NEW YORK (Reuters Health) - The eye disorder optic neuritis is often a harbinger of multiple sclerosis, but in people with normal brain scan findings, the long-term risk of MS is relatively low, a new study shows.
Optic neuritis is an inflammation of the optic nerve that causes pain and sudden, short-term vision loss.
It is often the first sign of MS, a disease that attacks the protective myelin sheath covering the nerves of the brain and spinal cord -- leading to symptoms like numbness, impaired mobility and balance and coordination problems.
However, not everyone who suffers an episode of optic neuritis develops MS. The presence of brain lesions on MRI scans has been shown to be a prime predictor of a person's risk.
In the new study, of 389 patients who developed optic neuritis in one eye, researchers found that for those who had normal MRI findings at the time, the odds of developing MS over the next 15 years were only 25 percent.
The risk was highest in the first five years, then declined over time.
That compared with a 72 percent likelihood of developing MS among patients with at least one brain lesion on MRI.
Robin L. Gal, of the Jaeb Center for Health Research in Tampa, Florida, and colleagues report the findings in the Archives of Neurology.
According to the researchers, optic neuritis patients with abnormal MRI findings are already showing evidence of "disseminated disease and could be considered to have MS at the time of the optic neuritis episode."
They recommend that such patients have additional testing to decide on whether treatment might be appropriate.
In contrast, they write, "with normal brain MRI findings, MS is extremely unlikely to develop more than 10 years after the initial optic neuritis episode."
"Although our follow-up is only 15 years," the researchers add, "it seems reasonable to conclude that the future risk for these patients will remain exceedingly low."
SOURCE: Archives of Neurology, June 2008.
