Freezing of gait subtypes have different cognitive correlates in Parkinson's disease

Cognitive Profiles Stratified by Education Using Montreal Cognitive Assessment in Parkinson's Disease Patients with Freezing of Gait

Purpose

Parkinson's disease (PD) patients with freezing of gait (FOG) may present with complex and heterogeneous cognitive profiles. Owing to limited access to comprehensive neuropsychological battery in ordinary clinical practice, the Montreal Cognitive Assessment (MoCA) is likely to be easily available cognitive data for comparisons among studies. This study aims to explore the cognitive profiles stratified by education using MoCA in PD patients with FOG.

Patients and Methods

PD patients with FOG (FOG+, n = 52) and without FOG (FOG-, n = 71) were included in our study. MoCA items were categorized into five subsections (attention/working memory, executive function, episodic memory, language, and visuospatial function) referring to previously published criteria. Cognitive assessments were compared based on five subsections between groups stratified by three education levels (0-6 years, 7-12 years, and >12 years). The association of cognitive measurements with FOG were analyzed using binary logistic regression models with adjustment for variables.

Results

The total scores and subscores of each subsection of MoCA were similar between two groups of each education level. Further detailed analysis showed that a composite measure labeled "Attention/working memory-Composite" (abbreviated to Attention-C), consisting of the scores of four items (target detection task, serial sevens, digit forward and backward, and sentence repetition), were lower significantly in FOG+ group compared with FOG- group in patients with education year ≤6 years. The significant association of Attention-C with FOG held true when controlling for disease duration, but not for H-Y stage, MDS-UPDRS III, HAMA, and HAMD.

Conclusion

Overall, our findings gave a hint that Attention-C derived from MoCA might be a potential factor associated with FOG in PD patients with lower education level (education year ≤ 6 years), which will need to be validated in future studies.

Neuromelanin-sensitive MRI correlates of cognitive and motor function in Parkinson's disease with freezing of gait

Substantia nigra pars compacta (SNc) and locus coeruleus (LC) are neuromelanin-rich nuclei implicated in diverse cognitive and motor processes in normal brain function and disease. However, their roles in aging and neurodegenerative disease mechanisms have remained unclear due to a lack of tools to study them in vivo. Preclinical and post-mortem human investigations indicate that the relationship between tissue neuromelanin content and neurodegeneration is complex. Neuromelanin exhibits both neuroprotective and cytotoxic characteristics, and tissue neuromelanin content varies across the lifespan, exhibiting an inverted U-shaped relationship with age. Neuromelanin-sensitive MRI (NM-MRI) is an emerging modality that allows measurement of neuromelanin-associated contrast in SNc and LC in humans. NM-MRI robustly detects disease effects in these structures in neurodegenerative and psychiatric conditions, including Parkinson's disease (PD). Previous NM-MRI studies of PD have largely focused on detecting disease group effects, but few studies have reported NM-MRI correlations with phenotype. Because neuromelanin dynamics are complex, we hypothesize that they are best interpreted in the context of both disease stage and aging, with neuromelanin loss correlating with symptoms most clearly in advanced stages where neuromelanin loss and neurodegeneration are coupled. We tested this hypothesis using NM-MRI to measure SNc and LC volumes in healthy older adult control individuals and in PD patients with and without freezing of gait (FOG), a severe and disabling PD symptom. We assessed for group differences and correlations between NM-MRI measures and aging, cognition and motor deficits. SNc volume was significantly decreased in PD with FOG compared to controls. SNc volume correlated significantly with motor symptoms and cognitive measures in PD with FOG, but not in PD without FOG. SNc volume correlated significantly with aging in PD. When PD patients were stratified by disease duration, SNc volume correlated with aging, cognition, and motor deficits only in PD with disease duration >5 years. We conclude that in severe or advanced PD, identified by either FOG or disease duration >5 years, the observed correlations between SNc volume and aging, cognition, and motor function may reflect the coupling of neuromelanin loss with neurodegeneration and the associated emergence of a linear relationship between NM-MRI measures and phenotype.

Topological reorganization of functional hubs in patients with Parkinson's disease with freezing of gait

BACKGROUND AND PURPOSE

Resting-state functional MRI (rs-fMRI) studies in Parkinson's disease (PD) patients with freezing of gait (FOG) have implicated dysfunctional connectivity over multiple resting-state networks (RSNs). While these findings provided network-specific insights and information related to the aberrant or altered regional functional connectivity (FC), whether these alterations have any effect on topological reorganization in PD-FOG patients is incompletely understood. Understanding the higher order functional organization, which could be derived from the "hub" and the "rich-club" organization of the functional networks, could be crucial to identifying the distinct and unique pattern of the network connectivity associated with PD-FOG.

METHODS

In this study, we use rs-fMRI data and graph theoretical approaches to explore the reorganization of RSN topology in PD-FOG when compared to those without FOG. We also compared the higher order functional organization derived using the hub and rich-club measures in the FC networks of these PD-FOG patients to understand whether there is a topological reorganization of these hubs in PD-FOG.

RESULTS

We found that the PD-FOG patients showed a noticeable reorganization of hub regions. Regions that are part of the prefrontal cortex, primary somatosensory, motor, and visuomotor coordination areas were some of the regions exhibiting altered hub measures in PD-FOG patients. We also found a significantly altered feeder and local connectivity in PD-FOG.

CONCLUSIONS

Overall, our findings demonstrate a widespread topological reorganization and disrupted higher order functional network topology in PD-FOG that may further assist in improving our understanding of functional network disturbances associated with PD-FOG.

Effectiveness of Center of Pressure Trajectory as Anticipatory Postural Adjustment Measurement in Parkinson's Disease With Freezing of Gait History

BACKGROUND

Evidence showed that patients with Parkinson's disease (PD) who have a history of freezing of gait (FOG) have hypometric anticipatory postural adjustment (APA) during gait initiation (GI) compared to PD without FOG.

OBJECTIVES

This study aimed to test the feasibility of center of pressure (COP) displacement during GI as the measure of APA in PD with and without a history of FOG.

METHODS

Patients with PD underwent COP trajectory measurements, including duration, length, velocity, and acceleration in different phases of APA (APA1, APA2a, APA2, and LOC), as well as evaluation of New Freezing of Gait Questionnaire (NFOG-Q), Tinetti balance and gait score, and Postural Instability and Gait Difficulty (PIGD) score in the on and off medication states.

RESULTS

The duration (seconds) of APA2a, APA2b, and LOC were highest while velocity in mediolateral direction (X) (m/s), including APA1, APA2a, APA2b, and LOC showed lowest in PD with FOG. Velocity in the mediolateral direction in different phases of APA increased in patients with FOG after dopaminergic therapy. APA2a (seconds) and APA2b (X) (m/s) were significantly associated with NFOG-Q part II, APA2b (X) (m/s) was significantly associated with NFOG-Q part III, and APA2a (seconds) was significantly associated with Tinetti balance and gait and PIGD score.

CONCLUSIONS

PD with FOG history showed a favorable response of APAs to dopaminergic replacement. The APA parameters by COP trajectory, especially lateral COP shift toward the stance foot (APA2b (X) (m/s) and APA2a (seconds)) are surrogate markers to assess PD with FOG history.

