Brief CommunicationSalzburg Consensus Criteria for Non-Convulsive Status Epilepticus – approach to clinical application
Introduction
Status epilepticus (SE) is a potentially life-threatening condition with mortality rates of up to 39% in convulsive SE in population-based studies [1]. However, data for nonconvulsive SE (NCSE) are sparse compared to convulsive forms [2]. Furthermore, clinical and EEG definitions for NCSE have changed over time [3], [4], [5], [6]. A consensus panel at the 4th London–Innsbruck Colloquium on status epilepticus and acute seizures held in Salzburg (2013) proposed working criteria for the EEG diagnosis of NCSE (Salzburg Consensus Criteria for Non-Convulsive Status Epilepticus, SCNC) [6]. The American Clinical Neurophysiology Society (ACNS) had published proposals for a Standardized Critical Care EEG Terminology [7], [8], which are now widely used and have a high interrater agreement [9]. The ACNS criteria were intended to be used in EEG studies of hypoxic patients [10], but not yet for nonhypoxic patients with NCSE. We performed a single center investigation to test the influence of ACNS criteria on test performance of SCNC regarding specificity and sensitivity in nonhypoxic patients with NCSE. In addition, we used the two currently available outcome scores, Status Epilepticus Severity Score (STESS) [11] and Epidemiology based Mortality Score in SE (EMSE) [12] to allow for risk stratification for bad outcome (death) in this patient group.
Section snippets
Methods
We investigated fifty consecutive nonhypoxic patients with diagnoses of NCSE (identified by final diagnosis at discharge) from January to October 2014 and 50 consecutive controls without clinical suspicion of NCSE but abnormal EEGs (identified by EEG reports) in the first six days of 2014 at the Department of Neurology, Paracelsus Medical University, Salzburg, Austria. The investigations were done in four steps.
In all four parts, the following criteria were applied to EEGs of patients without
Results
Demographics of patients with diagnosis of NCSE at discharge and controls are presented in Table 1.
Strategies of EEG reading had a statistically significant influence on the false positive diagnosis of NCSE in controls (Fig. 1).
The various criteria upon which the diagnosis of NCSE was established are depicted in Table 2.
There were two false negatives (FNs) in 50 patients with NCSE. One patient with absence status had no continuous spike–wave activity for 10 s but many paroxysms filling
Test performance of SCNC
Implementing the ACNS definition of rhythmic delta activity significantly increased the specificity of SCNC. Another mild increase in specificity (not significant) by adding the ACNS criterion of fluctuation was accompanied by a minimal decrease in sensitivity because a patient with RDT without fluctuation with a clinically definite diagnosis of NCSE gave one false negative. As pathological EEGs without suspicion of NCSE (recruiting time for 50 consecutive abnormal EEGs in our center: one week)
Conclusion
Salzburg Consensus Criteria for Non-Convulsive Status Epilepticus implementing the ACNS definitions for rhythmic delta activity avoid numerous false positives. The ACNS criterion for fluctuation further reduces false positives marginally but, in turn, leads to small loss of sensitivity. Further studies are needed to identify correct procedure. Epidemiology based Mortality Score in SE was superior to STESS-3 and STESS-4 in this cohort. We propose a modified SCNC (mSCNC) for further research and
Acknowledgments
We would like to thank all medical staff in the EEG laboratory, normal ward, and intensive care unit for taking best care of their patients. We thank Manuela Schmidlechner for substantial technical support.
Funding
None.
Conflict of interests
E Trinka has acted as a paid consultant for Eisai, Ever Neuropharma, Biogen Idec, Medtronic, Bial, Takeda, and UCB. He has received research funding from UCB, Biogen Idec, Sanofi-Aventis, FWF, Jubiläumsfond der Österreichischen Nationalbank, and Red Bull. He
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