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Brain cells continue to die weeks after injury NEW YORK, Aug 03 (Reuters) -- Brain cell death does not cease within a few hours of severe head trauma, but may instead continue for weeks and even months after injury, researchers report. With a better understanding of this process, "we'll be able to ascertain when and where cells die in the brain and use that information to develop new therapeutic strategies to treat injury," said Dr. Tracy McIntosh, senior author of a study conducted by researchers at the University of Pennsylvania School of Medicine in Philadelphia. Their findings appear in the current issue of the Journal of Neuroscience. Severe head injury can lead to the death of millions of neurons within the brain. Until now, most experts had believed that this cell death (or apoptosis) was limited to a relatively short period of time immediately following injury. The Philadelphia team sought to test this theory by inducing brain damage in mice, and then examining their brain tissue at points ranging from 12 hours to 2 months after injury. They discovered "both acute (short-term) and delayed patterns of cell death" among the injured brains. Brain cell death patterns were found to be "regionally distinct" as well, peaking at different times in different brain areas. For example, structures near the site of impact (such as the outer cortex) experienced cell death (apoptosis) soon after injury. On the other hand, brain cells in the thalamus -- a structure located deep in the brain which plays a role in various functions, including sensation and movement -- seemed relatively unaffected by trauma in the first few days after injury. Eventually, however, the thalamus exhibited "a dramatic and delayed increase in the number of apoptotic cells... by 2 weeks post-injury," the authors report. This peak then subsided, so that thalamic brain cell death returned to normal levels by 2 months after injury. Overall, the researchers noted a chronological "progression of apoptotic cell death from injured cortex through (to) deeper structures" in the days and weeks following injury. McIntosh believes "this study points to the fact that things are not so quiet" during what physicians have traditionally labeled a post-trauma period of patient recovery. "A brain-injured patient may look stable, but cells are still dying," she said in a statement issued by the University of Pennsylvania Medical Center. "Realizing this will be important for coming up with ways to recover, regenerate, and stem the loss of brain tissue." McIntosh believes "these findings could eventually effect protocols in rehabilitation and lead to ways to pharmacologically block cell death." Journal of Neuroscience 1998;18:5663-5672. -- Judith Richards, London, Ontario, Canada [log in to unmask]