The role of 123I-MIBG cardiac scintigraphy in the patients with movement disorders (MD).

Aim/Introduction: The differential diagnosis between Parkinson’s disease (PD) and atypical parkinsonism disorders
(APD) is often difficult with undeniable prognostic and treatment repercussions. 123I-Ioflupane SPECT is usually employed to distinguish degenerative parkinsonism from essential (ET) and
vascular (VT) tremors, but in the last years 123I-MIBG scintigraphy, which evaluates cardiac sympathetic denervation, proved good performance in discriminating PD from APD (PSP, MSA and CBD),
improving Ioflupane imaging accuracy. Materials and Methods:Among a large series of over 300 MD patients submitted to 123I-MIBG cardiac scintigraphy, in the present study, we retrospectively enrolled 135 consecutive patients who had vascular damage in basal ganglia at MRI and pathologic but inconclusive
123I-Iofluopane SPECT for definitive differential MD diagnosis. After 111 MBq of 123I MIBG i.v. injection, cardiac scintigraphy was performed (anteroposterior and anterior-left oblique planar
views) after 15 min (early-E) and 240 min (delayed-D). The images were analyzed by qualitative and quantitative methods, the latter with heart/mediastinum (H/M) ratio calculation in interest regions
with 1.55 cut-off value. Results: At qualitative evaluation, MIBG uptake was slight to severe reduced in 77/135 patients (Group 1), while preserved uptake was observed in 58/135 cases (Group 2). The quantitative method showed H/M ratio <1.55 in 75/77 Group 1 patients, in both E (1.32±0.16) and D (1.27±0.18) phases, not statistically significant (p=0.074). These patients were classified as PD. The remaining two Group 1 patients had borderline H/M ratio in both E and D phases and APD was diagnosed. In Group 2 patients, H/M ratio was >1.55 in all 58 cases, mean values being 1.71±0.16 (E) and 1.75±0.22 (D), not statistically significant (p=0.25). APD was diagnosed in 47 Group 2 patients and VT in 11
cases. Comparing H/M ratio of Group 1 with Group 2 patients in both phases, the difference was statistically significant (p<0.0001). H/M comparison between all 49 APD and 75 PD patients, in both phases, showed a significant (p<0.0001) difference as well as between PD and VT. Patient diagnosis was confirmed with careful clinical long-term follow up during specific treatments. Conclusion: In the present study, 123I-MIBG cardiac scintigraphy proved a valuable tool for discriminating PD from APD and VT. In particular, H/M ratio showed better performance than qualitative diagnostic method. No statistical difference was found comparing E and D phases, thus suggesting that E evaluation alone can
be sufficient for disease diagnosis. A larger cardiac 123I-MIBG scintigraphy use is suggested in the diagnostic MD strategy.