Optimizing odor identification testing as quick and accurate diagnostic tool for Parkinson's disease

Modulation of time in Parkinson's disease: a review and perspective on cognitive rehabilitation

Time cognition is an essential function of human life, and the impairment affects a variety of behavioral patterns. Neuropsychological approaches have been widely demonstrated that Parkinson's disease (PD) impairs time cognitive processing. Many researchers believe that time cognitive deficits are due to the basal ganglia, including the striatum or subthalamic nucleus, which is the pathomechanism of PD, and are considered to produce only transient recovery due to medication effects. In this perspective, we focus on a compensatory property of brain function based on the improved time cognition independent of basal ganglia recovery and an overlapping structure on the neural network based on an improved inhibitory system by time cognitive training, in patients with PD. This perspective may lead to restoring multiple functions through single function training.

Potential convergence of olfactory dysfunction in Parkinson's disease and COVID-19: The role of neuroinflammation

Parkinson's disease (PD) is a prevalent neurodegenerative disorder that affects 7-10 million individuals worldwide. A common early symptom of PD is olfactory dysfunction (OD), and more than 90% of PD patients suffer from OD. Recent studies have highlighted a high incidence of OD in patients with SARS-CoV-2 infection. This review investigates the potential convergence of OD in PD and COVID-19, particularly focusing on the mechanisms by which neuroinflammation contributes to OD and neurological events. Starting from our fundamental understanding of the olfactory bulb, we summarize the clinical features of OD and pathological features of the olfactory bulb from clinical cases and autopsy reports in PD patients. We then examine SARS-CoV-2-induced olfactory bulb neuropathology and OD and emphasize the SARS-CoV-2-induced neuroinflammatory cascades potentially leading to PD manifestations. By activating microglia and astrocytes, as well as facilitating the aggregation of α-synuclein, SARS-CoV-2 could contribute to the onset or exacerbation of PD. We also discuss the possible contributions of NF-κB, the NLRP3 inflammasome, and the JAK/STAT, p38 MAPK, TLR4, IL-6/JAK2/STAT3 and cGAS-STING signaling pathways. Although olfactory dysfunction in patients with COVID-19 may be reversible, it is challenging to restore OD in patients with PD. With the emergence of new SARS-CoV-2 variants and the recurrence of infections, we call for continued attention to the intersection between PD and SARS-CoV-2 infection, especially from the perspective of OD.

Relationships Between Rapid Eye Movement Sleep Behavior Disorder and Parkinson's Disease: Indication from Gut Microbiota Alterations

Rapid eye movement sleep behavior disorder (RBD) has a close relationship with Parkinson's disease (PD) and was even regarded as the most reliable hallmark of prodromal PD. RBD might have similar changes in gut dysbiosis to PD, but the relationship between RBD and PD in gut microbial alterations is rarely studied. In this study, we aim to investigate whether there were consistent changes between RBD and PD in gut microbiota, and found some specific biomarkers in RBD that might indicate phenoconversion to PD. Alpha-diversity showed no remarkable difference and beta-diversity showed significant differences based on the unweighted (R = 0.035, P = 0.037) and weighted (R = 0.0045, P = 0.008) UniFrac analysis among idiopathic RBD (iRBD), PD with RBD, PD without RBD and normal controls (NC). Enterotype distribution indicated iRBD, PD with RBD and PD without RBD were Ruminococcus-dominant while NC were Bacteroides-dominant. 7 genera (4 increased: Aerococcus, Eubacterium, Gordonibacter and Stenotrophomonas, 3 decreased: Butyricicoccus, Faecalibacterium and Haemophilus) were consistently changed in iRBD and PD with RBD. Among them, 4 genera (Aerococcus, Eubacterium, Butyricicoccus, Faecalibacterium) remained distinctive in the comparison between PD with RBD and PD without RBD. Through clinical correlation analysis, Butyricicoccus and Faecalibacterium were found negatively correlated with the severity of RBD (RBD-HK). Functional analysis showed iRBD had similarly increased staurosporine biosynthesis to PD with RBD. Our study indicates that RBD had similar gut microbial changes to PD. Decreased Butyricicoccus and Faecalibacterium might be potential hallmarks of phenoconversion of RBD to PD.

Impact of deep brain stimulation (DBS) on olfaction in Parkinson's disease: Clinical features and functional hypotheses

Deep brain stimulation (DBS) is a surgical therapy typically applied in Parkinson's disease (PD). The efficacity of DBS on the control of motor symptoms in PD is well grounded while the efficacity on non-motor symptoms is more controversial, especially on olfactory disorders (ODs). The present review shows that DBS does not improve hyposmia but can affect positively identification/discrimination scores in PD. The functional hypotheses suggest complex mechanisms in terms of cerebral connectivity and neurogenesis process which could act indirectly on the olfactory bulb and olfactory pathways related to specific cognitive olfactory tasks. The functional hypotheses also suggest complex mechanisms of cholinergic neurotransmitter interactions involved in these pathways. Finally, the impact of DBS on general cognitive functions in PD could also be beneficial to identification/discrimination tasks in PD.

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.

α-Synuclein Pathology and Reduced Neurogenesis in the Olfactory System Affect Olfaction in a Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is characterized by multiple symptoms including olfactory dysfunction, whose underlying mechanisms remain unclear. Here, we explored pathologic changes in the olfactory pathway of transgenic (Tg) mice of both sexes expressing the human A30P mutant α-synuclein (α-syn; α-syn-Tg mice) at 6-7 and 12-14 months of age, representing early and late-stages of motor progression, respectively. α-Syn-Tg mice at late stages exhibited olfactory behavioral deficits, which correlated with severe α-syn pathology in projection neurons (PNs) of the olfactory pathway. In parallel, olfactory bulb (OB) neurogenesis in α-syn-Tg mice was reduced in the OB granule cells at six to seven months and OB periglomerular cells at 12-14 months, respectively, both of which could contribute to olfactory dysfunction. Proteomic analyses showed a disruption in endocytic and exocytic pathways in the OB during the early stages which appeared exacerbated at the synaptic terminals when the mice developed olfactory deficits at 12-14 months. Our data suggest that (1) the α-syn-Tg mice recapitulate the olfactory functional deficits seen in PD; (2) olfactory structures exhibit spatiotemporal disparities for vulnerability to α-syn pathology; (3) α-syn pathology is restricted to projection neurons in the olfactory pathway; (4) neurogenesis in adult α-syn-Tg mice is reduced in the OB; and (5) synaptic endocytosis and exocytosis defects in the OB may further explain olfactory deficits.SIGNIFICANCE STATEMENT Olfactory dysfunction is a characteristic symptom of Parkinson's disease (PD). Using the human A30P mutant α-synuclein (α-syn)-expressing mouse model, we demonstrated the appearance of olfactory deficits at late stages of the disease, which was accompanied by the accumulation of α-syn pathology in projection neurons (PNs) of the olfactory system. This dysfunction included a reduction in olfactory bulb (OB) neurogenesis as well as changes in synaptic vesicular transport affecting synaptic function, both of which are likely contributing to olfactory behavioral deficits.

