Colonic neuropathology is independent of olfactory dysfunction in Parkinson's disease

Olfactory dysfunction (OD) and constipation are two frequent and early non-motor features of Parkinson's disease (PD). Colonic PD neuropathology, the putative cause of constipation, can be analyzed and quantified using routine colonic biopsies and parallels disease severity. The present study was aimed at investigating whether the severity of neuropathology in the colon in PD is related to OD. Twenty-six PD patients were included. Colonic neuropathology, i.e., the density of Lewy pathology and the number of submucosal neurons, was unrelated to OD as assessed using the University of Pennsylvania Smell Identification. This suggests that unlike colonic Lewy pathology, OD is unrelated to disease severity.