A multicenter study for the analysis of early onset Parkinson’s disease population: the role of 123I-FP-CIT and 123I-MIBG

Background-Aim: Parkinson disease (PD) is the most common neurodegenerative movement disorder. Functional imaging with 123I-ioflupane (FP-CIT) has proved its importance in the diagnosis of PD. 123I-FP-CIT SPECT assess presynaptic dopamine neuronal dysfunction and can distinguish patients with PD from healthy subjects, essential tremor, non-degenerative vascular and drug-induced parkinsonism with high sensitivity and specificity. However, 123I-FPCIT SPECT cannot differentiate PD from atypical forms of neurodegenerative parkinsonian syndromes (non-PD) such as progressive supranuclear palsy (PSP), multiple system atrophy (MSA), corticobasal degeneration (CBD). Data obtained with 123I-FP-CIT can be combined with those from myocardial 123I-metaiodobenzyl guanidine (mIBG) scintigraphy. This radiotracer defines cardiac sympathetic nerve fibers integrity, typically lost in PD. The aim of this multicenter study is to determine whether the use of both molecular imaging techniques can help diagnose PD with higher sensitivity in patients with early onset disease. The diagnosis was confirmed after 3 years of clinical follow-up. Methods: This retrospective study was conducted on 260 patients of two different centers with suspected diagnosis of PD or non-PD syndrome. The selected patients underwent both 123I-FP-CIT and 123I-mIBG scintigraphy. The ratios considered were the caudate nuclei to the non-specific occipital region (C/O) and putamina to the non-specific occipital region (P/O) in both basal ganglia. Regarding mIBG studies, the early and late heart-to-mediastinum ratio (eH/M and lH/M) were calculated Results: 260 subjects with suggestive motor and non-motor symptoms appeared in less than 1 year were analyzed. Mean age at baseline was 66 ± 9.8 years, with males being slightly more numerous than females (147 vs 113). Clinical diagnosis after 3 years of follow-up was PD in 143 patients and non-PD in 117 patients. Diagnostic odds ratio (OR) with 95% confidence interval (CI) was calculated for both 123I-FP-CIT and 123I-mIBG. 123I-FP-CIT OR was 0.98 (95% CI 0.93–1.03) for right C/O (p = 0.55); 0.98 (95% CI 0.93–1.03) for right P/O (p = 0.46); 0.97 (95% CI 0.91–1.02) for left C/O (p = 0.28) and 0.97 (95% CI 0.91–1.02) for left P/O (p = 0.25). 123I-mIBG OR was 0.22 (95% CI 0.19–0.26) for eH/M and 0.29 (95% CI 0.25–0.32) for lH/M (p = 0.001). ROC curves showed an AUC value of 0.954 for both eH/M and lH/M. Conclusions: This retrospective multicenter study showed that 123ImIBG scintigraphy has higher positive predictive value than 123I-FPCIT scintigraphy in early onset PD. The combined use of these molecular imaging studies does not seem mandatory. In fact, at this stage of disease the evaluation of the cardiac sympathetic nerve fibers integrity seems to offer a greater contribute to clinicians for the diagnosis of neurodegenerative motor disord