123I-Meta-iodobenzylguanidine (MIBG) myocardial scintigraphy in patients showing scans without evidence of dopaminergic deficits (SWEDDs).

OBJECTIVE: Scans without evidence of dopaminergic deficits (SWEDDs) in dopamine transporter single-photon emission computed tomography (DAT-SPECT) are found in 3.6-19.6% of patients with clinically suspected Parkinson's disease (PD). We investigated whether combined use of 123I-meta-iodobenzylguanidine (MIBG) myocardial scintigraphy would be helpful to differentiate PD among SWEDDs patients. PATIENTS AND METHODS: 145 patients with clinically suspected PD underwent both DAT-SPECT and MIBG myocardial scintigraphy. Striatal binding ratio (SBR) of DAT-SPECT and heart-to-mediastinal (H/M) ratio and washout rate (WR) of MIBG myocardial scintigraphy were calculated. RESULTS: Among 18 SWEDDs patients (12.4%), 11 were finally diagnosed with PD based on follow-up for at least two years after the DAT-SPECT and MIGB myocardial scintigraphy scans. Among the latter group, 8 patients showed an H/M ratio of less than 2.2, and 9 showed WR above 30%. CONCLUSION: Our results indicate that the combination of low H/M ratio and high WR of MIBG myocardial scintigraphy of SWEDDs patients may be helpful for detection of PD patients.

Combined use of dopamine transporter imaging (DAT-SPECT) and 123I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy for diagnosing Parkinson's disease.

BACKGROUND: To examine whether combined use of 123I-FP-CIT dopamine transporter single photon emission computed tomography (DAT-SPECT) and 123I-MIBG myocardial scintigraphy (MIBG) is superior to either modality alone for diagnosing Parkinson's disease (PD). METHODS: Patients with probable PD (n=120) who underwent both DAT-SPECT and MIBG myocardial scintigraphy within short intervals were enrolled. Specific binding ratio (SBR) of DAT-SPECT images and heart-to-mediastinum (H/M) ratio of MIBG images were used as quantitative measures. We classified patients into 4 groups based on SBR value and H/M ratio, or into two groups based on the striatal asymmetry index (SAI) of DAT-SPECT, and examined the clinical features of each group. We also investigated the characteristics of SWEDDs (scans without evidence of dopaminergic deficits) patients. Finally, we calculated the sensitivity and specificity of each method and the combined method. RESULTS: SBR value was significantly correlated with both early and delayed H/M ratio values. Motor complications and hallucinations were observed at high frequency in the group with both lower SBR and H/M ratio, and hallucinations appeared in the group with larger SAI. SWEDDs were observed 8.3% of patients. The sensitivity and specificity of diagnosing PD were 91.7% and 15.0% by SBR of DAT-SPECT, 78.3% and 90.0% by H/M ratio of MIBG uptake, and 74.2% and 95.0% by the combined modalities, respectively. CONCLUSIONS: Combined use of DAT-SPECT and MIBG myocardial scintigraphy increases the specificity of PD diagnosis, and is helpful for understanding the clinical features or predicting complications.