Association between Cognitive Impairment and Freezing of Gait in Patients with Parkinson's Disease

Background: Freezing of gait (FOG) is a common disabling symptom in Parkinson's disease (PD). Cognitive impairment may contribute to FOG. Nevertheless, their correlations remain controversial. We aimed to investigate cognitive differences between PD patients with and without FOG (nFOG), explore correlations between FOG severity and cognitive performance and assess cognitive heterogeneity within the FOG patients. Methods: Seventy-four PD patients (41 FOG, 33 nFOG) and 32 healthy controls (HCs) were included. Comprehensive neuropsychological assessments testing cognitive domains of global cognition, executive function/attention, working memory, and visuospatial function were performed. Cognitive performance was compared between groups using independent t-test and ANCOVA adjusting for age, sex, education, disease duration and motor symptoms. The k-means cluster analysis was used to explore cognitive heterogeneity within the FOG group. Correlation between FOG severity and cognition were analyzed using partial correlations. Results: FOG patients showed significantly poorer performance in global cognition (MoCA, p < 0.001), frontal lobe function (FAB, p = 0.015), attention and working memory (SDMT, p < 0.001) and executive function (SIE, p = 0.038) than nFOG patients. The FOG group was divided into two clusters using the cluster analysis, of which cluster 1 exhibited worse cognition, and with older age, lower improvement rate, higher FOGQ3 score, and higher proportion of levodopa-unresponsive FOG than cluster 2. Further, in the FOG group, cognition was significantly correlated with FOG severity in MoCA (r = -0.382, p = 0.021), Stroop-C (r = 0.362, p = 0.030) and SIE (r = 0.369, p = 0.027). Conclusions: This study demonstrated that the cognitive impairments of FOG were mainly reflected by global cognition, frontal lobe function, executive function, attention and working memory. There may be heterogeneity in the cognitive impairment of FOG patients. Additionally, executive function was significantly correlated with FOG severity.

Cognition and freezing of gait in Parkinson's disease: A systematic review and meta-analysis

Freezing of gait (FOG) is a common and disabling symptom in people with Parkinson's Disease (PwPD). Although cognition is thought to be worse in PwPD who freeze, a comprehensive analysis of this relationship will inform future research and clinical care. This systematic review and meta-analysis compared cognition between PwPD who do and do not exhibit FOG across a range of cognitive domains and assessed the impact of disease severity and medication status on this relationship. 145 papers (n = 9010 participants) were included in the analysis, with 144 and 138 articles meeting the criteria to assess moderating effects of disease severity and medication status, respectively. PwPD who freeze exhibited worse cognition than PwPD without FOG across global cognition, executive function/attention, language, memory, and visuospatial domains. Greater disease severity and "ON" levodopa medication status moderated the FOG status-cognition relationship in global cognitive performance but not in other cognitive domains. This meta-analysis confirmed that cognition is worse in PwPD with FOG and highlights the importance of disease severity and medication status in this relationship.

Comparing Backward Walking Performance in Parkinson's Disease with and without Freezing of Gait-A Systematic Review

INTRODUCTION

Parkinson's disease (PD) is a neurodegenerative disease characterized by motor symptoms and gait impairments. Among them, freezing of gait (FOG) is one of the most disabling manifestations. Backward walking (BW) is an activity of daily life that individuals with PD might find difficult and could cause falls. Recent studies have reported that gait impairments in PD were more pronounced in BW, particularly in people presenting FOG. However, to the best of our knowledge, no systematic review has synthetized the literature which compared BW performance in PD patients with and without FOG.

OBJECTIVE

The aim of this study was to evaluate the differences in BW performance between PD patients with FOG and PD patients without FOG.

METHODS

Two databases, PubMed and Web of Science, were systematically searched to identify studies comparing BW performance in PD patients with and without FOG. The National Institutes of Health (NIH) tool was used to assess the quality of the studies included.

RESULTS

Seven studies with 431 PD patients (179 PD with FOG and 252 PD without FOG) met the inclusion criteria and were included in this review. Among them, 5 studies reported walking speed, 3 studies step length, stride length and lower limb range of motion, 2 studies functional ambulation profile, toe clearance height, swing, and stance percent and 1 study reported the decomposition index and stepping coordination. Compared to PD patients without FOG, PD patients with FOG showed slower walking speed and reduced step length in 3 studies, shorter stride length, lower functional ambulation profile and decreased ankle range of motion in 2 studies, and smaller swing percent, higher stance percent, worse stepping coordination, greater decomposition between movements, and lower toe clearance height in one study.

CONCLUSION

Despite the small number of included studies, the findings of this review suggested that PD patients with FOG have worse gait performance during the BW task than PD without FOG.

Freezing of gait is a risk factor for cognitive decline in Parkinson's disease

BACKGROUNDS

Freezing of gait (FOG) and cognitive impairment are serious symptoms of Parkinson's disease (PD). Understanding the association between FOG and cognition may help formulate specific interventions for PD individuals.

OBJECTIVES

We aimed to investigate the associations of cognitive impairment in different domains with FOG status using multiple neuropsychological tests.

METHODS

Two cohorts including 691 and 104 participants were recruited from Parkinson's progression markers initiative (PPMI) and central China, respectively. All participants underwent FOG assessment and neuropsychological tests, and 595 individuals from PPMI and 51 from central China were enrolled for longitudinal observation. Cross-sectional and longitudinal associations between cognition and FOG status were evaluated using multivariable-adjusted models.

RESULTS

Worse cognitive performances were observed in patients with FOG compared to those without FOG in both cohorts (β = - 0.020, p < 0.001) using multivariate-adjusted models. Moreover, patients with progressive FOG during follow-up manifested more serious cognitive declines (HR = 1.40, 95% CI = 1.07-1.80). The FOG was mainly associated with the decline of executive, attention, and orientation. Furthermore, FOG was associated with higher levels of cognition-related biomarkers including T-tau, P-tau, and NfL in cerebrospinal fluid (p < 0.050).

CONCLUSIONS

FOG is a risk factor for cognitive decline in PD, which emphasizes the need for early detection and monitoring of cognitive changes and interventions on cognitive impairments in PD patients with FOG.

Functional topologies of spatial cognition predict cognitive and motor progression in Parkinson’s

Background

Spatial cognition deteriorates in Parkinson’s disease (PD), but the neural substrates are not understood, despite the risk for future dementia. It is also unclear whether deteriorating spatial cognition relates to changes in other cognitive domains or contributes to motor dysfunction.

Objective

This study aimed to identify functional connectivity abnormalities in cognitively normal PD (PDCN) in regions that support spatial cognition to determine their relationship to interfacing cognitive functions and motor disability, and to determine if they predict cognitive and motor progression 2 years later in a PDCN subsample.

Methods

Sixty-three PDCN and 43 controls underwent functional MRI while judging whether pictures, rotated at various angles, depicted the left or right hand. The task activates systems that respond to increases in rotation angle, a proxy for visuospatial difficulty. Angle-modulated functional connectivity was analyzed for frontal cortex, posterior cortex, and basal ganglia regions.

Results

Two aberrant connectivity patterns were found in PDCN, which were condensed into principal components that characterized the strength and topology of angle-modulated connectivity. One topology related to a marked failure to amplify frontal, posterior, and basal ganglia connectivity with other brain areas as visuospatial demands increased, unlike the control group (control features). Another topology related to functional reorganization whereby regional connectivity was strengthened with brain areas not recruited by the control group (PDCN features). Functional topologies correlated with diverse cognitive domains at baseline, underscoring their influences on spatial cognition. In PDCN, expression of topologies that were control features predicted greater cognitive progression longitudinally, suggesting inefficient communications within circuitry normally recruited to handle spatial demands. Conversely, stronger expression of topologies that were PDCN features predicted less longitudinal cognitive decline, suggesting functional reorganization was compensatory. Parieto-occipital topologies (control features) had different prognostic implications for longitudinal changes in motor disability. Expression of one topology predicted less motor decline, whereas expression of another predicted increased postural instability and gait disturbance (PIGD) feature severity. Concurrently, greater longitudinal decline in spatial cognition predicted greater motor and PIGD feature progression, suggesting deterioration in shared substrates.

