In rats, diffuse brain damage can occur with no signs of 'concussion'

March 21, 2014

A standard experimental model of concussion in rats causes substantial brain damage—but no behavioral changes comparable to those seen in patients with concussion, reports a study in the April issue of Neurosurgery, official journal of the Congress of Neurological Surgeons.

The results highlight the "disconnect" between preclinical and clinical studies of concussion, according to the report by Dr. Charles L. Rosen of West Virginia University, Morgantown, and colleagues. The study also adds to concerns over the possible long-term effects of repeated, "subconcussive" brain trauma—causing no concussion symptoms—in humans.

Despite Diffuse Brain Damage, No Signs of 'Concussion' in Rats

Concussions are thought to be a form of "mild traumatic brain injury." However, there is no definitive diagnostic test to determine when a concussion has occurred. Instead, concussion is diagnosed on the basis of symptoms such as headache, nausea, dizziness, and confusion.

In contrast, animal studies of concussion have focused on directly observed injury to brain tissues, with little attention to the possible behavioral and functional consequences of the brain trauma. Thus there is a "clear disconnect" between experimental and clinical studies of concussion, according to Dr. Rosen and colleagues.

To address this discrepancy, they used a standard technique, called the "impact-acceleration model," to induce brain injury in rats. As reported by previous studies, this technique caused "diffuse axonal injury" to the brain, with visible evidence of damage on the cellular level.

The researchers also compared injured and uninjured animals on a wide range of functional and behavioral tests. The tests were chosen to reflect symptoms and functions similar to those used to diagnose concussion in humans—for example, locomotor activity, coordination/balance, cognitive function, and anxiety- and depression-like behaviors.

But despite a rather extensive pattern of brain injury, the rats had no significant abnormalities on any of the tests. That was so on the day after brain injury as well as up to one week afterward. "The lack of functional deficits is in sharp contrast to neuropathological findings indicating neural degeneration, astrocyte reactivity, and microglial activation." Dr. Rosen and colleagues write.

Findings Support Concerns about 'Subconcussive Injury'

The new study comes at a time when new researchers are finding evidence of long-term neurodegenerative changes in the brains of people who have never been diagnosed with a concussion. One key study in high school football players found changes in neurological function and health in athletes who never had concussion symptoms, but had sustained "repetitive subconcussive blows."

Traditionally, has been regarded as a temporary problem that resolves with no long-term effects. But that view has changed in recent years, with studies in athletes and others showing chronic traumatic encephalopathy linked to repetitive head injury—both the concussive and subconcussive types.

The new experiments support the concept that significant may be present in individuals who have completely normal results on symptom-based assessments currently used to diagnose concussions. Dr. Rosen and coauthors write, "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 emphasize that their short-term study in rats provides no direct evidence of long-term changes caused by "mild" in humans. They discuss the need for further research to clarify the effects of traumatic over time, and to develop new models for understanding the long-term impact of repeated head trauma.

Explore further: Teen concussions increase risk for depression

Related Stories

Teen concussions increase risk for depression

January 10, 2014

Teens with a history of concussions are more than three times as likely to suffer from depression as teens who have never had a concussion, finds a new study in the Journal of Adolescent Health.

NATA: Recommendations issued for sport concussion management

March 17, 2014

(HealthDay)—Recommendations have been developed for management of sport-related concussion. The recommendations have been published online March 7 in the Journal of Athletic Training as a National Athletic Trainers' Association ...

Blood test might help spot, monitor concussions

March 13, 2014

(HealthDay)—When someone suffers a concussion, it can be hard to tell how serious it is and how long recovery will take, but a new blood test might help answer those questions.

NIH, NFL team up to take on concussion research

December 16, 2013

(HealthDay)—The U.S. National Institutes of Health is teaming up with the National Football League on research into the long-term effects of repeated head injuries and improving concussion diagnosis.

Brain still injured from concussion after symptoms fade

November 20, 2013

After a mild concussion, special brain scans show evidence of brain abnormalities four months later, when symptoms from the concussion have mostly dissipated, according to research published in the November 20, 2013, online ...

Recommended for you

Imaging technique maps serotonin activity in living brains

October 20, 2016

Serotonin is a neurotransmitter that's partly responsible for feelings of happiness and for mood regulation in humans. This makes it a common target for antidepressants, which block serotonin from being reabsorbed by neurons ...

ALS study reveals role of RNA-binding proteins

October 20, 2016

Although only 10 percent of amyotrophic lateral sclerosis (ALS) cases are hereditary, a significant number of them are caused by mutations that affect proteins that bind RNA, a type of genetic material. University of California ...

Overcoming egocentricity increases self-control

October 19, 2016

Neurobiological models of self-control usually focus on brain mechanisms involved in impulse control and emotion regulation. Recent research at the University of Zurich shows that the mechanism for overcoming egocentricity ...

Exercise may help ward off memory decline

October 19, 2016

Exercise may be associated with a small benefit for elderly people who already have memory and thinking problems, according to new research published in the October 19, 2016, online issue of Neurology, a medical journal of ...

Going for a run could improve cramming for exams

October 19, 2016

Ever worried that all the information you've crammed in during a study session might not stay in your memory? The answer might be going for a run, according to a new study published in Cognitive Systems Research.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.