Drug-induced Parkinsonism versus idiopathic Parkinson disease: Utility of nigrosome 1 with 3-T imaging

Purpose: To explore the utility of nigrosome 1 with 3-T magnetic resonance (MR) imaging to differentiate idiopathic Parkinson disease (IPD) from drug-induced parkinsonism (DIP). Materials and Methods: The institutional review board approved this study, and participants gave informed consent. This study enrolled patients with DIP (n = 20) and IPD (n = 29) who underwent N-3-fluoropropyl-2-β-carbomethoxy-3-beta;-(4-iodophenyl) nortropane (¹⁸F-FP-CIT) positron emission tomography (PET) and healthy participants (n = 20). All participants underwent 0.5×0.5×1.0 mm³ oblique axial three-dimensional multiecho-data image combination imaging to view the nigrosome 1 with 3-T imaging. Two reviewers independently assessed the nigrosome 1 without clinical information. DIP was diagnosed when no abnormality was seen at 18F-FP-CIT PET. Diagnostic sensitivity, specificity, and accuracy of the nigrosome 1 imaging were evaluated between the IPD and DIP patients and between the IPD patients and healthy participants. Interrater agreement was assessed with Cohen κ. Results: Both reviewers agreed in 63 of 69 participants (91.3%) for the presence of any abnormality on either side of the nigrosome 1 (κ = 0.825). Findings in all 29 IPD patients (100%) and three of 20 DIP patients (15%) were rated as abnormal and in 17 of 20 DIP patients (85%) they were interpreted as normal on the basis of imaging of the nitgrosome 1 (sensitivity, 100% (29 of 29); specificity, 85.0% (17 of 20); accuracy, 93.9% (46 of 49) between IPD and DIP patients). Findings in 3 of 20 healthy participants (15.0%) were interpreted as abnormal on the basis of imaging the nigrosome 1 while in the other 17 of 20 healthy participants (85.0%) they were rated as normal (sensitivity, 100% [29 of 29]; specificity, 85.0% [17 of 20]; accuracy, 93.9% [46 of 49] between IPD patients and healthy participants [κ = 0.831]). Conclusion: The imaging of nigrosome 1 with 3-T imaging can differentiate DIP from IPD with high accuracy and may help to screen patients who need dopamine transporter imaging in those suspected of having DIP.