Conclusion

These novel discoveries elucidate functional mechanisms of visuospatial cognition in PDCN, which foreshadow future cognitive and motor disability.

Vestibular Sensory Conflict During Postural Control, Freezing of Gait, and Falls in Parkinson's Disease

BACKGROUND

The vestibular system has been implicated in the pathophysiology of episodic motor impairments in Parkinson's disease (PD), but specific evidence remains lacking.

OBJECTIVE

We investigated the relationship between the presence of freezing of gait and falls and postural failure during the performance on Romberg test condition 4 in patients with PD.

METHODS

Modified Romberg sensory conflict test, fall, and freezing-of-gait assessments were performed in 92 patients with PD (70 males/22 females; mean age, 67.6 ± 7.4 years; Hoehn and Yahr stage, 2.4 ± 0.6; mean Montreal Cognitive Assessment, 26.4 ± 2.8).

RESULTS

Failure during Romberg condition 4 was present in 33 patients (35.9%). Patients who failed the Romberg condition 4 were older and had more severe motor and cognitive impairments than those without. About 84.6% of all patients with freezing of gait had failure during Romberg condition 4, whereas 13.4% of patients with freezing of gait had normal performance (χ²  = 15.6; P < 0.0001). Multiple logistic regression analysis showed that the regressor effect of Romberg condition 4 test failure for the presence of freezing of gait (Wald χ²  = 5.0; P = 0.026) remained significant after accounting for the degree of severity of parkinsonian motor ratings (Wald χ²  = 6.2; P = 0.013), age (Wald χ²  = 0.3; P = 0.59), and cognition (Wald χ²  = 0.3; P = 0.75; total model: Wald χ²  = 16.1; P < 0.0001). Patients with PD who failed the Romberg condition 4 (45.5%) did not have a statistically significant difference in frequency of patients with falls compared with patients with PD without abnormal performance (30.5%; χ²  = 2.1; P = 0.15).

CONCLUSIONS

The presence of deficient vestibular processing may have specific pathophysiological relevance for freezing of gait, but not falls, in PD. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Levodopa ONOFF-state freezing of gait: Defining the gait and non-motor phenotype

Background

Freezing in the levodopa-medicated-state (ON-state) is a debilitating feature of Parkinson’s disease without treatment options. Studies detailing the distinguishing features between people with freezing of gait that improves with levodopa and those whose freezing continues even on levodopa are lacking.

Objective

To characterize the gross motor, gait, and non-motor features of this phenotype.

Methods

Instrumented continuous gait was collected in the levodopa-medicated-state in 105 patients: 43 non-freezers (no-FOG), 36 with freezing only OFF-levodopa (OFF-FOG) and 26 with freezing both ON- and OFF-levodopa (ONOFF-FOG). Evaluation of motor and non-motor disease features was undertaken using validated scales. A linear mixed model with age, sex, disease duration, and motor UPDRS scores as covariates was used to determine differences in spatiotemporal gait and non-motor disease features among the groups.

Results

Compared to OFF-FOG, the ONOFF-FOG group had greater disease severity (on the Unified Parkinson’s disease Rating Scale) and worse cognition (on the Montreal Cognitive Assessment, Frontal Assessment Battery and Scales for Outcome in Parkinson’s disease-Cognition scales) and quality of life (on the PDQ-39), but similar mood (on the Hamilton depression and anxiety scales) and sleep quality (on Epworth sleepiness scale and RBD questionnaire). For several gait features, differences between the ONOFF-OFF groups were at least as large and in the opposite direction as differences between OFF-no groups, controlling for disease severity. Variability in ONOFF-FOG was greater than in other groups. Using results from our study and others, a power analysis for a potential future study reveals sample sizes of at least 80 ONOFF and 80 OFF-FOG patients would be needed to detect clinically meaningful differences.

Conclusions

Intra-patient variability in spatiotemporal gait features was much greater in ONOFF-FOG than in the other two groups. Our results suggest that multifactorial deficits may lead to ONOFF-FOG development.

Parkinson's Disease Subtyping Using Clinical Features and Biomarkers: Literature Review and Preliminary Study of Subtype Clustering

The second most common progressive neurodegenerative disorder, Parkinson’s disease (PD), is characterized by a broad spectrum of symptoms that are associated with its progression. Several studies have attempted to classify PD according to its clinical manifestations and establish objective biomarkers for early diagnosis and for predicting the prognosis of the disease. Recent comprehensive research on the classification of PD using clinical phenotypes has included factors such as dominance, severity, and prognosis of motor and non-motor symptoms and biomarkers. Additionally, neuroimaging studies have attempted to reveal the pathological substrate for motor symptoms. Genetic and transcriptomic studies have contributed to our understanding of the underlying molecular pathogenic mechanisms and provided a basis for classifying PD. Moreover, an understanding of the heterogeneity of clinical manifestations in PD is required for a personalized medicine approach. Herein, we discuss the possible subtypes of PD based on clinical features, neuroimaging, and biomarkers for developing personalized medicine for PD. In addition, we conduct a preliminary clustering using gait features for subtyping PD. We believe that subtyping may facilitate the development of therapeutic strategies for PD.

Cerebrospinal fluid biomarkers in Parkinson's disease with freezing of gait: an exploratory analysis

We explore the association between three Alzheimer’s disease-related and ten inflammation-related CSF markers and freezing of gait (FOG) in patients with Parkinson’s disease (PD). The study population includes PD patients with FOG (PD-FOG, N = 12), without FOG (PD-NoFOG, N = 19), and healthy controls (HC, N = 12). Age and PD duration are not significantly different between groups. After adjusting for covariates and multiple comparisons, the anti-inflammatory marker, fractalkine, is significantly decreased in the PD groups compared to HC (P = 0.002), and further decreased in PD-FOG compared to PD-NoFOG (P = 0.007). The Alzheimer’s disease-related protein, Aβ42, is increased in PD-FOG compared to PD-NoFOG and HC (P = 0.001). Group differences obtained in individual biomarker analyses are confirmed with multivariate discriminant partial least squares regression (P < 0.001). High levels of Aβ42 in PD-FOG patients supports an increase over time from early to advanced state. Low levels of fractalkine might suggest anti-inflammatory effect. These findings warrant replication.

Executive function and dopamine response in Parkinson's disease freezing of gait

BACKGROUND

This investigation examined whether aspects of attention and executive functioning differed between Parkinson's Disease (PD) patients with freezing of gait (FOG) based on responsiveness to dopamine. We also explored association of cognition with FOG severity and gait metrics.

METHODS

Fifty-four individuals with PD completed the study protocol: 17 without freezing (PDC), 23 with dopa-responsive FOG (RFOG), and 14 with dopa-unresponsive (URFOG). Standardized neuropsychological tests assessed attention (focused and sustained), psychomotor speed, and set-switching (time and errors). FOG severity was measured using the new FOG Questionnaire (nFOG-Q). Metrics from timed up and go (TUG) tasks were obtained while "on" and "off" dopamine, with and without dual cognitive tasks.

