Olfactory Deficits in the Freezing of Gait Phenotype of Parkinson's Disease.

Aliyah Glover,Lakshmi Pillai,Tuhin Virmani,Rohit Dhall

doi:10.3389/fneur.2021.656379

Aliyah Glover, Lakshmi Pillai + Show 2 more

Open Access

https://doi.org/10.3389/fneur.2021.656379

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Abstract

Background: Olfactory dysfunction often occurs before motor onset in Parkinson's disease (PD) and can be detected with the University of Pennsylvania Smell Identification Test (UPSIT). Based on the Braak hypothesis, the olfactory bulb is one of two sites where disease pathology may start and spread to deeper brain structures.Objective: To evaluate whether a specific pattern of odorant identification on the UPSIT discriminated Parkinson's disease patients with and without freezing of gait.Methods: One hundred and twenty four consecutive participants (33 controls, 31 non-freezers, and 60 freezers) were administered the UPSIT. Using the chi-square test, each odorant on the UPSIT was ranked based on the differential ability of freezers and non-freezers to identify them correctly. Using predictive statistics and confusion matrices, the best combination of odorants and a cut-off score was determined.Results: Freezers had a shift toward a more severe hyposmia classification based on age and sex based normative values. The correct identification of nine odors (bubblegum, chocolate, smoke, wintergreen, paint thinner, orange, strawberry, grass, and peanut) was significantly worse in freezers compared to non-freezers. Correctly identifying ≤ 2 out of 3-odorants (bubblegum, chocolate, and smoke) had a 77% sensitivity and 61% specificity for categorizing freezers. The 3-odorant score was not correlated with disease duration, motor or total UPDRS scores, MoCA scores or age at testing. The predictive statistics were similar when sexes were separately categorized.Conclusions: A 3-odorant score helped categorize freezers and non-freezers with similar sensitivity and specificity to short odorant Parkinson's disease identification batteries.

Highlights

Olfactory dysfunction is reported in 46–98% of patients with Parkinson’s Disease (PD) [1,2,3]
If participants Montreal cognitive assessment (MoCA) scores dropped below 10 at any time during their active participation in the study, participants were asked to re-consent before they could continue participation with a power of attorney (POA)/spouse serving as a cosigner
Utilizing the age and sex based normative score classification for the University of Pennsylvania Smell Identification Test (UPSIT) provided with the test, freezers had a significant shift toward more severe phenotypes compared to non-freezers (Figure 1) using a chi-square test (p = 0.041), TABLE 1 | Participant demographics and potential olfactory modulators

Summary

Introduction

Olfactory dysfunction is reported in 46–98% of patients with Parkinson’s Disease (PD) [1,2,3]. The 40-item University of Pennsylvania Smell Identification Test (UPSIT) is an effective instrument to detect olfactory dysfunction in PD [7,8,9], the time and cost to administer it has limited clinical use. Whether the severity of smell deficit in PD patients correlates with disease duration or severity is still a matter of debate, with some studies reporting worsened olfactory deficit with disease severity [14,15,16], and others reporting no relationship [17,18,19,20]. Olfactory dysfunction often occurs before motor onset in Parkinson’s disease (PD) and can be detected with the University of Pennsylvania Smell Identification Test (UPSIT). Based on the Braak hypothesis, the olfactory bulb is one of two sites where disease pathology may start and spread to deeper brain structures

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