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 impairment in mild cognitive impairment with Lewy bodies and Alzheimer's disease

OBJECTIVES

Impaired olfaction may be a biomarker for early Lewy body disease, but its value in mild cognitive impairment with Lewy bodies (MCI-LB) is unknown. We compared olfaction in MCI-LB with MCI due to Alzheimer's disease (MCI-AD) and healthy older adults. We hypothesized that olfactory function would be worse in probable MCI-LB than in both MCI-AD and healthy comparison subjects (HC).

DESIGN

Cross-sectional study assessing olfaction using Sniffin' Sticks 16 (SS-16) in MCI-LB, MCI-AD, and HC with longitudinal follow-up. Differences were adjusted for age, and receiver operating characteristic (ROC) curves were used for discriminating MCI-LB from MCI-AD and HC.

SETTING

Participants were recruited from Memory Services in the North East of England.

PARTICIPANTS

Thirty-eight probable MCI-LB, 33 MCI-AD, 19 possible MCI-LB, and 32HC.

MEASUREMENTS

Olfaction was assessed using SS-16 and a questionnaire.

RESULTS

Participants with probable MCI-LB had worse olfaction than both MCI-AD (age-adjusted mean difference (B) = 2.05, 95% CI: 0.62-3.49, p = 0.005) and HC (B = 3.96, 95% CI: 2.51-5.40, p < 0.001). The previously identified cutoff score for the SS-16 of ≤ 10 had 84% sensitivity for probable MCI-LB (95% CI: 69-94%), but 30% specificity versus MCI-AD. ROC analysis found a lower cutoff of ≤ 7 was better (63% sensitivity for MCI-LB, with 73% specificity vs MCI-AD and 97% vs HC). Asking about olfactory impairments was not useful in identifying them.

CONCLUSIONS

MCI-LB had worse olfaction than MCI-AD and normal aging. A lower cutoff score of ≤ 7 is required when using SS-16 in such patients. Olfactory testing may have value in identifying early LB disease in memory services.

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.

Smell tests can discriminate Parkinson's disease patients from healthy individuals: A meta-analysis

BACKGROUND

Olfactory impairment is common in Parkinson's disease (PD). The authors aimed to identify the clinical tests used to assess olfactory function and examine their ability to distinguish PD with different disease duration from healthy individuals with physiological aging.

METHODS

Cross-sectional studies published until May 2020 that assessed the olfaction of individuals with PD using search terms related to PD, olfactory function, and assessment were searched on PubMed, PsycInfo, Cinahl, and Web of Science databases.

RESULTS

Twelve smell tests were identified from the reviewed studies (n = 125) that assessed 8776 individuals with PD. Data of 6593 individuals with PD and 8731 healthy individuals were included in the meta-analyses. Individuals with PD presented worse performance than healthy individuals, regardless of the smell test used. The University of Pennsylvania Smell Identification Test (UPSIT) was used by most studies (n = 2310 individuals with PD) and presented smaller heterogeneity. When the studies were subclassified according to the years of PD duration, there were no significant differences.

CONCLUSION

All smell tests were able to discriminate the olfactory function of PD from that of healthy individuals, although the UPSIT was widely used. The abnormal olfaction was not related to the disease duration. Systematic review protocol registration (PROSPERO/2020-CRD42020160878).

Rapid Eye Movement Sleep Behavior Disorder: Abnormal Cardiac Image and Progressive Abnormal Metabolic Brain Pattern

BACKGROUND

Isolated rapid eye movement sleep behavior disorder (iRBD) is prodromal for α-synucleinopathies.

OBJECTIVE

The aim of this study was to determine whether pathological cardiac [¹²³ I]meta-iodobenzylguanidine scintigraphy ([¹²³ I]MIBG) is associated with progression of [¹⁸ F]fluorodeoxyglucose-positron emission tomography-based Parkinson's disease (PD)-related brain pattern (PDRP) expression in iRBD.

METHODS

Seventeen subjects with iRBD underwent [¹⁸ F]fluorodeoxyglucose-positron emission tomography brain imaging twice ~3.6 years apart. In addition, [¹²³ I]MIBG and [¹²³ I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane single-photon emission computed tomography ([¹²³ I]FP-CIT-SPECT) at baseline were performed. Olfactory, cognitive, and motor functions were tested annually.

RESULTS

Twelve of 17 subjects had pathological [¹²³ I]MIBG. At baseline, 6 of 12 of these expressed the PDRP (suprathreshold PDRP z score). At follow-up, 12 of 17 subjects had suprathreshold PDRP z scores, associated with pathological [¹²³ I]MIBG in 92% and with pathological [¹²³ I]FP-CIT-SPECT in 75%. Subjects with pathological [¹²³ I]MIBG had higher PDRP z score change per year (P = 0.027). Three subjects phenoconverted to PD; all had pathological [¹²³ I]MIBG and [¹²³ I]FP-CIT-SPECT, suprathreshold baseline PDRP z scores, and hyposmia.

CONCLUSIONS

Pathological [¹²³ I]MIBG was associated with progressive and suprathreshold PDRP z scores at follow-up. Abnormal [¹²³ I]MIBG likely identifies iRBD as prodromal PD earlier than pathological [¹²³ I]FP-CIT-SPECT. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Systematic review and meta-analysis of Sniffin Sticks Test performance in Parkinson's disease patients in different countries

INTRODUCTION

Olfaction impairment occurs in about 90% of patients with Parkinson's disease. The Sniffin Sticks Test is a widely used instrument to measure olfactory performance and is divided into three subtests that assess olfactory threshold, discrimination and identification. However, cultural and socioeconomic differences can influence test performance.

OBJECTIVES

We performed a systematic review and meta-analysis of the existent data about Sniffin Sticks Test performance of Parkinson's disease patients and healthy controls in different countries and investigated if there are other cofactors which could influence the olfactory test results. A subgroup analysis by country was performed as well as a meta-regression using age, gender and air pollution as covariates.

