Status epilepticus is the second most frequent neurological emergency by incidence, and in nearly half of cases it proves refractory to first- and second-line therapies. When such refractory status arises in someone without a clear etiology, clinicians label it NORSE, and when it follows a febrile infection beginning between twenty-four hours and two weeks before onset, the subtype is called FIRES, the febrile infection-related epilepsy syndrome. Although rare, these syndromes are devastating, frequently leaving survivors with cognitive decline and drug-resistant epilepsy. Over the past decade, research has increasingly framed cryptogenic NORSE as a syndrome with distinct biological features, including sustained neuroinflammation, dysregulation of the autoimmune response, excessive cytokine release, and direct neuronal injury, yet reliable prognostic markers on brain imaging have remained elusive.

The claustrum itself is one of the most extensively connected regions in the mammalian brain, sending organized projections to essentially the entire cortical mantle. Its principal inputs arrive from limbic, associative, and motor areas of the frontal cortex, with additional one-way connections from the thalamus, the basolateral amygdala, and the hippocampus, as well as serotonergic neuromodulation from the dorsal raphe nucleus. Functionally, activation of the claustrum strongly recruits inhibitory interneurons that suppress cortical pyramidal cells, a feedforward inhibition that limits excessive firing across neural networks and helps synchronize spike timing. This architecture places the claustrum at the heart of the seizure network, and it has also been implicated in amplifying cortical oscillations, allocating attention, and supporting consciousness and cognition, which makes its involvement in prolonged seizures especially intriguing.

To characterize the claustrum sign systematically, the researchers followed PRISMA guidelines and registered their protocol on PROSPERO. Their search, restricted to literature published from 2018 onward, when international consensus definitions of NORSE and FIRES were first established, initially identified 785 records. After deduplication and blinded screening by two reviewers with expertise in status epilepticus and neuroimaging, with disagreements resolved by a third reviewer, 41 publications comprising 25 single case reports and 16 case series met the inclusion criteria, encompassing 206 patients. Of these, 72 exhibited the claustrum sign and 134 did not. The team extracted demographics, prodromal symptoms, seizure semiology, treatment responsiveness, intensive care requirements, immunotherapy use, MRI findings, and outcomes including survival and chronic epilepsy, and assessed study quality with the QUADAS-2 tool.

The resulting portrait of claustrum sign patients is remarkably consistent. After excluding one patient with autoimmune encephalitis, 71 individuals remained, almost all of whom tested negative for neurotropic viruses and autoantibodies and therefore fulfilled the definition of cryptogenic NORSE. They were predominantly young, with a median age of twenty-three years, and just over half were female. Fever was the presenting symptom in 93 percent of cases, typically accompanied by other neurological complaints such as seizures, impaired awareness, psychosis, headache, memory impairment, or language disturbance, and the prodromal phase preceded status epilepticus by an average of about six and a half days. Because no EEG correlates were available during this prodrome, the authors caution that subtle seizures may already have been smoldering before the overt emergency began.

The acute phase was almost uniformly convulsive. Eighty-nine percent of patients with known semiology presented in generalized convulsive status epilepticus or focal seizures evolving into bilateral convulsive seizures, and motor seizures accounted for 98 percent of classified cases. Nearly half of the patients rapidly became refractory to benzodiazepines and antiseizure medications, while the other half progressed to super-refractory status, continuing or recurring despite more than twenty-four hours of anesthetic therapy. Thirty-seven patients required intensive care admission and twenty-five needed anesthesia. On MRI, the signature was overwhelmingly bilateral: 68 of 69 patients imaged during the acute phase showed hyperintensity in both claustra, typically appearing around seven days after seizure onset, though detection ranged from one to twenty-five days, and in one case the sign emerged only after the status had resolved.

Crucially, the claustrum rarely lights up alone. Isolated claustrum hyperintensity occurred in only 24 percent of cases; far more often the abnormality extended into limbic and paralimbic territory, most commonly the medial temporal lobe, followed by the insula, the anterior cingulate gyrus, the pulvinar, the basal ganglia, and diffuse cortical regions. The authors interpret this pattern as evidence that the claustrum sign reflects widespread network dysfunction rather than a focal structural lesion. Follow-up imaging, available for only 45 patients, showed complete resolution in just six cases, while five patients developed bilateral temporal lobe cortical atrophy, suggesting the sign may mark either reversible inflammatory dysfunction or enduring injury that could contribute to epileptogenesis.

