Objective: To investigate the connection between striatal dopamine transporter binding and cardinal motor symptoms of Parkinson’s disease.

Background: The three cardinal motor symptoms of Parkinson’s disease include rigidity, bradykinesia and rest tremor. Rigidity and bradykinesia are known to correlate with contralateral nigrostriatal degeneration and striatal dopamine deficit, but association between dopamine function and rest tremor has remained unclear. Here we investigated the possible link between dopamine function and rest tremor using the data obtained from the Parkinson’s Progression Markers Initiative (PPMI), the largest prospective neuroimaging cohort data of patients with Parkinson’s disease.

Method: Data used in the preparation of this article were obtained from the Parkinson’s Progression Markers Initiative (PPMI) database (https://www.ppmi-info.org/access-data-specimens/download-data). For up-to-date information on the study, visit www.ppmi-info.org. The processed data included [¹²³I]-FP-CIT SPECT images of 314 early PD patients and 166 healthy controls at baseline. We performed a careful linear registration between individual SPECT and MRI scans, allowing non-linear mapping to a standard space and voxelwise analyses. Association between the cardinal motor symptoms and tracer binding were investigated using voxelwise regression models.

Results: As expected, severity of both rigidity and bradykinesia were negatively correlated with contralateral striatal DAT binding. However, severity of rest tremor was associated with increased ipsilateral DAT binding. The association between rest tremor and DAT binding remained practically identical when controlling for Hoehn & Yahr stage, MDS-UPDRS-III score, bradykinesia-rigidity score or Parkinson phenotype, was independent from bradykinesia and rigidity, and also replicated after 2-year follow-up.

Conclusion: In agreement with the existing literature, we did not find consistent association between rest tremor and contralateral dopamine defect. However, the results demonstrate a link between rest tremor and increased ipsilateral DAT binding. These results provide novel information about the dopaminergic correlates of parkinsonian tremor and may provide new insight into the neurobiological mechanisms of rest tremor.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/rest-tremor-in-parkinsons-disease-is-associated-with-increased-ipsilateral-dat-binding/