Motor and non-motor correlates of olfactory dysfunction in Parkinson's disease

Recent progress in the applications of presynaptic dopaminergic positron emission tomography imaging in parkinsonism

Nowadays, presynaptic dopaminergic positron emission tomography, which assesses deficiencies in dopamine synthesis, storage, and transport, is widely utilized for early diagnosis and differential diagnosis of parkinsonism. This review provides a comprehensive summary of the latest developments in the application of presynaptic dopaminergic positron emission tomography imaging in disorders that manifest parkinsonism. We conducted a thorough literature search using reputable databases such as PubMed and Web of Science. Selection criteria involved identifying peer-reviewed articles published within the last 5 years, with emphasis on their relevance to clinical applications. The findings from these studies highlight that presynaptic dopaminergic positron emission tomography has demonstrated potential not only in diagnosing and differentiating various Parkinsonian conditions but also in assessing disease severity and predicting prognosis. Moreover, when employed in conjunction with other imaging modalities and advanced analytical methods, presynaptic dopaminergic positron emission tomography has been validated as a reliable in vivo biomarker. This validation extends to screening and exploring potential neuropathological mechanisms associated with dopaminergic depletion. In summary, the insights gained from interpreting these studies are crucial for enhancing the effectiveness of preclinical investigations and clinical trials, ultimately advancing toward the goals of neuroregeneration in parkinsonian disorders.

Correlations between Gustatory, Olfactory, Cognitive Function, and Age in Healthy Women

Aging is a progressive physiological degeneration associated with a decline in chemosensory processes and cognitive abilities and a reduction in synaptic plasticity. The biological bases of ageing are still not completely understood, and many theories have been proposed. This study aimed to evaluate the occurrence of age-related changes affecting the chemosensory function (gustatory and olfactory) and general cognitive abilities and their potential associations in women. To this aim, 319 women (the age ranging from 18 to 92 years) were recruited and divided into four different age groups: 18-34 years, 35-49 years, 50-64 years, and ≥65 years. Our results confirmed that in women, gustatory, olfactory, and cognitive functions decline, though in a different manner during aging. Olfactory and cognitive function showed a slight decline along the first three age classes, with a dramatic decrease after age 65 years, while gustatory function decreased more gradually. Olfactory and gustatory deficits may have a high degree of predictivity for general cognitive function as well as for specific cognitive subdomains such as visuospatial/executive abilities, language, memory, and attention. Our study highlighted the importance of using chemosensory assessments for the early diagnosis of cognitive decline and for the development of appropriate personalized risk prevention strategies.

Clinical features and neurobiochemical mechanisms of olfactory dysfunction in patients with Parkinson disease

This study aimed to investigate clinical features, influencing factors and neurobiochemical mechanisms of olfactory dysfunction (OD) in Parkinson disease (PD). Total 39 patients were divided into the PD with OD (PD-OD) and PD with no OD (PD-nOD) groups according to overall olfactory function, including threshold, discrimination and identification, assessed by Sniffin' Sticks test. Motor function and non-motor symptoms were rated by multiple scales. Dopamine, acetylcholine, norepinephrine and 5-hydroxytryptamine levels in cerebrospinal fluid (CSF) were measured. We found that the PD-OD group showed significantly lower score of Montreal Cognitive Assessment Scale, higher scores of rapid eye movement sleep behavior disorder (RBD) Screening Questionnaire and Epworth Sleepiness Scale than the PD-nOD group (p < 0.05). RBD Screening Questionnaire score was independently associated with the scores of overall olfactory function and discrimination (p < 0.05). Dopamine and acetylcholine levels in CSF from the PD-OD group was significantly lower than that from the PD-nOD group (p < 0.05). Dopamine and acetylcholine levels in CSF were significantly and positively correlated with the scores of overall olfactory function, threshold, discrimination and identification in PD patients (p < 0.05). RBD Screening Questionnaire score was significantly and negatively correlated with acetylcholine level in CSF in PD patients with poor olfactory detection (p < 0.05). This investigation reveals that PD-OD is associated with cognitive impairment, probable RBD and excessive daytime sleepiness. PD-OD is correlated with the decreased levels of dopamine and acetylcholine in CSF. RBD is an independent influencing factor of overall olfactory function and discrimination, and the decreased acetylcholine level in CSF may be the common neurobiochemical basis of RBD and OD in PD patients.

Hyposmia correlates with axial signs and gait disorder in Parkinson's disease: an Italian Olfactory Identification Test study

BACKGROUND

Olfactory dysfunction is a non-motor symptom and an important biomarker of Parkinson's disease (PD) because of its high prevalence (> 90%). Whether hyposmia correlates with motor symptoms is unclear. In the present study, we aim to investigate the relationship between olfactory impairment with both motor and non-motor features and disease variables (disease duration, stage, and severity).

METHODS

One-hundred fifty-four PD patients were evaluated. Odor identification ability was tested using Italian Olfactory Identification Test (IOIT). A comprehensive spectrum of motor and non-motor features was assessed. Cognitive function was investigated through MMSE. Patients were divided into 3 different clinical phenotypes using UPDRS-III: tremor-dominant type (TDT), akinetic-rigid type (ART), and mixed type (MXT).

RESULTS

Three of the 33 IOIT items were most frequently misidentified: basil (74.3%), coffee (66.9%), and mushroom (59.6%). Hyposmia was found in 93%. Hyposmic patients were older than controls (p = 0.01). Hoehn & Yahr (H&Y) score of 2 or greater was associated with higher probability of being hyposmic (OR = 5.2, p = 0.01). IOIT score did not significantly differ between TDT, ART, and MXT of analyzed PD patients. Performance to IOIT inversely correlated with age (p < 0.01), disease duration (p = 0.01), and H&Y score of 2 or higher (p < 0.01). Clinical features that associated with higher IOIT score were freezing of gait (FOG) (p < 0.001) and camptocormia (p < 0.05).

CONCLUSIONS

In our cohort, IOIT scores showed a positive correlation with axial motor signs, but not with non-motor symptoms. IOIT may be a useful tool not only for supporting PD diagnosis but also for providing prognostic information about motor function.

Underestimated olfactory domains in Huntington's disease: odour discrimination and threshold

BACKGROUND

Olfaction has recently found clinical value in prediction, discrimination and prognosis of some neurodegenerative disorders. However, data originating from standard tests on olfactory dysfunction in Huntington's disease are limited to odour identification, which is only one domain of olfactory perceptual space.

METHOD

Twenty-five patients and 25 age- and gender-matched controls were evaluated by the Sniffin' Sticks test in three domains of odour threshold, odour discrimination, odour identification and the sum score of them. Patients' motor function was assessed based on the Unified Huntington's Disease Rating Scale.

RESULTS

Compared with controls, patients' scores of all olfactory domains and their sum were significantly lower. Besides, our patients' odour threshold and odour discrimination impairments were more frequently impaired than odour identification impairment (86 per cent and 81 per cent vs 34 per cent, respectively).

CONCLUSION

Olfactory impairment is a common finding in patients with Huntington's disease; it is not limited to odour identification but is more pronounced in odour discrimination and odour threshold.

Aquaporin 4 beyond a water channel; participation in motor, sensory, cognitive and psychological performances, a comprehensive review

Aquaporin 4 (AQP4) is a protein highly expressed in the central nervous system (CNS) and peripheral nervous system (PNS) as well as various other organs, whose different sites of action indicate its importance in various functions. AQP4 has a variety of essential roles beyond water homeostasis. In this article, we have for the first time summarized different roles of AQP4 in motor and sensory functions, besides cognitive and psychological performances, and most importantly, possible physiological mechanisms by which AQP4 can exert its effects. Furthermore, we demonstrated that AQP4 participates in pathology of different neurological disorders, various effects depending on the disease type. Since neurological diseases involve a spectrum of dysfunctions and due to the difficulty of obtaining a treatment that can simultaneously affect these deficits, it is therefore suggested that future studies consider the role of this protein in different functional impairments related to neurological disorders simultaneously or separately by targeting AQP4 expression and/or polarity modulation.

