Laura Saari1, Katri Kivinen1, Maria Gardberg1, Juho Joutsa1, Tommi Noponen1, Valtteri Kaasinen2. 1. From the Division of Clinical Neurosciences (L.S., J.J., V.K.), Turku University Hospital, Turku, Finland; Department of Neurology (L.S., J.J., V.K.) and Turku PET Centre (J.J., T.N., V.K.), University of Turku; and Departments of Pathology (K.K., M.G.) and Clinical Physiology and Nuclear Medicine (T.N.), Turku University Hospital and University of Turku, Finland. 2. From the Division of Clinical Neurosciences (L.S., J.J., V.K.), Turku University Hospital, Turku, Finland; Department of Neurology (L.S., J.J., V.K.) and Turku PET Centre (J.J., T.N., V.K.), University of Turku; and Departments of Pathology (K.K., M.G.) and Clinical Physiology and Nuclear Medicine (T.N.), Turku University Hospital and University of Turku, Finland. valtteri.kaasinen@tyks.fi.
Abstract
OBJECTIVE: To examine possible associations between in vivo brain dopamine transporter SPECT imaging and substantia nigra pars compacta (SNc) neuronal survival in Parkinson disease (PD). METHODS: Nigral neuron numbers were calculated for 18 patients (11 patients with neuropathologically confirmed PD) who had been examined with dopamine transporter (DAT) SPECT before death. Correlation analyses between SNc tyrosine hydroxylase (TH)-positive and neuromelanin-containing neuron counts and DAT striatal specific binding ratios (SBRs) were performed with semiquantitative region of interest-based and voxel-based analyses. RESULTS: Mean putamen SBR did not correlate with the number of substantia nigra TH-positive (r = -0.11, p = 0.66) or neuromelanin-containing (r = -0.07, p = 0.78) neurons. Correlations remained clearly nonsignificant when the time interval between SPECT and death was used as a covariate, when the voxel-based analysis was used, and when only patients with PD were included. CONCLUSIONS: This cohort study demonstrates that postmortem SNc neuron counts are not associated with striatal DAT binding in PD. These results fit with the theory that there is no correlation between the number of substantia nigra neurons and striatal dopamine after a certain level of damage has occurred. Striatal DAT binding in PD may reflect axonal dysfunction or DAT expression rather than the number of viable neurons.
OBJECTIVE: To examine possible associations between in vivo brain dopamine transporter SPECT imaging and substantia nigra pars compacta (SNc) neuronal survival in Parkinson disease (PD). METHODS: Nigral neuron numbers were calculated for 18 patients (11 patients with neuropathologically confirmed PD) who had been examined with dopamine transporter (DAT) SPECT before death. Correlation analyses between SNc tyrosine hydroxylase (TH)-positive and neuromelanin-containing neuron counts and DAT striatal specific binding ratios (SBRs) were performed with semiquantitative region of interest-based and voxel-based analyses. RESULTS: Mean putamen SBR did not correlate with the number of substantia nigra TH-positive (r = -0.11, p = 0.66) or neuromelanin-containing (r = -0.07, p = 0.78) neurons. Correlations remained clearly nonsignificant when the time interval between SPECT and death was used as a covariate, when the voxel-based analysis was used, and when only patients with PD were included. CONCLUSIONS: This cohort study demonstrates that postmortem SNc neuron counts are not associated with striatal DAT binding in PD. These results fit with the theory that there is no correlation between the number of substantia nigra neurons and striatal dopamine after a certain level of damage has occurred. Striatal DAT binding in PD may reflect axonal dysfunction or DAT expression rather than the number of viable neurons.
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