123 I-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 123 I-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.