How Can We Tell If a Comatose Patient Is Conscious?

Neurologist Steven Laureys looks for signs of consciousness in unresponsive patients

Steven Laureys greets me with a smile as I enter his office overlooking the hills of Liège. Although his phone rings constantly, he takes the time to talk to me about the fine points of what consciousness is and how to identify it in patients who seem to lack it.

Doctors from all over Europe send their apparently unconscious patients to Laureys—a clinician and researcher at the University of Liège—for comprehensive testing. To provide proper care, physicians and family members need to know whether patients have some degree of awareness. At the same time, these patients add to Laureys’ understanding. The interview has been edited for clarity.

What is consciousness?

It is difficult enough to define “life,” even more so to define “conscious” life. There is no single definition. But of course, in clinical practice we need unambiguous criteria. In that setting, everyone needs to know what we mean by an “unconscious” patient. Consciousness is not “all or nothing.” We can be more or less awake, more or less conscious. Consciousness is often underestimated; much more is going on in the brains of newborns, animals and coma patients than we think.

So how is it possible to study something as complex as consciousness?

There are a number of ways to go about it, and the technology we have at our disposal is crucial in this regard. For example, without brain scanners we would know much, much less than we now do. We study the damaged brains of people who have at least partially lost consciousness. We examine what happens during deep sleep, when people temporarily lose consciousness. We’ve also been working with Buddhist monks because we know that meditation can trigger alterations in the brain; connections that are important in the networks involved in consciousness show changes in activity. Hypnosis and anesthesia can also teach us a great deal about consciousness. In Liège, surgeons routinely operate on patients under hypnosis (including Queen Fabiola of Belgium). Just as under anesthesia, the connections between certain brain areas are less active under hypnosis. And finally, we are curious to understand what near-death experiences can tell us about consciousness. What does it mean that some people feel they are leaving their bodies, whereas others suddenly feel elated?

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