[Non-motor disorders in Parkinson's disease]

Parkinson's disease (PD) is a progressive disorder that is strongly linked to non-motor symptoms (NMS). Unfortunately, these symptoms have been almost neglected for many years and only recently have researchers begun to assess how they affect the quality of life in patients with PD.

To review our current understanding of the subject and to highlight the importance of NMS in PD.

Recent studies have emphasised the fact that the basal ganglia play an important role in a number of non-motor functions. At the same time, the exclusive involvement of the substantia nigra in PD is being reviewed and the development of PD has been defined as a continuum that covers a range of different stages, including non-dopaminergic systems and nuclei. This would account for the constellation of non-motor symptoms that do not respond to dopamine replacement therapy and which affect patients with PD, such as depression, apathy, sialorrhea and urinary incontinence, among others.

NMS make a significant contribution to the morbidity and mortality rates of PD and are often the main cause of hospitalisation of patients with PD. Current evidence suggests that some NMS, such as constipation, hyposmia and REM sleep disorders, could even be preclinical markers of PD. Both of these reasons stress the importance of reaching a diagnosis faster and earlier.