Focus Shifts to Gray Matter in Search for the Cause of Multiple Sclerosis

Most researchers have suspected MS is a disease of the brains white matter. A new study suggests the debilitating disorder originates in gray matter, and raises hopes for faster diagnoses

By Julianne Chiaet

MRI Scan of Brain Image: Flickr/Reigh LeBlanc

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It has taken a century so far for scientists to not figure out the cause of multiple sclerosis (MS). The inflammatory disease, which affects more than 2.1 million people worldwide, has been blamed on toxins, viruses and even food. Most recently, scientists have placed their bets on two major ideas: The first (and far more popular) hypothesis suggests MS begins in white matter, which influences how parts of the brain work together. White matter consists of bundles of axons covered in myelin, a white insulating fatty layer. In people with MS myelin degrades and nerve fibers are left exposed, causing problems in motor coordination and loss of senses.

The second hypothesis suggests that MS begins in the gray matter, which affects thinking and learning. The white matter hypothesis overshadows its alternative in part because white matters impact is easier to observe. When using a microscope to look at brain tissue, scientists are struck by the degradation in the myelin in samples from patients with MS. And when analyzing MS in the clinic, the overt symptoms experienced by a person with the disease can be attributed to the myelin. Symptoms associated with dysfunctions in gray matter are less obvious, such as the loss of an IQ point. Now, new evidence lends support to the less-favored gray matter hypothesis.

Scientists at Rutgers University in Newark tried a new approach to look into the gray matter of MS patients. They analyzed proteins in cerebrospinal fluid (CSF), which can be thought of as the central nervous systems blood. By comparing the quantity of specific CSF proteins in patients who were newly diagnosed or had the relapsing remitting variety of MS with that of healthy patients, the researchers found an uneven distribution of 20 proteins among the three groups.

They discovered at least 75 percent of the proteins affect gray matter, not myelin, and used the quantities of gray matter protein associated with each group to distinguish between the healthy control and newly diagnosed MS patients. The finding suggests there are issues happening extremely early in the gray matter that precede myelin loss, says co-investigator Patricia Coyle, a neurologist at Stony Brook University, S.U.N.Y. The study appeared in the September 2013 PLoS One.

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Focus Shifts to Gray Matter in Search for the Cause of Multiple Sclerosis