Revealing hidden consciousness

Revealing hidden consciousness

When a patient is in a vegetative state after a serious injury or heart attack, it’s extremely difficult for clinicians to decide on a long-term prognosis. Which patients will wake up? When will they wake up?

If doctors knew which patients would regain consciousness, they could target treatment more effectively and help manage the expectations of families. In Cambridge, researchers have been doing ground-breaking work with patients and have developed world class expertise in this area using MRI scanners, but there are many patients scattered around the country who don’t have access to such expensive diagnostic technology.

Dr Srivas Chennu, a researcher at the Wolfson Brain Imaging Centre in Cambridge, realised that many more patients could receive an accurate diagnosis of consciousness if there was technology available that could be used in any location. Dr Chennu and his team are now part way through a long term project, funded by the Evelyn Trust, to develop this technology. His starting point was the EEG – the electroencephalogram – which measures brain activity.

“The EEG is not new technology, but what we’ve done is to develop a bedside device - an electrode-studded net which is easy to fit over the head. In 10 minutes, it can produce a map of the electrical activity generated by the networks of neurons in the brain. This output from the device is then analysed using software we have developed using our expertise in graph theory. The brain ‘signatures’ that are produced are a very visual way of showing how active the brain is when at rest. We have shown that vegetative patients who produce robust signatures also show hidden signs of consciousness: these patients can’t respond to requests to make a physical action, such as moving their fingers, but they can visualise complex activities like imagining playing tennis when asked to do so in an fMRI scanner.  When someone is conscious, there are patterns of synchronised neural activity arcing across the brain that can be detected using EEG and quantified with our software. We have found several patients who could not respond to requests for movement, but had signatures very similar to a conscious brain,” says Srivas.

This information can be critical for families caught between hope and despair, as it can give them more objective information about what to expect. For clinicians, it gives them vital evidence that they can use to develop and test treatments targeted to the needs of individual patients and their potential for having, or regaining, some consciousness.

Dr Chennu is now using the funding from the Evelyn Trust to assess and follow the results of the treatment and rehabilitation of 50 patients over three years, supported by regular periodic assessment of their brain activity. He is also continuing to develop the scalp net device with industry as part of the National Institute for Health Research Healthcare Technology Co-operative for Brain Injury, hosted by the Department of Clinical Neurosciences at the University of Cambridge.

You can find out more on Dr Chennu’s research page.

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