How Long Is Too Long? Seizure Duration Emerges as a Context-Dependent Clue to Status Epilepticus Outcomes

When a seizure refuses to stop, every passing minute feels decisive in the emergency department. Status epilepticus, the neurological emergency defined by continuous or rapidly recurrent seizure activity, has long been taught as a race against the clock: the longer the seizure lasts, the worse the patient fares. A new systematic review published in the Journal of Neurology by Fabio Iannaccone, Chiara Pizzanelli and colleagues at the University of Pisa, together with collaborators in Barcelona and at IRCCS Neuromed, puts that intuition to one of its most rigorous tests to date. Pooling evidence from forty-three studies published between 1994 and 2025, the team set out to quantify how the duration of status epilepticus relates to three outcomes that matter most to patients and clinicians: death, long-term functional impairment, and resistance to treatment.

The answer, distilled from three decades of clinical research, is more nuanced than the simple dictum that time equals damage. The reviewers found that longer seizure duration was more consistently and more independently associated with worse functional outcome, meaning lasting motor or cognitive impairment, than with mortality itself. The link between duration and death, while present in many individual studies, proved weaker and less reliable once other determinants were taken into account. The reason, the authors argue, is that mortality in status epilepticus is shaped by a crowded field of competing forces: the underlying cause of the seizure, the patient’s premorbid vulnerability, and the severity of systemic complications such as hypoxia, hyperthermia, and metabolic derangement. Duration, in other words, is only one voice in a chorus.

To appreciate why this finding matters, it helps to understand what happens to the brain during prolonged seizure activity. Experimental work dating back to the classic 1973 studies by Meldrum and colleagues in paralyzed, artificially ventilated baboons demonstrated that even when systemic factors are controlled, prolonged seizures injure neurons. Later human autopsy studies, including work by Fujikawa and colleagues published in 2000, documented neuronal loss in patients who died of status epilepticus without systemic complications. Excitotoxic mechanisms, in which excessive glutamate signaling floods neurons with calcium, combined with GABAergic receptor internalization that makes seizures progressively resistant to standard antiseizure drugs, create a vicious cycle in which the seizure itself remodels the circuits that should terminate it. This pharmacoresistance is precisely why early treatment matters: benzodiazepines work far better in the first minutes than after an hour of continuous firing.

Yet the new review exposes a methodological Achilles heel that has haunted this literature since its inception. The definition and measurement of seizure duration varied enormously across the forty-three included studies. Some counted duration from the onset of clinically visible convulsions; others anchored it to electrographic onset on continuous EEG. Some measured the time to seizure termination under treatment; others summed cumulative seizure time across recurrences. Analytical strategies diverged just as widely, with some studies treating duration as a continuous variable and others dichotomizing patients at thresholds that ranged from thirty minutes to several hours, often without explicit justification. The reviewers assessed risk of bias with the QUIPS tool and synthesized the outcome-specific associations narratively, precisely because the heterogeneity made a formal meta-analysis of pooled effect estimates untenable.

The mortality signal illustrates the problem vividly. Thirty-one of the included studies examined death as an outcome, spanning settings from population-based cohorts in Richmond, Virginia and Auckland, New Zealand to intensive care units across Europe and tertiary centers in Asia. Landmark work such as the 1994 study by Towne and colleagues on determinants of mortality, and more recent analyses of long-term survival trajectories using the ACD score, consistently identified etiology, age, and level of consciousness as dominant predictors. Against those heavyweight variables, duration often lost statistical independence. A brief seizure caused by a massive stroke can be lethal, while a prolonged but eventually controlled seizure in a young patient with a reversible metabolic trigger may leave no lasting deficit. Duration, the review concludes, should be read as a context-dependent prognostic marker rather than an absolute threshold.

