People diagnosed with benign multiple sclerosis may in fact see a significant progression of the debilitating disease, a new Canadian study suggests.

"We need to be careful what we tell people, and not give them false hope that their symptoms may never get worse," lead author Dr. Ana-Luiza Sayao said in a news release.

Patients who are told they have benign MS should be regularly assessed to see whether subtle neurological changes that might herald later progression of the disease could be picked up early, the researchers with the University of British Columbia Hospital MS Clinic recommend.

Those who experience few symptoms for the first 10 years are often told they have a mild form of the illness and will never suffer severe problems. But the researchers found that after 20 years the disease had progressed in nearly half of those diagnosed with benign MS, including 20 per cent who needed a cane to walk.

More research needed

"We hoped to identify risk factors that make people more likely to progress in the disease after 10 years of a benign course, but we did not find that gender, the symptoms when the disease began or age when the disease began were associated with either disease progression or remaining benign," said study co-author Dr. Virginia Devonshire.

"More research needs to be done to identify criteria to determine which people will remain with mild disability over the long term."

The study was published in Tuesday's issue of Neurology, the scientific journal of the American Academy of Neurology.

Multiple sclerosis is an autoimmune disease that attacks the protective covering — called myelin — of the brain and spinal cord, causing inflammation and often destroying the myelin in patches. Symptoms include numbness or tingling in the hands and feet, feeling off-balance, clumsiness and visual and cognitive problems. In severe cases, it can lead to paralysis and even blindness.

Canada has high incidence rates

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.

Canada has one of the highest rates of MS in the world. Roughly 1,000 Canadians are diagnosed each year with MS and more than 75,000 live with it. Three-quarters are women.

'It's like the tip of the iceberg'

About 10 to 15 per cent of cases are considered benign, said Marianne Chilco, a spokeswoman for the Multiple Sclerosis Society of Canada.
  
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.

With files by Canadian Press