By Helen Phillips
New Scientist
A study of the "miraculous" recovery of a man who spent 19 years in a minimally conscious state has revealed the likely cause of his regained consciousness.
The findings suggest the human brain shows far greater potential for recovery and regeneration then ever suspected. It may also help doctors predict their patients’ chances of improvement. But the studies also highlight gross inadequacies in the system for diagnosing and caring for patients in vegetative or minimally conscious states.
In 1984, 19-year-old Terry Wallis was thrown from his pick-up truck during an accident near his home in Massachusetts, US. He was found 24 hours later in a coma with massive brain injuries.
Within a few weeks he had stabilised in a minimally conscious state, which his doctors thought would last indefinitely. It did indeed persist for 19 years. Then, in 2003, he started to speak.
Over a three day period, Wallis regained the ability to move and communicate, and started getting to know his now 20 year old daughter – a difficult process considering he believed himself to be 19, and that Ronald Reagan was still president.
To try and find out what was going on inside Wallis's brain, Nicholas Schiff and colleagues from the Weill Medical College of Cornell University in New York City, used a new brain imaging technique called diffusion tensor imaging (DTI). The system tracks water molecules and so reveals the brain’s white matter tracts – akin to a wiring diagram. They combined this with more traditional PET scanning, to show which brain areas were active.
The team's findings suggest that Wallis’s brain had, very gradually, developed new pathways and completely novel anatomical structures to re-establish functional connections, compensating for the brain pathways lost in the accident.
They found that new axons – the branches that connect neurons together – seemed to have grown, establishing novel working brain circuits.
Surprisingly, the circuits look nothing like normal brain anatomy. A lot of the damage had been to axons that passed from one side of the brain to the other, torn by the force of the accident. But Schiff says that new connections seem to have grown across around the back of the brain, forming structures that do not exist in normal brains.
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