Objective: To investigate the dysfunction of the serotonergic system related to impulse control disorders in patients with Parkinson’s disease.

Background: Impulse control disorders (ICDs, including pathological gambling, compulsive buying, hypersexuality and eating disorders) are particularly burdensome and challenging symptoms in Parkinson’s disease, which are related to striatal dopaminergic dysfunction and modulated by dopaminergic treatments. However, serotonergic dysfunction may also contribute to ICDs, as observed in pathological gambling in the general population.

Method: We conducted a prospective, case-control, double-tracer PET study to compare the pre- and post-synaptic serotonergic innervation, using 11C-DASB and 18F-altanserin PET imaging, which binds to the serotonin transporter and serotonin receptor type 2A respectively. We recruited 15 patients with Parkinson’s disease and impulse control disorders (Ardouin Scale of Behavior in Parkinson’s disease>=2 for at least one ICD among pathological gambling, compulsive buying, hypersexuality and eating disorders), 15 patients with Parkinson’s disease without impulse control disorders and 15 healthy controls, matched for age and sex. We performed a group-comparison for 11C-DASB and 18F-altanserin PET binding potentials using permutation-based analysis in FSL, correcting for multiple comparisons.

Results: Patients with ICDs had eating disorders (n=6), hypersexuality (n=5) and compulsive buying (n=4), with multiple ICDs in six patients (40%). Patients with ICDs had more severe depressive symptoms, whereas anxiety, motor impairment and motor complications were similar in patients with or without ICDs. Montreal Cognitive Assessment and Frontal Assessment Battery were similar in all groups. Pre-synaptic binding of 11C-DASB to the serotonin transporter was decreased in the striatum for patients with Parkinson’s disease in comparison to healthy controls. Moreover, we observed that pre-synaptic binding of 11C-DASB in the putamen was higher in patients with ICDs in comparison to patients without ICDs, indicating a relative preservation of binding to the serotonin transporter. Binding of 18F-altaserin was higher in the frontal cortex in patients with ICDs.

Conclusion: Patients with ICDs have greater preservation of the striatal pre-synaptic serotonergic system, indicating serotonergic dysfunction related to ICDs in Parkinson’s disease for the first time.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/serotonergic-dysfunction-and-impulse-control-disorders-in-parkinsons-disease-a-double-tracer-pet-study/