UPSIT subitems may predict motor progression in Parkinson's disease

Background

The relationship between hyposmia and motor progression is controversial in Parkinson's disease (PD). The aim of this study was to investigate whether preserved identification of Chinese-validated University of Pennsylvania Smell Identification Test (UPSIT) odors could predict PD motor progression.

Methods

PD patients with two consecutive clinical visits while taking medication were recruited. Based on mean changes in Movement Disorder Society Unified Parkinson's Disease Rating Scale part 3 score and levodopa equivalent daily dosage, the participants were categorized into rapid progression, medium progression, and slow progression groups. Odors associated with the risk of PD motor progression were identified by calculating the odds ratios of UPSIT item identification between the rapid and slow progression groups. Receiver operating characteristic curve analysis of these odors was conducted to determine an optimal threshold for rapid motor progression.

Results

A total of 117 PD patients were screened for group classification. Preserved identification of neutral/pleasant odors including banana, peach, magnolia, and baby powder was significantly correlated with rapid motor progression. The risk of rapid progression increased with more detected risk odors. Detection of ≥1.5 risk odors could differentiate rapid progression from slow progression with a sensitivity of 85.7%, specificity of 45.8%, and area under the receiver operating characteristic curve of 0.687.

Conclusion

Preserved identification of neutral/pleasant odors may help to predict PD motor progression, and detection of ≥1.5 UPSIT motor progression risk odors could improve the predictive power. In PD patients with a similar level of motor disability during initial screening, preserved pleasant/neutral odor identification may imply relatively better cortical odor discriminative function, which may suggest the body-first (caudo-rostral) subtype with faster disease progression.

Evaluating cognitive impairment in the early stages of Parkinson's disease using the Cambridge brain sciences-cognitive platform

BACKGROUND

Non-motor symptoms (NMS) such as cognitive impairment are among common presentations in patients with Parkinson's disease (PD). In parallel with motor symptoms, these impediments can affect PD patients' quality of life. However, cognitive impairment has received less attention in early PD. On the other hand, the relationship between olfactory symptoms and cognitive impairment is unclear in early PD. Considering the importance of accurate and timely assessment of cognitive function in PD patients using readily available/validated tests, this study has employed the Cambridge Brain Sciences-Cognitive Platform (CBS-CP) as a computer-based tool to assess cognitive presentations in early PD patients.

METHODS

Thirty-four eligible males and females were assigned to PD and healthy controls (HCs). The cognitive performance was assessed using CBS-CP and Mini-Mental State Examination (MMSE), and olfactory function was measured through the standardized olfactory Quick Smell test (QST).

RESULTS

PD patients had poorer performance in all CBS-CP tasks, including short-term memory, attention, and reasoning domains than HCs. Meanwhile, the verbal domain task scores showed no significant difference between groups. PD MMSE results were in the normal range (mean=26.96), although there was a significant difference between the PD and HCs groups (P = 0.000). Our results revealed no correlation between cognitive impairment and olfactory function in PD patients.

CONCLUSION

Given the widely studied features of CBS-CP and its reliability across published evidence, CBS-CP appears to be a suitable measurement to evaluate cognitive impairment in early PD with normal MMSE scores. It seems cognitive and olfactory impairments are independent in early PD.

DATA AVAILABILITY STATEMENT

The datasets generated during the current study are available from the corresponding author upon reasonable request.

Sequential change in olfaction and (non) motor symptoms: the difference between anosmia and non-anosmia in Parkinson's disease

Introduction

Hyposmia is a common prodrome in patients with Parkinson's disease (PD). This study investigates whether olfactory changes in PD differ according to the degree of olfactory dysfunction and whether there are changes in motor and non-motor symptoms.

Methods

The 129 subjects with PD were divided into two groups: anosmia and non-anosmia. All cases were reassessed within 1-3 years after the initial assessment. The assessment included the MDS-Unified PD Rating Scale (MDS-UPDRS), the University of Pennsylvania Smell Identification Test (UPSIT), Beck's Depression Inventory-II (BDI-II), Montreal Cognitive Assessment (MoCA), and equivalence dose of daily levodopa (LEDD). The generalized estimating equation (GEE) model with an exchangeable correlation structure was used to analyze the change in baseline and follow-up tracking and the disparity in change between these two groups.

Results

The anosmia group was older and had a longer disease duration than the non-anosmia group. There was a significant decrease in UPSIT after follow-up in the non-anosmia group (β = -3.62, p < 0.001) and a significant difference in the change between the two groups (group-by-time effect, β = 4.03, p < 0.001). In the third part of the UPDRS motor scores, there was a tendency to increase the score in the non-anosmia group compared to the anosmia group (group-by-time effect, β = -4.2, p < 0.038). There was no significant difference in the group-by-time effect for UPDRS total score, LEDD, BDI-II, and MoCA scores.

Discussion

In conclusion, this study found that olfactory sensation may still regress in PD with a shorter disease course without anosmia, but it remains stable in the anosmia group. Such a decline in olfaction may not be related to cognitive status but may be associated with motor progression.

Olfactory Function and Diffusion Tensor Imaging as Markers of Mild Cognitive Impairment in Early Stages of Parkinson's Disease

Parkinson's disease (PD) is a neurodegenerative disorder that is typified by motor signs and symptoms but can also lead to significant cognitive impairment and dementia Parkinson's Disease Dementia (PDD). While dementia is considered a nonmotor feature of PD that typically occurs later, individuals with PD may experience mild cognitive impairment (PD-MCI) earlier in the disease course. Olfactory deficit (OD) is considered another nonmotor symptom of PD and often presents even before the motor signs and diagnosis of PD. We examined potential links among cognitive impairment, olfactory functioning, and white matter integrity of olfactory brain regions in persons with early-stage PD. Cognitive tests were used to establish groups with PD-MCI and with normal cognition (PD-NC). Olfactory functioning was examined using the University of Pennsylvania Smell Identification Test (UPSIT) while the white matter integrity of the anterior olfactory structures (AOS) was examined using magnetic resonance imaging (MRI) diffusion tensor imaging (DTI) analysis. Those with PD-MCI demonstrated poorer olfactory functioning and abnormalities based on all DTI parameters in the AOS, relative to PD-NC individuals. OD and microstructural changes in the AOS of individuals with PD may serve as additional biological markers of PD-MCI.

Evaluation of the complete Sniffin Sticks Test versus its subtests in differentiating Parkinson's disease patients from healthy controls

BACKGROUND

Hyposmia is one of the most common, as well as the first nonmotor condition in Parkinson disease (PD). The sniffin sticks test (SST) evaluates three different aspects of olfactory function: threshold (T), discrimination (D), and identification (I). The sum of the scores of these three subtests produce a global score of olfaction, the Threshold-Discrimination-Identification (TDI) score.

OBJECTIVE

The aim of this study was to investigate if the TDI score or one of its subtests is better to discriminate PD patients from controls.

METHODS

We recruited 27 PD patients and 17 healthy age-matched controls (HC) who were evaluated through a clinical interview, the Montreal Cognitive Assessment and Movement Disorders Society - Unified Parkinson Disease Rating Scale. The olfaction was assessed using the complete SST.

RESULTS

The performance of PD patients on the olfactory test was significantly worse when compared with the HC (T: 3.0 vs. 6.5, p < 0.001; D: 8.1 vs. 11.2, p < 0.001; I: 7.3 vs. 11.7, p < 0.001; TDI: 18.8 vs. 29.9, p < 0.001). The prevalence of olfaction impairment in our study (PD: 100%, and HC: 56%) was greater than that found in the literature. Cognition influenced the performance on TDI. The olfactory subtests were impaired proportionally between patients and controls. Furthermore, D and I were correlated, but only in PD patients. The TDI showed a tendency to better discriminate PD patients from HC, when compared with its subtests.

