Abstract
Background: Multiple system atrophy (MSA), progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) have overlapping signs and symptoms with Parkinson’s disease (PD), and these similarities complicate their clinical diagnostics. Although presynaptic dopaminergic brain imaging with PET and SPECT is clinically widely used for patients with suspected PD, the benefit of functional imaging in atypical parkinsonism syndromes remains unclear. We compared striatal presynaptic dopaminergic function in MSA parkinsonism variant (MSA-P), MSA cerebellar variant (MSA-C), PSP, CBS and PD using combined quantitative data from all published studies. Methods: PubMed database was searched from inception to August 2018 for terms “dopamine” OR “dopaminergic” AND “PET” OR “SPECT” OR “SPET” and keywords related to PD, MSA, PSP and CBS. A total of 1711 publications were identified. PET or SPECT studies comparing patients with atypical parkinsonism to another diagnostic group (PD, MSA, PSP or CBS) were included. Tracers for dopamine transporter (DAT), aromatic amino acid decarboxylase (AADC) or vesicular monoamine type 2 (VMAT2) were investigated. Tracer binding data were extracted from the original articles. Heterogeneity of the data were examined using I2 statistics and a random effect model was used to summarize data. Hedges g was used as an estimator of effect size in group comparisons. Results are reported according to PRISMA guidelines. Results: Thirty-five studies (29 DAT, 6 AADC, no VMAT2 studies) with 356 MSA-P patients, 204 PSP patients, 79 CBS patients and 62 MSA-C patients were included in the meta-analysis. Caudate nucleus and putamen DAT functions were clearly lower in PSP as compared to PD (caudate: 34.1% difference, g=-1.08, 95%CI= -1.52 to -0.64; putamen: 18.2% , g=-0.86, 95%CI=-1.50 to -0.21) and MSA-P (striatum: 31.4%, g=-0.70, 95%CI=-1.21 to -0.19), and in MSA-P as compared to MSA-C (striatum: 46.0%, g=1.46, 95%CI=0.23 to 2.68). Although not significant due to limited data, aromatic L-amino acid decarboxylase (AADC) results paralleled the DAT findings. Conclusion: Striatal presynaptic DAT function is clearly lower in PSP patients as compared to PD and MSA-P patients, and in MSA-P patients as compared to MSA-C patients.
- Copyright © 2019 by the Society of Nuclear Medicine and Molecular Imaging, Inc.