By Laurie Barclay, WebMD Medical News Archive
For years, scientists have thought that nerve cells in the brain and spinal cord of adult humans have very limited capacity to regenerate, or grow back, after injury. But now, new research suggests that healthy brain cells can grow into new areas of the brain, taking over the function of nerve cells that are no longer functioning normally.
According to data from the University of Alabama National Spinal Cord Injury Statistical Center, there are approximately 250,000 people with spinal cord injuries in the U.S., with approximately 11,000 new injuries occurring each year. Developing effective treatments and preventing new injuries could save the U.S. up to $400 billion on future direct and indirect lifetime costs related to these injuries.
More than half of spinal cord injuries occur in young adults aged 16 to 30 years, and almost three-quarters occur in males. About 90% of the people with spinal cord injuries survive, and have near-normal life spans.
In the new study, monkeys with a spinal cord injury that caused loss of feeling in their arms had extensive new growth of nerve fibers in the brainstem -- the lower part of the brain connecting the spinal cord to higher brain centers. The brainstem is small -- about as thick as a Magic Marker -- but very densely packed with nerve cells and fibers carrying sensory information from the body to the brain. The growth of even a few new fibers in the brainstem can have far-reaching effects on how nerve cells in the brain are reorganized.
"For the first time, we have shown that growth can span ... distinct groups of nerve cells in the brainstem," Neeraj Jain, PhD, tells WebMD. He is lead researcher of the study, which was sponsored by the Christopher Reeve Paralysis Foundation and the National Institutes of Health and reported in the April 25 issue of the journal Proceedings of the National Academy of Sciences.
"This type of large-scale growth across the primate brain has not been seen before," says Jain, who is also assistant professor of psychology at Vanderbilt University in Nashville, Tenn. These findings suggest that the adult brain and spinal cord may be more capable of regeneration than previously believed.
"The more we learn about these types of changes, the more we may be able to help patients in the future," Vilayanur S. Ramachandran, MD, PhD, tells WebMD. "These findings are equally applicable to treatment of spinal cord injury and brain injury." Ramachandran is professor and director of the Center for Brain and Cognition at the University of California, San Diego.
Jain agrees that this research might eventually lead to new treatment approaches in spinal cord injury and stroke. "Even without intervention, the brain is capable of this kind of growth," he says. Perhaps we could encourage remodeling of the brain to allow healthy parts of the brain to take over functions ordinarily assumed by impaired areas."
Ramachandran explains that patients with spinal cord injury or stroke that causes their arm to not have normal feeling may think you are touching their arm if you touch their face. "The brain cells that ordinarily receive sensation from the hand area are 'hungry' for sensory input, as the spinal cord injury or stroke cuts off sensation from the affected hand and prevents it from reaching the appropriate brain area," he says. "So sensory input from the face now is redirected to the hand area of the brain."
And that's just what Jain found. Touching the spinal cord-injured monkeys on the chin triggered nerve impulses that were recorded over the part of the brain ordinarily receiving sensory input from the hand. Additionally, nerve fibers grew from the area that responds to face stimuli to the area that responds to hand stimuli in the brainstem.
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Source: WebMD Medical News Archive
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