CONCLUSIONS

Although the complete olfactory evaluation is time consuming, it seems to be a superior tool to identify olfaction impairment in PD patients, when compared with the isolated subtests.

Olfactory dysfunction and striatal dopamine transporter binding in motor subtypes of Parkinson's disease

BACKGROUND

Olfactory dysfunction is one of the earliest non-motor symptoms (NMS) in Parkinson's disease (PD). There are contradictory results regarding the association of olfactory dysfunction and dopamine uptake in striatal nuclei among PD patients. It has been suggested that different motor subtypes of PD vary in the disease pathophysiology and progression. Thus, we hypothesized that there might be different associations between olfactory dysfunction and striatal dopaminergic neuronal loss among three motor subtypes of PD, namely, indeterminate, postural instability and gait difficulty (PIGD), and tremor-dominant (TD).

METHODS

We recruited 162 healthy controls (HCs) and 464 drug-naïve PD patients from PPMI who underwent common PD scaling tests. Striatal binding ratios (SBRs) of DaTSCAN images in caudate and putamen nuclei were calculated. To assess the olfactory function, the University of Pennsylvania Smell Identification Test (UPSIT) was carried out.

RESULTS

The UPSIT score was significantly correlated with MDS-UPDRS part I (p value: 0.002, correlation coefficient: - 0.160), MDS-UPDRS part III (p value: 0.000, correlation coefficient: - 0.248), and SBR score in right (p value: 0.000, correlation coefficient: 0.240) and left caudate (p value: 0.000, correlation coefficient: 0.221) and right (p value: 0.000, correlation coefficient: 0.323) and left putamen (p value: 0.000, correlation coefficient: 0.335) nucleus in TD subtype. There were no significant correlations in HC, PIGD, and indeterminate subjects.

CONCLUSION

The olfactory dysfunction was correlated with dopamine transporter activity in striatal nuclei only in the TD subtype. Therefore, the olfactory dysfunction in PIGD and indeterminate subtype may not be a predictive factor for the future decrease in dopamine uptake.

Dysosmia Is a Predictor of Motor Function and Quality of Life in Patients with Parkinson's Disease

(1) Background: The correlation between dysosmia with quality of life (QoL) in patients with PD was rarely reported. The study aimed to examine the effect of dysosmia on motor function and QoL in PD. (2) Methods: This cross-sectional study, performed between October 2016 and February 2021, recorded the traditional Chinese version of the University of Pennsylvania Smell Identification Test (UPSIT), the Montreal Cognitive Assessment (MoCA), the Movement Disorder Society-sponsored revision of the Unified Parkinson’s Disease Rating Scale (MDS UPDRS), and the 39-item Parkinson’s Disease Questionnaire (PDQ-39) in patients with PD. UPSIT = 19 was applied to separate the total anosmia and non-anosmia groups. (3) Results: 243 patients with PD were recruited. The total anosmia group had higher MDS UPDRS total, part II, and part III scores than the non-anosmia group. They also had worse scores on the dimensions of activities of daily living (ADL) and cognition of the PDQ-39 than the non-anosmia group. The UPSIT score correlated MDS UPDRS part III score (p < 0.0001), PDQ-39 ADL quartile (p = 0.0202), and Dopamine transporter scan (p = 0.0082) in the linear regression. (4) Conclusions: Dysosmia in PD predicted a phenotype with defective motor function, ADL, and cognition QoL. The findings supported the olfactory transmission of α-synuclein to the cortices, substantia nigra.

Parkinson's disease, temporomandibular disorder pain and bruxism and its clinical consequences: a protocol of a single-centre observational outpatient study

INTRODUCTION

A recent questionnaire-based study suggested that bruxism and painful temporomandibular disorders (TMD pain) may be more prevalent in patients with Parkinson's disease (PD) compared with controls. The presence of both bruxism and TMD pain may negatively influence patients' quality of life. The present study is designed to clinically and more objectively investigate the presence of bruxism and TMD pain in patients with PD. The secondary aim of the study is to identify factors associated with bruxism and TMD pain in patients with PD, such as disease severity and dopaminergic medication usage. Furthermore, the presence of tooth wear in patients with PD will be studied as this can be a major consequence of bruxism. Finally, deviations in saliva composition that may contribute to tooth wear will be studied.

METHODS AND ANALYSIS

This is a single-centre observational outpatient study at the Amsterdam University Medical Centres, location VUmc. All patients with a clinical diagnosis of PD will be eligible for inclusion. Participants will fill in a set of questionnaires. Subsequently, patients will be examined clinically for, among others, TMD pain, presence and severity of tooth wear, and deviations in saliva composition. Sleep-time registrations will take place for 5 nights with the GrindCare GC4 (ie, a portable, single-channel electromyographic recorder) to assess sleep bruxism and simultaneously by the use of the BruxApp for 5 days to assess awake bruxism. We will partly use data collected during standard clinical care to minimise patient burden.

ETHICS AND DISSEMINATION

The scientific and ethical aspects of this study protocol have been approved by the Medical Ethics Review Committee of the Amsterdam UMC, location VUmc; NL. 2019.143. Informed consent will be obtained from all participants. The results will be published in a peer-reviewed journal, if relevant presented at conferences, and published as part of a PhD thesis.

TRIAL REGISTRATION NUMBER

NL8307.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

The Role of Olfactory System in the Etiogenesis of Parkinson’s Diseases: An Overview

Parkinson’s disease (PD) mainly affects the dopaminergic neuronal networks of the substantia nigra, which leads to both motor and nonmotor symptoms of the disease. Based on the reports from the previous studies, 95% of the cases are presented along with olfactory dysfunction. The relevant publications from 2002 to 2021 were searched and shortlisted using PubMed and Google Scholar. In this review, we have discussed the correlation between olfactory dysfunction and PD. Olfactory damage presents earlier than the motor symptoms. Because there are no current methodologies for the early detection of PD, olfactory dysfunction can be used as a potential marker for the early detection of PD and hence paving the way for better therapeutic approaches.

Motor and non-motor circuit disturbances in early Parkinson disease: which happens first?

For the last two decades, pathogenic concepts in Parkinson disease (PD) have revolved around the toxicity and spread of α-synuclein. Thus, α-synuclein would follow caudo-rostral propagation from the periphery to the central nervous system, first producing non-motor manifestations (such as constipation, sleep disorders and hyposmia), and subsequently impinging upon the mesencephalon to account for the cardinal motor features before reaching the neocortex as the disease evolves towards dementia. This model is the prevailing theory of the principal neurobiological mechanism of disease. Here, we scrutinize the temporal evolution of motor and non-motor manifestations in PD and suggest that, even though the postulated bottom-up mechanisms are likely to be involved, early involvement of the nigrostriatal system is a key and prominent pathophysiological mechanism. Upcoming studies of detailed clinical manifestations with newer neuroimaging techniques will allow us to more closely define, in vivo, the role of α-synuclein aggregates with respect to neuronal loss during the onset and progression of PD.

The Association of Olfactory Dysfunction With Depression, Cognition, and Disease Severity in Parkinson's Disease

Background: Non-motor subtypes of Parkinson's disease (PD) include the limbic, cognitive, and brainstem phenotype, which may have different pathological pathways with olfaction. In this work, we aim to clarify the association between olfactory dysfunction, depression, cognition, and disease severity in PD.

Methods: A total of 105 PD subjects were included and divided into anosmia and non-anosmic groups, using the University of Pennsylvania Smell Identification Test (UPSIT). All patients were evaluated with the movement disorder society unified Parkinson's disease rating scale (MDS-UPDRS), the Beck depression inventory (BDI)-II, and the Montreal cognitive assessment (MoCA).

