The usefulness of myocardial segmental analysis on I-123 MIBG SPECT in Parkinson’s disease

Objectives Cardiac SPECT using I-123 metaiodobenzylguanidine (MIBG) is widely used to evaluate cardiac sympathetic denervation in Parkinson’s disease (PD). Early and delayed heart/mediastinum (H/M) ratio were commonly used. However, there were few studies reporting the usefulness of segmental analysis of MIBG SPECT. The aim of this study was to evaluate the usefulness of myocardial segmental analysis on I-123 MIBG SPECT in PD patients.

Methods Total 36 patients with clinically diagnosed Parkinson’s disease (n=26) or essential tremor (n=10) were enrolled. The H/M ratio in early and delayed chest image with I-123 MIBG was acquired. For segmental analysis of cardiac SPECT, we evaluated the summed defect score (SDS) in 17 segments model. We further analyzed the 17 segments into 3 vessel territories (anteroseptal, lateral and inferior wall). Student t-test was performed to detect differences in the cardiac sympathetic innervations between patient groups. Receiver-operating-curve analysis was used to assess diagnostic ability of H/M ratios and segmental analysis on I-123 MIBG SPECT.

Results The early and delayed H/M ratio were significantly lower in patients with PD than those with ET (early H/M ratio PD:ET=1.52 :1.93, p=0.02,delayed H/M ratio PD:ET=1.44:2.01,p=0.008). The result of SDS analysis demonstrated the degree of cardiac I-123 MIBG uptake was significantly lower in PD patients than in ET patients (p=0.006). On segmental analysis, anteroseptal wall showed significant difference between two groups (p=0.002) but not at lateral (p=0.918) and inferior wall (p=0.102). The ROC analysis suggested only SDS (AUC=0.785,p=0.0003), anteroseptal wall (AUC=0.800,p<0.0001) and inferior wall (AUC=0.667,p=0.013) scores showed significant diagnostic ability for PD from ET.

Conclusions In Parkinson’s disease, cardiac MIBG uptake is significantly reduced in anteroseptal wall area on segmental analysis. Therefore, myocardial segmental analysis on I-123 MIBG SPECT is useful method to diagnosis Parkinson’s disease.