Jan. 28, 2003 12:00 AM
It's one of the biggest frustrations in treating multiple sclerosis: Someone with debilitating symptoms can have an MRI scan of the brain that, inexplicably, shows only a tiny spot of damage.
A Duke University scientist calls that spot the tip of the iceberg, discovering that MS patients actually can have 2 1/2 times more damage there than the regular MRI detected plus more abnormalities lurking elsewhere.
A new scan that adds just 10 minutes to a standard MRI uncovered the trouble, tracking damage building deep in the brain by measuring how water flows through nerve fibers.
Testing of the new scans is in early stages, but the government-invented technology could lead to earlier diagnosis and better treatment of MS, as well as improvements in other brain diseases from schizophrenia to cancerous tumors.
In fact, Duke physicians consider the new scans so useful that the North Carolina hospital is believed the first to give this "tensor diffusion imaging" to every person prescribed a standard brain MRI regardless of the reason, resulting in a unique library of normal and abnormal brain anatomy.
Water may look still in a cup, but under a microscope, its molecules move constantly, bumping into each other and then bouncing away. Put a drop of dye in that cup and it will spread out, or diffuse, in a spherical shape, thanks to that molecular motion.
Water enmeshed in the celery stalklike tracts that are the brain's nerve fibers diffuses not just outwardly but also in the direction in which those tiny tubes run.
Scientists at the National Institutes of Health invented a way to measure the direction and speed of that diffusion, with software that modified regular MRI machines. So if something blocks part of a nerve fiber, the tensor diffusion imaging detects the resulting water changes, signaling damage.
To Duke neuroradiology chief Dr. James Provenzale, those new scans promise to clear up some of the mystery surrounding multiple sclerosis.
The disease, which afflicts 350,000 Americans, occurs when the immune system attacks and destroys nerve fiber insulation, called myelin. Eventually, scar tissue builds up to prevent those nerves from working, causing muscle weakness or paralysis, fatigue, dim or blurred weakness, memory loss and other cognitive problems.
"Lots of people are called crazy and malingerers who really have MS" because it takes years for a regular MRI to spot the characteristic scarring, Provenzale explained. "My premise is a lot of areas that look normal on MRI really are abnormal."
In a series of small studies, Provenzale says diffusion scans detected areas of MS nerve damage in people that were 2 1/2 times bigger than regular MRI had detected and uncovered similarly damaged areas in other spots the MRI missed altogether.
The MS Society cautions that diffusion scans still are experimental, and Provenzale's next step is to prove if the new scans accurately predict symptoms. If so, they could be used to determine when a patient is about to worsen and thus needs a treatment change.
Scientists at Washington University in St. Louis await funding for similar research, using the new scans to track how MS patients fare depending on whether nerve fibers are damaged or destroyed.
But tensor diffusion imaging will play a role in many more diseases,
NIH inventor Peter Basser says.
© Copyright 2003, azcentral.com