RESULTS

Four hundred and thirty studies were found and 66 articles were included in the meta-analysis. Parkinson's disease patients showed significantly lower scores on the Sniffin Sticks Test and all its subtests than healthy controls. Overall, the heterogeneity among studies was moderate to high as well as the intra-country heterogeneity. The subgroup analysis, stratifying by country, maintained a high residual heterogeneity.

CONCLUSION

The meta-regression showed a significant correlation with age and air pollution in a few subtests. A high heterogeneity was found among studies which was not significantly decreased after subgroup analysis by country. This fact signalizes that maybe cultural influence has a small impact on the Sniffin Sticks Test results. Age and air pollution have influence in a few olfactory subtests.

Olfaction in Neuropathologically Defined Progressive Supranuclear Palsy

BACKGROUND

Hyposmia is characteristic of idiopathic Parkinson's disease (PD) and dementia with Lewy bodies (DLBs), whereas progressive supranuclear palsy (PSP) typically has normal sense of smell. However, there is a lack of pathologically confirmed data.

OBJECTIVE

The objective is to study hyposmia in pathologically confirmed PSP patients and compare to PD patients and nondegenerative controls.

METHODS

We studied autopsied subjects in the Arizona Study of Aging and Neurodegenerative Disorders who had antemortem olfactory testing and a neuropathological diagnosis of either PD, PSP, or control.

RESULTS

This study included 281 cases. Those with neuropathologically confirmed PSP (N = 24) and controls (N = 174) had significantly better sense of smell than those with PD (N = 76). Although most PSP patients had normal olfaction, there were some with hyposmia, resulting in an overall reduced sense of smell in PSP compared to controls. The sensitivity of having PSP pathologically in those presenting with parkinsonism and normosmia was 93.4% with a specificity of 64.7%. Cases with both PSP and PD pathologically had reduced sense of smell similar to PD alone (N = 7). Hyposmic PSP patients had significantly higher Lewy body burden not meeting criteria for additional PD/DLB diagnosis.

CONCLUSIONS

Pathologically confirmed PD had reduced olfaction compared with PSP or controls. In the setting of parkinsonism in this sample, the presence of normosmia had high sensitivity for PSP. Hyposmia in PSP suggests the presence of additional Lewy body pathology. © 2021 International Parkinson and Movement Disorder Society.

Smell tests to distinguish Parkinson's disease from other neurological disorders: a systematic review and meta-analysis

Introduction: Olfactory impairment has been considered for differential diagnosis in Parkinson's disease (PD) patients. The authors aimed to identify the tests used to assess the olfactory function in PD patients and examine these tests' ability to distinguish them from other neurological disorders.Areas covered: Cross-sectional studies published until May 2020 comparing the olfactory function of PD patients to other neurological disorders were searched on PubMed, PsycInfo, Cinahl, and Web of Science databases using search terms related to PD, olfactory function, and assessment. Five thousand three hundred and four studies were screened, and 35 were included in the systematic review. Six smell tests that evaluated a total of 1,544 PD patients were identified. Data of 1,144 patients included in the meta-analyses revealed worse smell performance than individuals with other neurological disorders, such as progressive supranuclear palsy and essential tremor, but not with idiopathic rapid eye movement sleep behavior disorder.Expert opinion: The University of Pennsylvania Smell Identification Test was the most used test to assess the olfactory function of PD. Smell loss was worse in PD than in some neurological disorders. The smell tests' ability in differentiating PD from other neurological disorders still deserves more attention in future studies. Protocol register (PROSPERO/2018-CRD42018107009).

Olfactory impairment as an early marker of Parkinson's disease in REM sleep behaviour disorder: a systematic review and meta-analysis

Olfactory impairment and rapid eye movement sleep behaviour disorder (RBD) are prodromal symptoms of Parkinson's disease (PD) that may be associated with each other. This review aims to investigate the significance of olfaction in the diagnosis and prognosis of patients with RBD and to assess moderating factors affecting olfactory performance. We searched articles on olfaction in RBD and PD in five electronic databases. We identified 32 studies for the systematic review and used 28 of those, including 2858 participants for meta-analysis. Results revealed significant deficits in odour identification (g=-1.80; 95% CI: -2.17 to -1.43), threshold (g=-1.29; 95% CI: -1.67 to -0.91), discrimination (g=-1.08; 95% CI: -1.28 to -0.87) and overall olfactory function (g=-1.64; 95% CI: -1.94 to -1.35) in patients with RBD. Except for the Unified Parkinson's Disease Rating Scale Part III scores, none of the known moderating variables (including age, sex, disease duration and years of education) accounted for the olfactory function heterogeneity in patients with RBD. We identified similar olfactory impairments in patients with RBD and patients with PD (either with or without underlying RBD). These findings suggest that olfactory impairment may be a sensitive and stable diagnostic biomarker of RBD and appears to be useful for identifying patients with idiopathic RBD at high risk for early conversion to PD.

α-Synuclein-induced Kv4 channelopathy in mouse vagal motoneurons drives nonmotor parkinsonian symptoms

No disease-modifying therapy is currently available for Parkinson's disease (PD), the second most common neurodegenerative disease. The long nonmotor prodromal phase of PD is a window of opportunity for early detection and intervention. However, we lack the pathophysiological understanding to develop selective biomarkers and interventions. By using a mutant α-synuclein selective-overexpression mouse model of prodromal PD, we identified a cell-autonomous selective Kv4 channelopathy in dorsal motor nucleus of the vagus (DMV) neurons. This functional remodeling of intact DMV neurons leads to impaired pacemaker function in vitro and in vivo, which, in turn, reduces gastrointestinal motility, a common early symptom of prodromal PD. We identify a chain of events from α-synuclein via a biophysical dysfunction of a specific neuronal population to a clinically relevant prodromal symptom. These findings will facilitate the rational design of clinical biomarkers to identify people at risk for developing PD.

Olfactory Testing in Parkinson Disease and REM Behavior Disorder: A Machine Learning Approach

OBJECTIVE

We sought to identify an abbreviated test of impaired olfaction amenable for use in busy clinical environments in prodromal (isolated REM sleep behavior disorder [iRBD]) and manifest Parkinson disease (PD).

METHODS

Eight hundred ninety individuals with PD and 313 controls in the Discovery cohort study underwent Sniffin' Stick odor identification assessment. Random forests were initially trained to distinguish individuals with poor (functional anosmia/hyposmia) and good (normosmia/super-smeller) smell ability using all 16 Sniffin' Sticks. Models were retrained using the top 3 sticks ranked by order of predictor importance. One randomly selected 3-stick model was tested in a second independent PD dataset (n = 452) and in 2 iRBD datasets (Discovery n = 241, Marburg n = 37) before being compared to previously described abbreviated Sniffin' Stick combinations.

