Does reduced [(123)I]-FP-CIT binding in Huntington's disease suggest pre-synaptic dopaminergic involvement?

Objective: To evaluate the usefulness of SPECT in assessing damage to the pre-synaptic dopaminergic system in Huntington's disease (HD) using [(123)I]-FP-CIT (DaTSCAN), a selective radioligand with regulatory approval as the diagnostic test for investigating functional dopaminergic neuron loss in the striatum in Parkinson's disease.

Methods: We studied twelve symptomatic HD patients using DaTSCAN/SPECT imaging. [(123)I]-FP-CIT caudate and putamen uptake levels were qualitatively and semi-quantitatively analyzed to assess pre-synaptic damage in the striatal dopamine system. Possible correlations were analyzed between HD severity on the Unified Huntington's Disease Rating Scale (UHDRS), duration of clinical symptoms, and [(123)I]-FP-CIT/SPECT striatal uptake.

Results: DaTSCAN/SPECT qualitative analysis showed reduced striatal uptake in eight patients. Semi-quantitative analysis revealed a significant reduction in four. Of these four, uptake reduction was at putamen level in all, and also at caudate level in one. Although we observed no linear correlation between HD severity and reduced striatal [(123)I]-FP-CIT uptake, the patients with the worst UHDRS scores had more severe reductions in radioligand uptake.

Conclusion: This is the first study to use in vivo [(123)I]-FP-CIT/SPECT imaging to confirm prior descriptions using PET of a pre-synaptic dopaminergic system defect in HD.