CC BY 4.0 · Semin Neurol 2022; 42(03): 259-272
DOI: 10.1055/a-1883-0861
Review Article

New Behavioral Signs of Consciousness in Patients with Severe Brain Injuries

Beril Mat
1   Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
2   Department of Neurology, University of Wisconsin–Madison, Madison, Wisconsin
Leandro R.D. Sanz
1   Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
3   Centre du Cerveau2, University Hospital of Liège, Liège, Belgium
Anat Arzi
4   Paris Brain Institute, Paris, France
5   Department of Medical Neurobiology and Cognitive Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
Melanie Boly
2   Department of Neurology, University of Wisconsin–Madison, Madison, Wisconsin
6   Department of Psychiatry, University of Wisconsin–Madison, Madison, Wisconsin
Steven Laureys
1   Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
3   Centre du Cerveau2, University Hospital of Liège, Liège, Belgium
7   Joint International Research Unit on Consciousness, CERVO Brain Research Centre, CIUSS, Laval University, Québec, Canada
Olivia Gosseries
1   Coma Science Group, GIGA Consciousness, University of Liège, Liège, Belgium
3   Centre du Cerveau2, University Hospital of Liège, Liège, Belgium
› Author Affiliations
Funding The study was supported by the University and University Hospital of Liège, the Belgian National Funds for Scientific Research (FRS-FNRS), the European Union's Horizon 2020 Framework Programme for Research and Innovation under the specific grant agreement no. 945539 (Human Brain Project SGA3), the European Space Agency (ESA) and the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Programme, the BIAL Foundation, the Mind Science Foundation, the fund Generet of the King Baudouin Foundation, the Léon Fredericq Foundation, the Mind-Care foundation, the AstraZeneca Foundation, the Télévie and the Fondation Contre le Cancer, and a Marie Curie Individual Fellowship (840711) awarded to A.A. L.R.D.S. is research fellow, O.G. is research associate, and S.L. is research director at FRS-FNRS.


Diagnostic and prognostic assessment of patients with disorders of consciousness (DoC) presents ethical and clinical implications as they may affect the course of medical treatment and the decision to withdraw life-sustaining therapy. There has been increasing research in this field to lower misdiagnosis rates by developing standardized and consensual tools to detect consciousness. In this article, we summarize recent evidence regarding behavioral signs that are not yet included in the current clinical guidelines but could detect consciousness. The new potential behavioral signs of consciousness described here are as follows: resistance to eye opening, spontaneous eye blink rate, auditory localization, habituation of auditory startle reflex, olfactory sniffing, efficacy of swallowing/oral feeding, leg crossing, facial expressions to noxious stimulation, and subtle motor behaviors. All of these signs show promising results in discriminating patients' level of consciousness. Multimodal studies with large sample sizes in different centers are needed to further evaluate whether these behaviors reliably indicate the presence of consciousness. Future translation of these research findings into clinical practice has potential to improve the accuracy of diagnosis and prognostication for patients with DoC.

Publication History

Accepted Manuscript online:
23 June 2022

Article published online:
13 September 2022

© 2022. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (

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