RESULTS

After controlling for clinical and demographic factors, analysis of covariance revealed a significant between-group difference for set-switching errors; planned contrasts revealed increased set-switching errors in URFOG relative to RFOG and PD control groups. Groups were not different in other cognitive domains. FOG severity was modestly associated with set-switching errors in RFOG but not URFOG. TUG performances while "on" were associated with set-switching errors in PD controls, and with focused attention in RFOG.

CONCLUSION

PD patients with dopa-unresponsive FOG are more prone to set-switching errors than those who respond to treatment. Furthermore, executive function appears relevant to FOG severity only in patients who show dopamine response. Together, these findings suggest disruption of a common dopamine-mediated pathway for FOG and ability to monitor rules while alternating cognitive processes. Consideration of dopa-response could be useful in characterizing cohorts and treating FOG in PD.

Disorganized resting-state functional connectivity between the dorsal attention network and intrinsic networks in Parkinson's disease with freezing of gait

Freezing of gait (FOG) is a common and complex manifestation of Parkinson's disease (PD) and is associated with impairment of attention. The purpose of this study was to evaluate the functional network connectivity (FNc) changes between the dorsal attention network (DAN) and the other seven intrinsic networks relevant to attention, visual-spatial, executive and motor functions in PD with or without FOG. Forty-three idiopathic PD patients (21 with FOG [FOG+] versus 22 without FOG [FOG-]) and 18 healthy controls (HC) were recruited in this study. The data-driven independent component analysis (ICA) method was used to extract and analyze the above-mentioned resting-state networks (RSNs). Compared with FOG-, FOG+ displayed decreased positive connectivity between the DAN and medial visual network (mVN) and sensory-motor network (SMN) and increased negative connectivity between the DAN and default mode network (DMN). The within-network connectivity in the SMN and visual networks were decreased, whereas the connectivity within DMN was increased significantly in FOG+. Correlation analysis showed that the clock drawing test (CDT) scores were positively correlated with the functional connectivity of mVN (r = 0.573, p = 0.008) and lateral visual network (lVN) (r = 0.510, p = 0.022), the Timed Up and Go Test (TUG) duration were negatively correlated with the connectivity of SMN (r = -0.629, p = 0.003), and the Frontal Assessment Battery (FAB) scores were negatively correlated with the connectivity of DMN in FOG+. Functional connectivity was changed in multiple intra-networks in patients with FOG. Inordinate inter-network connectivity between the DAN and other intrinsic networks may partly contribute to the mechanism of freezing.

Relating Response Inhibition, Brain Connectivity, and Freezing of Gait in People with Parkinson's Disease

OBJECTIVE

Freezing of gait (FoG) in Parkinson's disease (PD) has been associated with response inhibition. However, the relationship between response inhibition, neural dysfunction, and PD remains unclear. We assessed response inhibition and microstructural integrity of brain regions involved in response inhibition [right hemisphere inferior frontal cortex (IFC), bilateral pre-supplementary motor areas (preSMA), and subthalamic nuclei (STN)] in PD subjects with and without FoG and elderly controls.

METHOD

Twenty-one people with PD and FoG (PD-FoG), 18 without FoG (PD-noFoG), and 19 age-matched controls (HC) completed a Stop-Signal Task (SST) and MRI scan. Probabilistic fiber tractography assessed structural integrity (fractional anisotropy, FA) among IFC, preSMA, and STN regions.

RESULTS

Stop-signal performance did not differ between PD and HC, nor between PD-FoG and PD-noFoG. Differences in white matter integrity were observed across groups (.001 < p < .064), but were restricted to PD versus HC groups; no differences in FA were observed between PD-FoG and PD-noFoG (p > .096). Interestingly, worse FoG was associated with higher (better) mean FA in the r-preSMA, (β = .547, p = .015). Microstructural integrity of the r-IFC, r-preSMA, and r-STN tracts correlated with stop-signal performance in HC (p ≤ .019), but not people with PD.

CONCLUSION

These results do not support inefficient response inhibition in PD-FoG. Those with PD exhibited white matter loss in the response inhibition network, but this was not associated with FoG, nor with response inhibition deficits, suggesting FoG-specific neural changes may occur outside the response inhibition network. As shown previously, white matter loss was associated with response inhibition in elderly controls, suggesting PD may disturb this relationship.

Prevalence of freezing of gait in Parkinson's disease: a systematic review and meta-analysis

BACKGROUND

Freezing of gait (FOG) is considered one of the most disturbing and least understood symptoms in Parkinson's disease (PD). The reported prevalence rates of FOG in PD vary widely, ranging from 5 to 85.9%.

OBJECTIVE

We conducted a systematic review and meta-analysis to provide a reliable estimate of the average point prevalence of FOG in PD, and we further investigated the study characteristics that might have influenced the estimate.

METHODS

We searched different databases to identify studies that report the prevalence of FOG in PD or include relevant raw data for further calculation. The last inclusion date was February 20, 2020. The modified Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool was used for the quality assessment, and articles that met the predefined criteria were included in the quantitative analysis.

RESULTS

Sixty-six studies were selected from 3392 references. A weighted prevalence of 50.6% in 9072 PD patients experienced FOG based on the special questionnaires (the FOG-Q and NFOG-Q), which was about twice as high as that assessed by the specific items of the clinical rating scales (UPDRS item2.14 and MDS-UPDRS item3.11) (23.2%) or simple clinical questions (25.4%). The weighted prevalence was 37.9% for early stage (≤ 5 years) and 64.6% for advanced stage (≥ 9 years). Moreover, a higher prevalence was calculated from the population-based studies than that in multicenter and single-center studies (47.3% vs. 33.5% and 37.1%, respectively).

CONCLUSION

The result from this systematic review confirms that FOG is very common in PD and its prevalence is usually underestimated in hospital settings. Importantly, a more accurate assessment of FOG in future clinical researches would involve the use of special FOG scale rather than a single item on a scale or a general clinical inquiry.

Comparing the Clinical and Neuropsychological Characteristics of Parkinson's Disease With and Without Freezing of Gait

Introduction

Freezing of gait (FOG) is one of the most common walking problems in Parkinson’s disease (PD). Impaired cognitive function is believed to play an important role in developing and aggravating FOG in PD. But some evidence suggests that motor function discrepancy may affect testing results. Therefore, we think it is necessary for PD-FOG(+) and PD-FOG(−) patients to complete neuropsychological tests under similar motor conditions.

Methods

This study recruited 44 idiopathic PD patients [PD-FOG(+) n = 22, PD-FOG(−) n = 22] and 20 age-matched healthy controls (HC). PD-FOG(+) and PD-FOG(−) patients were matched for age, year of education, and Hoehn and Yahr score (H&Y). All participants underwent a comprehensive battery of neuropsychological assessment, and demographical and clinical information was also collected.

Results

PD patients showed poorer cognitive function, higher risks of depression and anxiety, and more neuropsychiatric symptoms compared with HC. When controlling for age, years of education, and H&Y, there were no statistical differences in cognitive function between PD-FOG(+) and PD-FOG(−) patients. But PD-FOG(+) patients had worse motor and non-motor symptoms than PD-FOG(−) patients. PD patients whose motor symptoms initiated with rigidity and initiated unilaterally were more likely to experience FOG.

Conclusion

Traditional neuropsychological testing may not be sensitive enough to detect cognitive impairment in PD. Motor symptoms initiated with rigidity and initiated unilaterally might be an important predictor of FOG.

