Hemichorea in systemic lupus erythematosus: significance of MRI findings.

A young man with systemic lupus (SLE) developed hemichorea 13 years after the onset of his illness. For the first time in the course of his illness he had a positive test for anticardiolipin antibodies (aCL). Magnetic resonance imaging (MRI) of his brain showed lesions of presumed vascular cause in the ipsilateral basal ganglia. The findings support the contention that an immune phenomenon, invisible on proton imaging by MRI, is responsible for the striatal neuronal activation. Chorea, the clinical expression of this activation, was probably blocked on the side previously affected by vascular pathology.