Striatal dopamine activity and myocardial I-metaiodobenzylguanidine uptake in early Parkinson's disease.

INTRODUCTION

Dopamine transporter imaging and myocardial I-metaiodobenzylguanidine (I-MIBG) scintigraphy have been widely used to diagnose and discriminate degenerative parkinsonism. Many studies have reported that both imaging findings are associated with a variety of motor and non-motor phenomena in Parkinson's disease (PD). However, the association between striatal dopamine activity and myocardial I-MIBG uptake has not been well investigated. The objective of this study is to identify the dopamine transporter activity of the corpus striatum and thalamus according to myocardial I-MIBG uptake in PD.

METHODS

Ninety-six newly diagnosed, non-medicated PD patients were enrolled. All patients underwent I-MIBG myocardial scintigraphy, positron emission tomography (PET) using FN-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane and T1-weighted magnetic resonance imaging (MRI). Patients were stratified into normal and decreased I-MIBG groups according to their delayed heart-to-mediastinum ratio (cutoff value = 1.78). After normalizing the PET images with spatially normalized MRI, the regional standardized uptake value ratios (SUVRs) were analyzed with a volume-of-interest template between the two groups.

RESULTS

Thirty-one patients showed normal myocardial I-MIBG uptake, and 65 patients showed reduced uptake. The SUVR of the globus pallidus in the group with reduced I-MIBG uptake was significantly lower than the SUVR in the normal I-MIBG uptake group. The heart-to-mediastinum ratio was correlated well with the SUVR of the globus pallidus, independent of age, disease duration, and the severity of motor symptoms.

CONCLUSION

Early PD patients with normal I-MIBG uptake showed a relatively preserved dopamine reserve in the globus pallidus than patients with reduced I-MIBG uptake.