ABSTRACT
Certain specific features on brain MRI make the diagnosis of MS more likely. MS lesions often have an irregular and confluent shape and are located in the periventricular region, especially around the frontal, occipital and temporal horn. A common feature is involvement of the corpus callosum, including the presence of subcallosal lesions and callosal atrophy. Furthermore, apart from scatter ing of lesions in the periventricular white matter, cortical and subcortical lesions can also be found. With improvements of MRI techniques, MRI of
the spinal cord has become common practice, and it shows focal and diffuse abnormalitiesJ3,4^
To improve the specificity of MRI in the diag nosis of MS, MR criteria have been defined. The diagnostic criteria of Paty et a l j1] consisting of the presence of four or more lesions on brain MRI scans or three lesions of which one is located in the periventricular region, has a sensitivity of 94% for MS but the specificity is rather low (57%). The specificity can be markedly improved if three or more lesions are visible on brain MRI with two of the three following features present:^ (a) size of a lesion > 6 mm; (b) lesion(s) abutting the ventricular bodies; or (c) an infratentorial lesion.
