Assessment of posterior fossa damage in MS using MRI

In multiple sclerosis (MS), brain stem and cerebellum are frequent sites of damage in clinically isolated syndromes at presentation and it is likely t hat lesions located in such structures can have an important impact on the development of disability in the definite forms of the disease. In patients presented with isolated brain stem syndromes, the symptomatic lesion was o ften not detected by magnetic resonance (MR) imaging. But patients with asy mptomatic infratentorial lesions progressed to clinically definite MS in 65 % of cases. Infratentorial lesions are included in various MR criteria desi gned to assist in the differential diagnosis of MS lesions from incidental lesions, to differentiate MS from subcortical encephalopathic arteriopathy. The preferred MR sequence to visualize infratentorial lesions is the fast spin echo sequence. It is preferred to conventional spin echo and fast flui d attenuated inversion recovery sequences because of its relatively short a cquisition time and good sensitivity. The correlation between disability an d infratentorial lesion load on T2 weighted sequences is controversial. How ever, it was recently shown that the correlations between clinical measures and TI lesion load, histogram magnetization transfer ratio and peak positi ons, and infratentorial volume measurements are strong. These findings sugg est that one of the major factors in the development of disability in patie nts with MS is the pathological damage in clinically eloquent sites such as the brain stem and cerebellum. (C) 2000 Elsevier Science B.V. All rights r eserved.