A bang to the head does not have to be severe to cause damage to brain tissue and result in thinking and memory problems. This was the finding of a new study reported in the journal Neurology that compared people with mild and moderate traumatic brain injury to people with no injury.

Traumatic brain injury (TBI) can occur when the head is hit suddenly and violently, or when an object pierces the skull and enters the brain. TBI can result in symptoms ranging from headaches and nausea to permanent brain damage and death.

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Even patients who suffered mild traumatic brain injury showed damage in white matter of the brain, according to researchers.

Senior author Andrew Blamire, professor of magnetic resonance physics at Newcastle University's Institute of Neuroscience, says most research tends to concentrate on people with severe and chronic traumatic brain injury:

"We studied patients who had suffered clinically mild injuries often from common accidents, such as falling from a bicycle, or slow speed car accidents. This finding is especially important, as 90% of all traumatic brain injuries are mild to moderate."

For their study, the researchers compared 53 people who had TBI (44 with mild TBI and nine with moderate TBI) with 33 individuals who had no brain injury.

All participants completed memory and thinking skills tests and underwent brain scans. The TBI patients had the tests and scans about 6 days after injury. Of these patients, 23 underwent the same tests and scans about a year later.

The brain scans were done using a sensitive type of magnetic resonance imaging (MRI) called diffusion tensor imaging, which is better at detecting brain cell damage than normal MRI and also helps map connections between brain regions.

Even mild TBI caused brain damage and lower scores on memory and thinking skills

When they analyzed the results of the tests and scans, the researchers found that, compared with the uninjured participants, those with mild or moderate TBI had damage in the white matter of their brains. This showed up as disruption to nerve axons - the fibers that connect brain cells and allow them to relay messages.

Also, the TBI patients scored on average 25% lower on a memory and thinking skills test that measures verbal fluency, and the researchers found this was strongly linked to extent of white matter damage.

A year later, there was no difference in memory and thinking skills scores between the TBI patients and healthy participants, despite the scans of the TBI patients showing there were still some areas of brain damage.

Prof. Blamire says these results "show that thinking skills were recovering over time. The areas of brain damage were not as widespread across the brain as previously, but focused in certain areas of the brain, which could indicate that the brain was compensating for the injuries."

Funding for the study came from the Sir Jules Thorn Charitable Trust.

Meanwhile, Medical News Today recently learned how a study of veterans suggested dementia risk rises with traumatic brain injury. TBI due to blast injury is common in American military personnel involved in active combat in Iraq and Afghanistan, say the US Department of Veterans Affairs.