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Researchers Investigate Long-Term Impact of Repeated, Subconcussive Brain Trauma

Study results indicate a “disconnect” between preclinical and clinical studies of concussion, according to a recent report. Charles L. Rosen, MD, of West Virginia University, Morgantown, and colleagues authored the report, which a news release from Wolters Kluwer Health suggests adds to concerns regarding the possible long-term effects of repeated “subconcusive” brain trauma—causing no concussion symptoms—in humans.

The study, which appears in the April issue of Neurosurgery, indicated that a standard experimental mode of concussion in rats causes substantial brain damage—but no behavioral changes comparable to those observed in patients with concussion.

The release states that while concussions are believed to be a form of “mild traumatic brain injury,” there is no definitive diagnostic test to determine when a concussion has occurred. Rather, the concussion is diagnosed based upon symptoms that include headache, nausea, dizziness, and confusion.

The release adds that animal studies offer a contrast to this, in that studies of concussion have focused on directly observed injury to brain tissues, with little attention to potential behavioral and functional consequences of the brain trauma.

According to Rosen and colleagues, this translates into a “clear disconnect” between experimental and clinical studies of concussion. In an effort to address the discrepancy, the release reports that the researchers used the “impact-acceleration model” to induce brain injury in rats. The results reflected those observed in previous studies, in which the technique caused “diffuse axonal injury” to the brain, with visible evidence of damage on the cellular level.

Additionally, the researchers compared injured and uninjured animals in a variety of functional and behavioral tests. The tests were reportedly selected to reflect symptoms and functions that mirror those used to diagnose concussion in humans, such as locomotor activity, coordination/balance, and cognitive function. The researchers say the rats exhibited no significant abnormalities on any of the tests. This remained true on the day following the brain injury, and up to one week afterward.

“The lack of functional deficits is in sharp contrast to neuropathological findings indicating degeneration, astrocyte reactivity, and microglial activation,” Rosen and colleagues state.

In the release, it is noted that conventionally, concussion has been regarded as a temporary issue, resolving with no long-term effects. This view has changed in recent years, and according to the release, the new experiments support the concept that significant brain damage may exist in individuals who have completely normal results on symptom-based assessments currently used to diagnose concussions.

Rosen and coauthors add, “It appears that even subconcussive injury, or injury below the current clinical threshold for detection using standard measures, may have lasting neurological effects.”

The researchers also acknowledge that their short-term study in rats provides no direct evidence of long-term changes caused by “mild” traumatic brain injury in humans. They also call for further research in order to pinpoint the impact of traumatic brain injury over time, and to develop new models for understanding repeated head trauma’s long-term impact.

Source(s): Medical News Today, Wolters Kluwer Health