Validation of the German Version of the New Freezing of Gait Questionnaire for People with Parkinson's Disease

Freezing of gait (FOG) in Parkinson's disease (PD) is a highly disabling symptom which impacts quality of life. The New FOG Questionnaire (NFOG-Q) is the most commonly used tool worldwide to characterize FOG severity in PD. This study aims to provide a German translation of the NFOG-Q and to assess its validity in people with PD. The questionnaire was translated using forward-backward translation. Validity was tested in 57 PD patients with FOG via Cronbach's alpha for internal consistency and Spearman correlations with several clinical measures to quantify disease severity, mobility, fall risk, and cognitive state for convergent and divergent validity. The German version of the NFOG-Q shows good internal consistency (Cα = 0.84). Furthermore, the NFOG-Q score was significantly correlated with the MDS-UPDRS III, H&Y stage, Timed Up and Go test, and the subjective fear of falling (FES-I). The lack of correlation with cognition (MoCA) points towards good divergent validity. This study provides a German version of the NFOG-Q which proved to be valid for the assessment of FOG severity in individuals with PD.

Freezing of Gait in Parkinson's Disease: Risk Factors, Their Interactions, and Associated Nonmotor Symptoms

Background

Freezing of gait (FOG) is a debilitating and incompletely understood symptom in Parkinson's disease (PD).

Objective

To determine the principal clinical factors predisposing to FOG in PD, their interactions, and associated nonmotor symptoms.

Methods

164 PD subjects were assessed in a cross-sectional retrospective study, using the MDS-UPDRS scale, MMSE, and Clinical Dementia Rating Scale. Clinical factors associated with FOG were determined using univariate analysis and nominal logistic regression. Receiver operating characteristic curves were computed, to obtain measures of sensitivity and specificity of predictors of FOG. Subgroups of patients with FOG were compared with those without FOG, based on defining aspects of their clinical phenotype.

Results

Relative to non-FOG patients, those with FOG had a longer disease duration, higher PIGD and balance-gait score, higher LED, and more motor complications (p < 0.0001) and were more likely to exhibit urinary dysfunction (p < 0.0003), cognitive impairment, hallucinations, and psychosis (p=0.003). The balance-gait score and motor complications, at their optimum cutoff values, together predicted FOG with 86% accuracy. Interactions were noted between cognitive dysfunction and both the Bal-Gait score and motor complication status, cognitive impairment or dementia increasing the likelihood of FOG in subjects without motor complications (p=0.0009), but not in those with motor complications.

Conclusions

Both disease and treatment-related factors, notably LED, influence the risk of FOG in PD, with a selective influence of cognitive dysfunction in patients with balance-gait disorder but not in those with motor fluctuations. These findings may help to inform clinical management and highlight distinct subgroups of patients with PD-FOG, which are likely to differ in their network pathophysiology.

The Relationship of Rapid Eye Movement Sleep Behavior Disorder and Freezing of Gait in Parkinson's Disease

Rapid eye movement sleep behavior disorder (RBD) contributes to injury due to the alteration of the expected atonia during rapid eye movement (REM) sleep. It occurs before the overt signs of Parkinson's disease (PD). The co-expression of PD and RBD is characterized by non-tremor predominant subtype and higher incidence of freezing. Freezing of gait (FOG) is a debilitating symptom seen in PD patients that lead to falls. While this phenomenon is understood poorly, the involvement of the pedunculopontine nucleus (PPN) and the neural circuits that control locomotion and gait have been examined. This network has also the same control for REM sleep and arousal. The close relationship between PD and RBD and FOG's consequences has led us to explore the relationship between RBD and PD with FOG. This review provides an overview of the neural connections that control gait, locomotion, and REM sleep. The neural changes were seen in PD with FOG and RBD, and sensory and motor changes observed in these two diseases. The functional neuroanatomy that controls REM sleep, arousal, and locomotion overlap significantly with multiple neural circuits affected in RBD and PD with FOG. Visual perception dysfunction and motor symptoms that primarily affect gait initiation are common to both patients with RBD and FOG in PD, leading to freezing episodes. Prospective studies should be conducted to elucidate the relationship of RBD and PD with FOG subtype and find innovative treatment approaches and diagnostic tools for PD with FOG.

Freezing of gait: understanding the complexity of an enigmatic phenomenon

Diverse but complementary methodologies are required to uncover the complex determinants and pathophysiology of freezing of gait. To develop future therapeutic avenues, we need a deeper understanding of the disseminated functional-anatomic network and its temporally associated dynamic processes. In this targeted review, we will summarize the latest advances across multiple methodological domains including clinical phenomenology, neurogenetics, multimodal neuroimaging, neurophysiology, and neuromodulation. We found that (i) locomotor network vulnerability is established by structural damage, e.g. from neurodegeneration possibly as result from genetic variability, or to variable degree from brain lesions. This leads to an enhanced network susceptibility, where (ii) modulators can both increase or decrease the threshold to express freezing of gait. Consequent to a threshold decrease, (iii) neuronal integration failure of a multilevel brain network will occur and affect one or numerous nodes and projections of the multilevel network. Finally, (iv) an ultimate pathway might encounter failure of effective motor output and give rise to freezing of gait as clinical endpoint. In conclusion, we derive key questions from this review that challenge this pathophysiological view. We suggest that future research on these questions should lead to improved pathophysiological insight and enhanced therapeutic strategies.

Behavioural manifestations and associated non-motor features of freezing of gait: A narrative review and theoretical framework

Over the past decade, non-motor related symptoms and provocative contexts have offered unique opportunities to gain insight into the potential mechanisms that may underpin freezing of gait (FOG) in Parkinson's disease (PD). While this large body of work has informed several theoretical models, to date, few are capable of explaining behavioural findings across multiple domains (i.e. cognitive, sensory-perceptual and affective) and in different behavorial contexts. As such, the exact nature of these interrelationships and their neural basis remain quite enigmatic. Here, the non-motor, behavioural evidence for cognitive, sensory-perceptual and affective contributors to FOG are reviewed and synthesized by systematically examining (i) studies that manipulated contextual environments that provoke freezing of gait, (ii) studies that uncovered factors that have been proposed to contribute to freezing, and (iii) studies that longitudinally tracked factors that predict the future development of freezing of gait. After consolidating the evidence, we offer a novel perspective for integrating these multi-faceted behavioural patterns and identify key challenges that warrant consideration in future work.

Association Between Motor Subtype and Visuospatial and Executive Function in Mild-Moderate Parkinson Disease

OBJECTIVE

To compare participants with Parkinson disease (PD) motor subtypes, postural instability and gait difficulty (PIGD) (n=46) and tremor dominant (TD) (n=28), in cognitive and motor-cognitive assessments with the purpose of identifying associations between subtype and visuospatial, whole-body spatial, inhibition and/or switching, and planning and/or organizational aspects of cognitive and motor-cognitive function.

DESIGN

Retrospective cohort study. Fisher exact test was used for categorical variables, while 2-sample independent t tests were used to analyze continuous variables.

SETTING

Assessments took place at Emory University.

