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

•We investigated if 123I-MIBG myocardial scintigraphy can identify PD among SWEDDs.•We encountered 18 SWEDDs (12.4%) among 145 patients with clinically suspected PD.•Eleven SWEDDS (61.1%) were finally diagnosed as PD after two years follow-up.•Low delayed H/M ratio (30%) may be markers of PD among SWEDDs. 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. 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. 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%. 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.