Patients with scans without evidence of dopaminergic deficit (SWEDD) do not have early Parkinson's disease: Analysis of the PPMI data

Abstract

Background To evaluate whether patients with scans without evidence of dopaminergic deficit (SWEDD) have early Parkinson's disease (PD). Methods The clinical characteristics, striatal specific binding ratios (SBRs), and the indices of I-123 FP-CIT SPECT images of 50 SWEDD patients, 304 PD patients, and 141 healthy controls were acquired from the Parkinson's Progression Markers Initiative (PPMI) data and evaluated during a 2-year clinical follow-up period. Results Of the 50 subjects with SWEDD, PD was confirmed in 13 subjects (the PD-SWEDD group), while the remaining 37 subjects had other diseases (the Other-SWEDD group). Striatal SBR values and striatal asymmetry indices of the PD group were significantly different with those of the PD-SWEDD and Other-SWEDD groups at both baseline and after 2 years (p < 0.001). Putaminal SBR values of the PD-SWEDD group were significantly decreased after 2 years (p < 0.05). There was no difference of the SBR values between baseline and after 2 years in the Other-SWEDD group. A baseline MDS-UPDRS III score matched comparison of the PD and PD-SWEDD group was done due to the large difference of the subject numbers. Striatal SBR values and striatal asymmetry indices were significantly different (p < 0.001) between the two groups at both baseline and after 2 years, but there were no significant difference with respect to the MDS-UPDRS III scores after 2 years between the two groups. Conclusion The different SBR values and asymmetry indices between the PD and PD-SWEDD groups at baseline and after 2 years indicate that SWEDD may not be early PD, but rather a different disease entity.