Abstract
Background and Purpose: Olfactory dysfunction (OD) is a common non-motor symptom of Parkinson disease (PD). However, the relationship between OD and neuropathologic proteins in cerebrospinal fluid (CSF) from PD patients remains unclear.Methods: 166 PD patients were included in the study. Overall olfactory function was assessed by summing up the scores of olfactory threshold, discrimination, and identification by a Sniffin' Sticks test, based on which, patients were divided into PD with OD (PD-OD) and PD with no OD (PD-NOD) groups. CSF samples were obtained from 76 PD patients. The levels of neuropathologic proteins, including α-Synuclein, Aβ1-42, total tau (T-tau), and multiple forms of phosphorylated tau (P-tau) in CSF were measured by an enzyme-linked immunosorbent assay.Results: out of the 166 PD patients, 103 cases (62.0%) had OD. The scores of overall olfactory functions, and olfactory threshold, discrimination, and identification in the PD-OD group were all significantly lower than that in the PD-NOD group (P < 0.001). α-Synuclein level in CSF was significantly higher in the PD-OD group than the PD-NOD group (P < 0.05), and was significantly and negatively correlated with the scores of overall olfactory function, and olfactory discrimination and identification (P < 0.05). Aβ1-42 level in CSF was higher in the PD-OD group than the PD-NOD group, and was significantly and negatively correlated with the olfactory identification score (P < 0.05). T-tau level in CSF was significantly lower in the PD-OD group than the PD-NOD group (P < 0.05), and was significantly and positively correlated with the olfactory discrimination score (P < 0.05). There was no significant difference in P-tau level in CSF between the PD-OD and PD-NOD groups and no correlation between OD score and P-tau level in CSF.Conclusions: PD-OD includes the impairments of olfactory threshold, discrimination, and identification, and is associated with the significant elevation of α-Synuclein and the decrease of the T-tau level in CSF.
Highlights
Background and PurposeOlfactory dysfunction (OD) is a common non-motor symptom of Parkinson disease (PD)
This study aimed to investigate the correlation between the levels of neuropathologic proteins, including α-Synuclein, Aβ1-42, T-tau, and multiple forms of Ptau in cerebrospinal fluid (CSF) and olfactory function, including olfactory THR, DIS, and ID in PD patients
166 PD patients were required to describe the status of their olfactory function, among which, 79 cases (47.6%) reported that they had olfactory dysfunction (OD)
Summary
Olfactory dysfunction (OD) is a common non-motor symptom of Parkinson disease (PD). A pathological hallmark of Parkinson disease (PD) is Lewy bodies (LBs), which deposit in the substantia nigra (SN) and cause the progressive degeneration and death of dopaminergic neurons, leading to dopamine depletion in striatum and subsequent motor symptoms. Recent pathological investigations demonstrated that LBs beyond SN were associated with numerous non-motor symptoms (Khoo et al, 2013), including neuropsychiatric symptoms, autonomic dysfunction, sleep disorders, and abnormal sensation, etc., among which, olfactory dysfunction (OD) was a common non-motor symptom of abnormal sensation. According to the Braak stage of PD pathology (Braak et al, 2003), LBs in the brain start firstly in the olfactory bulb and anterior olfactory nucleus, and subsequently in nuclei in the lower brainstem, advancing in a topographically predictable sequence, to the upper brainstem and to the cerebral cortex. OD is considered as an indicator of the preclinical or early stage of PD (Doty, 2012)
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