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No link between striatal dopaminergic axons and dopamine transporter imaging in Parkinson's disease
Emma A Honkanen1,2, Laura Saari1,2, Katri Orte3
1Department of Neurology, University of Turku, Turku, Finland.
Background:
Brain dopamine transporter binding has been considered a possible biomarker for nigrostriatal degeneration in PD.
Objective:
To investigate whether dopamine transporter binding is associated with the number of dopaminergic neurites in the putamen.
Methods:
Tyrosine hydroxylase-positive nerve fibers were counted from postmortem putamen sections taken from 14 parkinsonism patients who had been scanned with dopamine transporter single-photon emission computed tomography antemortem. Fiber counts were correlated with putamen dopamine transporter binding and SN neuron counts.
Results:
The putamen dopamine transporter specific binding ratio did not correlate with the putamen tyrosine hydroxylase-positive axon counts (r = 0.00; P = 1.0; PD patients: r = 0.07; P = 0.86). The nigra neuron counts had a positive correlation with the putamen tyrosine hydroxylase-positive axon counts.
Conclusions:
Striatal dopamine transporter imaging does not associate with axonal nor somal loss of the nigrostriatal neurons in PD. It may reflect dopaminergic activity rather than number of surviving neurons or their striatal projection axons. © 2019 International Parkinson and Movement Disorder Society.