PARTICIPANTS

Participants (N=72) were 40 years and older, had a clinical diagnosis of PD, exhibited 3 of the 4 cardinal signs of PD, had shown benefit from antiparkinsonian medications, and were in Hoehn and Yahr stages I-IV. Participants could walk 3 m or more with or without assistance.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Balance and mobility tests included Fullerton Advanced Balance Scale and the time needed to turn 360 degrees. Cognitive assessments included Montreal Cognitive Assessment, Brooks Spatial Memory Task, Color-Word Interference Test, Tower of London, Trail Making Test, Corsi Blocks, Serial 3s Subtraction, and Body Position Spatial Task. Motor-cognitive function measures included Four Square Step Test and Timed Up and Go.

RESULTS

Participants with PIGD performed lower than those with TD symptoms on mental status (P=.005), spatial memory (P=.027), executive function (P=.0001-.034), and visuospatial ability (P=.048).

CONCLUSIONS

Findings suggest that PIGD subtype is linked to greater deficits in spatial cognition, attentional flexibility and organizational planning, and whole-body spatial memory domains. These findings support the need for more personalized approaches to clinically managing PD.

Cognitive function in people with and without freezing of gait in Parkinson's disease

Freezing of gait (FOG) is common in people with Parkinson’s disease (PD) which is extremely debilitating. One hypothesis for the cause of FOG episodes is impaired cognitive control, however, this is still in debate in the literature. We aimed to assess a comprehensive range of cognitive tests in older adults and people with Parkinson’s with and without FOG and associate FOG severity with cognitive performance. A total of 227 participants took part in the study which included 80 healthy older adults, 81 people with PD who did not have FOG and 66 people with PD and FOG. A comprehensive battery of neuropsychological assessments tested cognitive domains of global cognition, executive function/attention, working memory, and visuospatial function. The severity of FOG was assessed using the new FOG questionnaire and an objective FOG severity score. Cognitive performance was compared between groups using an ANCOVA adjusting for age, gender, years of education and disease severity. Correlations between cognitive performance and FOG severity were analyzed using partial correlations. Cognitive differences were observed between older adults and PD for domains of global cognition, executive function/attention, and working memory. Between those with and without FOG, there were differences for global cognition and executive function/attention, but these differences disappeared when adjusting for covariates. There were no associations between FOG severity and cognitive performance. This study identified no significant difference in cognition between those with and without FOG when adjusting for covariates, particularly disease severity. This may demonstrate that complex rehabilitation programs may be undertaken in those with FOG.

Diphasic Worsening of Freezing of Gait in Parkinson's Disease

Background

The relationship between freezing of gait (FOG) and levodopa response is complex. Some patients respond, some have no response and in some patients levodopa causes FOG. We present 2 cases demonstrating a diphasic worsening of FOG after levodopa dosing.

Cases

Two PD patients with FOG were examined during the practically defined off state, the transition from off to on (15 and 22 minutes postdose), and in the full on state (45 and 60 minutes postdose). FOG was measured using Movement Disorder Society-Unified Parkinson's Disease Rating Scale part III, item 11: freezing of gait. Both patients experienced worsening of FOG during the transition followed by improvement during the on state. Case 1 had serum levodopa levels measured. Videos are provided.

Conclusions

To our knowledge, this diphasic pattern of worsening of FOG has not been previously reported. The cause of this phenomenon is unknown but may relate to an inhibitory action of subthreshold levels of levodopa.

Freezing of Gait can persist after an acute levodopa challenge in Parkinson's disease

Study objectives included testing whether presumed levodopa-unresponsive freezing of gait (FOG) in Parkinson's disease (PD) actually persists in the presence of adequate dopaminergic dosing and to investigate whether the presence of other parkinsonian features and their responsiveness to therapy varies across patients without FOG (NO-FOG), with levodopa-responsive FOG (OFF-FOG), and with levodopa-unresponsive FOG (ONOFF-FOG). Fifty-five PD patients completed levodopa challenges after >12-h OFF with supratherapeutic doses of dopaminergic medications. Observed responses in FOG, measured with MDS-UPDRS-III during the patient reported full "ON", were used to classify them as NO-FOG, OFF-FOG, or ONOFF-FOG. Serum levodopa levels were measured. Only those with ≥20% improvement in MDS-UPDRS-III score were included in analyses. Levodopa challenge was sufficient to bring about a full "ON" state with ≥20% improvement in 45 patients. Levodopa-equivalent-dose utilized was 142 ± 56% of patients' typical morning doses. Overall, 19/45 patients exhibited FOG in the full "ON" state (ONOFF-FOG), 11 were classified as OFF-FOG, and 15 NO-FOG. Linear mixed models revealed a highly significant association between serum levodopa level and total MDS-UPDRS-III score that was similar across groups. The ONOFF-FOG group exhibited significantly higher New-FOG-questionnaire and MDS-UPDRS-II scores compared to the OFF-FOG group. Among MDS-UPDRS-III subdomains significant effects of group (highest in ONOFF-FOG) were identified for other axial parkinsonian features. We found that FOG can persist in the full "ON" state brought about by ample dopaminergic dosing in PD. Other axial measures can also be levodopa-unresponsive among those with ONOFF-FOG only. These data provide evidence that ONOFF-FOG is distinct from responsive freezing.

Changing views of the pathophysiology of Parkinsonism

Studies of the pathophysiology of parkinsonism (specifically akinesia and bradykinesia) have a long history and primarily model the consequences of dopamine loss in the basal ganglia on the function of the basal ganglia/thalamocortical circuit(s). Changes of firing rates of individual nodes within these circuits were originally considered central to parkinsonism. However, this view has now given way to the belief that changes in firing patterns within the basal ganglia and related nuclei are more important, including the emergence of burst discharges, greater synchrony of firing between neighboring neurons, oscillatory activity patterns, and the excessive coupling of oscillatory activities at different frequencies. Primarily focusing on studies obtained in nonhuman primates and human patients with Parkinson's disease, this review summarizes the current state of this field and highlights several emerging areas of research, including studies of the impact of the heterogeneity of external pallidal neurons on parkinsonism, the importance of extrastriatal dopamine loss, parkinsonism-associated synaptic and morphologic plasticity, and the potential role(s) of the cerebellum and brainstem in the motor dysfunction of Parkinson's disease. © 2019 International Parkinson and Movement Disorder Society.

Lower Limb Rigidity Is Associated with Frequent Falls in Parkinson's Disease

Background and Objective

The role of muscle rigidity as an etiological factor of falls in Parkinson's disease (PD) is poorly understood. Our objective was to determine whether lower leg rigidity was differentially associated with frequent falls in PD compared to upper limb, neck, and total rigidity measures.

Methods

We examined the associations between Unified Parkinson's Disease Rating Scale-Part III (motor) rigidity subscores and the history of monthly or more frequent falls in 216 individuals with PD (age, 66 ± 10 years; 36% female; disease duration, 7 ± 5 years) with logistic regression.

Results

A total of 35 individuals were frequent fallers. Significant associations were identified between lower limb rigidity and frequent falls (P = 0.01) after controlling for age, sex, PD duration, total Unified Parkinson's Disease Rating Scale- Part III score, and presence of freezing of gait. No significant associations (P ≥ 0.14) were identified for total, arm, or neck rigidity.

Conclusion

Lower limb rigidity is related to frequent falls in people with PD. Further investigation may be warranted into how parkinsonian rigidity could cause falls.