RESULTS

In differentiating poor from good smell ability, the overall area under the curve (AUC) value associated with the top 3 sticks (anise/licorice/banana) was 0.95 in the Development dataset (sensitivity 90%, specificity 92%, positive predictive value 92%, negative predictive value 90%). Internal and external validation confirmed AUCs ≥0.90. The combination of the 3-stick model determined poor smell, and an RBD screening questionnaire score of ≥5 separated those with iRBD from controls with a sensitivity, specificity, positive predictive value, and negative predictive value of 65%, 100%, 100%, and 30%.

CONCLUSIONS

Our 3-Sniffin'-Stick model holds potential utility as a brief screening test in the stratification of individuals with PD and iRBD according to olfactory dysfunction.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that a 3-Sniffin'-Stick model distinguishes individuals with poor and good smell ability and can be used to screen for individuals with iRBD.

Dysphagia management in Parkinson's disease: Comparison of the effect of thickening agents on taste, aroma, and texture

Dysphagia is a frequent symptom in Parkinson's disease (PD). Thickening liquids facilitates safe swallowing, however, low treatment compliance is a major issue, due to patients' dislike of thickened liquids. Some studies suggest a negative impact of gum-based thickeners, currently most used in clinical practice, on sensory properties compared to starch-based thickeners. This has not yet been investigated in PD. This study's aim was to compare taste, texture, and aroma of gum-based and starch-based thickened soups in participants with PD. Gum-based resource thicken up clear (RTUC) and starch-based kitchen products potato starch (PS) and quinoa flour (QF) were evaluated in broccoli soup. Texture, aroma, and taste were characterized by rheology, volatile, and sensory profiling. Thickened soups were evaluated in participants with PD and controls through a paired comparison test. Reduced release of 61.4%, 46.2%, and 38.5% of volatiles was observed after thickening with RTUC, PS, and QF, respectively. Overall taste intensity was reduced in RTUC- and PS-thickened soup, respectively. Taste and aroma of PS-thickened soup were considered more intense by 70.3% and 63.8% of all participants, respectively (n = 36 PD, n = 41 controls), 56.3% preferred the PS-thickened soup's texture . Taste and aroma of QF-thickened soup were considered more intense by 68.1% and 65.6% of all participants, respectively (n = 47 PD, n = 31 controls), 58.0% preferred the QF-thickened soup's texture. Starch-based thickeners demonstrated higher taste and aroma intensity. However, volatile and sensory profiling demonstrated reduced taste and aroma in all thickeners. Combining kitchen products with flavor enhancers may increase palatability of thickened beverages.

Towards subgroup-specific risk estimates: A meta-analysis of longitudinal studies on olfactory dysfunction and risk of Parkinson's disease

BACKGROUND

Interest has risen in identifying individuals at high risk of incident Parkinson's disease (PD) to facilitate inclusion in neuroprotective treatment trials. Current risk estimates of prodromal markers are based on aggregated data of an entire population, but this approach disregards differences in risk estimates by subgroups of a population. In this proof of concept, we determine subgroup-specific risk estimates of olfactory dysfunction for incident PD.

METHODS

PubMed, EMBASE and Cochrane were searched for prospective studies investigating the association between olfactory dysfunction and incident PD. Random-effects meta-analysis, subgroup analyses and meta-regression were performed to investigate general and subgroup risk estimates.

RESULTS

Individuals with odor identification dysfunction seemed to be at greater risk of incident PD compared to controls without olfactory dysfunction (OR = 4.18; 95%CI [2.47-7.07]). Risk estimates were higher in studies that included higher percentages of women (regression slope β = 0.053 increase in log odds ratio per 1% increase 1%, p = 0.0006), increased with mean study age (β = 0.21 per one year increase; p = 0.005) and in REM-sleep behavior disorder cohorts (β = 1.95; p = 0.03). Furthermore, the association between olfactory dysfunction and incident PD was most distinct in studies with shorter follow-up duration (ß = -0.56; p = 0.0047).

CONCLUSION

The presence of olfactory dysfunction conveys a considerably elevated risk of incident PD, likely more in studies with a higher proportion of women, older individuals or short follow-up duration. Individual patient data are warranted to confirm these findings and to yield subgroup-specific risk estimates of other common markers to refine prodromal PD criteria.

Clinical assessment of olfactory function

Approximately 5% of the general population is affected by functional anosmia with approximately additional 15% exhibiting decreased olfactory function. Many of these individuals ask for help. Because the subjective rating of olfactory function is biased, assessment of olfactory function is important. Olfactory measurements are needed for patient counseling and the tracking of changes in the sense of smell over time. The present review provides an overview of frequently used psychophysical tests for olfactory function, discusses differences between threshold and suprathreshold aspects of olfactory function, and gives examples on how to apply psychophysical tests.

Olfactory loss and aging: connections with health and well-being

Age-related olfactory dysfunction, or presbyosmia, is a common sensory impairment in aging adults. People in this demographic group with comorbid conditions or exposure to viral, traumatic, or environmental insults remain at the greatest risk for impairment. Several methods for assessing olfaction exist, but they are only available in special settings and require consideration of age, sex, ancestry, and cognition. Perhaps most importantly, olfactory dysfunction has been suggested as an early sign of Alzheimer's and Parkinson's disease and therefore may serve as a tool in the diagnosis and prognosis of these neurodegenerative conditions. Outside of this context, olfactory loss also impacts nutrition, safety, and social relationships, and even predicts mortality itself. This review covers the detection and manifestations of olfactory decline in aging individuals and the myriad ways in which olfactory impairment is connected to their health and well-being.

Olfactory Dysfunction and Its Association With Neuropathologic Proteins in Cerebrospinal Fluid From Patients With Parkinson Disease

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.

Olfactory dysfunction in essential tremor versus tremor dominant Parkinson disease

BACKGROUND

Essential tremor (ET) and tremor dominant Parkinson disease (TDPD) variant constitute the main causes of geriatric tremor which differentiation is not always an easy mission. The objective of this work was to study the olfactory performance in ET and PD patients for possible consideration as a differentiating biomarker.

METHODS

This study was performed on 36ET, 22 TDPD variant and 24 healthy controls subjects (HCS) submitted to extended n-butanol Sniffin' Sticks test (SST) and olfactory bulbs volumetry (OBV).

RESULTS

There were significant decreases in SST threshold, discrimination, identification and TDI variables in TDPD patients compared to ET and HCS. ET patients showed significant decrease in the same variables compared to HCS. Regarding OBV, there were significant decreases in TDPD patients compared to ET and HCS with nonsignificant difference between the 2-latter groups. Our results showed that TDI score of 25 can differentiate between TDPD and ET patients with sensitivity and specificity (94 %, 91 %) respectively.

