Elsevier

Clinical Neurophysiology

Volume 127, Issue 4, April 2016, Pages 2056-2064
Clinical Neurophysiology

Review
Ictal–interictal continuum: A proposed treatment algorithm

https://doi.org/10.1016/j.clinph.2016.02.003Get rights and content

Highlights

  • Periodic and rhythmic EEG patterns that fall along the ictal–interictal continuum -IIC- are encountered frequently during continuous EEG monitoring in critically ill patients.

  • There are clinical scenarios where the occurrence of an IIC pattern is highly suspicious for ictal activity and may contribute to secondary neuronal injury.

  • A treatment algorithm is proposed based on actual IIC knowledge and best current practice in adults.

Abstract

The ictal–interictal continuum (IIC) is characterized by periodic and/or rhythmic EEG patterns that occur with relative high frequency in critically ill patients. Several studies have reported that some patterns seen within the continuum are independently associated with poor outcome. However there is no consensus regarding when to treat them or how aggressive treatment should be. In this review we examine peer-reviewed original scientific articles, guidelines and reviews indexed in PubMed and summarize current knowledge related to the ictal–interictal continuum. A treatment algorithm to guide management of critically ill patients with EEG patterns that fall along the IIC is proposed. The algorithm-based on best current practice in adults-takes into account associated clinical events, risk factors for developing seizures, response to medication trials and biomarkers of neuronal injury.

Section snippets

Background

Continuous electroencephalographic (cEEG) monitoring in the intensive care arena has brought increasing recognition to complex periodic and rhythmic electrographic patterns that occur with relatively high frequency in critically ill patients. These patterns are typically recognized during coma and do not meet definitive criteria for either an ictal or interictal pattern but rather lie along a spectrum commonly referred to as the ictal–interictal continuum (IIC) (Brenner, 2009, Chong and Hirsch,

Proposed treatment algorithm

We propose a practical treatment algorithm that could help decision making when confronted with EEG patterns that fall along the ictal–interictal continuum in critically ill adult patients (Fig. 1). This algorithmic approach takes into account associated clinical events, clinical risk factors as well as what is currently known regarding the association of seizures and potential neuronal injury of various EEG patterns and characteristics. In addition, response to the administration of a

Case examples

Below we present case examples of patients with patterns that lie along the IIC. Management of these different clinical situations is presented for the purpose of illustrating use of the proposed treatment algorithm.

Conclusion

Continuous EEG monitoring in ICU is a field that has been rapidly expanding in the last 10 years. The technique provides physicians with a sensitive and quick way to identify malignant EEG patterns in critically ill patients that may impact their clinical course and prognosis. There are a number of lines of evidence supporting the idea that nonconvulsive seizures and possibly PDs may result in secondary neuronal injury and worse outcome, therefore warranting treatment (Drislane, 1999,

Conflict of interest

Valia Rodríguez and Megahn F. Rodden declare that they have no conflict of interest. Suzette M. LaRoche declares that she has received royalties from Demos Publishing.

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      Based on EEG response, a second ASM can be added if clinical or electrographic improvement is not seen. The alternative method is to start more aggressively with intravenous anesthetics which will increase the risk of cardiorespiratory depression but provides greater chance of a rapid and effective treatment in order to prevent secondary neuronal injury [68]. Sometimes, these patterns can be refractory to initial therapies and could require continuous infusion of sedative-anesthetic drugs such as midazolam and propofol for adequate treatment [72].

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    1

    These authors contributed equally to this article.

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