Role of [123I]I-mIBG cardiac scintigraphy in the differential diagnosis of Parkinson's disease - our experience.

BACKGROUND

The clinical diagnostic accuracy of idiopathic Parkinson's disease (IPD) remains suboptimal, with the most common neuropathological findings in misdiagnosed patients being atypical neurodegenerative parkinsonism - progressive supranuclear palsy (PSP), multiple system atrophy (MSA), or corticobasal degeneration (CBD). The purpose of this study was to evaluate cardiac mIBG scintigraphy as an imaging biomarker in the differential diagnosis of IPD.

MATERIAL AND

METHODS

A total of 129 patients with parkinsonism were referred to Center for Nuclear Medicine with PET, University Clinical Center of Serbia, for evaluation of cardiac sympathetic innervation from January 2012 to February 2025. Planar chest scintigrams were obtained 15 min and 4 h after [¹²³I]I-mIBG administration, and early and late heart-to-mediastinum ratio (HMRE and HMRL) and washout rate (WR) were calculated. The final diagnosis was made by a movement disorder specialist.

RESULTS

Final diagnosis was available in 103 patients, with IPD in 52 cases, atypical parkinsonism (MSA, PSP or CBD) in 35 patients, and other parkinsonism forms in 16 cases. The areas under the curve (AUCs) for correctly differentiating IPD from other forms of parkinsonism for HMRE, HMRL and WR were 0.769 (95% CI 0.676-0.862), 0.842 (95% CI 0.763-0.921) and 0.748 (95% CI 0.652-0.845), respectively. Sensitivity, specificity, and accuracy of HMRL at a cut-off value of 1.875 were 84.6%, 78.4% and 81.6%, and positive predictive value (PPV) and negative predictive value (NPV) 80% and 83.3%. The AUC for differentiating IPD from MSA using HMRL was 0.829 (95% CI 0.725-0.934), with specificity of 75% for HMRL at cut-off of 1.875.

CONCLUSIONS

Cardiac [¹²³I]I-mIBG scintigraphy represents a useful biomarker for differentiating IPD from other forms of parkinsonism, showing high sensitivity and specificity at a cut-off value of 1.875 for late heart-to-mediastinum ratio in our group.