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On the fringes of the human mind

A study found that a significant number of people labelled ‘vegetative’ have some degree of consciousness.

A study found that a significant number of people labelled ‘vegetative’ have some degree of consciousness.

People with severe brain injuries sometimes emerge from a coma awake but unresponsive, leaving families with painful questions. Are they aware? Can they think and feel? Do they have any chance of recovery?

A new study has found that PET scans may help answer these wrenching questions. It found that a significant number of people labelled vegetative had received an incorrect diagnosis and actually had some degree of consciousness and the potential to improve. Previous studies using electroencephalogram machines and MRI scanners have also found signs of consciousness in supposedly vegetative patients.

“I think these patients are kind of neglected by both medicine and society,” said Dr Steven Laureys, an author of the new study and the director of the Coma Science Group at the University of Liège in Belgium. “Many of them don’t even see a medical doctor or a specialist for years. So I think it’s very important to ask the question, are they unconscious?”

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In the United States, 100,000 to 300,000 people are thought to be minimally conscious, and an additional 25,000 are vegetative. In Belgium, the combined incidence of the two conditions is about 150 new cases per year, Laureys said.

An article about the new research was published this week in The Lancet.

Laureys and his colleagues studied 122 patients with brain injuries, including 41 who had been declared vegetative — awake but with no behavioural signs of awareness. People vegetative for a year are thought to have little or no chance of recovering, and the condition can become grounds for withdrawing medical treatment. Terri Schiavo, in a vegetative state for 15 years, died in 2005 in Florida after courts allowed the removal of her feeding tube.


In the study, 81 other patients were considered “minimally conscious”, meaning they showed intermittent signs of awareness and responsiveness. Such patients have a better chance of improving than those who are vegetative, although recovery may take a long time.

For both groups, the initial diagnoses were made by doctors performing neurological exams that included a detailed one using a guide called the coma recovery scale, which is considered the most reliable assessment.

Then most of the patients were given brain imaging tests. PET scans measured brain activity in regions needed for consciousness, and the patients’ results were compared to scans of healthy people. A lack of activity was interpreted as a vegetative state.


Some of the patients were also given a type of MRI scan used to measure brain activity while being told to imagine playing tennis or walking around their homes.

The imaging tests found minimal consciousness in 13 of the 41 vegetative patients. After a year, nine of the 13 had progressed into “minimally conscious states or a higher level of consciousness”, the researchers said. Overall, PET scans were a better measure than MRI scans.

But doctors caution that this type of PET scan is not widely available and not ready for routine use. Laureys also said the test might show signs of awareness in people who turn out to have little or no chance of meaningful recovery.
“We shouldn’t give false hope,” Laureys said. “But it’s just a very complex medical reality. Quantifying consciousness is tricky.”

An expert not involved in the study, Dr Joseph J Fins, the chief of the medical ethics division at Weill Cornell Medical College in New York, said PET scans could help doctors resolve puzzling cases in which patients are unresponsive but have healthy-looking brains.

Too often, he said, patients are labelled vegetative and sent to nursing homes where no effort is made to rehabilitate them. “The first thing we owe them is a credible diagnosis,” Fins said.

First published on: 20-04-2014 at 12:15:18 am
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