Super-Refractory Status Epilepticus Linked With Unknown Etiologies, High Mortality Rates

Christoph P. Beier

In a meta-analysis understanding the differences of super-refractory status epilepticus (SRSE), findings showed that patients with SRSE had more often acute or unknown etiologies, and that established prognostic factors for first-time overall SE did not reliably predict in-hospital mortality in patients with SRSE. While treatment was successful in stopping seizures for most patients, the risk of death or severe disability at discharge was high, with an in-hospital mortality rate of 24.1%.

To assess clinical characteristics, causes, outcomes, prognostic factors, and treatment approaches for patients with SRSE, investigators pulled 95 articles and 30 conference abstracts that included 1200 patients with nonanoxic SRSE. Senior investigator Christoph P. Beier, medical specialist in neurology at the University of Southern Denmark, and colleagues included all studies of patients diagnosed with SRSE, which was defined as SE that continues or recurs 24 hours or more after the onset of anesthetic therapy, including cases where SE recurs on reduction or after withdrawal of anesthesia.

Aside from the high in-hospital mortality, 81.3% of all patients had their SRSE successfully ceased through treatment. Of all patients analyzed in the meta-analysis, 26.8% were discharged from the hospital with no or minor to moderate disability. The remainder were either dead or severely disabled at discharge. Notably, the rate of successful seizure termination continued to rise with increasing duration; however, the proportion of patients with substantial disability defined as a modified Rankin Scale (mRS) score of 3 to 5 also increased substantially with longer duration of SRSE.

"Patients with reported SRSE differed significantly from unselected patients with first-time overall SE," Beier et al wrote. "The treating physicians may have prioritized patients with an expected more favorable overall prognosis and unknown diagnoses and avoided treatment with poorer prospects, eg, patients with brain tumors or more fragile, older patients. This may explain why established prognostic factors for in-hospital mortality, such as age and etiology, did not apply for SRSE."

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The investigators continued, "The plateau in mortality after 28 days of treatment might be due to a combination of survival of the most robust patients and the reluctance of the treating physicians to terminate treatment once they had decided to continue treatment for more than 1 month (effort justification bias). The continuously increasing rate of seizure cessation after 28 days of treatment probably results from a combination of genuine treatment successes, reporting bias, and, conceivably, substantial brain damage destroying the epileptic focus after many weeks of continuous seizures."

Patients with SRSE had a distinct pattern of etiologies where acute cerebral events and unknown etiologies accounted for 41.6% and 22.3% of all etiologies, respectively. While there were only slight differences between patients with SRSE in the meta-analysis and those in larger cohort studies, investigators observed substantial differences between patients in the meta-analysis and those with first-time overall SE from a historical, retrospective, unselected cohort.

In an analysis of clinical characteristics of patients with SRSE according to their outcome (n = 266), findings showed that favorable functional outcome was associated with younger age and lower number of ASMs tried but not duration of SE. In addition, the status epilepticus severity score was not consistently associated with in-hospital mortality (nonsignificant for a cutoff of 3; P = .02), and there were insufficient data for the analysis of other prognostic scores.

Additional findings from the meta-analysis revealed that half (50%) of the cohort tried between 3 to 6 antiseizure medications (ASMs), with levetiracetam, valproic acid, phenytoin, and lacosamide as the most frequently used. The number of ASMs reported was associated with higher disability at discharge but not with reduced in-hospital mortality or higher rates of treatment success. Investigators also found no data indicating altered outcomes after treatment with barbiturates, ketamine, vagus nerve stimulator, or ketogenic diet.

REFERENCE
1. Cornwall CD, Kroigard T, Kristensen JSS, et al. Outcomes and treatment approaches for super-refractory status epilepticus. JAMA Neurol. 2023;80(9):959-968. doi:10.1001/jamaneurol.2023.2407