[I-123]beta-CIT and SPECT in essential tremor and Parkinson's disease

Resting and postural tremor may occur in essential tremor (ET) and Parkinso n's disease (PD). The aim of the present study was to investigate the cocai ne derivative [I-123]beta-CIT, which labels striatal dopamine transporters, and SPECT in differentiating these diseases. Methods: 30 healthy volunteers, 32 patients with ET and 29 patients with id iopathic PD of Hoehn/Yahr stage I were investigated. Specific over nondispl aceable binding ratios (target/cerebellum-1) were calculated for the striat um. the caudate nucleus and the putamen separately as well as a ratio putam en/caudate and the percent deviation of each patient's ratio from age-expec ted control values. Results: Striatal [I-123]beta-CIT binding ratios in ET were within normal r anges and showed only a discrete elevation to age-expected control values ( +14.6%). In PD significantly reduced specific binding was evident not only contralaterally to the clinically affected side (putamen: -62%, caudate nuc leus: -35%), but also ipsilaterally (putamen: -45%, caudate nucleus: -22%). All investigated parameters differed significantly between PD and controls and ET respectively. Conclusion: Imaging striatal dopamine transporters with [I-123]beta-CIT and SPECT could clearly distinguish between ET and PD in an early stage of the disease. Findings do not suggest a subclinical involvement of dopaminergic nigrostriatal neurons in ET.