MS May Take a Different Pathway Than Previously
WEDNESDAY, Dec. 7 (HealthDay News) -- Multiple sclerosis may
begin in the outer layer of the brain and work its way into the
deep interior, according to a new study that upends long-held
beliefs about the nervous system disease.
The new findings, which could spur changes in the way MS is
diagnosed and treated, appear to solidify a theory that's emerged
in recent years. This new premise suggests that gray matter, the
outer covering of the brain called the cortex, and the fluid that
surrounds and cushions it, is where MS originates, not in the bulky
white matter that composes most of the brain's core.
It's an "outside-in" process in other words, said study
co-author Dr. Claudia Lucchinetti, a professor of neurology at the
Mayo Clinic in Rochester, Minn.
"We already recognized before this study that the cortex -- the superficial layer where cells control memory, attention, and other key pathways in the nervous system -- was involved in MS. But most of what we knew came from autopsy studies, from patients who had longstanding disease, 30 to 50 years," said Lucchinetti. The new findings show the cortex is involved early on and may even be the initial target of the disease, she added.
Lucchinetti and her colleagues analyzed brain tissue of early MS
patients obtained through biopsies. The tissue was primarily white
matter, but about one-fourth of the biopsies (138 of 563 patient
screenings) also included tiny fragments of cortex. The scientists
used that tissue as the focus of their study.
The cortical tissues were viewed on a microscopic level. "The
early lesions were highly inflammatory," said Lucchinetti, whose
research is published in the Dec. 8 issue of the
New England Journal of Medicine.
The authors also noted that inflammation was also present in the
meninges, the protective membranes that cover the surface of the
brain and spinal cord, and was strongly associated with
inflammation in the cortex tissue.
About 400,000 Americans have MS, according to the National
Multiple Sclerosis Society. Its cause is unknown, but it is
believed to occur when the body's immune system chips away at the
protective myelin sheath, a fatty insulator that covers nerves, and
it can be debilitating. Symptoms can include weakness and numbness,
paralysis, poor vision, fatigue, dizziness, and tremor. Its
severity varies widely in patients, said Lucchinetti.
Lucchinetti said if scientists can understand the genesis of the
disease, better diagnostic procedures and treatments could be
"The findings are provocative," said Dr. Peter Calabresi, professor of neurology and director of the MS Center at Johns Hopkins Hospital, who wrote an accompanying editorial.
"It's an exciting study. For many years we thought MS was predominantly a disease of the white matter. More recently people have found there are some changes in the gray matter. This is the first time that anyone has definitively shown there's extensive inflammation in the gray matter early on in the disease," said Calabresi.
Calabresi likens the findings to leaves on a tree. "Everyone
thought the attack was on the leaves, the white matter, but now
people think it's more likely the trunk," he said.
Should patients get excited?
Dr. Jerome Graber, an assistant professor of neurology at Albert
Einstein College of Medicine in the Bronx, N.Y., said it's a good
study, but suggests no immediate clinical benefits. "My answer to
my patients is that it doesn't have an immediate implication for
them yet. I have no new treatment for you because of this study.
But I think it opens a lot of doors for researchers to ask a whole
new set of questions," he said. And the link with the meninges is
also intriguing, he said.
Calabresi agreed it offers hope. "I think it gives us a lot of
hope," he said. "It gives us yet one more tool to follow the
disease. There's a mysterious aspect to MS. It's hard to quantify.
But now we know gray matter is definitely involved, and we can
track it and see if a therapy is working or not, and if not, move
on to the next therapy."
Ultimately, this research "will allow us to understand [MS]
better and track and treat it better," he said.
For more on multiple sclerosis, visit the
U.S. National Library of Medicine.
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