Tourette's syndrome (TS) is a disease characterized by multiple motor and vocal tics as well as behavioral abnormalities. The anatomic substrates of this syndrome are not defined. We report a 48-year-old man with TS in whom motor tics disappeared after the onset of a midbrain syndrome related to thiamine deficiency (Wernicke's encephalopathy). MRI study showed a lesion in the dorsal area of the midbrain. This case suggests that loops located in the midbrain tegmentum may influence the presence of motor tics in patients with TS.