What are the Salzburg criteria for seizure evaluation and treatment?

Salzburg Criteria for Seizure Evaluation

The Salzburg Criteria are specifically designed for diagnosing non-convulsive status epilepticus (NCSE) and have high diagnostic accuracy with excellent inter-rater agreement, making them suitable for implementation in clinical practice. 1

Definition and Purpose

• The Salzburg Consensus Criteria (SCC) were proposed at the 4th London-Innsbruck Colloquium on status epilepticus in Salzburg in 2013 to standardize the diagnosis of non-convulsive status epilepticus (NCSE) 2
• NCSE is a challenging electroencephalographic (EEG) diagnosis that requires specific criteria to avoid misdiagnosis 3
• The criteria were developed to address the lack of universally accepted definitions for status epilepticus, which has traditionally been defined as at least 30 minutes of persistent seizures or recurrent seizures without complete return to consciousness 4

Salzburg Criteria Components

For patients without pre-existing epileptic encephalopathy, the following criteria apply:

1. Definite NCSE is diagnosed when one of the following is present:

   • More than 25 epileptiform discharges (ED) per 10-second epoch (>2.5/s) 2
   • EDs ≤2.5/s or rhythmic delta/theta activity (RDT) exceeding 0.5/s AND at least one of:
     • Clinical and EEG improvements from antiseizure medications (ASMs) 2
     • Subtle clinical phenomena during the EEG abnormalities 2
     • Typical spatiotemporal evolution of the EEG pattern 2

2. Possible NCSE is diagnosed when there is:

   • Fluctuation of EEG patterns without evolution 2
   • EEG improvement without clinical improvement after ASM administration 2

Implementation of Diagnostic ASM Trial

When using medication response as a diagnostic criterion:

• Either benzodiazepines or non-benzodiazepine ASMs can be used as first choice 5
• Non-benzodiazepines (levetiracetam, valproate, lacosamide, brivaracetam) should be considered in patients with impaired alertness or at risk of respiratory depression 5
• The recommended starting dose is approximately two-thirds to three-quarters of the full loading dose used for status epilepticus treatment 5
• ASMs should be administered during EEG recording under supervision with monitoring for at least 15 minutes 5

Assessing Response to ASM Trial

• Positive EEG response: Resolution of the ictal-interictal continuum pattern for at least three times the longest previously observed spontaneous interval of resolution (minimum one continuous minute) 5
• Clinical response: Should be assessed using a standardized examination before and after IV ASM administration, with at least one-step improvement on a dedicated NCSE response scale 5

Clinical Validation and Accuracy

• The Salzburg criteria have been clinically validated with high diagnostic accuracy (92.5%) 1
• Sensitivity of 97.7% and specificity of 89.6% in validation cohorts 1
• Positive predictive value of 84.0% and negative predictive value of 98.6% 1
• Excellent inter-rater agreement (k=0.87) 1

Clinical Applications and Outcomes

• Implementation of the Salzburg criteria has been shown to improve patient management and prognosis 3
• Therapeutic changes occur significantly more often in patients fulfilling Salzburg criteria (84%) compared to those who don't (16%) 1
• The presence of "plus" modifiers in the EEG (as defined by ACNS terminology) is associated with higher mortality in NCSE patients 6

Pitfalls and Caveats

• False positive diagnoses can occur if rhythmic delta/theta activity is not carefully defined according to ACNS criteria 2
• Using the American Clinical Neurophysiology Society's Standardized Critical Care EEG Terminology alongside Salzburg criteria reduces false positives from 28% to 0% 2
• Patients diagnosed with "possible NCSE" still require careful monitoring as 50% may have poor outcomes if left untreated 3
• Post-anoxic patients may have worse outcomes if NCSE is missed and left untreated 3

Recommendations for Practice

• Use Salzburg criteria in conjunction with ACNS terminology for optimal diagnostic accuracy 2
• Consider both clinical and EEG responses when evaluating treatment effectiveness 5
• Implement standardized approaches to ASM trials during EEG to improve diagnostic certainty 5
• Recognize that approximately 30% of unconscious patients in ICUs may have NCSE according to Salzburg criteria 6