Treatment reflected a strong presumption of immune-mediated disease. Ninety-two percent of claustrum sign patients received immunotherapy, with high-dose intravenous steroids used universally, intravenous immunoglobulins in 76 percent, plasma exchange in 22 percent, and biologic agents, including the IL-6 inhibitor tocilizumab, the B-cell-depleting antibody rituximab, and the IL-1 receptor blocker anakinra, administered to twenty patients. Notably, the claustrum sign has also been reported in other hyperinflammatory states, including acute necrotizing encephalopathy, COVID-19-related encephalopathy, and the neurotoxicity that complicates CAR T-cell therapy, supporting the hypothesis that it represents a radiologic correlate of cytokine-mediated neuroinflammation and network instability rather than a disease-specific lesion.

Outcomes carried a heavy long-term burden despite encouraging acute-phase signals. Five patients died during hospitalization, a mortality of 9 percent, and one more lapsed into a persistent vegetative state. Among 54 patients with follow-up data, 74 percent developed chronic epilepsy, mostly resistant to medication, and roughly half showed persistent cognitive deficits, most often affecting memory and executive or attentional function. Only twelve patients returned to their clinical baseline. When the claustrum sign group was compared with the 134 NORSE patients lacking the sign, several statistically significant differences emerged: fever was far more common as a prodrome, convulsive status was nearly universal, super-refractory disease and ICU admission were less frequent, and responsiveness to anesthetic therapy was markedly higher, with a non-significant trend toward lower in-hospital mortality, though the authors urge caution because non-convulsive status in comatose patients was overrepresented in the comparison group.

The review’s limitations are substantial and openly acknowledged. All included studies were case reports or case series without prospective enrollment, MRI protocols and timing varied widely, imaging was interpreted locally without standardization, and the exploratory univariate analysis precluded any claim of independent prognostic value. Even so, the authors conclude that the claustrum sign is a reproducible, time-dependent imaging marker in a distinct subset of NORSE patients characterized by febrile prodrome and convulsive seizures, and that early recognition could aid diagnostic stratification and prompt timely immunomodulatory intervention. They call for prospective, multicenter studies with standardized imaging and longitudinal follow-up to clarify whether this whisper-thin sheet of brain tissue can truly forecast the course of one of medicine’s most violent neurological storms.

Subject of Research: The claustrum sign as a neuroimaging marker in new-onset refractory status epilepticus and FIRES

Article Title: Claustrum Involvement in New Onset Refractory Status Epilepticus: A Systematic Review

Article References: Burani, M., Muccioli, L., Giovannini, G., Orlandi, N., Bisulli, F., & Meletti, S. (2026). Claustrum Involvement in New Onset Refractory Status Epilepticus: A Systematic Review. Annals of Clinical and Translational Neurology, 13(9), 1750-1758. https://doi.org/10.1002/acn3.70490

Image Credits: AI Generated

DOI: 10.1002/acn3.70490

Keywords: claustrum sign, status epilepticus, NORSE, FIRES, neuroinflammation, MRI, epilepsy, immunotherapy, cytokines, neurocritical care, systematic review, seizures

FIRES is a rare and ferocious epileptic encephalopathy that typically announces itself in a previously healthy child. After an ordinary febrile infection, often nothing more sinister than a fever, the child plunges into超 refractory status epilepticus, a prolonged convulsive storm that resists conventional anti-seizure drugs. The syndrome is classified as a subtype of new-onset refractory status epilepticus, or NORSE, and its underlying etiology remains stubbornly unknown. Survivors of the acute phase frequently emerge into a chronic phase marked by drug-resistant epilepsy, cognitive impairment, and profound disability. The condition’s trajectory is so bleak that neurologists have long searched for anything that might bend its course, and growing evidence implicates a runaway neuroinflammatory process, with elevated cytokines detected in the cerebrospinal fluid of affected children.

Among the inflammatory messengers implicated in that storm, interleukin-6 has attracted particular attention. Laboratory and clinical studies have linked higher interleukin-6 signaling to seizure generation and to worse outcomes in NORSE, making the cytokine pathway a logical therapeutic target. Tocilizumab, a monoclonal antibody that binds the interleukin-6 receptor and prevents the cytokine from delivering its signal, is already approved for rheumatoid arthritis and other inflammatory conditions, and international consensus recommendations have endorsed it as an anti-inflammatory option during the acute phase of FIRES. What has been far less clear is whether the drug helps after the acute storm has passed and the child has settled into the chronic, seizure-burdened phase of the illness, when the window for rescuing the brain may seem to have closed.

To answer that question, the Beijing team assembled a retrospective cohort of twenty-seven pediatric patients with chronic-phase FIRES who received tocilizumab. These were children whose epilepsy had already become entrenched: the median duration of seizures at the time the first dose was given was sixteen months, with an interquartile range spanning six to thirty-four months. Over the course of treatment, each patient received a median of four doses of the drug, with a range of three to six. The investigators defined the primary outcome as the response rate at sixteen weeks after initiation, counting as responders those patients whose seizure frequency fell by at least fifty percent. Secondary outcomes included the response rate at twenty-eight weeks, changes in disability measured by the modified Rankin Scale, and treatment-related adverse events.

