Synycleinopathies from autonomic point of view

Parkinson’s disease (PD) and multiple system atrophy (MSA) are major neurogenerative diseases characterized pathologically by abnormal alpha-synuclein aggregation. PD and MSA are clinically characterized by motor disorder and autonomic dysfunction; among these bladder (overactive bladder) and gut dysfunction (delayed gastric emptying, constipation) are most common. However, bladder dysfunction in MSA is more severe than that in PD for large post-void residual or urinary retention. These bladder dysfunctions presumably reflect the different nervous system pathology. Overactive bladder in PD reflects lesions in the brain, e.g., prefrontal-nigrostriatal D1 dopaminergic bladder-inhibitory pathway. Overactive bladder in MSA reflects lesions similar to PD and the cerebellum (inhibitory), while urinary retention in MSA presumably reflects lesions in the pontine micturition center and the sacral intermediolateral nucleus (facilitatory). Bladder dysfunction in MSA often predates motor disorder. This condition can be detected by sphincter electromyography in situ. Bladder dysfunction not only impairs the quality of life, but also causes emergency hospitalization due to acute retention, and early institutionalization in the patients. Gut dysfunction in MSA mainly reflects spinal cord pathology. In contrast, gut dysfunction in PD mainly reflects peripheral myenteric plexus pathology that often predates motor disorder. This condition can be detected by advanced neuroimaging by MIBG myocardial scintigraphy in situ. Postural hypotension in MSA reflects lesions in the medullary cardiovascular center and the thoracolumbar intermediolateral nucleus. In contrast, postural hypotension in PD reflects periarterial nerve pathology, which occasionally predates motor dysfunction. This review summarizes three autonomic disorders and their role in the early diagnosis of synucleinopathies.