Wearable Sensors System for an Improved Analysis of Freezing of Gait in Parkinson's Disease Using Electromyography and Inertial Signals

We propose a wearable sensor system for automatic, continuous and ubiquitous analysis of Freezing of Gait (FOG), in patients affected by Parkinson’s disease. FOG is an unpredictable gait disorder with different clinical manifestations, as the trembling and the shuffling-like phenotypes, whose underlying pathophysiology is not fully understood yet. Typical trembling-like subtype features are lack of postural adaptation and abrupt trunk inclination, which in general can increase the fall probability. The targets of this work are detecting the FOG episodes, distinguishing the phenotype and analyzing the muscle activity during and outside FOG, toward a deeper insight in the disorder pathophysiology and the assessment of the fall risk associated to the FOG subtype. To this aim, gyroscopes and surface electromyography integrated in wearable devices sense simultaneously movements and action potentials of antagonist leg muscles. Dedicated algorithms allow the timely detection of the FOG episode and, for the first time, the automatic distinction of the FOG phenotypes, which can enable associating a fall risk to the subtype. Thanks to the possibility of detecting muscles contractions and stretching exactly during FOG, a deeper insight into the pathophysiological underpinnings of the different phenotypes can be achieved, which is an innovative approach with respect to the state of art.

Impaired set shifting is associated with previous falls in individuals with and without Parkinson's disease

BACKGROUND

Individuals with Parkinson's disease (PD) are at increased risk for falls, which lead to substantial morbidity and mortality. Understanding the motor and non-motor impairments associated with falls in PD is critical to informing prevention strategies. In addition to motor symptoms, individuals with PD exhibit non-motor deficits, including impaired set shifting, an aspect of executive function related to cognitive flexibility that can be measured quickly with the Trailmaking Test.

RESEARCH QUESTION

To determine whether impaired set shifting is associated with fall history in people with and without PD.

METHODS

We examined associations between set shifting, PD status, and fall history (≥1 falls in the previous 6 months) in data from PD patients (n = 65) with and without freezing of gait (FOG) and community-dwelling neurologically-normal older adults (NON-PD) (n = 73) who had participated in our rehabilitation studies.

RESULTS

Impaired set shifting was associated with previous falls after controlling for age, sex, overall cognitive function, PD status, FOG, and PD disease duration (OR = 1.29 [1.03-1.60]; P = 0.02). Consistent with literature, PD and FOG were also independently associated with increased fall prevalence (PD OR = 4.15 [95% CI 1.65-10.44], P < 0.01; FOG OR = 3.63 [1.22-10.80], P = 0.02). Although the strongest associations between set shifting and falling were observed among PD without FOG (OR = 2.11) compared to HOA (OR = 1.14) and PD with FOG (OR = 1.46), no statistically-significant differences were observed across groups.

SIGNIFICANCE

Impaired set shifting is associated with previous falls in older adults with and without PD. Set shifting may be useful to include in fall risk assessments, particularly when global cognitive measures are within reference limits.

Managing Gait, Balance, and Posture in Parkinson's Disease

PURPOSE OF REVIEW

Postural instability and gait difficulties inexorably worsen with Parkinson's disease (PD) progression and become treatment resistant, with a severe impact on autonomy and quality of life. We review the main characteristics of balance instability, gait disabilities, and static postural alterations in advanced PD, and the available treatment strategies.

RECENT FINDINGS

It remains very difficult to satisfactorily alleviate gait and postural disturbances in advanced PD. Medical and surgical interventions often fail to provide satisfactory or durable alleviation of these axial symptoms, that may actually call for differential treatments. Exercise and adapted physical activity programs can contribute to improving the patients' condition. Gait, balance, and postural disabilities are often lumped together under the Postural Instability and Gait Difficulties umbrella term. This may lead to sub-optimal patients' management as data suggest that postural, balance, and gait problems might depend on distinct underlying mechanisms. We advocate for a multidisciplinary approach from the day of diagnosis.

Intercepting Parkinson disease non-motor subtypes: A proof-of-principle study in a clinical setting

The construct of non-motor symptoms (NMS) subtyping in Parkinson Disease (PD) is emerging as a line of research in the light of its potential role in etiopathological interpretation of PD heterogeneity. Different approaches of NMS subtyping have been proposed: an anatomical model suggests that NMS aggregate according to the underpinning pathology; other researchers find aggregation of NMS according to the motor phenotype; the contribution of genetic background to NMS has also been assessed, primarily focusing on cognitive impairment. We have analyzed NMS burden assessed through an extensive clinical and neuropsychological battery in 137 consecutive non-demented PD patients genotyped for MAPT haplotypes (H1/H1 vs H2 carriers) in order to explore the applicability of the "anatomo-clinical", "motor" or "genetic" models for subtyping PD in a clinical setting; a subsequent independent analysis was conducted to verify a possible cluster distribution of NMS. No clear-cut NMS profiles according to the previously described models emerged: in our population, the autonomic dysfunctions and depressive symptoms represent the leading determinant of NMS clusters, which seems to better fit with the hypothesis of a "neurotransmitter-based" model. Selective preferential neurotransmitter network dysfunctions may account for heterogeneity of PD and could address translational research.

Predictors of freezing of gait in Chinese patients with Parkinson's disease

OBJECTIVE

To explore the clinical predictors of freezing of gait (FOG) in Chinese patients with Parkinson's disease (PD).

METHODS

This study included 225 patients with PD who completed a three-year follow-up visit. The end-point was the presence of FOG (freezers), which was assessed during the follow-up visit. Group comparisons were conducted, followed by a further forward binary logistic regression analysis.

RESULTS

Eighty-five patients with PD (38%) had developed FOG at the end of study. At baseline, freezers exhibited higher age, longer disease duration, higher scores in Unified PD Rating Scale (UPDRS) III and Hamilton Depression/Anxiety Rating Scale, lower Frontal Assessment Battery (FAB) score, higher subscores (e.g., "urgency") and frequencies (e.g., "hallucinations") in Non-Motor Symptoms Scale, higher annual changes in MoCA, UPDRS III and FAB scores, and higher incidences of festination and falls than nonfreezers (p < .05). The forward binary logistic regression model indicated that a longer disease duration, a higher UPDRS III score, higher annual changes in UPDRS III score and "visuospatial/executive abilities" subscore, onset in lower limbs, and the presence of festination, falls, and hallucinations were associated with the development of FOG.

CONCLUSIONS

Patients with onset in the lower limbs and the presence of festination, falls, and hallucinations may be prone to develop FOG episodes. FOG also likely occurs with the deterioration of PD severity and visuospatial function.

The role of neurotransmitters in the development of Parkinson's disease-related psychosis

Psychotic symptoms are common, disabling non-motor features of Parkinson's disease (PD). Despite noted heterogeneity in clinical features, natural history and therapy response, current dogma posits that psychosis generally progresses in a stereotypic manner through a cascade of events that begins with minor hallucinations and evolves to severe hallucinations and delusions. Further, the occurrence of psychotic symptoms is believed to indicate a poor prognosis. Here we propose a classification scheme that outlines the pathogenesis of psychosis as it relates to dysfunction of several neurotransmitter systems. We hypothesize that several subtypes exist, and that PD psychosis is not consistently indicative of a progressive cascade and poor prognosis. The literature was reviewed from 1990 to 2017. An overview of the features of PD psychosis is followed by a review of data indicating the existence of neurotransmitter-related subtypes of psychosis. We found that ample evidence exists to demonstrate the presence of multiple subtypes of PD psychosis, which are traced to dysfunction of the following neurotransmitter systems: dopamine, serotonin and acetylcholine. Dysfunction of each of these systems is recognizable through their clinical features and correlates, and the varied long-term prognoses. Identifying which neurotransmitter system is dysfunctional may help to develop targeted therapies. PD psychosis has various subtypes that differ in clinical features, underlying pathology and pathophysiology, treatment response and prognosis. A novel classification scheme is presented that describes the clinical subtypes with different outcomes, which could lead to the development of targeted therapies. Future research should focus on testing the viability of this classification.

