The contribution of MRI in the differential diagnosis of posterior fossa damage

In multiple sclerosis patients, magnetic resonance imaging (MRI) frequently detects lesions in the brain stem and cerebellum. However various patholog ies that have a predelection to occur in posterior fossa parenchyma may sha re similar features with inflammatory-demyelinating lesions. In this paper, we review the contribution of MRI to the differential diagnosis of posteri or fossa pathology. Vascular lesions due to chronic hypoperfusion and arter iolosclerosis or occlusion of the main supplying arteries of the posterior circulation leading to acute infarction frequently produce characteristic p ontine or cerebellar lesions. Neoplastic disease, in particular pontine gli omas in younger patients may have similar MRI features and may be difficult to distinguish from inflammatory-demyelinating lesions. Central pontine my elinolysis usually occurs in severely ill patients but the pontine MRI chan ges have an overlapping profile with inflammatory demyelination. Diffuse ax onal injury of the midbrain and brainstem after head trauma and atrophy of posterior fossa structures in degenerative diseases may appear similar on M RI to tissue changes also seen frequently in MS. Analysis of the MRI appear ance and clinical information is most often useful to narrow the fairly lon g list of differential diagnoses of posterior fossa pathology. (C) 2000 Els evier Science B.V. All rights reserved.