Dopaminergic molecular imaging in familial and idiopathic Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease classically characterized by a progressive degeneration of the dopaminergic neurons of the nigrostriatal system, which gives rise to the typical motor symptoms. A complete study of the pathophysiology of the dopaminergic system is considered essential for the comprehension of the events, leading to the development of the symptoms and to identify targets for therapeutic intervention. Thanks to the availability of dedicated radiotracers, positron emission tomography (PET) and single photon emission computerized tomography (SPECT) can study, in vivo, the function of presynaptic and the postsynaptic dopaminergic system in PD with a precision unparalleled by any other imaging technique. A small percentage of PD cases recognize a clear family history, and in the past decades, a growing number of genetic mutations have been associated with typical and atypical forms of familial PD. The study of familial forms of PD, in relationship with findings in idiopathic cases, can reveal similarities and differences that can shed light on the pathophysiology underlying these forms. This chapter will review the most recent PET and SPECT studies using tracers for the dopaminergic system, conducted in idiopathic and familial forms of PD, and discuss the clinical implications of the findings.