Seminars in epileptology: How to diagnose status epilepticus in adults and children

Abstract

Status epilepticus (SE) can be regarded as the most severe expression of seizure activity characterized by a low probability of spontaneous cessation and mechanisms leading to metabolic and inflammatory derangements with increased risk of brain damage, alterations of neural networks, and potentially life-threatening systemic complications. Time-based criteria are fundamental in diagnosing SE as response to treatment and outcomes worsen with increasing duration in terms of neurological impairment and mortality. Classification of status epilepticus includes four axes: semiology, EEG correlates, etiology, and age. Semiology, especially when evolving from SE with prominent motor phenomena (SE-PM) to nonconvulsive status epilepticus (NCSE) with impaired consciousness, is associated with drug resistance and poor prognosis. The Salzburg EEG criteria define four subcategories of NCSE. The umbrella term ictal-interictal continuum (IIC) includes a wide spectrum of EEG changes ranging from almost non-epileptic situations to conditions that just fail to fulfill the criteria of NCSE. From a pathophysiologic point of view, EEG patterns on the IIC might be generated by both the underlying etiology and the superimposed hypersynchronous epileptic activity. It is impossible to disentangle their relative contributions by visual inspection of the EEG. However, it is essential to identify the contribution of ictal activity in an individual patient as it may be amenable to treatment with antiseizure medication (ASM). The main approach is to perform a diagnostic intravenous ASM trial (diagnostic IV-ASM trial) during EEG recording and to assess for both EEG and clinical response. Furthermore, CT- and MRI-perfusion studies help to clarify the diagnosis. Early and consequent treatment is necessary to minimize the total time spent in status, also called seizure burden. This educational review focuses on the diagnosis of status epilepticus in children and adults, excluding neonatal status.

Keywords: ASM trial; Salzburg criteria; etiology; ictal‐interictal continuum; nonconvulsive.

FIGURE 1

Overview over the diagnostic criteria of NCSE for patients without pre‐existing epileptic encephalopathy. Modified with permission from Hirsch et al. 2021.

FIGURE 2

The figure shows the two forms of electrographic SE (ESE). Both need to last at least 10 continuous minutes or at least 20% of any our recording. (A) Epileptiform discharges (EDs) exceeding 2.5 Hz (measured as 25 EDs in 10 s) shown in bipolar (upper trace) and common average montage (lower trace). (B) Evolution in frequency, location, or morphology referring to ACNS Critical Care terminology, bipolar montage. (A and B) 30 mm/s, 7 μV/mm, .53 Hz/30 Hz; Reproduced with permission from Leitinger et al. in Brigo et al. 2024.

FIGURE 3

The figure shows the two forms of electroclinical SE (ECSE). Both need to last at least 10 continuous minutes or at least 20% of any our recording. (A) A clinical correlate time‐locked to EEG pattern, bipolar montage. Oblique green arrows indicate LPDs 1 Hz, the vertical blue arrows point to time locked jerks of the jaw. (B) EEG AND clinical improvement to a diagnostic IV ASM trial, before (upper trace) and after (lower trace) intravenous anti‐seizure medication, bipolar montage. A and B: 30 mm/s, 7 μV/mm, .53 Hz/30 Hz; Reproduced with permission from Leitinger et al. in Brigo et al. 2024.

FIGURE 4

Hepatic failure. The figure shows bifrontal triphasic waves in a 70 year old patient with hepatic encephalopathy due to alcohol‐mediated liver cirrhosis with serum ammonia level of 118 mmol/L (normal range 17–47). (A) Bipolar montage. (B) common average montage. (A and B) 30 mm/s, 7 μV/mm, .53 Hz/30 Hz; Reproduced with permission from Leitinger et al. in Brigo et al.

FIGURE 5

Diagnosing status epilepticus automatically implicates the meticulous and instantaneous search for its etiology as this could need emergency treatment like the status epilepticus itself. Ischemic stroke is both the most important differential diagnosis of SE and its most important underlying etiology in some parts of the world. (yellow: History, ocre: Investigations; light orange: EEG; green: First potential etiologies and in case of NCSE also differential diagnoses). P applies to children, A applies to adults.