Results: The BDI-II and UPSIT scores had a trend of reverse correlation without statistical significance (β-coefficient −0.12, p = 0.232). However, the odds ratio (OR) in anosmia was 2.74 (95% CI 1.01–7.46) for depression and 2.58 (95% CI 1.06–6.29) for cognitive impairment. For the MDS-UPDRS total and Part 3 score, the anosmia had a β-coefficient of 12.26 (95% CI 5.69–18.82) and 8.07 (95% CI 3.46–12.67), respectively. Neither depression nor cognitive impairment is associated with motor symptoms.

Conclusion: More severe olfactory dysfunction in PD is associated with cognitive impairment and greater disease severity. Depression in PD may involve complex pathways, causing relatively weak association with olfactory dysfunction.

Frontal lobe dysfunction is associated with reduced DAT-SPECT accumulation in Lewy body disease

INTRODUCTION

Lewy body disease (LBD) causes olfactory or cognitive dysfunction even before motor symptoms emerge. Recent reports indicate that the dopamine transporter (DAT), which can be imaged using single-photon emission computed tomography (¹²³I-ioflupane SPECT), is related to olfactory and cognitive dysfunction in LBD patients. We suspected that decreased cerebral blood flow (CBF) in the frontal lobe might be involved in these relationships. If so, then the results of these examinations may be useful in assessing the pathological progression of Lewy bodies.

METHODS

We retrospectively analyzed the data of 139 de novo consecutive patients with LBD. We used the Odor Stick Identification Test for Japanese (OSIT-J) and the Frontal Assessment Battery (FAB) to evaluate olfactory and frontal lobe dysfunction, respectively. Among the 139 patients, ultimately 84 patients were analyzed and underwent ¹²³I-ioflupane SPECT within 3 months (before or after) of the OSIT-J and FAB. We categorized patients on the basis of whether frontal lobe CBF was reduced (n = 28) or normal (n = 56).

RESULTS

The average OSIT-J and FAB scores were 4.0 and 14.1, respectively, and the scores on the two tests were significantly correlated. Furthermore, OSIT-J scores were significantly correlated with the specific binding ratio (SBR) in both groups. The SBR was correlated with FAB scores in patients with reduced CBF in the frontal lobe, but not in those with normal CBF.

CONCLUSION

Frontal lobe dysfunction and striatum dysfunction are correlated in LBD patients only after CBF has declined. Also, there is a time lag in the appearance of olfactory dysfunction and frontal lobe dysfunction in LBD patients. As with pathological development, olfaction is impaired earliest, followed by striatal, and then frontal lobe dysfunction.

Dopamine Transporter Imaging, Current Status of a Potential Biomarker: A Comprehensive Review

A major goal of current clinical research in Parkinson's disease (PD) is the validation and standardization of biomarkers enabling early diagnosis, predicting outcomes, understanding PD pathophysiology, and demonstrating target engagement in clinical trials. Molecular imaging with specific dopamine-related tracers offers a practical indirect imaging biomarker of PD, serving as a powerful tool to assess the status of presynaptic nigrostriatal terminals. In this review we provide an update on the dopamine transporter (DAT) imaging in PD and translate recent findings to potentially valuable clinical practice applications. The role of DAT imaging as diagnostic, preclinical and predictive biomarker is discussed, especially in view of recent evidence questioning the incontrovertible correlation between striatal DAT binding and nigral cell or axon counts.

Olfative and taste perception in Parkinson's disease

PURPOSE

To analyze the olfactory and gustatory perception and discrimination and self-perception of smell and taste in people with Parkinson's disease, comparing them with healthy nodes.

METHODS

Observational, analytical, cross-sectional, and quantitative study. Olfactory and gustatory perception and discrimination were verified following Parkinson's disease, compared to a control group, matched by sex and age, using the Olfactory Perception and Taste Strips Tests, respectively, after nasal cleaning and oral brushing. Self-perception was assessed by the Visual Analogue Scale before and after specific tests of perception and discrimination.

RESULTS

We included individuals of both sexes, 35 with Parkinson's Disease and 20 assigned to the control group, matched for mean age. The olfactory self-perception of the group with Parkinson's disease improved after the olfactory test. There was no difference in taste self-perception in the Parkinson's disease group before and after the taste test. In the olfactory perception assessment test, the Parkinson's disease group discriminated fewer essences than the control group. Both groups have similar generation and taste discrimination.

CONCLUSION

The olfactory perception of people with Parkinson's disease was lower, compared to the group of healthy desires, and the self-perception of olfactory efficacy improved after the test, in both groups. As for taste, there was no difference in perception and discrimination between groups, the sour taste was the most identified and there was an improvement in self-perception of taste efficiency in the group without Parkinson's disease after the test.

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

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.

Role of Hydrazine-Related Chemicals in Cancer and Neurodegenerative Disease

Hydrazine-related chemicals (HRCs) with carcinogenic and neurotoxic potential are found in certain mushrooms and plants used for food and in products employed in various industries, including aerospace. Their propensity to induce DNA damage (mostly O⁶-, N⁷- and 8-oxo-guanine lesions) resulting in multiple downstream effects is linked with both cancer and neurological disease. For cycling cells, unrepaired DNA damage leads to mutation and uncontrolled mitosis. By contrast, postmitotic neurons attempt to re-enter the cell cycle but undergo apoptosis or nonapoptotic cell death. Biomarkers of exposure to HRCs can be used to explore whether these substances are risk factors for sporadic amyotrophic laterals sclerosis and other noninherited neurodegenerative diseases, which is the focus of this paper.

Comparison between four published definitions of hyposmia in Parkinson's disease

OBJECTIVES

Hyposmia is a common feature of Parkinson's disease (PD), yet there is no standard method to define it. A comparison of four published methods was performed to explore and highlight differences.

MATERIALS AND METHODS

Olfactory testing was performed in 2097 cases of early PD in two prospective studies. Olfaction was assessed using various cut-offs, usually corrected by age and/or gender. Control data were simulated based on the age and gender structure of the PD cases and published normal ranges. Association with age, gender, and disease duration was explored by method and study cohort. Prevalence of hyposmia was compared with the age and gender-matched simulated controls. Between method agreement was measured using Cohen's kappa and Gwet's AC1.

RESULTS

Hyposmia was present in between 69.1% and 97.9% of cases in Tracking Parkinson's cases, and between 62.2% and 90.8% of cases in the Parkinson's Progression Marker Initiative, depending on the method. Between-method agreement varied (kappa 0.09-0.80, AC1 0.55-0.86). The absolute difference between PD cases and simulated controls was similar for men and women across methods. Age and male gender were positively associated with hyposmia (p < .001, all methods). Odds of having hyposmia increased with advancing age (OR:1.06, 95% CI:1.03, 1.10, p < .001). Longer disease duration had a negative impact on overall olfactory performance.

CONCLUSIONS

Different definitions of hyposmia give different results using the same dataset. A standardized definition of hyposmia in PD is required, adjusting for age and gender, to account for the background decline in olfactory performance with ageing, especially in men.

Clinical and Dopamine Depletion Patterns in Hyposmia- and Dysautonomia-Dominant Parkinson's Disease

BACKGROUND

Olfactory or autonomic dysfunction is one of the earliest prodromal symptoms of Parkinson's disease (PD). It has not been investigated whether PD patients have different phenotypes depending on the presence of these prodromal symptoms.

OBJECTIVE

To investigate whether hyposmia-dominant and dysautonomia-dominant patients with early PD have different clinical manifestations and nigrostriatal degeneration.

METHODS

This cross-sectional study recruited 168 drug-naive PD patients and 34 control subjects. PD patients were classified as patients without hyposmia and dysautonomia (PD-H-D-, n = 51), hyposmia-dominant patients (PD-H+D-, n = 36), dysautonomia-dominant patients (PD-H-D+, n = 33), and patients with hyposmia and dysautonomia (PD-H+D+, n = 48). We then compared the baseline clinical characteristics, striatal specific to non-specific binding ratio (SNBR), neuropsychological performance, and neuropsychiatric symptoms among the groups.

