The Relationship between Rem Sleep Behaviour Disorder and Parkinson’s Disease Revisited – Are They One and the Same?

Abstract

This paper reviews the relationship between RBD and PD and the pathophysiology. Most RBD patients develop PD within 14 years. PD pathophysiology is α-synucleinopathy with dopamine degeneration in nigrostriatal pathways. RBD pathology is poorly understood. Anomalies suggest RBD and PD are different, evidenced by smoking. RBD and PD are associated with glucocerebrosidase gene mutations (GBA gene), suggesting RDB with GBA gene mutation predicts PD. PET imaging, assessing vesicular monoamine transporter 2 (VMAT2), indexing nigrostriatal dopamine innervation, is lower in PD and RBD, in the putamen, ventral striatum and globus pallidus but not substantia nigra or subthalamus, compared with controls. VMAT2 may not contribute to pathophysiology of RBD in PD. Treatments for RBD and PD differ. PD with RBD had more depression, compared to PD without RBD. Only PD with RBD had statistically significant increased depression, compared with controls, and non-significant lowered cognition. PD patients, with and without RBD, had decreased ligand binding, compared to healthy controls, indicating no difference in VMAT2 within the caudate and putamen. Research showed differences in cholinergic levels, noradrenaline and glucose metabolism for PD with and without RBD. RBD with PD, is multi-systematic, affecting regions beyond dopaminergic pathways. Treatment of RBD does not affects PD neurodegeneration. Researchers continue to search for neuro-protective intervention. There is a relationship between PD and RBD but it is not absolute. PD nigrostriatal degeneration is independent of RBD. Pathophysiological differences may explain why treatment of RBD does not alter its natural history.