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Crit Care. 2018 Aug 2;22(1):184. doi: 10.1186/s13054-018-2104-z.

Value and mechanisms of EEG reactivity in the prognosis of patients with impaired consciousness: a systematic review.

Author information

1
Department of Physiology and Department of Critical Care Medicine, Raymond Poincaré Hospital, Assistance Publique - Hôpitaux de Paris (AP-HP), Inserm UMR 1173 Infection and Inflammation, University of Versailles Saint Quentin (UVSQ), University Paris-Saclay, Garches, Paris, France. eric.azabou@aphp.fr.
2
Clinical Neurophysiology Unit, Raymond Poincaré Hospital - Assistance - Publique Hôpitaux de Paris, INSERM U1173, University of Versailles-Saint Quentin (UVSQ), 104 Boulevard Raymond Poincaré, Garches, 92380, Paris, France. eric.azabou@aphp.fr.
3
Department of Clinical Neurophysiology, Pitié-Salpêtrière Hospital, AP-HP, Inserm UMRS 1127, CNRS UMR 7225, Sorbonne Universities, Université Pierre et Marie Curie - UPMC Université Paris 06, Paris, France.
4
Department of Clinical Physiology, Lariboisière Hospital, AP-HP, Inserm U965, University of Paris Diderot, Sorbonne Paris Cité, Paris, France.
5
Department of Clinical Neurophysiology, Sainte-Anne Hospital, Inserm U894, University Paris-Descartes, Paris, France.
6
Department of Physiology and Department of Critical Care Medicine, Raymond Poincaré Hospital, Assistance Publique - Hôpitaux de Paris (AP-HP), Inserm UMR 1173 Infection and Inflammation, University of Versailles Saint Quentin (UVSQ), University Paris-Saclay, Garches, Paris, France.
7
Medical ICU, Cochin Hospital, AP-HP, Paris Cardiovascular Research Center, INSERM U970, Université Paris Descartes Sorbonne Paris Cité, Paris, France.
8
Department of Neuro-Intensive Care Medicine, Sainte-Anne Hospital, Paris-Descartes University, Paris, France.

Abstract

BACKGROUND:

Electroencephalography (EEG) is a well-established tool for assessing brain function that is available at the bedside in the intensive care unit (ICU). This review aims to discuss the relevance of electroencephalographic reactivity (EEG-R) in patients with impaired consciousness and to describe the neurophysiological mechanisms involved.

METHODS:

We conducted a systematic search of the term "EEG reactivity and coma" using the PubMed database. The search encompassed articles published from inception to March 2018 and produced 202 articles, of which 42 were deemed relevant, assessing the importance of EEG-R in relationship to outcomes in patients with impaired consciousness, and were therefore included in this review.

RESULTS:

Although definitions, characteristics and methods used to assess EEG-R are heterogeneous, several studies underline that a lack of EEG-R is associated with mortality and unfavorable outcome in patients with impaired consciousness. However, preserved EEG-R is linked to better odds of survival. Exploring EEG-R to nociceptive, auditory, and visual stimuli enables a noninvasive trimodal functional assessment of peripheral and central sensory ascending pathways that project to the brainstem, the thalamus and the cerebral cortex. A lack of EEG-R in patients with impaired consciousness may result from altered modulation of thalamocortical loop activity by afferent sensory input due to neural impairment. Assessing EEG-R is a valuable tool for the diagnosis and outcome prediction of severe brain dysfunction in critically ill patients.

CONCLUSIONS:

This review emphasizes that whatever the etiology, patients with impaired consciousness featuring a reactive electroencephalogram are more likely to have a favorable outcome, whereas those with a nonreactive electroencephalogram are prone to having an unfavorable outcome. EEG-R is therefore a valuable prognostic parameter and warrants a rigorous assessment. However, current assessment methods are heterogeneous, and no consensus exists. Standardization of stimulation and interpretation methods is needed.

KEYWORDS:

Brain dysfunction; Coma; EEG reactivity; Intensive care unit; Lateral lemniscus; Mortality; Prognosis; Spinothalamic tract

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