3 Total lesion load, based on MRI, has been found to correlate with neuropsychological testing impairment. Other common abnormalities include nystagmus, oscillopsia, and internuclear ophthalmoplegia. These reflect spinothalamic, posterior column, or dorsal root entry zone lesions. Pyramidal tract dysfunction is often mixed with impairment of the cerebellar pathways, as well as involvement of bladder, bowel, and sexual functions. This is quite limited in the setting of a young adult with 2 or more clinically distinct episodes.
Problems arise with progressive illness, monophasic episodes, and atypical presentations.
Sarcoidosis, Wegener's, lymphomatoid granulomatosis. 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.