CONCLUSION

Olfactory assessment is a rapid, safe, and easily applicable biomarker that could differentiate TDPD from ET in doubtful cases.

Four-Year Follow-up of [18 F]Fluorodeoxyglucose Positron Emission Tomography-Based Parkinson's Disease-Related Pattern Expression in 20 Patients with Isolated Rapid Eye Movement Sleep Behavior Disorder Shows Prodromal Progression

Background

Isolated rapid eye movement sleep behavior disorder is known to be prodromal for alpha‐synucleinopathies, such as Parkinson's disease (PD) and dementia with Lewy bodies. The [¹⁸F]fluorodeoxyglucose‐positron emission tomography (PET)–based PD‐related brain pattern can be used to monitor disease progression.

Objective

We longitudinally investigated PD‐related brain pattern expression changes in 20 subjects with isolated rapid eye movement sleep behavior disorder to investigate whether this may be a suitable technique to study prodromal PD progression in these patients and to identify potential phenoconverters.

Methods

Subjects underwent two [¹⁸F]fluorodeoxyglucose‐PET brain scans ~3.7 years apart, along with baseline and repeated motor, cognitive, and olfactory testing within roughly the same time frame.

Results

At baseline, 8 of 20 (40%) subjects significantly expressed the PD‐related brain pattern (with z scores above the receiver operating characteristic–determined threshold). At follow‐up, six additional subjects exhibited significant PD‐related brain pattern expression (70% in total). PD‐related brain pattern expression increased in all subjects (P = 0.00008). Four subjects (20%), all with significant baseline PD‐related brain pattern expression, phenoconverted to clinical PD.

Conclusions

Suprathreshold PD‐related brain pattern expression and greater score rate of change may signify greater shorter‐term risk for phenoconversion. Our results support the use of serial PD‐related brain pattern expression measurements as a prodromal PD progression biomarker in patients with isolated rapid eye movement sleep behavior disorder. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Prodromal Markers of Parkinson's Disease in Patients With Essential Tremor

Background: Essential tremor (ET) is manifested as an isolated syndrome of bilateral upper limb action tremor. Parkinson's disease (PD) is the second most common neurodegenerative disease, with typical motor symptoms of bradykinesia, rigidity, and resting tremor. ET-PD describes the new-onset of PD in ET patients. Recently, numerous studies on epidemiology, genetics, pathology, clinical features, and neuroimaging studies are challenging the idea that ET is an isolated disease, suggesting that patients with ET have the tendency to develop PD. Methods: In this review article, we collected recent findings that reveal prodromal markers of PD in patients with ET. Results: Substantia nigra hyperechogenicity serves as a prodromal marker for predicting the development of PD in patients with ET and provides a reference for therapeutic strategies. Additional potential markers include other neuroimaging, clinical features, heart rate, and genetics, whereas others lack sufficient evidence. Conclusion: In consideration of the limited research of PD in patients with ET, we are still far from revealing the prodromal markers. However, from the existing follow-up studies on ET patients, Substantia nigra hyperechogenicity may enable further exploration of the relationship between ET and PD and the search for pathogenesis-based therapies.

Age-Related Olfactory Dysfunction: Epidemiology, Pathophysiology, and Clinical Management

Like other sensory systems, olfactory function deteriorates with age. Epidemiological studies have revealed that the incidence of olfactory dysfunction increases at the age of 60 and older and males are more affected than females. Moreover, smoking, heavy alcohol use, sinonasal diseases, and Down’s syndrome are associated with an increased incidence of olfactory dysfunction. Although the pathophysiology of olfactory dysfunction in humans remains largely unknown, studies in laboratory animals have demonstrated that both the peripheral and central olfactory nervous systems are affected by aging. Aged olfactory neuroepithelium in the nasal cavity shows the loss of mature olfactory neurons, replacement of olfactory neuroepithelium by respiratory epithelium, and a decrease in basal cell proliferation both in the normal state and after injury. In the central olfactory pathway, a decrease in the turnover of interneurons in the olfactory bulb (OB) and reduced activity in the olfactory cortex under olfactory stimulation is observed. Recently, the association between olfactory impairment and neurodegenerative diseases, such as Alzheimer’s disease (AD) and Parkinson’s disease (PD), has gained attention. Evidence-based pharmacotherapy to suppress or improve age-related olfactory dysfunction has not yet been established, but preliminary results suggest that olfactory training using odorants may be useful to improve some aspects of age-related olfactory impairment.

The Discriminative Power of Different Olfactory Domains in Parkinson's Disease

Background and Purpose: Olfactory dysfunction is one of the most common non-motor symptoms in Parkinson's disease (PD) preceding the motor symptoms for years. This study aimed to evaluate different olfactory domains in PD patients in comparison with healthy controls and to explore the relationships among olfactory deficit and other clinical manifestations in patients with PD.

Methods: Sniffin' Sticks test, which detects olfactory threshold, discrimination, and identification (TDI), were conducted in 500 PD patients and 115 controls. Furthermore, demographic and clinical data including motor and other non-motor symptoms were collected.

Results: In the single olfactory model, the identification test showed the area under the receiver operating characteristic (ROC) curve (AUC = 0.818), followed by threshold test (AUC = 0.731) and discrimination test (AUC = 0.723). Specifically, the identification test has a similar discriminative power as the TDI score (0.818 and 0.828, respectively, p = 0.481). In the integrated olfactory model involved with other non-motor manifestations, identification test scores performed as good as the TDI score in differentiating PD patients from controls (0.916 and 0.918, respectively, p = 0.797). In PD patients, age and cognition together explained 7.5% of the variance of the threshold score, while age, cognition, and gender accounted for the 15.2% explained variance of the discrimination score, while cognition, age, the ability of daily living, and gender together interpreted 11.1% of the variance of the identification score.

Conclusion: Our results indicated that the identification domain was the most practical olfactory factor in differentiating PD patients, and the combination of several different manifestations was better than a single symptom. Furthermore, the olfactory identification score may be associated with the ability of daily living.

