Predicting the onset of freezing of gait: A longitudinal study

Disease progression subtypes of Parkinson's disease based on milestone events

BACKGROUND

Parkinson's disease (PD) demonstrates considerable heterogeneity in the manifestation of clinical symptoms and disease progression. Recently, six clinical milestones have been proposed to evaluate disease severity in PD. However, the identification of PD progression subtypes based on these milestone events has not yet been performed.

METHODS

Latent class analysis (LCA) was employed to identify subtypes of PD progression based on the timing of the first occurrence of six milestones within a 6-year follow-up period in Parkinson's Progression Markers Initiative (PPMI) database.

RESULTS

The study cohort consisted of 354 early PD patients, of whom 42.9% experienced at least one milestone within six years. LCA identified two distinct subtypes of PD progression: slow progression (83%) and rapid progression (17%). The total number of milestones over six years was significantly higher in the rapid progression subtype compared to the slow progression subtype (median: 3.00 vs. 0.00, p < 0.001). At baseline, the rapid progression subtype, compared to the slow progression subtype, was characterized by an older age at onset and more severe motor and non-motor symptoms. On biomarkers, the rapid progression subtype demonstrated elevated CSF p-tau and serum NFL, but decreased mean striatal DAT uptake. Five clinical variables (age, SDMT score, MDS-UPDRS I score, MDS-UPDRS II + III scores, and RBD) were selected to construct the predictive model. The original predictive model achieved an AUC of 0.82. In internal validation using bootstrap resampling, the model achieved an AUC of 0.82, with a 95%CI ranging from 0.76 to 0.87. The model's performance was acceptable regarding both calibration and clinical utility.

CONCLUSION

Approximately 17% of early PD patients exhibited the rapid progression subtype, characterized by the occurrence of more and earlier-onset milestones. The nomogram predictive model, incorporating five baseline clinical variables (age, SDMT score, MDS-UPDRS I score, MDS-UPDRS II + III scores, RBD), serves as a valuable tool for prognostic counseling and patient selection in PD clinical trials.

Motivational and cognitive predictors of apathy after subthalamic nucleus stimulation in Parkinson's disease

Postoperative apathy is a frequent symptom in Parkinson's disease patients who have undergone bilateral deep brain stimulation of the subthalamic nucleus. Two main hypotheses for postoperative apathy have been suggested: (i) dopaminergic withdrawal syndrome relative to postoperative dopaminergic drug tapering; and (ii) direct effect of chronic stimulation of the subthalamic nucleus. The primary objective of our study was to describe preoperative and 1-year postoperative apathy in Parkinson's disease patients who underwent chronic bilateral deep brain stimulation of the subthalamic nucleus. We also aimed to identify factors associated with 1-year postoperative apathy considering: (i) preoperative clinical phenotype; (ii) dopaminergic drug management; and (iii) volume of tissue activated within the subthalamic nucleus and the surrounding structures. We investigated a prospective clinical cohort of 367 patients before and 1 year after chronic bilateral deep brain stimulation of the subthalamic nucleus. We assessed apathy using the Lille Apathy Rating Scale and carried out a systematic evaluation of motor, cognitive and behavioural signs. We modelled the volume of tissue activated in 161 patients using the Lead-DBS toolbox and analysed overlaps within motor, cognitive and limbic parts of the subthalamic nucleus. Of the 367 patients, 94 (25.6%) exhibited 1-year postoperative apathy: 67 (18.2%) with 'de novo apathy' and 27 (7.4%) with 'sustained apathy'. We observed disappearance of preoperative apathy in 22 (6.0%) patients, who were classified as having 'reversed apathy'. Lastly, 251 (68.4%) patients had neither preoperative nor postoperative apathy and were classified as having 'no apathy'. We identified preoperative apathy score [odds ratio (OR) 1.16; 95% confidence interval (CI) 1.10, 1.22; P < 0.001], preoperative episodic memory free recall score (OR 0.93; 95% CI 0.88, 0.97; P = 0.003) and 1-year postoperative motor responsiveness (OR 0.98; 95% CI 0.96, 0.99; P = 0.009) as the main factors associated with postoperative apathy. We showed that neither dopaminergic dose reduction nor subthalamic stimulation were associated with postoperative apathy. Patients with 'sustained apathy' had poorer preoperative fronto-striatal cognitive status and a higher preoperative action initiation apathy subscore. In these patients, apathy score and cognitive status worsened postoperatively despite significantly lower reduction in dopamine agonists (P = 0.023), suggesting cognitive dopa-resistant apathy. Patients with 'reversed apathy' benefited from the psychostimulant effect of chronic stimulation of the limbic part of the left subthalamic nucleus (P = 0.043), suggesting motivational apathy. Our results highlight the need for careful preoperative assessment of motivational and cognitive components of apathy as well as executive functions in order to better prevent or manage postoperative apathy.

