It can be nearly impossible to know what is happening in the mind of someone who has experienced a severe brain injury, but two new methods could offer some clues. Together, they provide not only a better indication of consciousness but also a more effective way to communicate with some vegetative people.
The way that a seemingly unconscious person behaves does not always reflect their mental state. Someone in a completely vegetative state may still be able to smile simply through reflex, while a perfectly alert person may be left unable to do so if a brain injury has affected their ability to move.
So a different way to assess mental state is needed. Marcello Massimini at the University of Milan in Italy and his colleagues have developed a possible solution by stimulating brains with an electromagnetic pulse and then measuring the response. The pulse acts like striking a bell, they say, and neurons across the entire brain continue to “ring” in a specific wave pattern, depending on how active the connections between individual brain cells are.
The team used this method to assess 20 people with brain injuries who were either in a vegetative state, in a minimally conscious state, or in the process of emerging from a coma. The team compared the patterns from these people with the patterns recorded from 32 healthy people who were awake, asleep or under anaesthesia. In each of the distinct states of consciousness, the researchers found, the neurons “shook” in a distinctive pattern in response to the electromagnetic pulse.
Massimini’s team proposes that each of these different patterns is a signature of a particular state of consciousness. Eventually, a doctor could use this scale, or index, to assess whether a patient is aware of their surroundings – and treat them accordingly.
Big step forward
“This is a big step forward,” says Joseph Giacino of Harvard Medical School, who was not involved in the study. He says the technique needs to be replicated with more patients and will need to be corroborated with other methods, but it may provide a starting point for developing a much-needed gold standard for assessing consciousness.
A consciousness index could be used in other ways too. For instance, it might help to improve our broader understanding of exactly what consciousness is and how it can be measured, says George Mashour at the University of Michigan in Ann Arbor.
Giacino says that an index could eventually help identify which seemingly unconscious people with brain injuries are in fact sufficiently conscious to communicate with medical staff and friends or family members.
Adrian Owen at the University of Western Ontario in London, Canada, has previously shown that such communication is possible. In 2010, he asked people in a vegetative state a series of questions with yes/no answers, and asked them to imagine performing a complex task, such as playing tennis, whenever the answer was yes. A scanner picked up a unique pattern of brain activity that indicated whether the person is visualising this task.
However, this method is very inexact. In fact, only about three-quarters of healthy conscious people can perform the task in a way that the scanner can interpret. So when someone in a vegetative state shows little brain activity, doctors are left to wonder whether the patients are actually unconscious or simply not performing the task in a way the scanner can pick up on.
Locked-in but alert
Owen and Lorina Naci, also at the University of Western Ontario, have now developed a simpler method of determining the answers to yes/no questions given by people in a vegetative state.
The researchers began with a training exercise. Participants were told to either ignore or focus on a target word – “yes” or “no” – by counting how many times it was repeated by someone reading out a random sequence of words. The researchers scanned the participants’ brains during this exercise to help recognise when the brain was focusing. Then Owen and Naci asked each participant a question with a yes/no answer and repeated the sequence of spoken words. This time the participant was told to listen out for and focus on only the word “yes” or “no”, depending on the answer they wished to give.
They tested this on three people, two of whom were minimally conscious and one who had been in a persistent vegetative state for 12 years. All three patients were able to correctly answer questions about their names, for instance, or whether they were in a hospital.
Naci suspects this relatively straightforward method may reveal consciousness in more patients than had been previously thought to have it – 100 per cent of healthy, conscious people can communicate in this way. “We realise we really have to work hard to treat every patient as if they can understand and process what’s around them,” she says.
Nicholas Schiff of Weill Cornell Medical College in New York City says the study is a great start, although the technique is far from ready for general use in the clinic. But in future, an extensive suite of such tools may be available to give each individual their best chance to communicate – especially as each brain injury has its own unique characteristics. “[Treating] brain injury is the ultimate in personalised medicine,” he says.
Journal references: Massimi et al paper Science Translational Medicine, 10.1126/scitranslmed.3006294; Owen and Naci paper JAMA Neurology, DOI: 10.1001/jamaneurol.2013.3686
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