Findings from imaging data support the presence of two subtypes of Parkinson’s disease (PD) – “brain-first” and “body-first” – defined by where Lewy bodies originate in the nervous system. Importantly, the two subtypes might track with the presence or absence of rapid eye movement sleep disorder behaviors prior to PD development or in patients with de novo PD.
Why this matters
It has been suggested that Lewy bodies in the nervous systems of people with PD behave like prions, ‘spreading’ by propagation to adjacent cells.
Evidence points to some instances where the Lewy body pathology starts in the body (e.g. the enteric nervous system) and spreads via the vagus nerve and sympathetic connectome towards the brain; however, alternative research suggests that the pathology begins in the brain itself or olfactory bulb, and spreads downwards towards the periphery.
The appearance of isolated rapid eye movement sleep behavior disorder (iRBD) prior to parkinsonism or the presence of RBD in patients with de novo PD may be a strong indicator of the body-first subtype.