NORSE and FIRES are rare, severe clinical presentations in which refractory status epilepticus develops in a person without active epilepsy or another immediately clear explanation. They are syndromic descriptions rather than single diseases, and the underlying cause can be autoimmune, infectious, genetic, toxic, metabolic or remain cryptogenic.
What does NORSE mean?
New-onset refractory status epilepticus (NORSE) describes refractory status epilepticus in a person without active epilepsy and without a clear acute structural, toxic or metabolic cause identified at presentation. It can occur in adults or children.
NORSE is not itself an aetiological diagnosis. It signals a clinical emergency in which the cause must be sought while status epilepticus is treated.
What is FIRES?
Febrile infection-related epilepsy syndrome (FIRES) is a subtype of NORSE. It is defined by a febrile illness beginning between about 24 hours and two weeks before the onset of refractory status epilepticus, with or without fever when status epilepticus begins.
FIRES occurs predominantly in children and young people but can occur in adults.
Why the cause can be difficult to find
Investigations can include neuroimaging, cerebrospinal fluid studies, microbiology, autoimmune and inflammatory testing, toxicology, metabolic studies and, in selected cases, genetic testing. No single test can rule NORSE or FIRES in or out.
In a substantial proportion of cases, no definite cause is found despite extensive investigation. These cases are usually described as cryptogenic NORSE.
Why continuous EEG matters
Convulsive activity may evolve into electrographic or non-convulsive status epilepticus. Continuous EEG is therefore important for detecting ongoing seizure activity, monitoring treatment effect and identifying patterns that may otherwise be invisible clinically.
The EEG may also change over time, so a short routine recording can miss clinically important activity.
Treatment is broader than antiseizure medicines
NORSE and FIRES frequently require intensive-care treatment because seizures persist despite first- and second-line antiseizure medicines. Anaesthetic therapies may be needed for refractory status epilepticus.
International consensus recommendations also support early consideration of immunotherapy when an inflammatory or autoimmune mechanism is suspected and early ketogenic dietary therapy in selected NORSE/FIRES cases. The evidence base remains limited, and treatment must be individualised in specialist centres.
What happens after the acute phase
Survivors can have long-term epilepsy, cognitive difficulties, behavioural or psychiatric problems, physical disability and a prolonged rehabilitation need.
Post-acute care can therefore involve epilepsy specialists, rehabilitation, neuropsychology, mental-health support, education or occupational support and family counselling.
Why research is difficult
NORSE and FIRES are rare, heterogeneous and clinically severe. Randomised trials are difficult, so much current guidance comes from observational evidence and international expert consensus.
Registries, common terminology and multicentre collaboration are especially important in improving future evidence.
Related reading
Sources and further reading
- International consensus recommendations for NORSE/FIRES — supporting evidence
- NORSE/FIRES consensus summary and clinical tools
- NORSE/FIRES consensus statements and evidence
Evidence checked: September 2026.