123I-FP-CIT semi-quantitative SPECT detects preclinical bilateral dopaminergic deficit in early Parkinson's disease with unilateral symptoms

Background and aim123I-FP-CIT SPECT has been successfully used to detect the loss of dopaminergic nigrostriatal neurons in Parkinson's disease at an early stage. In this study we evaluated the capacity of 123I-FP-CIT SPECT to assess bilateral dopamine transporter (DAT) loss in de-novo hemi-Parkinson's disease (PD) patients with one-sided clinical symptoms. Patients and methodsTwenty-nine de-novo hemi-PD patients at an early stage (Hoehn & Yahr stage 1) and 18 gender and age matched healthy subjects were studied. SPECT imaging was always performed at 4 h post-injection. The ratios of striatal (S) to non-specific occipital (O) binding for the entire striatum (S/O), caudate nuclei (C/O), putamina (Pput/O), and the putamen to caudate nucleus index (Pput/C) were calculated in both the basal ganglia. ResultsIn PD patients S/O, C/O and Pput/O ratio values contralateral to the clinically affected side were significantly lower (P<0.001) than in the control group (−38%, −34% and −42%, respectively). A significant reduction (P<0.001) of the striatal binding ratios was also found ipsilaterally (S/O, −31%; C/O, −28%; Pput/O, −33%). The Pput/C index was also bilaterally significantly reduced (P<0.01). DAT loss was significantly greater (P<0.001) in the contralateral than in the ipsilateral S; and putamen bilaterally presented a higher dopaminergic deficit than did caudate. ConclusionOur results indicate that semi-quantitative 123I-FP-CIT SPECT detects a bilateral dopaminergic deficit in early PD with unilateral symptoms and preclinical DAT loss in the ipsilateral striatal binding, corresponding to the side not yet affected by motor signs. Semi-quantitative analysis may thus be used to diagnose PD at an early stage as well as to identify individuals developing bilateral dopaminergic damage.