Idiopathic Parkinson's disease (PD) is the most common neurodegenerative disorder. An important step in diagnosing the disease has been achieved with the development of the cocaine derivative [123I] beta-CIT for single photon emission computed tomography (SPECT). The aim of this study was to demonstrate the disease progression by repeated measuring presynaptic dopamine transporter density and relating it to clinical data.
Methods: The presynaptic dopamine transporter density of 15 PD patients was measured two times with a mean interval of 15 months. All patients were clinically assessed at the time of the experiments according to the classification scheme of Hoehn and Yahr. 11 healthy volunteers were used as a control group. [123I] [-CIT was injected intravenously and measured with a triple-headed camera twenty hours later. The pictures were evaluated semiquantitatively by using the ratio of specific to non-displaceable binding.
Results: Presynaptic dopamine transporter density differed significantly between controls and PD patients. A significant correlation between imaging data and clinical stages (H/Y I -27%, H/Y II -40%, H/Y III -58%) was observed for the patient group in the initial experiment. The subsequent decrease of dopamine transporter binding depended on the initial clinical stage (H/Y I -6.81%; H/Y II -6.05%; H/Y III -1.25%) of the patients, and regression analysis revealed that. 91.4% of the variance of the second measurement were predicted by the initial measurement. No correlations were found for age, gender and disease progression. All patients were treated with L-DOPA and those given a higher dose showed a more rapid decrease of dopamine transporter density. This result could be interpreted as an indication for in vivo neurotoxicity of high concentrations of L-DOPA.
Conclusion: We conclude that combining [123I] beta-CIT with SPECT imaging is not only a powerful tool for diagnosing PD patients, but may also be used to demonstrate neurodegeneration in vivo.