cognitive and behavioral difficulties. Herein we describe the features of the chronic epilepsy and critically review evidence for the etiology of this syndrome.

Methods: Seven patients with FIRES were studied. The duration of follow-up in six survivors was 5-17 years. Clinical, electroencephalography (EEG), neuroimaging, and other investigative findings during the acute and chronic phases were reviewed.

Key Findings: These previously normal children presented with a febrile illness and status epilepticus that was refractory to antiepileptic medications in all children, to immunotherapies (including immunoglobulin, corticosteroids, plasma exchange, and rituximab) in four, and to acute vagus nerve stimulation in one. Markers of cerebral inflammation were few and response to antiepileptic and immunomodulatory therapies was poor. Evolution to chronic epilepsy occurred without a silent period. Seizure characteristics in the chronic phase were strikingly stereotyped and similar to the acute phase, with head and eye version, unilateral facial jerking, asymmetric tonic posturing, and unilateral limb jerking in all patients. Electrographic ictal onset was lateralized in all recorded seizures, unilateral in one patient, and independent bilateral in three. Seizures were refractory to multiple antiepileptic medications in all patients and partly responsive to chronic vagus nerve stimulation in two patients. Moderate to severe intellectual impairment was noted in four patients, and borderline intellectual abilities were noted in two. Magnetic resonance imaging (MRI) in the chronic phase was normal in three patients and showed mild diffuse cortical atrophy and/or mild hippocampal atrophy or sclerosis in three.

Significance: The similar perirolandic and perisylvian features of acute and chronic seizures, the lack of a silent period, the absence of evidence of cerebral inflammation, and the poor response to immunotherapies suggest FIRES is best conceptualized as a chronic epilepsy with explosive onset, not a remote-symptomatic epilepsy with an acute inflammatory antecedent.