Initial Versus Follow-up Sequential Myocardial 123I-MIBG Scintigraphy to Discriminate Parkinson Disease From Atypical Parkinsonian Syndromes

Abstract

Purpose Previous single-center or meta-analysis studies analyzed myocardial 123I-metaiodobenzylguanidine (123I-MIBG) scintigraphy in a single image session and demonstrated low sensitivity and high specificity for discriminating Parkinson disease (PD) from atypical Parkinsonian syndromes (APS). This study aimed to assess diagnostic ability of myocardial 123I-MIBG scintigraphy at 2 phases to discriminate PD from APS. Patients and Methods This hospital-based prospective study enrolled 162 PD and 26 APS patients who underwent 2 sequential 123I-MIBG scintigraphy evaluations. Patients were stratified into normal and decreased 123I-MIBG groups according to early and delayed heart-to-mediastinum (H/M) ratios. Patients with PD and normal 123I-MIBG uptake (initial delayed H/M ratio, ≥1.78) were considered scans without evidence of cardiac norepinephrine deficit (SWEND). Early and delayed H/M ratios on the initial and 2-year follow-up scintigraphs were studied. The diagnostic sensitivity and specificity were calculated from these confusion matrices and were analyzed according to receiver-operating characteristic curve analysis. A repeated-measures general linear model was used to investigate differences among groups over time in H/M ratio changes and washout rates. Results Follow-up 123I-MIBG scintigraphy analysis had a higher diagnostic sensitivity (89.5%) than the initial imaging (72.2%). The improved sensitivity was associated with a steeper decrease in H/M ratio in the SWEND group than in the APS group. Conclusions Follow-up 123I-MIBG scintigraphy can identify cardiac sympathetic denervation and its progression in patients with PD and may be effective in discriminating PD from APS. A later decrease in myocardial 123I-MIBG uptake in the group with SWEND meets the Braak staging threshold hypothesis for synucleinopathy.

123I‐Metaiodobenzylguanidine Myocardial Scintigraphy in Discriminating Degenerative Parkinsonisms

“…The study demonstrated that sequential 123 I-MIBG scintigraphies may improve the diagnostic ability to discriminate between PD and atypical parkinsonisms. 28 Our findings are in line with the latter observations, since evidence of cardiac sympathetic denervation was found in 80% PD patients with a relatively brief disease course (mean disease duration of 3.5 AE 2.8 years). In terms of specific diagnostic utility, 123 I-MIBG scintigraphy improved the diagnostic accuracy in 22% of our sample.…”

Relationship between the washout rate of I-123 MIBG scans and autonomic function in Parkinson’s disease

“…Therefore, I-123 MIBG cardiac scans have been widely used to assess non-invasively the presynaptic cardiac sympathetic nerve endings. Many studies have focused on the differential diagnosis of PD from atypical parkinsonism, such as multiple system atrophy or corticobasal degeneration [9][10][11][12][13][14][15][16][17]. Those studies consistently showed that I-123 MIBG cardiac scans were very useful in distinguishing early PD, and that the heart-to-mediastinal ratio (HMR) was a good diagnostic indicator in discriminating those diseases.…”

“…However, further study with a larger population is needed. As mentioned earlier, the normal range of the WR has not yet been determined, and various studies have used various normal ranges [12,22,26,38]. To predict OH in PD patients with a decreased HMR, we obtained the optimal cutoff value of the WR by ROC analysis.…”

Cardiac sympathetic burden reflects Parkinson disease burden, regardless of high or low orthostatic blood pressure changes

“…Tracer uptake was measured within each region of interest to calculate the H/M ratio. The lower limit of the reference value for delayed H/M ratio was calculated to be 1.78 12 , 13 . A delayed H/M ratio < 1.78 was defined as abnormal.…”

“…Some PD patients have a normal 123 I-MIBG uptake analogous to APS, and this imaging phenotype was previously given the term “scans without evidence of cardiac norepinephrine deficit (SWEND)” 13 . PD patients with SWEND had mild Hoehn and Yahr (H&Y) stage, short disease duration, slow progression of motor dysfunction, a lower incidence of the wearing-off phenomenon, and a lower prevalence of nonmotor symptoms 7 , 10 – 12 , 14 , 15 .…”