Parkinson’s
disease (PD) is a common neurodegenerative movement disorder. The motor
symptoms of PD are linked to the degeneration of dopaminergic neurons of the
substantia nigra, which leads to dopamine depletion in the striatum. Non-motor
symptoms (NMSs), such as depression, hallucinations and impulse control
disorders (ICDs), are important manifestations of PD. The role of dopamine in
the pathophysiology of these symptoms is less clear. This thesis investigated
NMSs in PD and their association with brain dopamine function using dopamine
transporter (DAT) single-photon emission computed tomography (SPECT) imaging.
Furthermore, factors that predict the DAT imaging outcome were investigated.

The results
suggest that ICDs of PD are associated with multiple other psychiatric
symptoms. Furthermore, an older age, longer motor symptom duration and
asymmetric motor symptoms are associated with an abnormal DAT imaging outcome.
The results also demonstrate that lower DAT binding in the limbic striatum is
associated with the development of hallucinations in PD. Finally, although PD
patients suffer from multiple NMSs, the total burden of these symptoms does not
differentiate PD patients from parkinsonism patients with normal DAT binding.

The results
demonstrate that the total NMS burden is not a specific manifestation for Parkinson’s
disease and is unrelated to brain dopamine function. Clinical factors, such as
patient age, motor symptom duration and motor symptom asymmetry, may be useful
for selecting which patients should undergo DAT SPECT imaging. Moreover, DAT
imaging may be useful in predicting subsequent NMS manifestations, such as
visual hallucinations; however, further studies are required.