Freezing of Gait in Parkinsonism and its Potential Drug Treatment

Freezing of gait (FOG) is a heterogeneous symptom. Studies of treatment for FOG are scarce. Levodopa and monoamine oxidase inhibitors (rasagiline and selegiline) have shown effective improvement for FOG. Other drugs, such as L-threo-3, 4-dihydroxyphenylserine, amantadine, and botulinum toxin have exhibited some beneficial effects. The present review summarizes the potential drug treatment for FOG in Parkinsonism.

A smartphone-based architecture to detect and quantify freezing of gait in Parkinson's disease

INTRODUCTION

The freezing of gait (FOG) is a common and highly distressing motor symptom in patients with Parkinson's Disease (PD). Effective management of FOG is difficult given its episodic nature, heterogeneous manifestation and limited responsiveness to drug treatment.

METHODS

In order to verify the acceptance of a smartphone-based architecture and its reliability at detecting FOG in real-time, we studied 20 patients suffering from PD-related FOG. They were asked to perform video-recorded Timed Up and Go (TUG) test with and without dual-tasks while wearing the smartphone. Video and accelerometer recordings were synchronized in order to assess the reliability of the FOG detection system as compared to the judgement of the clinicians assessing the videos. The architecture uses two different algorithms, one applying the Freezing and Energy Index (Moore-Bächlin Algorithm), and the other adding information about step cadence, to algorithm 1.

RESULTS

A total 98 FOG events were recognized by clinicians based on video recordings, while only 7 FOG events were missed by the application. Sensitivity and specificity were 70.1% and 84.1%, respectively, for the Moore-Bächlin Algorithm, rising to 87.57% and 94.97%, respectively, for algorithm 2 (McNemar value=28.42; p=0.0073).

CONCLUSION

Results confirm previous data on the reliability of Moore-Bächlin Algorithm, while indicating that the evolution of this architecture can identify FOG episodes with higher sensitivity and specificity. An acceptable, reliable and easy-to-implement FOG detection system can support a better quantification of the phenomenon and hence provide data useful to ascertain the efficacy of therapeutic approaches.

Patterns and predictors of freezing of gait improvement following rasagiline therapy: A pilot study

OBJECTIVES

Freezing of gait (FoG) is a challenging clinical symptom in Parkinson's disease with variable improvements in FoG with rasagiline. In this prospective, uncontrolled, pre-/post- treatment pilot study, we explore the clinical variables that contribute to this variability and those that predict improvement.

PATIENTS AND METHODS

Frequency and duration of FoG, along with other standardized scales, were evaluated in 18 optimally medicated PD participants with intractable FoG, prior to and after completion of a 90-day course of 1mg daily rasagiline. Gait tasks were video-recorded and analyzed by two independent reviewers. After evaluating the simple main effect, hierarchical cluster analysis was used to identify subgroups for treatment responsiveness. Bidirectional elimination stepwise regression analysis was conducted to identify which clinical variables predicted reduction in frequency of FoG events post-treatment.

RESULTS

There were no overall pre-/post- treatment improvements, a result driven by a heterogeneous response to treatment. Three subgroups were identified: improved (n=6) with a 136% and 162% reduction in FoG count and duration; worsened (n=5) with 154% and 141% increase in FoG count and duration; and no change (n=3). The final predictive model had good explanatory power (adjusted-R²=0.9898, p<0.01), explaining 99% of the variance between the improved and worsened groups. In this model, lower UPDRS gait scores, higher LEDD dose, lower anxiety scores, lower FOG-Q scores, and higher UPDRS scores for lower extremity rigidity and rise from chair, predicted FoG-related rasagiline benefit.

CONCLUSION

Using both objective and subjective measures for FoG, the current pilot study identified a set of clinical variables that may elucidate the heterogeneous FoG-responsiveness following rasagiline treatment and aid in predicting improvement.

Pathophysiology of Motor Dysfunction in Parkinson's Disease as the Rationale for Drug Treatment and Rehabilitation

Cardinal motor features of Parkinson's disease (PD) include bradykinesia, rest tremor, and rigidity, which appear in the early stages of the disease and largely depend on dopaminergic nigrostriatal denervation. Intermediate and advanced PD stages are characterized by motor fluctuations and dyskinesia, which depend on complex mechanisms secondary to severe nigrostriatal loss and to the problems related to oral levodopa absorption, and motor and nonmotor symptoms and signs that are secondary to marked dopaminergic loss and multisystem neurodegeneration with damage to nondopaminergic pathways. Nondopaminergic dysfunction results in motor problems, including posture, balance and gait disturbances, and fatigue, and nonmotor problems, encompassing depression, apathy, cognitive impairment, sleep disturbances, pain, and autonomic dysfunction. There are a number of symptomatic drugs for PD motor signs, but the pharmacological resources for nonmotor signs and symptoms are limited, and rehabilitation may contribute to their treatment. The present review will focus on classical notions and recent insights into the neuropathology, neuropharmacology, and neurophysiology of motor dysfunction of PD. These pieces of information represent the basis for the pharmacological, neurosurgical, and rehabilitative approaches to PD.

Freezing of gait in Parkinson's disease is associated with altered functional brain connectivity

BACKGROUND

Patients with Parkinson's disease (PD) may develop several gait disturbances during the course of illness and Freezing of gait (FOG) is one of them. Several neuroimaging studies have been conducted to identify the neural correlates of FOG but results have not been uniform. Resting state functional MRI (rs-fMRI) is relatively less explored in PD patients with FOG. This study aims to compare the whole brain resting state connectivity of PD patients with and without FOG using rs-fMRI.

METHODS

rs-fMRI was obtained for 28 PD patients (15 with and 13 patients without FOG) who were matched for various demographic and clinical characteristics. Seed to voxel analysis was performed at whole brain level and compared between the two groups.

RESULTS

When compared to patients without FOG, the patients with FOG had reduced functional connectivity across multiple seeds. Major finding was reduced inter-hemispheric connectivity of left parietal opercular cortex with multiple regions of the brain primarily involving the primary somatosensory and auditory areas, which also negatively correlated with the FOGQ scores.

CONCLUSION

Our findings suggest that alterations in the resting state functional connectivity of the opercular parietal cortex may be one of the substrates of FOG. Reduced interhemispheric connectivity probably is the reason for impairment of control and coordination in bilateral leg movements while walking.

Neuromechanical principles underlying movement modularity and their implications for rehabilitation

Neuromechanical principles define the properties and problems that shape neural solutions for movement. Although the theoretical and experimental evidence is debated, we present arguments for consistent structures in motor patterns, i.e., motor modules, that are neuromechanical solutions for movement particular to an individual and shaped by evolutionary, developmental, and learning processes. As a consequence, motor modules may be useful in assessing sensorimotor deficits specific to an individual and define targets for the rational development of novel rehabilitation therapies that enhance neural plasticity and sculpt motor recovery. We propose that motor module organization is disrupted and may be improved by therapy in spinal cord injury, stroke, and Parkinson's disease. Recent studies provide insights into the yet-unknown underlying neural mechanisms of motor modules, motor impairment, and motor learning and may lead to better understanding of the causal nature of modularity and its underlying neural substrates.