Advances in the Research of Risk Factors and Prodromal Biomarkers of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world. With the advent of an aging population and improving life expectancy worldwide, the number of PD patients is expected to increase, which may lead to an urgent need for effective preventive and diagnostic strategies for PD. Although there is increasing research regarding the pathogenesis of PD, there is limited knowledge regarding the prevention of PD. Moreover, the diagnosis of PD depends on clinical criteria, which require the occurrence of bradykinesia and at least one symptom of rest tremor or rigidity. However, converging evidence from clinical, genetic, neuropathological, and imaging studies suggests the initiation of PD-specific pathology prior to the initial presentation of these classical motor clinical features by years or decades. This latent stage of neurodegeneration in PD is a particularly important stage for effective neuroprotective therapies, which might retard the progression or prevent the onset of PD. Therefore, the exploration of risk factors and premotor biomarkers is not only crucial to the early diagnosis of PD but is also helpful in the development of effective neuroprotection and health care strategies for appropriate populations at risk for PD. In this review, we searched and summarized ∼249 researches and 31 reviews focusing on the risk factors and prodromal biomarkers of PD and published in MEDLINE.

Rapid eye movement sleep behavior disorder and the link to alpha-synucleinopathies

Rapid eye movement (REM) sleep behavior disorder (RBD) involves REM sleep without atonia in conjunction with a recurrent nocturnal dream enactment behavior, with vocalizations such as shouting and screaming, and motor behaviors such as punching and kicking. Secondary RBD is well described in association with neurological disorders including Parkinson's disease (PD), multiple system atrophy (MSA), and other conditions involving brainstem structures such as tumors. However, RBD alone is now considered to be a potential harbinger of later development of neurodegenerative disorders, in particular PD, MSA, dementia with Lewy bodies (DLB), and pure autonomic failure. These conditions are linked by their underpinning pathology of alpha-synuclein protein aggregation. In RBD, it is therefore important to recognize the potential risk for later development of an alpha-synucleinopathy, and to investigate for other potential causes such as medications. Other signs and symptoms have been described in RBD, such as orthostatic hypotension, or depression. While it is important to recognize these features to improve patient management, they may ultimately provide clinical clues that will lead to risk stratification for phenoconversion. A critical need is to improve our ability to counsel patients, particularly with regard to prognosis. The ability to identify who, of those with RBD, is at high risk for later neurodegenerative disorders will be paramount, and would in addition advance our understanding of the prodromal stages of the alpha-synucleinopathies. Moreover, recognition of at-risk individuals for neurodegenerative disorders may ultimately provide a platform for the testing of possible neuroprotective agents for these neurodegenerative disorders.

Impairment of cross-modality of vision and olfaction in Parkinson disease

OBJECTIVE

To determine whether Parkinson disease (PD) affects cross-modal function of vision and olfaction because it is known that PD impairs various cognitive functions, including olfaction.

METHODS

We conducted behavioral experiments to identify the influence of PD on cross-modal function by contrasting patient performance with age-matched normal controls (NCs). We showed visual effects on the strength and preference of odor by manipulating semantic connections between picture/odorant pairs. In addition, we used brain imaging to identify the role of striatal presynaptic dopamine transporter (DaT) deficits.

RESULTS

We found that odor evaluation in participants with PD was unaffected by visual information, while NCs overestimated smell when sniffing odorless liquid while viewing pleasant/unpleasant visual cues. Furthermore, DaT deficit in striatum, for the posterior putamen in particular, correlated to few visual effects in participants with PD.

CONCLUSIONS

These findings suggest that PD impairs cross-modal function of vision/olfaction as a result of posterior putamen deficit. This cross-modal dysfunction may serve as the basis of a novel precursor assessment of PD.

Optimizing olfactory testing for the diagnosis of Parkinson's disease: item analysis of the university of Pennsylvania smell identification test

The 40-item University of Pennsylvania Smell Identification Test (UPSIT) is an effective instrument to detect olfactory dusfunction in Parkinson's disease (PD). It is not clear, however, whether tests of this length are necessary to detect such dysfunction. Several studies have suggested that detection of certain odors is selectively compromised in PD, and that a test comprised of these odors could be shorter and more specific for this purpose. Therefore, we attempted to identify a subset of UPSIT odors that distinguish PD from controls with similar or improved test characteristics compared to the full test. The discriminatory power of each odor was examined using UPSIT data from a discovery cohort of 314 PD patients and 314 matched controls and ranked using multiple methods (including odds ratios, regression coefficients and discriminant analysis). To validate optimally discriminant subsets, we calculated test characteristics using data from two independent cohorts (totaling 306 PD and 343 controls). In the discovery cohort, multiple novel 12-item subsets (and the previously described Brief Smell Identification Test-B) performed similarly or improved upon the UPSIT and were better than 12 random items. However, in validation studies from independent cohorts, multiple subsets retained test characteristics similar to the full UPSIT, but did not outperform 12 random items. Differential discriminatory power of individual items is not conserved across independent cohorts arguing against selective hyposmia in PD. However, multiple 12-item subsets performed as well as the full UPSIT. These subsets could form the basis for shorter olfactory tests in the clinical evaluation of Parkinsonism.

Idiopathic REM sleep behaviour disorder and neurodegeneration - an update

So-called idiopathic rapid eye movement (REM) sleep behaviour disorder (RBD), formerly seen as a rare parasomnia, is now recognized as the prodromal stage of an α-synucleinopathy. Given the very high risk that patients with idiopathic RBD have of developing α-synucleinopathies, such as Parkinson disease (PD), PD dementia, dementia with Lewy bodies or multiple system atrophy, and the outstandingly high specificity and very long interval between the onset of idiopathic RBD and the clinical manifestations of α-synucleinopathies, the prodromal phase of this disorder represents a unique opportunity for potentially disease-modifying intervention. This Review provides an update on classic and novel biomarkers of α-synuclein-related neurodegeneration in patients with idiopathic RBD, focusing on advances in imaging and neurophysiological, cognitive, autonomic, tissue-specific and other biomarkers. We discuss the strengths, potential weaknesses and suitability of these biomarkers for identifying RBD and neurodegeneration, with an emphasis on predicting progression to overt α-synucleinopathy. The role of video polysomnography in providing quantifiable and potentially treatment-responsive biomarkers of neurodegeneration is highlighted. In light of all these advances, and the now understood role of idiopathic RBD as an early manifestation of α-synuclein disease, we call for idiopathic RBD to be reconceptualized as isolated RBD.

Diagnostic Value of Combined Acute Levodopa Challenge and Olfactory Testing to Predict Parkinson's Disease

BACKGROUND

The diagnosis of Parkinson's disease (PD) can be challenging early in the disease course, when motor features are subtle. The objective of this study was to explore the diagnostic value of combining acute levodopa challenge and olfactory testing to predict PD.

METHODS

Data from 210 patients with a recent onset of parkinsonism who had at least 2 years of follow-up and underwent acute levodopa challenge for the clinical prediction of long-term dopaminergic response and had olfactory testing with Sniffin' Sticks Test were evaluated. Single and combined diagnostic measures were analyzed.

