TORONTO - People who have had multiple sclerosis for a decade with few disabling symptoms are often told they have a mild form of the disease and will continue to do well. But a Canadian study has found that so-called "benign MS" doesn't always remain benign.
In fact, researchers found that half of those patients said to have benign MS 10 years after initial diagnosis saw their disease actually progress over the next decade, including 20 per cent who ended up needing a cane or other assistive device to walk.
Study co-author Dr. Virginia Devonshire, head of the University of British Columbia Hospital MS Clinic, said she and her fellow researchers were somewhat surprised at the finding, which was based on analysis of a detailed database of 169 benign MS patients followed over 20 years.
"We really did think that we would be able to say that there was a group of people who had certain symptoms from the beginning who did well for a period of time, that they were always going to do well, that you could feel comfortable telling them that," Devonshire said Monday from Vancouver.
"Unfortunately, that's not the case."
"Nobody wants to find out 10 years later that they've got disability and impairment. And . . . we can't always tell somebody because they have certain symptoms at the beginning or because they've gone so long without disability that they're always going to go without disability, and therefore don't need treatment early on."
Devonshire said the study - published in Tuesday's issue of the journal Neurology - suggests that patients who are told they have benign MS still must be regularly assessed to see if subtle neurological changes that might herald later progression of the disease could be picked up early.
Multiple sclerosis is an auto-immune disease that attacks the protective covering - called myelin - of the brain and spinal cord, causing inflammation and often destroying the myelin in patches. An estimated 55,000 to 75,000 Canadians have the disease, 75 per cent of them women. Canada has one of the highest prevalence rates of MS in the world.
About 10 to 15 per cent of cases are considered benign, said Marianne Chilco, a spokeswoman for the Multiple Sclerosis Society of Canada.
Symptoms include numbness or tingling in the hands and feet, feeling off-balance, clumsiness and visual and cognitive problems. Most patients experience what's known as relapsing and remitting MS, in which they will have an attack of symptoms that will last days to weeks. "Then the patient gets better, fully or partially," Devonshire said.
Or, the patient seems to get better, at least on the surface.
"In between attacks, during remission - which is not a true remission - there are no new symptoms, but in fact if we watch an MRI in this 'remission' phase, we see new inflammation coming and going all the time," she said. (MRIs can pick up lesions on brain and spinal tissue.)
During the first 10 years, attacks come and go, the person recovers and there seems to be little residual disability, she explained. "But we think between attacks, there are little bits of damage occurring in the brain and spinal cord all the time. And after 15, 20 years, all those bits of damage add up."
"It's like the tip of the iceberg: suddenly, then, you see the disability and impairment."
Devonshire said doctors don't know whether benign MS patients would benefit from starting treatment with immune-modulating medications aimed at limiting neurological damage - drugs that many patients are loathe to begin because they are administered by injection and are expensive.
That's something only further study can determine, she said.
In an editorial accompanying the study, Dr. Sean Pittock said that if doctors had an effective, safe and inexpensive oral medication for MS patients, "few would argue against the 'treat-all' approach." However, disease-modulating agents (DMAs) are expensive and have side-effects that can cause skin reactions and flu-like symptoms, and their long-term effects are unknown, he noted.
"There are no data on the advisability of commencing DMA in MS patients who have experienced a favourable course over many years and lack clinical or radiologic (MRI) evidence of recent deterioration," writes Pittock of the department of neurology, laboratory medicine and pathology at the Mayo Clinic in Rochester, Minn.
"A 'watchful waiting' approach with regular clinical and MRI monitoring before initiating treatment may be a preferable approach for some patients."
Devonshire and the MS Society both urge patients who have been told their disease is benign to maintain regular contact with their MS centre and neurologist for ongoing evaluation of their condition.
"But I think the bigger message is for physicians," Devonshire said. "I think physicians have to be cautious about telling people they have benign MS. I think it's reasonable to say: 'You're doing well now, but we can't predict the future and we must consider all the options.' "