RESULTS

The PD-H+D-group had a lower SNBR in the ventral striatum (p = 0.013), a greater asymmetric index of striatal SNBRs, and higher prevalence of apathy (p = 0.021) than the PD-H-D+ group. The PD-H-D+ group had older age at onset (p = 0.043) and a higher prevalence of REM sleep behavior disorder (p = 0.041) than the PD-H+D-group. The PD-H+D+ group had higher motor deficits, lower cognitive function, and lower SNBRs in all striatal subregions than the PD-H-D-group. Decreased SNBRs in the anterior caudate, posterior caudate, and ventral striatum were associated with the presence of apathy.

CONCLUSION

The present study suggests that hyposmia-dominant and dysautonomia-dominant PD have different clinical characteristics and patterns of striatal dopamine depletion.

Recent advances in the pathology of prodromal non-motor symptoms olfactory deficit and depression in Parkinson's disease: clues to early diagnosis and effective treatment

Parkinson’s disease (PD) is a progressive neurodegenerative disease characterized by movement dysfunction due to selective degeneration of dopaminergic neurons in the substantia nigra pars compacta. Non-motor symptoms of PD (e.g., sensory dysfunction, sleep disturbance, constipation, neuropsychiatric symptoms) precede motor symptoms, appear at all stages, and impact the quality of life, but they frequently go unrecognized and remain untreated. Even when identified, traditional dopamine replacement therapies have little effect. We discuss here the pathology of two PD-associated non-motor symptoms: olfactory dysfunction and depression. Olfactory dysfunction is one of the earliest non-motor symptoms in PD and predates the onset of motor symptoms. It is accompanied by early deposition of Lewy pathology and neurotransmitter alterations. Because of the correlation between olfactory dysfunction and an increased risk of progression to PD, olfactory testing can potentially be a specific diagnostic marker of PD in the prodromal stage. Depression is a prevalent PD-associated symptom and is often associated with reduced quality of life. Although the pathophysiology of depression in PD is unclear, studies suggest a causal relationship with abnormal neurotransmission and abnormal adult neurogenesis. Here, we summarize recent progress in the pathology of the non-motor symptoms of PD, aiming to provide better guidance for its effective management.

Hyposmia may predict development of freezing of gait in Parkinson's disease

To explore the effect of olfactory dysfunction on treatment of motor manifestations in Parkinson's disease (PD). The current longitudinal retrospective cohort study consecutively recruited 108 de novo PD patients. Of whom 29 were normosmia and 79 were hyposmia, respectively, which was determined by the Korean Version of Sniffin' Sticks Test II at the time of diagnosis. All the participants underwent serial clinical examinations including Unified Parkinson's Disease Rating Scale (UPDRS), Mini-Mental State Examination, and Montreal Cognitive Assessment. The normosmic group demonstrated a significantly greater reduction of the UPDRS III score (30.3 ± 5.9 to 21.9 ± 5.1) than that of the hyposmic group (34.5 ± 9.3 to 28.5 ± 8.1) from baseline to 1-year later (p, 0.003; Bonferroni correction for p < 0.0045). Of subdomains in UPDRS III, the axial domain revealed a remarkable decrease in the normosmic group. Further, the hyposmic group exhibited a higher development rate of freezing of gait (FOG) compared to the normosmic group (29/79 (36.7%) vs 2/29 (6.9%); p, 0.002) during 33.9 ± 7.7 months of the mean follow-up period. A Cox proportional hazards model demonstrated the hyposmia to be a significant risk factor for the future development of FOG (HR, 4.23; 95% CI 1.180-17.801; p, 0.05). Our data demonstrated the olfactory dysfunction to be a significant risk factor for the development of the FOG in PD. Hyposmic PD patients should be paid more careful attention to the occurrence of FOG in the clinical practice.

Relationship between 123I-FP-CIT-SPECT and motor severity in drug-naive patients with Parkinson's disease

INTRODUCTION

Although functional imaging is useful for the diagnosis and pathophysiological evaluation of Parkinson's disease (PD), little is known about the relationship between functional imaging findings and PD clinical features. The objective of this study was to determine the relationship between ¹²³I-FP-CIT-SPECT findings and motor symptoms, in particular gait disturbance.

METHODS

The study included 46 drug-naive patients with early-stage PD. The specific binding ratios (SBRs) in the striatum and its subregions, namely anterior/posterior putamen and caudate nucleus, were calculated in patients who underwent ¹²³I-FP-CIT-SPECT. Motor symptoms were evaluated using the modified Hoehn and Yahr (HY) stage and the Unified Parkinson's Disease Rating Scale (UPDRS) part III. Gait disturbance was evaluated by the mean gait cycle duration and the mean gait acceleration amplitude measured with a wearable sensor.

RESULTS

The mean SBRs of the striatum and anterior putamen were significantly associated with the modified HY stage and UPDRS part III score. The mean SBR of the caudate nucleus was significantly associated with the UPDRS part III score. The mean striatal SBR was also significantly associated with the mean gait cycle duration and mean gait acceleration amplitude.

CONCLUSION

The mean striatal SBR, as determined by ¹²³I-FP-CIT-SPECT, was significantly associated with motor severity and gait severity in drug-naive patients with PD.

Molecular and Genetic Factors Involved in Olfactory and Gustatory Deficits and Associations with Microbiota in Parkinson's Disease

Deficits in olfaction and taste are among the most frequent non-motor manifestations in Parkinson’s disease (PD) that start very early and frequently precede the PD motor symptoms. The limited data available suggest that the basis of the olfactory and gustatory dysfunction related to PD are likely multifactorial and may include the same determinants responsible for other non-motor symptoms of PD. This review describes the most relevant molecular and genetic factors involved in the PD-related smell and taste impairments, and their associations with the microbiota, which also may represent risk factors associated with the disease.

Is There a Shared Etiology of Olfactory Impairments in Normal Aging and Neurodegenerative Disease?

As we age, our olfactory function declines. In addition to occurring in normal aging, more rapid decrement of olfactory decline has been associated with several neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD). It has been argued that since olfactory deficits occur less frequently or are absent in diseases such as progressive supranuclear palsy, corticobasal degeneration, and multiple system atrophy, olfactory deficits can be used for differential diagnoses of AD and PD. The purpose of this review is to provide a survey of current knowledge about the molecular bases and differential patterns of olfactory deficits present in normal aging, AD, and PD. As substantial research has been conducted in this area, the majority of the content of this review focuses on articles published in the past decade. We hypothesize that olfactory deficits in normal aging, AD, and PD may have different underlying causes, and propose the use of model organisms with small, tractable nervous systems and/or easy to manipulate genomes to further investigate the cellular mechanisms responsible for these deficits.

α-Synuclein Spread from Olfactory Bulb Causes Hyposmia, Anxiety, and Memory Loss in BAC-SNCA Mice

BACKGROUND

Patients with Parkinson's disease (PD) show motor symptoms as well as various non-motor symptoms. Postmortem studies of PD have suggested that initial alpha-synuclein (α-Syn) pathology develops independently in the olfactory bulb and lower brainstem, spreading from there stereotypically. However, it remains unclear how these two pathological pathways contribute to the clinicopathological progression of PD.

OBJECTIVE

The objective of this study was to examine the clinicopathological contribution of α-Syn spread from the olfactory bulb.

METHODS

We conducted pathological and behavioral analyses of human α-Syn bacterial artificial chromosome transgenic mice injected with α-Syn preformed fibrils into the bilateral olfactory bulb up to 10 months postinjection.

RESULTS

α-Syn preformed fibril injections induced more widespread α-Syn pathology in the transgenic mice than that in wild-type mice. Severe α-Syn pathology in the transgenic mice injected with α-Syn preformed fibrils was initially observed along the olfactory pathway and later in the brain regions that are included in the limbic system and have connections with it. The α-Syn pathology was accompanied by regional atrophy, neuron loss, reactive astrogliosis, and microglial activation, which were remarkable in the hippocampus. Behavioral analyses revealed hyposmia, followed by anxiety-like behavior and memory impairment, but not motor dysfunction, depression-like behavior, or circadian rhythm disturbance.