Comparison of sleep characteristics between Parkinson's disease with and without freezing of gait: A systematic review

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a range of motor and non-motor symptoms. Among the motor complaints, freezing of gait (FOG) is a common and disabling phenomenon that episodically hinders patients' ability to produce efficient steps. Concurrently, sleep disorders are prevalent in PD and significantly impact the quality of life of affected individuals. Numerous studies have suggested a bidirectional relationship between FOG and sleep disorders. Therefore, our objective was to systematically review the literature and compare sleep outcomes in PD patients with FOG (PD + FOG) and those without FOG (PD-FOG). By conducting a comprehensive search of the PubMed and Web of Science databases, we identified 20 eligible studies for inclusion in our analysis. Our review revealed that compared to PD-FOG, PD + FOG patients exhibited more severe symptoms of rapid eye movement sleep behavior disorder in nine studies, increased daytime sleepiness in eight studies, decreased sleep quality in four studies, and more frequent and severe sleep disturbances in four studies. These findings indicate that PD + FOG patients generally experience worse sleep quality, higher levels of daytime sleepiness, and more disruptive sleep disturbances compared to those without FOG (PD-FOG). The association between sleep disturbances and FOG highlights the importance of evaluating and monitoring these symptoms in PD patients and open the possibility for future studies to assess the impact of managing sleep disturbances on the severity and occurrence of FOG, and vice versa.

Association of Family History and Polygenic Risk Score With Longitudinal Prognosis in Parkinson Disease

Background and Objectives

Evidence suggests that either family history or polygenic risk score (PRS) is associated with developing Parkinson disease (PD). However, little is known about the longitudinal prognosis of PD according to family history and higher PRS.

Methods

From the Parkinson's Progression Markers Initiative database, 395 patients with PD who followed up for more than 2 years were grouped into those with family history within first-degree, second-degree, and third-degree relatives (N = 127 [32.2%]) vs those without (N = 268 [67.8%]). The PRS of 386 patients was computed using whole-genome sequencing data. Longitudinal assessment of motor, cognition, and imaging based on dopaminergic degeneration was conducted during the regular follow-up period. Effects of family history, PRS, or both on longitudinal changes of cognition, motor severity, and nigrostriatal degeneration were tested using a linear mixed model. The risk of freezing of gait (FOG) according to family history was assessed using the Kaplan-Meier analysis and Cox regression models.

Results

During a median follow-up of 9.1 years, PD with positive family history showed a slower decline of caudate dopamine transporter uptake (β estimate of family history × time = 0.02, 95% CI = 0.002-0.036, p = 0.027). Family history of PD and higher PRS were independently associated with a slower decline of Montreal Cognitive Assessment (β estimate of family history × time = 0.12, 95% CI = 0.02-0.22, p = 0.017; β estimate of PRS × time = 0.09, 95% CI = 0.03-0.16, p = 0.006). In those 364 patients without FOG at baseline, PD with positive family history had a lower risk of FOG (hazard ratio of family history = 0.57, 95% CI = 0.38-0.84, p = 0.005).

Discussion

Having a family history of PD predicts slower progression of cognitive decline and caudate dopaminergic degeneration, and less FOG compared with those without a family history independent of PRS. Taken together, information on family history could be used as a proxy for the clinical heterogeneity of PD.

