For decades, Parkinson’s disease (PD) has been viewed as a disorder of the brain. This perspective was shaped by the presence of misfolded alpha-synuclein aggregates throughout the brain, combined with the loss of dopamine-producing neurons. Collectively, these dysfunctions drive the devastating motor symptoms, speech difficulties, and cognitive decline that characterise PD. However, recent research challenges this brain-centric view. Alpha-synuclein has been identified to appear in the...