Lights aren’t on but is anyone home? Detecting awareness in coma patients

A new study shows EEGs can detect consciousness in those thought to be in a vegetative state. Flickr/Basheem

Awareness can be detected in people previously thought to be in a permanent vegetative state using a cheap, portable electroencephalography (EEG) device, according to a study published in today’s Lancet.

British and Canadian authors assessed 16 patients in a vegetative state, along with 12 healthy controls. Three of the 16 patients who were thought to be unconscious could repeatedly and reliably generate appropriate EEG responses to two distinct commands, despite being physically unresponsive.

Ashley Craig, Professor of Rehabilitation Studies from the University of Sydney, explains how consciousness is currently tested in people thought to be in a vegetative state, and how that might be about to change:

We’ve known for some time that when someone appears to be in a coma, they may actually be conscious. The trouble is, this is incredibly difficult to assess.

This type of research has been going on for some time. Past studies have shown, for instance, that people in comas have similar heart rate responses to music to conscious people.

How is consciousness currently determined?

Very few hospitals would provide an EEG system and there are many limitations to fMRI scans, so most diagnoses would be based on behavioural observations. In the acute ward, clinicians would observe vital functions such as heart rate, respiration, and responses to commands and questions. If there’s no response, then it might be assumed the patient is in a coma.

What are the implications of this assumption?

It could be that families are asked to turn off vital supports. Or the patient might just be ignored. They might be left in a home where there’s no effort made to talk or communicate with them.

One of the recommendations in this paper is that EEG technology could be capable of communicating with people in a semi-vegetative state, where they are conscious but are hard to get to.

A patient wearing electrodes for an EEG. Aschoeke