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The changing spectrum of coma

Nature Clinical Practice Neurology volume 4, pages 544–546 (2008)Cite this article

Modern intensive care can sustain most of the body's vital functions after severe brain injury, except for those of the brain, and modern technology has dramatically increased acute survival in this setting. When some patients awake from their coma, however, they fail to show any signs of awareness or voluntary behavior (i.e. they are in a vegetative state), or they remain unable to consistently and reliably communicate their thoughts and wishes (i.e. they are in a minimally conscious state). The clinical management of these disorders of consciousness remains very difficult, but technological advances in neuroimaging and in EEG-based brain–computer interfaces are now offering new ways to improve the diagnostic, prognostic and therapeutic management of these challenging conditions. Here, we will discuss some recent studies that we believe are heralding a new era of coma research and management.

Historically, the seat of consciousness was widely believed to be in the heart, and the absence of heartbeat was regarded as the clinical sign of death. Neuroscientific evidence has superseded such thinking and has shown that consciousness, an emergent property of neural activity, resides in the brain.1 Since the invention of the positive-pressure mechanical respirator, it has become possible to sustain cardiorespiratory function in individuals who are in a coma, so that research can focus on brain function as a separate entity. Patients who would previously have died from apnea are now able to survive in profound comatose states that had never been encountered before. This technological progress forced modern medicine to redefine the diagnosis of death and move from its ancient cardiorespiratory-centered definition to a neurocentric one, where death is defined as the irreversible loss of all brainstem reflexes (including the breathing reflex). Since the introduction of this clinical definition, not a single patient who fulfils the criteria of brain death has ever regained consciousness.

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Figure 1: Patients in a coma might progress to a vegetative state (clinically defined as wakefulness solely accompanied by reflex behavior).

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Acknowledgements

S Laureys is a Senior Research Associate at the Belgian Fonds de la Recherche Scientifique (FNRS). M Boly is a Research Fellow at FNRS. The authors receive funding from the European Commission, Mind Science Foundation, James McDonnell Foundation, French Speaking Community Concerted Research Action, and Fondation Médicale Reine Elisabeth.

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  1. Cyclotron Research Centre and Neurology Department, University of Liège; S Laureys is also a Clinical Professor at the Department of Neurology, S Laureys and M Boly are neurologists at the Coma Science Group, University Hospital of Liège, Liège, Belgium.,

    Steven Laureys & Mélanie Boly

  2. S Laureys is also a Clinical Professor at the Department of Neurology, University Hospital of Liège, Liège, Belgium.,

    Steven Laureys & Mélanie Boly

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  1. Steven Laureys
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  2. Mélanie Boly
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Correspondence to Steven Laureys.

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Laureys, S., Boly, M. The changing spectrum of coma. Nat Rev Neurol 4, 544–546 (2008). https://doi.org/10.1038/ncpneuro0887

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