RESULTS

After 2 years of follow-up, a PD diagnosis was confirmed in 157 patients who fulfilled United Kingdom Parkinson's Disease Society Brain Bank criteria and was ruled out in 53. Sensitivity and specificity of acute levodopa challenge to predict PD diagnosis were 0.71 and 0.94, respectively. Sensitivity and specificity of olfactory tests were calculated according to the total olfactory score for hyposmia (0.61 and 0.77 respectively), the hyposmia identification subscore (0.63 and 0.74, respectively), and the anosmia score (0.40 and 0.85, respectively). The best combination identified was response to acute levodopa challenge together with hyposmia according to the total olfactory score (sensitivity, 0.90; specificity, 0.74; positive predictive value, 0.91; negative predictive value, 0.72; accuracy, 0.86).

CONCLUSION

The combination of response to acute levodopa challenge with hyposmia according to the total olfactory score improved sensitivity for the early diagnosis of PD.

Odor selectivity of hyposmia and cognitive impairment in patients with Parkinson's disease

Objective

Hyposmia is one of the earliest non-motor features of Parkinson’s disease (PD) and can precede the onset of motor symptoms by years. Most of the current olfactory detection tests are targeted at Western populations. The exact relationship between hyposmia and cognitive impairment is unknown. The purpose of the study was to find bromines that can effectively identify olfactory dysfunction and investigate the relationship between hyposmia and cognitive function in early, non-demented, drug-naïve patients with PD in the People’s Republic of China.

Methods

Sixty-three early, non-demented, drug-naïve patients with PD and 55 healthy controls were enrolled in the study. The T&T olfactometer and a Chinese version of Montreal Cognitive Assessment (MoCA) were applied to assess subjects’ olfactory and cognitive functions. Patients with PD also completed the Modified Unified Parkinson’s disease-rating scale (UPDRS) and Hoehn and Yahr (H&Y) scale.

Results

Patients with PD had lower scores of visuospatial and executive function (p=0.000), attention (p=0.03), and delayed recall (p=0.001) than controls. β-phenylethyl alcohol (floral smell, smell of rose petals) and isovaleric acid (smell of sweat, stuffy socks) were more sensitive for identifying hyposmia in patients with PD than three other odors. Multivariate logistic regression analysis showed that impaired visuospatial and executive function was associated with hyposmia (p=0.013), but was independent of other PD-associated variables.

Conclusion

Hyposmia was common in early, non-demented, drug-naïve PD patients. β-Phenylethyl alcohol and isovaleric acid were more superior for identifying hyposmia in early non-demented Chinese patients with PD. Hyposmia was associated with impaired visuospatial and executive function in patients with PD. Further prospective studies that apply a series of neuropsychological tests and functional magnetic resonance imaging methods in large samples in multicenter studies are needed to confirm our findings and to investigate the relationship between hyposmia and cognitive function with disease progression in patients with PD.

Characterization of patients with longstanding idiopathic REM sleep behavior disorder

OBJECTIVE

To evaluate the presence of prodromal markers of Parkinson disease (PD) in patients with longstanding idiopathic REM sleep behavior disorder (IRBD), a small subgroup of individuals with IRBD with long-term follow-up thought not to be at risk of developing PD.

METHODS

Demographic, clinical, and neuroimaging markers of PD were evaluated in 20 patients with polysomnographic-confirmed longstanding IRBD and in 32 matched controls.

RESULTS

Patients were 16 men and 4 women with mean age of 72.9 ± 8.6 years and mean follow-up from IRBD diagnosis of 12.1 ± 2.6 years. Patients more often had objective smell loss (35% vs 3.4%, p = 0.003), constipation (50% vs 15.6%, p = 0.008), and mild parkinsonian signs (45% vs 18.8%, p = 0.042) than controls. Unified Parkinson's Disease Rating Scale motor score was higher in patients than in controls (5.6 ± 3.5 vs 2.0 ± 2.1, p < 0.0001). Dopamine transporter imaging showed decreased striatal uptake in 82.4% of the patients and transcranial sonography found substantia nigra hyperechogenicity in 35.3%. α-Synuclein aggregates were found in 3 of 6 patients who underwent colon or submandibular gland biopsies. All 20 patients showed clinical, neuroimaging, or histologic markers of PD. Probability of prodromal PD (according to recent Movement Disorders Society research criteria) was higher in patients than in controls (<0.0001), and 45% of patients surpassed 80% probability.

CONCLUSIONS

Prodromal PD markers are common in individuals with longstanding IRBD, suggesting that they are affected by an underlying neurodegenerative process. This observation may be useful for the design of disease-modifying trials to prevent PD onset in IRBD.

Nonmotor Aspects of Parkinson's Disease-How Do They Help Diagnosis?

Not only are nonmotor aspects of Parkinson's disease important because of their impact, they also can help diagnose Parkinson's. This chapter summarizes the ways in which recognition of the nonmotor profile of Parkinson's can help in clinical diagnosis. It also emphasizes the essential role that nonmotor Parkinson's disease plays in the diagnosis of prodromal stages of disease.

Olfactory disturbances in ageing with and without dementia: towards new diagnostic tools

BACKGROUND

Olfactory disorders increase with age and often affect elderly people who have pre-dementia or dementia. Despite the frequent occurrence of olfactory changes at the early stages of neurodegenerative disorders such as Alzheimer's disease, olfactory disorders are rarely assessed in daily clinical practice, mainly due to a lack of standardised assessment tools. The aims of this review were to (1) summarise the existing literature on olfactory disorders in ageing populations and patients with neurodegenerative disorders; (2) present the strengths and weaknesses of current olfactory disorder assessment tools; and (3) discuss the benefits of developing specific olfactory tests for neurodegenerative diseases.

METHODS

A systematic review was performed of literature published between 2000 and 2015 addressing olfactory disorders in elderly people with or without Alzheimer's disease or other related disorders to identify the main tools currently used for olfactory disorder assessment.

RESULTS

Olfactory disorder assessment is a promising method for improving both the early and differential diagnosis of Alzheimer's disease. However, the current lack of consensus on which tests should be used does not permit the consistent integration of olfactory disorder assessment into clinical settings.

CONCLUSION

Otolaryngologists are encouraged to use olfactory tests in older adults to help predict the development of neurodegenerative diseases. Olfactory tests should be specifically adapted to assess olfactory disorders in Alzheimer's disease patients.