Trial Registration Information

The study was registered at clinicaltrials.gov (NCT01141023), and the enrollment began June 1, 2010.

A meta-analysis identifies factors predicting the future development of freezing of gait in Parkinson's disease

Freezing of gait (FOG) is a debilitating problem that is common among many, but not all, people with Parkinson's disease (PD). Numerous attempts have been made at treating FOG to reduce its negative impact on fall risk, functional independence, and health-related quality of life. However, optimal treatment remains elusive. Observational studies have recently investigated factors that differ among patients with PD who later develop FOG, compared to those who do not. With prediction and prevention in mind, we conducted a systematic review and meta-analysis of publications through 31.12.2022 to identify risk factors. Studies were included if they used a cohort design, included patients with PD without FOG at baseline, data on possible FOG predictors were measured at baseline, and incident FOG was assessed at follow-up. 1068 original papers were identified, 38 met a-priori criteria, and 35 studies were included in the meta-analysis (n = 8973; mean follow-up: 4.1 ± 2.7 years). Factors significantly associated with a risk of incident FOG included: higher age at onset of PD, greater severity of motor symptoms, depression, anxiety, poorer cognitive status, and use of levodopa and COMT inhibitors. Most results were robust in four subgroup analyses. These findings indicate that changes associated with FOG incidence can be detected in a subset of patients with PD, sometimes as long as 12 years before FOG manifests, supporting the possibility of predicting FOG incidence. Intriguingly, some of these factors may be modifiable, suggesting that steps can be taken to lower the risk and possibly even prevent the future development of FOG.

Prevention of Falls in Parkinson's Disease: Guidelines and Gaps

Background

People living with Parkinson's disease (PD) have a high risk for falls.

Objective

To examine gaps in falls prevention targeting people with PD as part of the Task Force on Global Guidelines for Falls in Older Adults.

Methods

A Delphi consensus process was used to identify specific recommendations for falls in PD. The current narrative review was conducted as educational background with a view to identifying gaps in fall prevention.

Results

A recent Cochrane review recommended exercises and structured physical activities for PD; however, the types of exercises and activities to recommend and PD subgroups likely to benefit require further consideration. Freezing of gait, reduced gait speed, and a prior history of falls are risk factors for falls in PD and should be incorporated in assessments to identify fall risk and target interventions. Multimodal and multi-domain fall prevention interventions may be beneficial. With advanced or complex PD, balance and strength training should be administered under supervision. Medications, particularly cholinesterase inhibitors, show promise for falls prevention. Identifying how to engage people with PD, their families, and health professionals in falls education and implementation remains a challenge. Barriers to the prevention of falls occur at individual, environmental, policy, and health system levels.

Conclusion

Effective mitigation of fall risk requires specific targeting and strategies to reduce this debilitating and common problem in PD. While exercise is recommended, the types and modalities of exercise and how to combine them as interventions for different PD subgroups (cognitive impairment, freezing, advanced disease) need further study.

Effects of Very Low- and High-Frequency Subthalamic Stimulation on Motor Cortical Oscillations During Rhythmic Lower-Limb Movements in Parkinson's Disease Patients

BACKGROUND

Standard high-frequency deep brain stimulation (HF-DBS) at the subthalamic nucleus (STN) is less effective for lower-limb motor dysfunctions in Parkinson's disease (PD) patients. However, the effects of very low frequency (VLF; 4 Hz)-DBS on lower-limb movement and motor cortical oscillations have not been compared.

OBJECTIVE

To compare the effects of VLF-DBS and HF-DBS at the STN on a lower-limb pedaling motor task and motor cortical oscillations in patients with PD and with and without freezing of gait (FOG).

METHODS

Thirteen PD patients with bilateral STN-DBS performed a cue-triggered lower-limb pedaling motor task with electroencephalography (EEG) in OFF-DBS, VLF-DBS (4 Hz), and HF-DBS (120-175 Hz) states. We performed spectral analysis on the preparatory signals and compared GO-cue-triggered theta and movement-related beta oscillations over motor cortical regions across DBS conditions in PD patients and subgroups (PDFOG-and PDFOG+).

