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Vegetative patients show awareness during scans

10:00am Friday 17th October 2014 content supplied byNHS Choices

"Vegetative patients may be more conscious of the world than we think," The Independent reports. Electrodes have detected what has been described as "well-preserved" networks of brain activity in patients in a vegetative state.

A vegetative state is when a person is awake and may have some basic motor reflexes, but no signs of awareness. It is one of a group of conditions known as disorders of consciousness and often develops after a severe head injury.

This study performed electroencephalogram (EEG) examinations to study the electrical signals and connections in the brains of 32 people with disorders of consciousness, comparing them with 26 healthy adults.

The researchers demonstrated that the networks of electrical connections thought to support awareness are impaired in people with disorders of consciousness. They also found the quality of people's brain connections correlates with their level of awareness.

Most interestingly, they also found a small number of people in a vegetative state may have more conscious awareness than it seems.

Four people in this state were found to show some signs of "hidden awareness" - they demonstrated brain activity on functional MRI scans when asked to imagine playing tennis (in neurological circles, this is known as the tennis test).

When looking at the EEG results, the researchers found some of the brain connections that support consciousness in healthy adults were also well preserved in these people.

The researchers suggest these results may help improve clinical assessments in the future, as well as help identify people who may still have some level of conscious awareness, despite not being able to demonstrate this.

 

What are the prospects of recovery?

It can be difficult to predict what the chances are of someone in a vegetative state improving. It largely depends on the severity and type of brain injury, as well as their age. Generally, the longer a person goes without showing any signs of improvement, the less likely they are to recover.

Where did the story come from?

The study was carried out by researchers from the University of Cambridge, the University of California, the University of Western Ontario, and the Universidad Diego Portales, Chile.

Funding was provided by various sources, including the Wellcome Trust, the UK Medical Research Council, and the National Institute for Health Research.

It was published in the peer-reviewed journal, PLOS Computational Biology, which is open access, so the study is available to read online for free.

The Independent and BBC News reported the study accurately. However, while the sentiment of the Daily Express' headline, "Talking to vegetative state patients can help recovery", may be well intentioned, it does not have a strong foundation.

Although the study found a small number of people in a vegetative state did seem to have some conscious awareness, despite this not being apparent, it did not look at their brain activity in response to friends and family talking to them. And it certainly has not examined whether this may or may not help them recover.

 

What kind of research was this?

This was a case control study that looked at electrical signals coming from the brains of people with disorders of consciousness, and compared them with normal healthy controls.

There are three conditions that generally fall into what are termed disorders of consciousness, which usually occur after a severe brain injury.

A minimally conscious state is where the person has very little consciousness, but demonstrates some variable response or awareness of their surroundings.

A vegetative state is the middle condition, where the person has no environmental awareness at all, but they still demonstrate a sleep-wake cycle and reflexive responses (such as to pain or sound).

A person in a coma is unconscious, with no awareness at all, does not respond to their environment, and has no sleep-wake cycle and no normal reflex responses.

This study aimed to further understand the distinctive brain networks that characterise the different disorders of consciousness.

 

What did the research involve?

This study took bedside EEG recordings of the electrical signals coming from the brains of 32 people with disorders of consciousness, as well as 26 healthy controls.

They looked at the amplitude of oscillations and then looked at the structure of brain networks connected by these oscillations.

The researchers then compared the electrical patterns and connections between the people with disorders of consciousness and the healthy controls.

They also examined what signalling abnormalities are present in people with disorders of consciousness, to what extent these patterns are consistent across patients, and how the patterns correlate with the level of behavioural response present.

 

What were the basic results?

The results of this study are quite complex, reporting the intricate differences in brain networks and connectivity between people with disorders of consciousness and healthy controls.

In general, the researchers found distinct differences in people with disorders of consciousness compared with the healthy controls.

They also found the quality of signalling networks in people with disorders of consciousness correlated with the degree of behavioural response they demonstrated.

Of the people in a vegetative state - who by definition have no behavioural responses - four out of 13 were surprisingly found to demonstrate some signs of brain activity when asked to imagine playing tennis while having their brain scanned by functional MRI scan.

When looking at the EEGs of this small number of vegetative patients with some signs of "hidden awareness", the researchers found they had well-preserved signalling networks similar to those of healthy adults.

 

How did the researchers interpret the results?

The researchers concluded that their findings "inform current understanding of disorders of consciousness by highlighting the distinctive brain networks that characterise them".

They say tests in a minority of people in a vegetative state indicate signalling pathways that could support mental function and consciousness, although these people have profound behavioural impairment.

 

Conclusion

This study performed EEG examinations to study the electrical signals and connections in the brains of 32 people with disorders of consciousness, comparing them with 26 healthy adults.

The researchers demonstrated the network of electrical connections that support awareness, and how these connections are impaired in people with disorders of consciousness. They also found the quality of people's brain connections correlates with their level of awareness.

Of most interest, they found a small number of people in a vegetative state may have more conscious awareness than it seems.

A vegetative state is characterised by a person maintaining spontaneous reflexes, such as to pain or sound, and having a normal sleep-wake cycle, but they cannot demonstrate behavioural responses or conscious awareness of their surroundings.

But in this study, four people in this state were found to show some signs of hidden awareness - they demonstrated brain activity on a functional MRI scan when asked to imagine playing tennis.

When looking at their EEGs, the researchers found some of the brain connections that support consciousness in healthy adults were also well preserved in these people, too.

The researchers suggest the distinct brain network connections seen in people with disorders of consciousness that they have identified in this study may help improve clinical assessments in the future.

This information may also help identify people who may still have some level of conscious awareness, despite not being able to demonstrate this.

Further research building on these findings is awaited. Despite one newspaper's report to the contrary, the results of this study are not suddenly going to lead to new treatments for disorders of consciousness - at least in the short term. But learning more about the relationship between brain activities and levels of awareness is always valuable.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Summary

"Vegetative patients may be more conscious of the world than we think," The Independent reports. Electrodes have detected what has been described as "well-preserved" networks of brain activity in patients in a vegetative state.

Links to Headlines

Vegetative patients may be more conscious of the world than we think. The Independent, October 16 2014

Vegetative patients show glimmers of consciousness. BBC News, 17 October 2014

Talking to vegetative state patients can help recovery. Daily Express, 16 October 2014

Links to Science

Chennu S, Finoia P, Kamau E, et al. Spectral Signatures of Reorganised Brain Networks in Disorders of Consciousness. PLOS Computational Biology. Published 16 October 2014

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