Relation of 18-F-Dopa PET with hypokinesia-rigidity, tremor and freezing in Parkinson’s disease

•A large study showed the relation between Parkinson symptoms and dopamine depletion.•Dopamine depletion and hypokinetic-rigidity are related in Parkinson patients.•Tremor was not related to dopamine depletion and relays on a different pathway.•Freezing of gait correlated with reduced dopamine values in the putamen.

IntroductionIn this retrospective study concerning patients with Parkinson's disease (PD) scanned with 18-F-Dopa PET (N = 129), we looked for an association between reduced 18-F-Dopa uptake and the key PD symptoms tremor and hypokinesia-rigidity. We hypothesized to find a stronger correlation between dopaminergic depletion in the striatum and hypokinesia-rigidity compared to tremor.MethodsThe onset side of symptoms (documented for 102 patients) as well as the first registered UPDRS (available for 79 patients) was used to correlate with F-Dopa uptake values in the caudate nucleus and putamen in this large retrospective sample.ResultsReduced F-Dopa uptake was contralateral to hypokinesia-rigidity symptoms and correlated with its severity (quantified by UPDRS). For tremor severity, no correlation was seen with F-Dopa reduction. Furthermore, freezing of gait correlated with reduced F-Dopa uptake in the putamen of the right hemisphere.Conclusion and discussionOur results, obtained in a large patient group, provides support for the concept that tremor in PD is not only based on a dopamine related pathway but may rely on a different pathway.