Study of Movement Disorders and Brain Iron by MR 397

Heavily T2-weighted high-field MR images provide a unique opportunity for the evaluation of the extrapyramidal motor system. The images are affected by the presence of small amounts of naturally occurring paramagnetic substances-principally ironthat delineate the neostriatum (caudate and putamen), globus pallidus, red nucleus, substantia nigra, and dentate nucleus, primarily by a decrease in signal secondary to the T2* effect. Movement disorders are associated with either increased or decreased signal or both in these structures, depending on the pathologic process. In the initial evaluation of 113 patients with a variety of movement disorders, good correlation of imaging abnormalities can be made with a simplified schema of the extrapyramidal pathways and a system of classification of abnormal movements, parkinsonism/tremor, dystonia, chorea, myoclonus, and hemiballismus. Parkinsonisms are characterized by abnormalities of the corti coonto-cerebello-dentato':rubro-thalamo-cortico-s ~a~ or the nigrostriatal tract. Dystonias are characterized by abnormalities of the neostriatum pre ominantly affecting the putamen. Choreas are also characterize y abnormalities of the neostriatum but redornrly_clt.tecti/l9-th.e..c..audate nucleus. Hemiballismus IS the subthalami leus or ssociated athwa .