MRI of the brain of a S-year-old boy performed 3 days after the onset
of hemichorea (Sydenham Chorea) revealed abnormal signal and enlargeme
nt of the contralateral caudate and putamen. Follow-up imaging 40 mont
hs later showed a persistent cystic appearance of the caudate and puta
men. This case is the first report of permanent MRI abnormalities afte
r Sydenham Chorea.