Olfactory deficit is a widely documented non-motor symptom in Parkinson’s disease (PD). Abnormal turning points trajectories through olfactory threshold testing have been recently reported in patients with olfactory dysfunction, who seem to adapt faster to olfactory stimuli, but data on PD patients are lacking. The aim of this study is to perform olfactory threshold test and explore the turning points trajectories in PD patients in comparison to normal controls. We recruited 59 PD patients without dementia, and no conditions that could influence evaluation of olfaction and cognition. Sixty healthy subjects served as controls. Patients and controls underwent a comprehensive olfactory evaluation with the Sniffin’ Sticks extended test assessing threshold, discrimination and identification and a full neuropsychological evaluation. Besides, threshold test data were analyzed examining all the turning points trajectories. PD patients showed a different olfactory threshold test pattern, i.e., faster olfactory adaptation, than controls with no effect of age. Normosmic PD patients showed different olfactory threshold test pattern, i.e., better threshold score, than normosmic controls. Visuospatial dysfunction was the only factor that significantly influenced this pattern. Olfactory threshold trajectories suggested a possible adaptation phenomenon in PD patients. Our data offered some new insights on normosmic PD patients, which appear to be a subset with a specific psychophysical profile. The analysis of the turning points trajectories, through an olfactory threshold test, could offer additional information on olfactory function in PD patients. Future larger studies should confirm these preliminary findings.

嗅觉缺陷是帕金森病 (PD) 中广泛记录的非运动症状。最近在嗅觉功能障碍患者中报告了通过嗅觉阈值测试的异常转折点轨迹，这些患者似乎更快地适应嗅觉刺激，但缺乏 PD 患者的数据。本研究的目的是进行嗅觉阈值测试并探索 PD 患者与正常对照组相比的转折点轨迹。我们招募了 59 名没有痴呆症的 PD 患者，并且没有可能影响嗅觉和认知评估的条件。六十名健康受试者作为对照。患者和对照组通过 Sniffin' Sticks 扩展测试评估阈值、辨别和识别以及完整的神经心理学评估进行了全面的嗅觉评估。除了，分析阈值测试数据，检查所有转折点轨迹。PD 患者表现出不同的嗅觉阈值测试模式，即比没有年龄影响的对照组更快的嗅觉适应。与正常对照组相比，正常 PD 患者表现出不同的嗅觉阈值测试模式，即更好的阈值评分。视觉空间功能障碍是显着影响这种模式的唯一因素。嗅觉阈值轨迹表明 PD 患者可能存在适应现象。我们的数据为正常 PD 患者提供了一些新见解，这些患者似乎是具有特定心理物理特征的子集。通过嗅觉阈值测试对转折点轨迹的分析可以提供有关 PD 患者嗅觉功能的更多信息。