The findings suggest that doctors should be cautious about using the term "benign multiple sclerosis" or "benign MS."
"We need to be careful what we tell people, and not give them false hope that their symptoms may never get worse," says Ana-Luiza Sayao, MD, in a news release.
Sayao works in Vancouver at the University of British Columbia.
She and her colleagues studied 169 patients with "benign MS," which the researchers defined as having a low level of disability 10 years after diagnosis.
Multiple sclerosis is a disease of the brain and spinal cord. Its symptoms may include vision problems, muscle weakness, and difficulty with walking, coordination, and balance.
Some patients experience relatively mild MS; other cases are severe.
Changes in 'Benign' MS
Sayao and colleagues checked the patients' medical records 20 years after MS diagnosis.
Just more than half the patients -- 52% -- still had "benign MS," meaning their disability was still relatively mild 20 years after MS diagnosis.
But disability had worsened in the other patients.
Of all the patients studied, roughly one in five needed a cane to walk 20 years after their MS diagnosis.
Sayao's team found no factors -- such as patients' sex or age at MS onset -- that predicted which cases would worsen.
The study questions the use of the term "benign multiple sclerosis."
"Although there is certainly a unique subgroup of patients with MS who remain mild in disability over the long term, a lack of consensus in the criteria that define 'benign' MS continues to exist," the researchers note.
Journal editorialist Scott Pittock, MD, agrees.
"Whether there is a benign form of multiple sclerosis continues to be a controversial issue," writes Pittock, who works at the Mayo Clinic in Rochester, Minn.
Pittock says "a 'watchful waiting approach,' with regular clinical and MRI monitoring" may be preferable for some patients with benign MS before starting MS drug treatment.
He also sees reason for optimism for such patients.
"The MS prognostic glass is half full for a high proportion of these most benign cases," Pittock writes.
SOURCES: Sayao, A. Neurology, Feb. 13, 2007; vol 68: pp 496-500. Pittock, S. Neurology, Feb. 13, 2007; vol 68: pp 480-481. News release, American Academy of Neurology.
By Miranda Hitti
Reviewed by Louise Chang