In many neurological diseases the topography of the lesion, whatever its nature, determines the clinical signs, whereas the nature of the lesion (vascular, inflammatory, degenerative, etc.) whatever its topography, determines the time course. According to J. P. Martin (1), this general principle cannot be simply applied to diseases of the basal ganglia since the nature of the lesions directly influence the clinical signs. Chorea, for instance, is associated with atrophy of the caudate nucleus but infarct of the caudate nucleus does not generally cause chorea.