WEDNESDAY, March 6 (HealthDay News) -- Besides problems with gait and vision, people who have multiple sclerosis often complain they have trouble remembering things, and now new research may explain why.

According to a small study from the Netherlands, people with MS who report memory and thinking problems have more extensive damage to the white matter in their brains than their counterparts with MS who don't report such problems.

Up to 70 percent of all people with MS will experience a mental decline at some point, said study author Hanneke Hulst at the VU University Medical Center, in Amsterdam. And the new research "confirmed that cognitive symptoms in MS have a biological basis," Hulst said.

The findings were published online March 6 in Neurology.

MS is an autoimmune disease that occurs when the body attacks myelin, a fatty substance that insulates the nerve fibers of the central nervous system. The brain's white matter is surrounded by myelin. Symptoms range in severity and may include problems with gait, balance, vision, memory and thinking abilities.

To get a better picture of what was going on in the brains of people with MS, Hulst and colleagues used a new type of brain scan called diffusion tensor imaging along with traditional MRI scans on 20 people with MS-related thinking problems, 35 people with MS whose thinking ability was not affected by the disease and 30 people without MS.

More damage appeared in the brain's white matter of people with MS who reported memory and thinking impairments than in those who had MS but no such complaints about mental declines: 76 percent vs. 49 percent, respectively. This was especially apparent in areas of the brain charged with memory, attention and concentration, the researchers said.

"Imaging can now be used to capture a wider spectrum of changes in the brains of people with MS, and will therefore help determine more accurately whether new treatments are helping with all aspects of the disease, including cognitive [mental] impairment," Hulst said. "Unfortunately, at the moment there are no treatments available to prevent or cure cognitive problems in MS."