CONCLUSION

Our data suggest that α-Syn spread from the olfactory bulb mainly affects the olfactory pathway and limbic system as well as its related regions, leading to the development of hyposmia, anxiety, and memory loss in PD. © 2021 International Parkinson and Movement Disorder Society.

Olfactory Dysfunction Predicts Disease Progression in Parkinson's Disease: A Longitudinal Study

Background and Objective

Olfactory dysfunction (hyposmia) is an important non-motor symptom of Parkinson's disease (PD). To investigate the potential prognostic value of hyposmia as a marker for disease progression, we prospectively assessed clinical manifestations and longitudinal changes of hyposmic PD patients and normosmic ones.

Methods

Olfactory function was evaluated with the Sniffin' Sticks in PD patients at baseline. One hundred five hyposmic PD patients and 59 normosmic PD patients were enrolled and followed up for 2 years. They were subsequently evaluated at baseline and during follow-up periods with neurological and neuropsychological assessments. Clinical manifestations and disease progressions were compared between hyposmic and normosmic patients. In addition, the relationship between disease progressions and olfactory function was analyzed.

Results

Our study suggested that hyposmic PD patients and normosmic ones were similar in gender, age, education levels, age of onset, disease duration, and clinical features at baseline. Hyposmic PD patients exhibited more severe Unified Parkinson's Disease Rating Scale Part II-III (UPDRS II-III) scores, higher levodopa equivalent dose (LED) needs, and poorer Mini-Mental State Examination (MMSE) score at follow-up visits compared to those in normosmic PD patients. Hyposmia also showed greater rates in the increase of LED needs, improvement of UPDRS III score, and deterioration of MMSE score. Both improvement of UPDRS III score and decline of MMSE score were associated with poorer odor identification.

Conclusion

Our prospective study demonstrated that hyposmic PD patients showed a relatively worse clinical course compared with normosmic patients. Olfactory dysfunction is a useful predictor of disease progression.

Is there a close association of depression with either constipation or dysosmia in Parkinson's disease?

A possible association between depression and either the severity of constipation or dysosmia in Parkinson’s disease (PD) patients was investigated in this cross-sectional study. One-hundred six patients who had the history of PD for less than 5 years were recruited. Depression was measured using the Beck Depression Inventory-II (BDI-II), and our patients were divided into depressive and non-depressive groups (DP: BDI-II ≥ 14; n = 22 and NDP: BDI-II < 14; n = 84). Olfactory dysfunction was assessed by the University of Pennsylvania Smell Identification Test (UPSIT). Constipation severity was defined by stool softener dosage and amount. Statistical analyses with one-tailed T- or chi-squared test, odds ratios (OR), and beta-coefficient were used to determine significant differences. Total scores based on the Unified Parkinson’s Disease Rating Scale (UPDRS) were significantly higher in the DP group. A significant relationship was observed between PD patients with depression and severe constipation; PD patients with depression were more likely to present with severe constipation (OR 5.81; 95% CI 1.24–27.29, p = 0.026, adjusted for age and gender); but the significance became marginal after adjusted for age, gender and UPDRS part 3 (OR 4.46, 95% CI 0.93–21.33; p = 0.061). However, no association between olfactory dysfunction and depression was detected. There were significant positive correlations between BDI-II scores and severe constipation (β ± SE 7.65 ± 2.02; p =  < 0.001, adjusted for age and gender; β ± SE 7.06 ± 2.04; p = 0.001, adjusted for age, gender, and UPDRS-3). Besides, we detected a marginally significant correlation that PD patients with higher BDI-II scores tended to present more severe motor symptoms. Olfactory dysfunction seemed to be less relevant to BDI-II scores. Based on our findings, we speculate that depression may be more closely related to brainstem nuclei than to the limbic pathway.

Association Between Olfactory Impairment and Disease Severity and Duration in Parkinson's Disease

Background

The association between olfactory dysfunction and disease duration and severity in Parkinson's disease (PD) remains controversial.

Objective

The objective of this study was to examine the relationship between olfactory dysfunction and disease severity and duration in patients with recently diagnosed parkinsonism and patients with PD with a previous diagnosis.

Methods

Olfactory function was evaluated in 79 patients with recently diagnosed parkinsonism, 71 patients with PD with a previous diagnosis-with patients in both groups free of cognitive impairment-and 128 age-matched controls. The Odor-Stick Identification Test for Japanese score was counted as the numbers of correct answers, responses of indistinguishable, and responses of odorless. Parkinsonism was evaluated using the Movement Disorder Society Criteria, the Unified Parkinson Disease Rating Scale (UPDRS) Part III, and ¹²³iodine-labeled N-(3-fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl) nortropane single photon emission computed tomography (DaTscan).

Results

In the patients with recently diagnosed parkinsonism having the UPDRS Part III score ≥5 (mean [standard deviation: SD] score: 6.3 [1.9]) and with a positive DaTscan, the mean (SD) numbers of correct answers, responses of indistinguishable and responses of odorless were 4.3 (2.2), 1.6 (2.0), and 1.2 (2.2), respectively. In patients with PD with a previous diagnosis (mean [SD] UPDRS Part III score: 10.9 [3.2]), these numbers were 2.5 (2.2), 2.2 (2.5), and 3.8 (4.6), respectively. The patients with PD with a previous diagnosis showed more significant deterioration than the patients with recently diagnosed parkinsonism in the numbers of correct answers and responses of odorless (P < 0.0001). Olfaction in the combined patient group was significantly impaired compared with age-matched controls in each category (P < 0.0001).

Conclusions

These findings imply a close association between olfactory dysfunction and disease severity and duration in PD.

Parkinson's disease and the non-motor symptoms: hyposmia, weight loss, osteosarcopenia

Non-motor symptoms (NMSs) are common in Parkinson's disease (PD) and can precede, sometimes for several years. NMSs include, other than gastrointestinal symptoms like constipation and dysphagia, also hyposmia, weight loss and osteosarcopenia. These three NMSs seem to be inter-related and affect patients' health and quality of life. Unfortunately, patients with these symptoms usually are not initially seen by a neurologist, and by the time they are consulted, nearly ~ 80% of the dopaminergic neurons in the substantia nigra have died. To date, no guidelines exist for screening, assessment and management of NMSs in general. A better understanding of these specific NMSs, likely in the context of others, will make it possible to approach and optimise the treatment of the motor symptoms thereby enhancing the welfare of PD patients. Identifying the NMSs could be very helpful, and among them, hyposmia, weight loss and osteosarcopenia may play an important role in solving the limitations in the diagnosis of PD. A strict collaboration between general practitioners, clinicians, geriatricians and neurologists can be one approach towards the diagnosis of pre-PD. Waiting until the motor symptoms develop and the patient is finally visited by the neurologist could be too late, considering the catastrophic prognosis of the disease.

Association between Olfactory Deficit and Motor and Cognitive Function in Parkinson's Disease

Objective

To investigate whether baseline olfactory dysfunction in Parkinson’s disease (PD) patients is associated with baseline and longitudinal motor and cognitive function.

Methods

We recruited 228 drug-naïve PD patients who were followed for a mean of 6 years. Patients underwent the Cross-Cultural Smell Identification Test (CCSIT), a neuropsychological test, and N-(3-[¹⁸F]fluoropropyl)-2β-carbomethoxy-3β-(4-iodophenyl) nortropane positron emission tomography within 6 months of the baseline evaluation. Olfactory dysfunction was categorized as normosmia (CCSIT score ≥ 9), hyposmia (CCSIT score 5–8), and anosmia (CCSIT score ≤ 4). During the follow-up period, we investigated changes in the levodopa-equivalent dose (LED) and the occurrence of wearing-off, levodopa-induced dyskinesia, and dementia.

