Summary: Objective: In 2015, the International League Against Epilepsy (ILAE) proposed a new definition of status epilepticus (SE): 5 minutes of ongoing seizure activity to diagnose convulsive SE (CSE, ie, bilateral tonic–clonic SE) and 10 minutes for focal SE and absence SE, rather than the earlier criterion of 30 minutes. Based on semiology, several types of SE with prominent motor phenomena at any time (including CSE) were distinguished from those without (ie, nonconvulsive SE, NCSE). We present the first population‐based incidence study applying the new 2015 ILAE definition and classification of SE and report the impact of the evolution of semiology and level of consciousness (LOC) on outcome.Methods: We conducted a retrospective population‐based incidence study of all adult patients with SE residing in the city of Salzburg between January 2011 and December 2015. Patients with hypoxic encephalopathy were excluded. SE was defined and classified according to the ILAE 2015.Results: We identified 221 patients with a median age of 69 years (range 20‐99 years). The age‐ and sex‐adjusted incidence of a first episode of SE, NCSE, and SE with prominent motor phenomena (including CSE) was 36.1 (95% confidence interval [CI] 26.2‐48.5), 12.1 (95% CI 6.8‐20.0), and 24.0 (95% CI 16.0‐34.5; including CSE 15.8 [95% CI 9.4‐24.8]) per 100 000 adults per year, respectively. None of the patients whose SE ended with or consisted of only bilateral tonic–clonic activity died. In all other clinical presentations, case fatality was lower in awake patients (8.2%) compared with patients with impaired consciousness (33%).Significance: This first population‐based study using the ILAE 2015 definition and classification of SE found an increase of incidence of 10% compared to previous definitions. We also provide epidemiologic evidence that different patterns of status evolution and LOCs have strong prognostic implications.

Objective: To characterize the clinical, EEG, and brain imaging findings in an adult case series of patients with de novo refractory status epilepticus (SE) occurring after a febrile illness. Methods: A retrospective study (2010–2013) was undertaken with the following inclusion criteria: (1) previously healthy adults with refractory SE; (2) seizure onset 0–21 days after a febrile illness; (3) lacking evidence of infectious agents in CSF; (4) no history of seizures (febrile or afebrile) or previous or concomitant neurologic disorder. Results: Among 155 refractory SE cases observed in the study period, 6 patients (17–35 years old) fulfilled the inclusion criteria. Confusion and stupor were the most common symptoms at disease onset, followed after a few days by acute repeated seizures that were uncountable in all but one. Seizures consisted of focal motor/myoclonic phenomena with subsequent generalization. Antiepileptic drugs failed in every patient to control seizures, with all participants requiring intensive care unit admission. Barbiturate coma with burst-suppression pattern was applied in 4 out of 6 patients for 5–14 days. One participant died in the acute phase. In each patient, we observed a reversible bilateral claustrum MRI hyperintensity on T2-weighted sequences, without restricted diffusion, time-related with SE. All patients had negative multiple neural antibodies testing. Four out of 5 surviving patients developed chronic epilepsy. Conclusions: This is a hypothesis-generating study of a preliminary nature supporting the role of the claustrum in postfebrile de novo SE; future prospective studies are needed to delineate the specificity of this condition, its pathogenesis, and the etiology.

New-onset refractory status epilepticus (NORSE) is a rare but challenging condition occurring in a previously healthy patient, often with no identifiable cause. We describe the electro-clinical features and outcomes in a group of patients with NORSE who all demonstrated a typical MRI sign characterized by bilateral lesions of the claustrum. The group includes 31 patients (12 personal and 19 previously published cases; 17 females; mean age of 25 years). Fever preceded SE in twenty-eight patients, by a mean of six days. SE was refractory/super-refractory in 74% of the patients, requiring third line agents and a median of 15 days staying in an intensive care unit. Focal motor and tonic-clonic seizures were observed in 90%, complex partial seizures in 14%, and myoclonic seizures in 14% of the cases. All patients showed T2/FLAIR hyper-intense foci in bilateral claustrum, appearing on average 10 days after SE onset. Other limbic (hippocampus, insular) alterations were present in 53% of patients. Within the personal cases, extensive search for known auto-antibodies was inconclusive, though in 7 of 11 patients had CSF lymphocytic pleocytosis and three cases had oligoclonal bands. Two subjects died during the acute phase, one in the chronic phase (probable sudden unexplained death in epilepsy), and one developed a persistent vegetative state. Among survivors, 80% developed drug-resistant epilepsy. Febrile-illness related SE associated with bilateral claustrum hyperintensity on MRI represents a homogeneous condition with defined clinical features and a presumed but unidentified autoimmune aetiology. A better characterization of de novo SE is mandatory for the search of specific etiologies.

Biomarkers of neuronal damage in status epilepticus (SE) would be of great relevance for clinical and research purposes. In a retrospective cross‐sectional study, serum neurofilament light chain (NfL) levels were measured in patients with SE (30 subjects), patients with drug‐resistant epilepsy (30 subjects), and healthy controls (30 subjects). Serum NfL levels were higher in patients with SE (median = 26.15 pg/ml) compared to both epilepsy patients (median = 7.35 pg/ml) and healthy controls (median = 6.81 pg/ml; p < .001). In patients with SE, serum NfL levels showed a high correlation with cerebrospinal fluid (CSF) NfL (τ = .68, p < .001) as well as with CSF total tau (t‐tau) levels (τ = .627, p < .001); they were higher in SE lasting >24 h (p = .013), in refractory/superrefractory SE (p = .004), and in patients who died within 30 days or who presented a worsening of clinical conditions (p = .001). Values of >28.8 pg/ml predicted 30‐day clinical worsening or death (odds ratio [OR] = 10.83, 95% confidence interval [CI] = 1.96–59.83, p = .006) and SE refractoriness (OR = 9.33, 95% CI = 1.51–57.65, p = .016). In conclusion, serum NfL levels are increased in SE and correlate with SE treatment response, duration, and outcomes, therefore representing a promising biomarker of seizure‐related neuronal damage.