May 12 (HealthDay News) -- A new way of analyzing MRI data can detect a subtle but serious kind of brain injury and help determine how a patient may recover, say researchers at the University of Texas Southwestern Medical Center at Dallas.

This kind of injury, called diffuse axonal injury (DAI), occurs when the head suddenly stops moving, such as during a motor vehicle crash, and axons are damaged or deformed. Axons are long, thin extensions that reach from one area to another.

"(DAI) may account for up to half of the traumatic brain injuries in accidents," according to study author Dr. Ramon Diaz-Arrastia, a professor of neurology, said in a prepared statement.

DAI doesn't show up on CT scans, and MRI hasn't been able to reliably detect it. The UT Southwestern team developed a mathematical analysis, called diffusion tensor tractography, to detect DAI on MRI scans. This type of analysis looks at how easily water moves around in areas surrounding brain cells. When axons are damaged, they swell and absorb the water around them, leaving less that can move between cells. As axons die, they release the water, which increases the amount of water surrounding cells.

In a study that included 12 people with severe closed-head brain injury, Diaz-Arrastia and colleagues compared multiple MRI images of the patients taken over time and found that their analysis technique could detect changes in water motion.

They also found that the degree of DAI, as reflected by reduction of water motion, was significantly associated with how much the patients improved over time.

"This is a new way of measuring a common injury that has been overlooked," Diaz-Arrastia said.

The study was published in the May issue of the Archives of Neurology. The researchers plan to conduct further studies.

SOURCE: University of Texas Southwestern Medical Center at Dallas, news release, May 12, 2008