Onset at a later age carries a less favorable prognosis, and the progressive form is more common in the older age group. Other entities such as ischemia, vasculitides, etc. make MRI criteria much less reliable for the diagnosis of MS in patients over the age of 50. Typical lesions include ovoid plaques in the periventricular region, corpus callosum, and centrum semiovale which appear hyperintense on proton density and T2 weighted images and hypodense on T1 weighted images. The pathological hallmark of MS are plaques, which are discrete regions of demyelination with relative preservation of axons. Myelin debris is found in clumps or within lipid laden macrophages.
Corticosteroids are the most commonly used agents for treating relapses or progressive illness.
Cyclophosphamide is an alkalating agent with cytotoxic effects on lymphocytes. Data from European centers and the USA indicated that cyclophosphamide arrested disease progression in a proportion of treated patients, with some suggestion that booster therapy was important, and that young women benefited most. A Canadian collaborative study did not show any benefit, but no booster therapy was employed. Low dose oral methotrexate has been tested in progressive MS, and although the expanded disability status score was unaffected, upper-limb dysfunction developed more slowly in treated than placebo patients. References Poser, C.M., Paty, D., Scheinberg, L., et al.