The results were striking for a syndrome with so few options. After sixteen weeks of tocilizumab, seventeen of the twenty-seven children, or 63 percent, had achieved at least a fifty percent reduction in seizure frequency, and two children, 7.4 percent, became entirely seizure free. Beyond seizure counts, the therapy appeared to change daily life: nineteen of twenty-seven patients, 70.4 percent, showed improvements in their modified Rankin Scale scores, a measure of functional disability. Perhaps equally telling, 81.5 percent of the children, twenty-two of twenty-seven, did not require any additional anti-seizure medications during the entire treatment period, suggesting that the drug’s benefit was not simply an artifact of polytherapy escalation. The benefits, however, were not uniformly durable. By twenty-eight weeks, the response rate had slipped to 48.1 percent, with thirteen of twenty-seven children still maintaining at least a halving of their seizures.

Safety data provided cautious reassurance. The most common adverse event was neutropenia, a depletion of a key class of infection-fighting white blood cells, which occurred in nine patients, or 33.3 percent of the cohort. Infections developed in four patients, 14.8 percent. Neither finding is surprising for a drug that deliberately dampens immune signaling, and both are manageable with monitoring, dose adjustment, and vigilance for early signs of infection. For families weighing the risks of a therapy against the relentless toll of uncontrolled seizures, the profile described in the study suggests that tocilizumab occupies a tolerable middle ground: powerful enough to matter, but not so hazardous that it cannot be given to children over repeated doses.

The study’s authors conclude that tocilizumab is effective in treating the epilepsy of chronic-phase FIRES, reducing seizure frequency in pediatric patients while remaining relatively safe. That conclusion carries weight beyond the twenty-seven patients enrolled. Because FIRES is so rare, randomized controlled trials are extraordinarily difficult to mount, and the field has advanced largely through case reports, small series, and expert consensus. A structured cohort study with predefined endpoints, quantified response rates, functional outcome measures, and systematic adverse-event tracking moves the evidence base a meaningful step forward. It also extends the therapeutic logic of the syndrome itself: if neuroinflammation ignites the acute catastrophe, the same inflammatory circuitry may continue to fuel seizures in the chronic phase, and blocking it can still yield clinical gains even after months of drug resistance.

The road ahead nevertheless demands caution. The study is retrospective, without a randomized control group, so spontaneous fluctuations in seizure burden or concurrent treatment changes cannot be fully excluded as contributors to improvement. The tapering of benefit between sixteen and twenty-eight weeks raises practical questions about dosing intervals, treatment duration, and whether maintenance strategies might consolidate early gains. Identifying which children are most likely to respond, perhaps through cytokine profiling or genetic markers, remains an open frontier. Larger, ideally prospective, multi-center studies will be needed to confirm the findings and to establish where tocilizumab belongs in the treatment algorithm relative to other immunotherapies such as anakinra, which blocks the related interleukin-1 pathway and has also shown promise in chronic-phase FIRES.

For now, the message for clinicians and families is one of tempered optimism. A child with chronic-phase FIRES who has endured more than a year of drug-resistant seizures may still respond to targeted immunotherapy, with nearly two-thirds of treated children in this cohort halving their seizure burden and most improving in functional status. In a field where therapeutic victories are measured in fewer seizures rather than cures, that is no small thing. The Beijing study gives neurologists a firmer evidence platform to offer tocilizumab earlier in the chronic phase, and it hands researchers a clear mandate: define the biology of interleukin-6 signaling in these young brains, and design the trials that will determine how long the benefit lasts.

Subject of Research: Efficacy and safety of tocilizumab, an interleukin-6 receptor antagonist, in treating chronic-phase febrile infection-related epilepsy syndrome in children

Article Title: Efficacy and safety of tocilizumab in the chronic phase of febrile infection-related epilepsy syndrome: a retrospective cohort study

Article References: Liu, W., Zhang, J., Deng, J., Yang, X.-L., Dong, H., Wu, Y., Sang, T., Ji, T.-Y., Zhu, Y., Jiang, Y.-W., & Wu, Y. (2026). Efficacy and safety of tocilizumab in the chronic phase of febrile infection-related epilepsy syndrome: a retrospective cohort study. World Journal of Pediatrics. https://doi.org/10.1007/s12519-026-01065-y

Image Credits: AI Generated

DOI: 10.1007/s12519-026-01065-y

Keywords: tocilizumab, FIRES, febrile infection-related epilepsy syndrome, new-onset refractory status epilepticus, interleukin-6 receptor, pediatric epilepsy, neuroinflammation, immunotherapy, seizure frequency, modified Rankin Scale, retrospective cohort study, World Journal of Pediatrics