Normal dopamine transporter binding in dopa responsive dystonia.

We report the clinical manifestations of dopa responsive dystonia (DRD) in 2 patients from the same family. The brain magnetic resonance images (MRI) were normal. The dopamine transporter (DAT) imaging with (99m)Tc-TRODAT-1 was performed in the 2 probands, 8 patients with young onset Parkinson disease (YOPD) and 16 normal controls. The ratios of (99m)Tc-TRODAT-1 brain SPECT in the striatum were 2.40 +/- 0.12 (right) and 2.30 +/- 0.17 (left) in these 2 DRD patients as compared with 1.38 +/- 0.18 (right), 1.41 +/- 0.20 (left) in YOPD patients, and 2.15 +/- 0.35 (right), 2.14 +/- 0.32 (left) in normal controls respectively. A normal DAT uptake was found in DRD suggesting a normal presynaptic nigrostriatal dopaminergic terminal. We conclude that a normal DAT in parkinsonian patients can differentiate DRD from YOPD. In addition, DAT with (99m)Tc-TRODAT-1 is a reliable and convenient tool to study the function of the presynaptic dopaminergic axonal terminals.