Non-motor symptoms and their use as markers for prodromal and early Parkinson's disease

Parkinson’s Disease (PD) is the second most common neurodegenerative disorder. It is a disease with a broad spectrum of symptoms, both motor and non-motor, but is often only diagnosed when the motor symptoms begin to appear. By this time however, a large amount of the dopaminergic neurons of the substantia nigra pars compacta have already deteriorated. It is therefore of great interest to be able to diagnose the disease earlier on in its progression and perhaps slow down or halt its course. Recent literature has supported the idea that non-motor symptoms begin to appear years, perhaps even decades, before the motor symptoms are visible. This makes them a prime candidate for diagnosing PD earlier on. With the aim of assessing the prevalence of different NMS in prodromal and early Parkinson’s, 19 studies addressing different NMS were analyzed. It was found that NMS are prevalent in both prodromal and early PD. The strongest prodromal predictors for PD were found to be olfactory dysfunction and REM-sleep behavior disorder (RBD).