Functional outcome told a different and arguably more coherent story. Twenty-six studies assessed motor or cognitive impairment after status epilepticus, and here longer duration aligned more reliably with worse results. Studies of prolonged and super-refractory status epilepticus, including cohorts from Basel and Erlangen and the French multicenter experience reported by Legriel and colleagues, found that patients whose seizures persisted for hours or days faced substantially higher risks of dependency and cognitive decline. Cognitive studies using formal neuropsychometric instruments, such as the analysis by Adachi and colleagues with the Wechsler Adult Intelligence Scale-Revised, documented measurable intellectual deterioration after prolonged episodes. The biological plausibility is strong: the longer networks remain in an ictal state, the more extensive the excitotoxic injury to hippocampal and neocortical structures that subserve memory and motor control.

Refractoriness, the tendency of a seizure to resist first- and second-line therapy, added a third dimension. Only seven studies examined this outcome, so the evidence base is thin, but the reviewers describe it as limited yet consistent: prolonged seizures were linked to treatment resistance. This relationship is bidirectional in practice, because delayed treatment extends duration and extended duration breeds pharmacoresistance through receptor trafficking. A 2021 study by Gutiérrez-Viedma and colleagues showed that therapy delay in status epilepticus extends its duration and worsens prognosis, while work by Guterman and colleagues demonstrated that the pattern of treatment progression itself shapes the burden of illness. Recent analyses, including a 2026 study suggesting that treatment adequacy outweighs treatment sequence in nonconvulsive status epilepticus, reinforce the message that what clinicians do, and how quickly, matters as much as the clock alone.

The review also grapples with the thorny question of where a seizure begins and ends, a problem that a companion 2026 scoping review by Khan and colleagues tackled directly by proposing a framework for standardizing the endpoint of status epilepticus. In convulsive seizures, onset is usually timed from the first observable motor manifestation, but in nonconvulsive status epilepticus, which can occur without any visible convulsion, onset may only be revealed by EEG, sometimes hours after the true start. Recurrence rules differ too: is a seizure that stops and restarts within an hour one prolonged event or two separate ones? Each choice changes the measured duration and can flip a patient across a categorical threshold. The reviewers call for standardized onset and termination criteria, explicit recurrence rules, and harmonized statistical modeling so that future studies can be compared and combined meaningfully.

For clinicians at the bedside, the practical takeaways remain reassuringly aligned with long-standing practice. Time is still brain, and the pharmacological window for terminating a seizure with benzodiazepines closes quickly. But the review cautions against reading duration as a standalone death sentence or a rigid cutoff for aggressive escalation. A patient’s trajectory is jointly determined by the electroclinical phenotype of the seizure, whether convulsive, focal, nonconvulsive, or the devastating post-anoxic variety, by the underlying etiology, whether acute structural injury, infection, autoimmune encephalitis, or drug withdrawal, and by systemic severity. Prognostic scores that integrate these domains, rather than duration alone, offer the most honest guidance for counseling families and calibrating intensive care.

For researchers, the message is a call to methodological discipline. The Pisa team’s synthesis, conducted under PRISMA 2020 reporting standards and published as Volume 273, article 644 of the Journal of Neurology, does not deliver a single magic number, and it deliberately refuses to invent one. Instead, it maps the terrain: duration matters most for functional recovery, less decisively for survival, and plausibly for refractoriness, but only when measured and modeled consistently. As continuous EEG monitoring spreads and machine-learning approaches to seizure detection mature, the raw material for precise duration measurement is finally becoming available at scale. The challenge now, the authors argue, is to agree on the rules of the game, so that the next systematic review can move beyond narrative synthesis and tell clinicians exactly how many minutes separate a good outcome from a devastating one.

Subject of Research: Association between duration of status epilepticus and mortality, functional outcome, and treatment refractoriness in adults

Article Title: Associations between duration of status epilepticus and clinical outcomes in adults: a systematic review

Article References: Iannaccone, F., Scarpitta, C., De Rossi, E., Milano, C., Turco, F., Bonanni, E., Fornai, F., Ceravolo, R., & Pizzanelli, C. (2026). Associations between duration of status epilepticus and clinical outcomes in adults: a systematic review. Journal of Neurology, 273(10), Article 644. https://doi.org/10.1007/s00415-026-14179-0

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14179-0

Keywords: status epilepticus, seizure duration, mortality, functional outcome, refractory status epilepticus, prognosis, systematic review, neurology, epilepsy, electroencephalography, neurocritical care, excitotoxicity