Results

Among the PD patients, 80.7% were hyposmic at the time of diagnosis, and 26.1% were anosmic. Baseline olfactory dysfunction was not associated with either initial parkinsonian motor symptoms or with the longitudinal LED increment and motor complications. Meanwhile, the anosmic group had lower baseline scores on the Korea version of the Boston Naming Test and Stroop color reading test than the normosmic and hyposmic groups. The anosmic group exhibited a higher rate of conversion to dementia than the normosmic [adjusted hazard ratio (HR) 3.99, 95% confidence interval (CI) 1.08–14.72] and hyposmic (adjusted HR 2.48, 95% CI 1.15–5.32) PD groups, regardless of baseline motor deficits and cognitive status.

Conclusion

Baseline olfactory dysfunction was not associated with motor deficits and complications, but it was associated with cognitive dysfunction and prognosis, suggesting that severe olfactory impairment may reflect early cortical involvement, probably in the frontotemporal region, and rapid spreading of Lewy body pathology.

Drp1, a potential therapeutic target for Parkinson's disease, is involved in olfactory bulb pathological alteration in the Rotenone-induced rat model

Olfaction is often affected in parkinsonian patients and its disturbances precede the classical cognitive and locomotor dysfunction. The olfactory bulb might be the region of onset in Parkinson's disease (PD) pathogenesis, evidenced by the presence of disease-related protein aggregates and disturbed olfactory information processing. However, the underlying molecular mechanism that governs the olfactory bulb impairments remains unclear. This study was designed to investigate the relationship between olfactory bulb and inflammatory pathological alterations and the potential mechanisms. Here we found that rotenone led to typical parkinsonian symptoms and decreased tyrosine hydroxylase (TH)-positive neurons in the olfactory bulb. Additionally, increased NF-κB nuclear translocation and NLRP3 inflammasome components expressions caused by rotenone injection were observed accompanied by the activation of microglia and astrocytes in the olfactory bulb. Rotenone also triggered Drp1-mediated mitochondrial fission and this in turn caused mitochondrial damage. Furthermore, Mdivi-1(a selective Drp1 inhibitor) markedly ameliorated the morphologic disruptions of mitochondria and Drp1 translocation, inhibited the nuclear translocation of NF-κB, eventually blocked the downstream pathway of the NLRP3/caspase-1/IL-1β axis and expression of iNOS. Overall, these findings suggest that Drp1-dependent mitochondrial fission induces NF-κB nuclear translocation and NLRP3 inflammasome activation that may further contribute to olfactory bulb disturbances.

Non-motor symptoms and striatal dopamine transporter binding in early Parkinson's disease

BACKGROUND

Non-motor symptoms (NMS) are common in Parkinson's disease (PD), but their relationships to nigrostriatal degeneration remain largely unexplored.

METHODS

We evaluated 18 NMS scores covering 5 major domains in relation to concurrent and future dopamine transporter (DAT) imaging in 344 PD patients from the Parkinson's Progression and Markers Initiative (PPMI). We standardized NMS assessments into z-scores for side-by-side comparisons. Patients underwent sequential DaTSCAN imaging at enrollment and at months 12, 24, and 48. Specific binding ratios (SBR) were calculated using the occipital lobe reference region. We evaluated the association of striatal DAT binding at the four time points with each baseline NMS using mixed-effects regression models.

RESULTS

Multiple baseline NMS were significantly associated with DAT binding at baseline and at follow-up scans. REM sleep behavior disorder (RBD) symptoms showed the strongest association - mean striatal SBR declined with increasing RBD symptom z-score (average of time-point-specific slopes per unit change in z-score: β_AVG = -0.083, SE = 0.017; p < 0.0001). In addition, striatal DAT binding was linearly associated with increasing baseline z-scores: positively for the memory (β_AVG=0.055, SE = 0.022; p = 0.01) and visuospatial (β_AVG=0.044, SE = 0.020; p = 0.03) cognitive domains, and negatively for total anxiety (β_AVG= -0.059, SE = 0.018; p = 0.001). Striatal DAT binding showed curvilinear associations with odor identification, verbal discrimination recognition, and autonomic dysfunction z-scores (p = 0.001, p = 0.0009, and p = 0.0002, respectively). Other NMS were not associated with DAT binding.

CONCLUSIONS

Multiple NMS, RBD symptoms in particular, are associated with nigrostriatal dopaminergic changes in early PD.

Olfactory dysfunction correlates with putaminal dopamine turnover in early de novo Parkinson's disease

Although olfactory dysfunction is one of the most well-established prodromal symptoms in Parkinson's disease (PD), its correlation with clinical disease progression or dopaminergic dysfunction still remains unclear. We here evaluated the association of striatal dopamine metabolism and olfactory function in a homogenous cohort of 30 patients with early untreated de novo PD. Striatal dopamine metabolism was assessed by the extended ¹⁸Fluorodopa PET scanning protocol to measure ¹⁸Fluorodopa uptake (K_occ) and the effective dopamine distribution volume ratio (EDVR) as the inverse of dopamine turnover. Olfactory function was estimated by the "Sniffin' Sticks" test including odor threshold (T), discrimination (D) and identification (I) assessment. We detected moderate correlations of the EDVR in the posterior putamen with the TDI composite score (r = 0.412; p = 0.024; Pearson's correlation test) and the odor identification score (r = 0.444; p = 0.014). These correlations were confirmed by multivariate regression analyses using age, sex, symptom duration and disease severity as measured by UPDRSIII motor score as candidate covariates. No other associations were observed between olfaction measures and K_occ and EDVR in all striatal regions. Together, olfactory dysfunction in early PD is not correlated with striatal ¹⁸Fluorodopa uptake as a measure for dopaminergic degeneration, but with putaminal dopamine turnover as a marker for dopaminergic presynaptic compensatory processes in early PD. These results should be treated as hypothesis generating and require confirmation by larger multicenter studies.

Hyposmia as a marker of (non-)motor disease severity in Parkinson's disease

The aim of this study was to evaluate the relationship of hyposmia in Parkinson’s disease (PD) with other motor and non-motor symptoms and with the degree of nigrostriatal dopaminergic cell loss. A total of 295 patients with a diagnosis of PD were included. Olfactory function was measured using the University of Pennsylvania Smell Identification Test (UPSIT). Motor symptoms were rated using the Unified Parkinson’s Disease Rating Scale motor subscale (UPDRS III). To evaluate other non-motor symptoms, we used the Mini-Mental State Examination (MMSE) as a measure of global cognitive function and validated questionnaires to assess sleep disturbances, psychiatric symptoms, and autonomic dysfunction. A linear regression model was used to calculate correlation coefficients between UPSIT score and motor and non-motor variables [for psychiatric symptoms a Poisson regression was performed]. In a subgroup of patients (n = 155) with a dopamine transporter (DaT) SPECT scan, a similar statistical analysis was performed, now including striatal DaT binding. In the regression models with correction for age, sex, disease duration, and multiple testing, all motor and non-motor symptoms were associated with UPSIT scores. In the subgroup of patients with a DaT-SPECT scan, there was a strong association between olfactory test scores and DaT binding in both putamen and caudate nucleus. Hyposmia in PD is associated with various motor and non-motor symptoms, like cognition, depression, anxiety, autonomic dysfunction and sleep disturbances, and with the degree of nigrostriatal dopaminergic cell loss. This finding adds further confirmation that hyposmia holds significant promise as a marker of disease progression.

Diagnostic Accuracy, Item Analysis and Age Effects of the UPSIT Spanish Version in Parkinson's Disease

OBJECTIVE

The University of Pennsylvania Smell Identification Test (UPSIT) is the most commonly used test to detect olfactory impairment in Parkinson's disease (PD), but the cut-off score for clinical purposes is often difficult to establish because of age and sex effects. The current work aims to study the sensitivity and specificity of the UPSIT Spanish version and its accuracy in discriminating PD patients at different age groups from healthy controls (HC), and to perform an item analysis.

