Objective: The purpose of this study was to evaluate the usefulness of cardiac 123I-metaiodobenzylguanidine (MIBG) uptake, Dopamine transporter (DAT) scan and midbrain/pontine ratio (M/P ratio) on magnetic resonance images (MRI) in differentiating Parkinson’s disease (PD) from atypical parkinsonian syndromes (APSs) such as multiple system atrophy (MSA) and progressive supranuclear palsy (PSP).

Background: Clinical differentiation between PD and APSs is sometimes difficult.

Method: Cardiac MIBG scintigraphy, DAT scan, and MRI were carried out in 89 patients with PD (age, 68.3±10.1 years), 23 patients with MSA (age, 67.9±8.7 years), and 17 patients with PSP (age, 72.3±8.3 years). The specific binding ratio (SBR) of the striatum was semi-quantitatively calculated using QSPECT or DAT view software. Striatal asymmetry index (SAI) of the SBR was calculated using the following formula [(SAI）=|(SBRRight-SBRLeft)/(SBRRight+SBRLeft)|×2×100(%)]. M/P ratio was manually measured using MRI sagittal section of T1 weighted images by the same neurologist blinded to the diagnosis and other clinical information.

Results: To differentiate PD from APSs, the delayed heart-to-mediastinum (H/M) ratio of cardiac 123I-MIBG uptake was significantly lower in patients with PD compared with those with APSs (2.06±0.98 vs. 3.04±0.71, P<0.001). SAI and M/P ratio were lower in patients with PD than those with APSs but the differences were not statistically significant (16.0±25.7 vs. 26.1±37.3, P=0.164; 0.24±0.035 vs. 0.26±0.093, p=0.839, respectively). In subgroup analysis, the delayed H/M ratio of MIBG and M/P ratio were significantly lower in patients with PD than those with MSA (3.24±0.51, p<0.001; 0.31±0.087, p=0.005, respectively). The delayed H/M ratio of MIBG and M/P ratio were significantly different in patients with PD and those with PSP (2.79±0.85, p=0.012; 0.20±0.050, p=0.002, respectively). SAI was lower in patients with PD than those with PSP (34.12±51.39, p=0.173), but the difference was not statistically significant. The area under the ROC curve for cardiac MIBG scintigraphy, SAI, and M/P ratio in differentiation of PD from APSs were 0.78 (95%CI, 0.69-0.88), 0.60 (95%CI, 0.46-0.75), and 0.51 (95%CI, 0.35-0.68) respectively.

Conclusion: Cardiac MIBG scintigraphy and M/P ratio may be useful in distinguishing PD from MSA and PSP.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/usefulness-of-cardiac-mibg-scintigraphy-dat-scan-and-midbrain-pontine-ratio-to-differentiate-parkinson-disease-from-atypical-parkinsonian-syndrome/