BACKGROUND: Salzburg Consensus Criteria for diagnosis of Non-Convulsive Status 
Epilepticus (SCNC) were proposed at the 4th London-Innsbruck Colloquium on 
status epilepticus in Salzburg (2013).
METHODS: We retrospectively analyzed the EEGs of 50 consecutive nonhypoxic 
patients with diagnoses of nonconvulsive status epilepticus (NCSE) at discharge 
and 50 consecutive controls with abnormal EEGs in a large university hospital in 
Austria. We implemented the American Clinical Neurophysiology Society's 
Standardized Critical Care EEG Terminology, 2012 version (ACNS criteria) to 
increase the test performance of SCNC. In patients without preexisting epileptic 
encephalopathy, the following criteria were applied: (1) more than 25 
epileptiform discharges (ED) per 10-second epoch, i.e., >2.5/s and (2) patients 
with EDs ≤ 2.5/s or rhythmic delta/theta activity (RDT) exceeding 0.5/s AND at 
least one of the additional criteria: (2a) clinical and EEG improvements from 
antiepileptic drugs (AEDs), (2b) subtle clinical phenomena, or (2c) typical 
spatiotemporal evolution. In case of fluctuation without evolution or EEG 
improvement without clinical improvement, "possible NCSE" was diagnosed. For 
identification of RDT, the following criteria were compared: (test condition A) 
continuous delta-theta activity without further rules, (B) ACNS criterion for 
rhythmic delta activity (RDA), and (C) ACNS criteria for RDA and fluctuation.
RESULTS: False positive rate in controls dropped from 28% (condition A) to 2% 
(B) (p = 0.00039) and finally to 0% (C) (p = 0.000042). Application of test 
condition C in the group with NCSE gives one false negative (2%). Various EEG 
patterns were found in patients with NCSE: (1) 8.2%, (2a) 2%, (2b) 12.2%, and 
(2c) 32.7%. Possible NCSE was diagnosed based on fluctuations in 57.1% and EEG 
improvement without clinical improvement in 14.2%.
CONCLUSION: The modified SCNC with refined definitions including the ACNS 
terminology leads to clinically relevant and statistically significant reduction 
of false positive diagnoses of NCSE and to minimal loss in sensitivity. This 
article is part of a Special Issue entitled "Status Epilepticus".