Olfactory dysfunction and dementia in newly diagnosed patients with Parkinson's disease

INTRODUCTION

Studies report that up to 90% of patients with idiopathic Parkinson's disease (PD) have olfactory dysfunction (hyposmia). Hyposmia has also been connected to cognitive impairment and dementia in PD, but no studies of newly diagnosed patients followed longer than three years exists. The present study investigates the prevalence of olfactory dysfunction at PD diagnosis, how it evolves over time and whether hyposmia increases the risk of dementia in Parkinson's disease.

METHODS

Olfactory function was assessed with Brief Smell Identification Test (B-SIT) in 125 newly diagnosed patients with PD. They were followed for a maximum of 10 years (median six years) with extensive investigations at baseline, 12, 36, 60 and 96 months. Patients with B-SIT<9 were considered hyposmic.

RESULTS

Hyposmia was found in 73% of the patients at diagnosis. During the follow up period of ten years 42 (46%) patients with hyposmia at baseline developed dementia compared to seven (21%) of the normosmic patients. Cox proportional hazards model showed that hyposmia at baseline (controlled for age, gender, UPDRS III and Mild Cognitive Impairment) increased the risk of developing dementia (hazard ratio (95%CI): 3.29 (1.44-7.52), p = 0.005). Only one of 22 patients with normal cognition and normal olfaction at baseline developed dementia.

CONCLUSIONS

Olfactory dysfunction was common at the time of PD diagnosis and increased the risk of dementia up to ten years after PD diagnosis regardless of baseline cognitive function. Normal olfaction together with normal cognition at baseline predicted a benign cognitive course up to ten years after diagnosis.

Sniffing the diagnosis: Olfactory testing in neurodegenerative parkinsonism

OBJECTIVE

To determine the diagnostic utility of olfactory testing in patients with neurodegenerative parkinsonism.

METHODS

The Sniffin' Sticks test battery for assessment of odor identification, discrimination, and threshold was applied to patients with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) as well as healthy controls (HC). Two different cohorts were analyzed: A PD/healthy control that included PD patients and HC as well as a PD/diseased control cohort for which patients PD, MSA and PSP were recruited. The former cohort was exploited to calculate cut-off values that discriminate PD patients from HC with a sensitivity (sensitivity-weighted cut-off) or specificity (specificity-weighted cut-off) exceeding 95%, respectively. The PD/diseased controls cohort was used to determine the diagnostic accuracy using these cut-off values in discriminating patients with neurodegenerative parkinsonism.

RESULTS

PD patients (n = 67) performed significantly worse in olfactory testing than HC (n = 41) and patients with MSA (n = 23) or PSP (n = 23). There was no significant difference in olfactory function between MSA and PSP patients. Diagnostic performance of the identification subscore was similar to the sum score of the Sniffin' Sticks test (AUC identification test 0.94, AUC sum score 0.96), while threshold and discrimination subscores were inferior. In patients with parkinsonism, the specificity-weighted cut-off predicted a diagnosis of PD with a sensitivity and specificity of 76.6 and 87.0%, respectively. The discriminative value of this cut-off in separating PD from MSA was 76.7% (sensitivity) and 95.7% (specificity). The corresponding, prevalence-adjusted positive predictive value of olfactory testing exceeded 95%.

CONCLUSIONS

Our data suggest that assessment of olfactory function, particularly odor identification, can be useful to discriminate PD from atypical parkinsonian disorders, particularly MSA patients.

Assessment of Olfactory Function in MAPT-Associated Neurodegenerative Disease Reveals Odor-Identification Irreproducibility as a Non-Disease-Specific, General Characteristic of Olfactory Dysfunction

Olfactory dysfunction is associated with normal aging, multiple neurodegenerative disorders, including Parkinson's disease, Lewy body disease and Alzheimer's disease, and other diseases such as diabetes, sleep apnea and the autoimmune disease myasthenia gravis. The wide spectrum of neurodegenerative disorders associated with olfactory dysfunction suggests different, potentially overlapping, underlying pathophysiologies. Studying olfactory dysfunction in presymptomatic carriers of mutations known to cause familial parkinsonism provides unique opportunities to understand the role of genetic factors, delineate the salient characteristics of the onset of olfactory dysfunction, and understand when it starts relative to motor and cognitive symptoms. We evaluated olfactory dysfunction in 28 carriers of two MAPT mutations (p.N279K, p.P301L), which cause frontotemporal dementia with parkinsonism, using the University of Pennsylvania Smell Identification Test. Olfactory dysfunction in carriers does not appear to be allele specific, but is strongly age-dependent and precedes symptomatic onset. Severe olfactory dysfunction, however, is not a fully penetrant trait at the time of symptom onset. Principal component analysis revealed that olfactory dysfunction is not odor-class specific, even though individual odor responses cluster kindred members according to genetic and disease status. Strikingly, carriers with incipient olfactory dysfunction show poor inter-test consistency among the sets of odors identified incorrectly in successive replicate tests, even before severe olfactory dysfunction appears. Furthermore, when 78 individuals without neurodegenerative disease and 14 individuals with sporadic Parkinson's disease were evaluated twice at a one-year interval using the Brief Smell Identification Test, the majority also showed inconsistency in the sets of odors they identified incorrectly, independent of age and cognitive status. While these findings may reflect the limitations of these tests used and the sample sizes, olfactory dysfunction appears to be associated with the inability to identify odors reliably and consistently, not with the loss of an ability to identify specific odors. Irreproducibility in odor identification appears to be a non-disease-specific, general feature of olfactory dysfunction that is accelerated or accentuated in neurodegenerative disease. It may reflect a fundamental organizational principle of the olfactory system, which is more "error-prone" than other sensory systems.

REM sleep behavior disorder (RBD): Update on diagnosis and treatment

Background

REM sleep behavior disorder (RBD) is parasomnia characterized by dream enactment and enabled by disruption of physiological muscle atonia during REM sleep. Over the past few years, diagnostic criteria and the methods used to confirm diagnosis have been updated.

Objective

In this review article, the current knowledge regarding RBD diagnosis and treatment is presented.

Methods

A selective literature search was carried out.

Results and discussion

Although several RBD screening questionnaires have been developed, diagnosis can only be definitely confirmed on the basis of polysomnography. New methods for scoring electromyography (EMG) activity during REM sleep have been proposed during recent years and cutoff values have been established. The latest cutoff values for scoring EMG activity during REM sleep are included in the International Classification of Sleep Disorders (ICSD). The cutoff of 27 % muscle activity during REM sleep suggested by the Sleep Innsbruck Barcelona (SINBAR) group was also included in the third edition of the ICSD. The best-researched treatments for RBD are clonazepam and melatonin.