METHOD

Ninety-seven non-demented PD patients and 65 HC were assessed with the UPSIT Spanish version. Sensitivity, specificity, and diagnostic accuracy for PD were calculated. Multiple regression analysis was used to define predictors of UPSIT scores.

RESULTS

Using the normative cut-off score for anosmia (≤18), the UPSIT showed a sensitivity of 54.6% with a specificity of 100.0% for PD. We found that, using the UPSIT cut-off score of ≤25, sensitivity was 81.4% and specificity 84.6% (area under the receiver operating characteristic curve = 0.908). Diagnosis and age were good predictors of UPSIT scores (B = -10.948; p < .001; B = -0.203; p < .001). When optimal cut-off scores were considered according to age ranges (≤60, 61-70, and ≥71), sensitivity and specificity values were >80.0% for all age groups.

CONCLUSIONS

In the Spanish UPSIT version, sensitivity and specificity are improved when specific cut-off scores for different age groups are computed.

Clinical practice guidelines for the management of olfactory dysfunction - Secondary publication

OBJECTIVE

To provide an evidence-based recommendation for the management of olfactory dysfunction in accordance with the consensus reached by the Subcommittee of the Japanese Clinical Practice Guideline for olfactory dysfunction in the Japanese Rhinologic Society.

METHODS

Seven clinical questions (CQs) regarding the management of olfactory dysfunction were formulated by the subcommittee of the Japanese Clinical Practice Guideline for olfactory dysfunction. We searched the literature published between April 1990 and September 2014 using PubMed, the Cochrane Library, and Ichushi Web databases. The main search terms were "smell disorder," "olfactory dysfunction," "olfactory loss," "olfactory disturbance," "olfactory impairments," "olfaction disorder," "smell disorder," "anosmia," "cacosmia," and "dysosmia." Based on the results of the literature review and the expert opinion of the Subcommittee, 4 levels of recommendation, from A-strongly recommended to D-not recommended, were adopted for the management of olfactory dysfunction.

RESULTS

Both oral and locally administered corticosteroids have been strongly recommended for patients with olfactory dysfunction due to chronic rhinosinusitis. Nasal steroid spray and antihistamine drugs have been moderately recommended for patients with allergic rhinitis. Although no drugs have been deemed to be truly effective for post-viral olfactory dysfunction by randomized-controlled trials (RCTs) or placebo-controlled trials, olfactory training using odorants has been reported to be effective for improving olfactory function. There is considerable evidence that olfactory testing is useful for differential diagnosis, prediction of disease progression, and early detection of cognitive decline in neurodegenerative diseases.

CONCLUSION

The Clinical Practice Guideline has developed recommendations for the management of various aspects of olfactory dysfunction.

Chemosensory dysfunction in neurodegenerative diseases

A number of neurodegenerative diseases are accompanied by disordered smell function. The degree of dysfunction can vary among different diseases, such that olfactory testing can aid in differentiating, for example, Alzheimer's disease (AD) from major affective disorder and Parkinson's disease (PD) from progressive supranuclear palsy. Unfortunately, altered smell function often goes unrecognized by patients and physicians alike until formal testing is undertaken. Such testing uniquely probes brain regions not commonly examined in physical examinations and can identify, in some cases, patients who are already in the "preclinical" stage of disease. Awareness of this fact is one reason why the Quality Standards Committee of the American Academy of Neurology has designated smell dysfunction as one of the key diagnostic criteria for PD. The same recommendation has been made by the Movement Disorder Society for both the diagnosis of PD and identification of prodromal PD. Similar suggestions are proposed to include olfactory dysfunction as an additional research criterion for the diagnosis of AD. Although taste impairment, i.e., altered sweet, sour, bitter, salty, and umami perception, has also been demonstrated in some disorders, taste has received much less scientific attention than smell. In this review, we assess what is known about the smell and taste disorders of a wide range of neurodegenerative diseases and describe studies seeking to understand their pathologic underpinnings.

Structural Changes Observed in the Piriform Cortex in a Rat Model of Pre-motor Parkinson's Disease

Early diagnosis of Parkinson’s disease (PD) offers perhaps, the most promising route to a successful clinical intervention, and the use of an animal model exhibiting symptoms comparable to those observed in PD patients in the early stage of the disease, may facilitate screening of novel therapies for delaying the onset of more debilitating motor and behavioral abnormalities. In this study, a rat model of pre-motor PD was used to study the etiology of hyposmia, a non-motor symptom linked to the early stage of the disease when the motor symptoms have yet to be experienced. The study focussed on determining the effect of a partial reduction of both dopamine and noradrenaline levels on the olfactory cortex. Neuroinflammation and striking structural changes were observed in the model. These changes were prevented by treatment with a neuroprotective drug, a glucagon-like peptide-1 (GLP1) receptor agonist, exendin-4 (EX-4).

Hyposmia in a simple smell test is associated with accelerated cognitive decline in early Parkinson's disease

OBJECTIVES

Olfactory dysfunction has been related to cognitive deficits in Parkinson's disease (PD), but evidence is conflicting and little is known about the relationship between these symptoms in early PD. Our objective was to study the association between smell deficits measured with a simple odor identification test at diagnosis of PD and the subsequent risk of cognitive decline.

MATERIALS & METHODS

One hundred and ninety two PD patients from a population-based study were examined at time of diagnosis, before initiation of dopaminergic treatment, with follow-up of 177 patients after 3 years, 162 patients after 5 years and 146 patients after 7 years. Cognitive function was assessed repeatedly with tests of global cognition, verbal memory, visuospatial abilities, processing speed, and executive function. Olfactory function was tested with a simple odor identification test at baseline. Associations between outcome measures and hyposmia were assessed by linear mixed effects models.

RESULTS

After 7 years, there were significant differences in global cognition (B: 1.96 (95% CI: 0.68, 3.24), P = 0.0031), verbal memory including immediate recall (B: 5.36 (95% CI: 2.04, 8.67), P = 0.0018) and delayed recall (B: 1.55 (95% CI: 0.51, 2.59), P = 0.0041) and word reading speed (B: 6.90 (95% CI: 2.17, 11.63), P = 0.0048) between hyposmic and normosmic PD patients.

CONCLUSIONS

The decline of cognitive function in early PD is more rapid in patients with hyposmia at diagnosis, compared to normosmic ones. A simple smell test may contribute to identify patients at risk of accelerated decline in global cognition, verbal memory, and processing speed within the first 7 years from diagnosis.

Dopaminergic Lesion in the Olfactory Bulb Restores Olfaction and Induces Depressive-Like Behaviors in a 6-OHDA Model of Parkinson's Disease

Olfactory impairments and depressive behavior are commonly reported by individuals with Parkinson's disease (PD) being observed before motor symptoms. The mechanisms underlying these clinical manifestations are not fully elucidated. However, the imbalance in dopaminergic neurotransmission seems to play an important role in this context. In patients and animal models of PD, an increase in the dopaminergic interneurons of the glomerular layer in olfactory bulb (OB-gl) is observed, which may contribute to the olfactory impairment. In addition, neuronal imbalance in OB is related to depressive symptoms, as demonstrated by chemical olfactory bulbectomy. In view of that, we hypothesized that a reduction in the number or density of dopaminergic neurons present in OB could promote an olfactory improvement and, in contrast, would accentuate the depressive-like behaviors in the 6-hydroxydopamine (6-OHDA) model of PD. Therefore, we performed single or double injections of 6-OHDA within the substantia nigra pars compacta (SNpc) and/or in the OB-gl. We observed that, after 7 days, the group with nigral lesion exhibited olfactory impairment, as well as the group with the lesion in the OB-gl. However, the combination of the lesions prevented the occurrence of hyposmia. In relation to depressive-like behaviors, we observed that the SNpc injury promoted depressive-like behavior, being accentuated after a double injury. Our results demonstrated the importance of the dopaminergic neurons of the OB-gl in different non-motor features of PD, since the selective reduction of these periglomerular neurons was able to induce olfactory impairment and depressive-like behaviors.