We performed two systematic searches in the PubMed database. The results have been updated until January 12, 2013. No ethical committee approval was deemed necessary for this literature review and meta-analysis.
Outcome of status epilepticus
For the first search, the term status epilepticus was combined with outcome, mortality, morbidity, fatality, prognosis, coma, death, incidence, prevalence and epidemiology. For a paper to be included in this literature review, status epilepticus had to be defined as a single continuous seizure or a series of epileptic seizures with clouded consciousness between ictal events; although most studies used a minimum duration of 30 minutes in the definition (in accordance with traditional guidelines), we did not use this as an inclusion criterion since modern data and guidelines use less stringent time criteria . We limited the search to human studies on adults written in English, Dutch or Turkish. We excluded review articles, case reports and treatment protocols. Full text screening and reviewing of the residual studies was conducted. We included studies on generalized and focal SE (or both), but excluded studies that focused on specific subgroups of SE such as refractory SE, elderly patients only or critically ill patients. To be included, a study had to have more than 5 tumor patients in the study group. Also, information on one or more of the following outcomes had to be available: short-term mortality, long-term morbidity and duration of SE. The screening and selection of papers from the original search was performed by one author (YA) and reviewed by the last author (TJS).
We defined mortality as short-term mortality, and we included data on 30-day mortality, case fatality or mortality at discharge. Long-term morbidity was defined as the occurrence of new neurological deficits that lasted beyond the regular post-ictal period. To be included, data had to be available on (a) either the ‘back to baseline’-percentages, or – conversely – the percentages of patients who had worsened clinically after SE, and (b) mortality. For inclusion in the analysis on duration of SE, data had to be available on the mean SE duration (in minutes or hours). For all the outcomes, we extracted separate data for tumor-related SE versus SE due to other causes.
Within the subgroup of SE due to causes other than tumors, the subgroup of patients with hypoxic/anoxic encephalopathy (HAE) after cardiopulmonary resuscitation represents a specific subgroup, in which the occurrence of SE itself is associated with a very poor prognosis . In these cases, the mortality is thought to be the consequence of the disease itself (HAE) rather than of the SE. To exclude an effect of such HAE-associated mortality on the outcomes, the outcome analyses were repeated after exclusion of cases with HAE-associated SE.
Authors were contacted by email if a study had missing or incomplete information.
Based on the data from the separate studies, we calculated the total number of patients with tumor-related SE and patients with SE due to another cause. We then calculated total mortality and morbidity and the median duration of SE for both groups. From these grouped data, we calculated the weighted averages for all outcomes, and expressed the difference between patient groups as relative risk (RR) and 95% confidence interval (95%-CI) for mortality and morbidity. For comparison of SE duration between groups, we used the Mann-Whitney test.