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TUESDAY, June 18 (HealthDay News) -- Concussion can lead to damage in the white matter of the brain that resembles abnormalities found in people in the early stages of Alzheimer's disease, a new study suggests.
Researchers at the University of Pittsburgh School of Medicine said their findings should prompt a re-evaluation of the long-term effects of concussion, which affects more than 1.7 million people in the United States annually. About 15 percent of concussion patients suffer persistent neurological symptoms.
"The previous thinking before was you get a concussion, and that causes a certain damage from bopping your head and you get these symptoms," said study author Dr. Saeed Fakhran, an assistant professor of radiology at the University of Pittsburgh School of Medicine. "We found it acts as a kind of trigger, and lights a fuse that causes a neurodegenerative cascade that causes all these symptoms down the line. Once you've hit your head, the injury isn't done."
The findings are published online June 18 in the journal Radiology.
The study drew some criticism from concussion and Alzheimer's disease experts who said the findings, while provocative, should not be interpreted as drawing a clear link between a concussion suffered early in life with the development of Alzheimer's.
"I don't want a mom to pick this up and say, 'Oh my god, my 10-year-old is going to get Alzheimer's now,' because that is not the case," said Dr. Ken Podell, a neuropsychologist and co-director of the Methodist Concussion Center in Houston. "It's very inconclusive at this time, and there's no clinical application of this at this point of time."
White matter serves as the tissue through which messages pass between different areas of gray matter within the brain and spinal cord. Think of gray matter as the individual computers in a network, and white matter as the cables that connect the computer.
The researchers reviewed past brain scans of 64 people who had suffered a concussion, focusing on scans that used an advanced MRI technique called diffusion-tensor imaging, which spots microscopic changes in the brain's white matter.
The investigators then compared these brain scans to symptoms reported by concussed patients in a post-concussion questionnaire. They focused on symptoms shared with Alzheimer's patients, including memory problems, disturbances in sleep cycles and hearing problems.
The results showed a significant correlation between high concussion symptom scores and reduced water movement in the parts of the brain's white matter related to auditory processing and sleep-wake disturbances. Further, the researchers said, the distribution of white matter abnormalities in mildly concussed patients resembled the distribution of abnormalities in people with Alzheimer's disease.
"Basically, it looks a lot like Alzheimer's," said study co-author Dr. Lea Alhilali, an assistant professor of radiology at the University of Pittsburgh School of Medicine. "You get the same distribution of damage in the way that Alzheimer's disease affects the brain."
These abnormalities could spark a series of reactions that lead to long-term problems with thinking and memory. "The cascade is what is the important factor," Alhilali said. "It doesn't appear what you're symptomatic from is the injury itself. What you're symptomatic from is how the brain responds to that injury."
However, brain experts believe that researchers may be going too far in trying to draw a link between the concussion damage they found and the chronic damage found in Alzheimer's.
"It's an interesting observation, but I think they are making a leap that the pattern of changes they see on the scan are indicative of what we see in Alzheimer's disease," said Dr. Ron Petersen, director of the Mayo Alzheimer's Disease Research Center. "Their correlation between the scores on the concussion instrument and white matter changes, that's nice and good and makes sense. But then they go into a rather extensive anatomical explanation of how this might be similar to Alzheimer's disease, and I find that a bit tenuous."
Podell listed a number of concerns with the article, including:
- The researchers' reliance on existing brain scans and symptom charts created by other people. "You don't know what questions were asked, who asked the questions, how they were asked," he said. "There are a lot of things you can't control for."
- The inclusion of young patients in the pool of subjects, who ranged in age from 10 to 38. "White matter is not fully developed in people until they are adults," he said. "You have 10-year-olds in this study. It is highly, highly unusual to mix young kids with adults, because the brain is so different."
- The use of sleep disturbance as a comparable symptom between concussion and Alzheimer's. "What's a common co-injury in concussion? Whiplash. You have neck pain, back pain," he said. "If you go to sleep, you don't think that pain wakes you up?"
"The issue is, does a single concussion in an individual mean they are at risk for developing Alzheimer's?" Podell said. "There are so many other factors involved, including genetic factors, management of a concussion and the general health and well-being of the individual throughout their life."
The study authors agreed that their findings are tentative.
"This is not a definitive study. This is not the end at all. This is the first step," Alhilali said. "We hope this will lead to more research that will further explore this potential link."
The researchers do believe their findings could lead to better treatments in the future, however.
"The first step in developing a treatment for any disease is understanding what causes it," Fakhran said. "If we can prove a link, or even a common pathway, between mild traumatic brain injury and Alzheimer's, this could potentially lead to treatment strategies that would be potentially efficacious in treating both diseases."
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