Wednesday, 5 July 2006

Brain Re-wiring

From 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.
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.

There were also significant changes between scans taken just two months after the recovery, and the most recent, at 18 months. Some of the new pathways had receded again, while others seem to have strengthened and taken over as Wallis continued to improve.

Krish Sathian, a neurologist and specialist in brain rehabilitation at Emory University School of Medicine in Atlanta, US, describes it as an amazing finding. “The bounds on the possible extent of neural plasticity just keep on shifting,” he says. “Classical teaching would not have predicted any of these changes.”

Did I ever blog about how much we don't know about this kind of thing? I have? Oh well, it's another data point.

Note though how long it took - 19 years. This is not so much a recovery as "learning how to become conscious", something newborns do in just a few years.

And in a related article :
A drug used to treat insomnia has paradoxically helped temporarily rouse three men who were each in a vegetative state following motor accidents, researchers claim. They believe that zolpidem (marketed as Ambien) activates dormant cells in the brain.
Before treatment with the drug, Patient L did not respond to any commands and showed no signs of language comprehension. According to Clauss, after taking his first, 10 milligram dose of zolpidem the patient could meaningfully interact with family, friends and strangers. He could name his favourite rugby player and make simple calculations.

The effects of the drug seemed to last for approximately 4 hours, after which Patient L would relapse into the vegetative state.

Patient N, who had been in a vegetative state for three years following a motor vehicle accident, showed no signs of language comprehension and was constantly screaming. With the drug he stopped screaming and appeared to react appropriately to scenes on television, laughing at funny moments.

Before taking zolpidem, Patient N scored 6 out of a possible 15 points on the Glasgow Coma Scale, a measure of responsiveness. With the medication, his score improved to 10. A coma score of 13 or higher correlates with mild brain injury while a score of 8 or less is generally considered severe brain injury.

The third man, Patient G, showed no response to language prior to drug treatment but could count to five after receiving the medication, the researchers write. His score on the Glasgow Coma Scale improved temporarily from 9 to 14 points.

All three patients have received daily doses of the drug since the study began.
Clauss and his colleagues have applied for a usage patent of zolpidem in brain damage. He says that drugs such as zolpidem, manufactured by Sanofi-Aventis, activate receptors for the neurotransmitter gamma aminobutyric acid (GABA) in the brain.

According to the researchers, brain injury may alter GABA receptors, causing regions of the brain to remain dormant. They speculate that zolpidem could possibly, temporarily, reverse this change.
Did I ever blog about how much we don't know about this kind of thing? I have? Must be short-term memory problems....

Sorry, I have to make jokes, otherwise instead of Patients L, N and G, they'd be people who have been terribly injured, and reliant on drugs to be able to add 2 and 2 - for up to 4 hours, anyway. And the loss of 19 years if Terry Wallis' life. The suffering of the families of these patients, never able to get closure.

Has anyone seen an Objectivity floating around somewhere? I appear to have temporarily lost mine.

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