RESULTS

Both VLF-DBS and HF-DBS decreased the linear speed of the pedaling task in PD, and HF-DBS decreased speed in both PDFOG-and PDFOG+. Preparatory theta and beta activities were increased with both stimulation frequencies. Both DBS frequencies increased motor cortical theta activity during pedaling movement in PD patients, but this increase was only observed in PDFOG + group. Beta activity was not significantly different from OFF-DBS at either frequency regardless of FOG status.

CONCLUSION

Results suggest that VL and HF DBS may induce similar effects on lower-limb kinematics by impairing movement speed and modulating motor cortical oscillations in the lower frequency band.

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.

Modulating arousal to overcome gait impairments in Parkinson's disease: how the noradrenergic system may act as a double-edged sword

In stressful or anxiety-provoking situations, most people with Parkinson's disease (PD) experience a general worsening of motor symptoms, including their gait impairments. However, a proportion of patients actually report benefits from experiencing-or even purposely inducing-stressful or high-arousal situations. Using data from a large-scale international survey study among 4324 people with PD and gait impairments within the online Fox Insight (USA) and ParkinsonNEXT (NL) cohorts, we demonstrate that individuals with PD deploy an array of mental state alteration strategies to cope with their gait impairment. Crucially, these strategies differ along an axis of arousal-some act to heighten, whereas others diminish, overall sympathetic tone. Together, our observations suggest that arousal may act as a double-edged sword for gait control in PD. We propose a theoretical, neurobiological framework to explain why heightened arousal can have detrimental effects on the occurrence and severity of gait impairments in some individuals, while alleviating them in others. Specifically, we postulate that this seemingly contradictory phenomenon is explained by the inherent features of the ascending arousal system: namely, that arousal is related to task performance by an inverted u-shaped curve (the so-called Yerkes and Dodson relationship). We propose that the noradrenergic locus coeruleus plays an important role in modulating PD symptom severity and expression, by regulating arousal and by mediating network-level functional integration across the brain. The ability of the locus coeruleus to facilitate dynamic 'cross-talk' between distinct, otherwise largely segregated brain regions may facilitate the necessary cerebral compensation for gait impairments in PD. In the presence of suboptimal arousal, compensatory networks may be too segregated to allow for adequate compensation. Conversely, with supraoptimal arousal, increased cross-talk between competing inputs of these complementary networks may emerge and become dysfunctional. Because the locus coeruleus degenerates with disease progression, finetuning of this delicate balance becomes increasingly difficult, heightening the need for mental strategies to self-modulate arousal and facilitate shifting from a sub- or supraoptimal state of arousal to improve gait performance. Recognition of this underlying mechanism emphasises the importance of PD-specific rehabilitation strategies to alleviate gait disability.

White matter hyperintensities burden in the frontal regions is positively correlated to the freezing of gait in Parkinson's disease

Objective

Previous studies have reported that white matter hyperintensities (WMHs) are associated with freezing of gait (FOG), but it is not clear whether their distribution areas have correlations with FOG in Parkinson's disease (PD) and the potential influencing factors about WMHs.

Methods

Two hundred and forty-six patients with PD who underwent brain MRI were included. Participants were divided into PD with FOG (n = 111) and PD without FOG (n = 135) groups. Scheltens score was used to assess the WMHs burden in the areas of deep white matter hyperintensities (DWMHs), periventricular hyperintensities (PVHs), basal ganglia hyperintensities (BGHs), and infratentorial foci of hyperintensities (ITF). Whole brain WMHs volume was evaluated by automatic segmentation. Binary logistic regression was used to evaluate relationships between WMHs and FOG. The common cerebrovascular risk factors that may affect WMHs were evaluated by mediation analysis.

Results

There were no statistical differences between PD with and without FOG groups in whole brain WMHs volume, total Scheltens score, BGHs, and ITF. Binary logistic regression showed that the total scores of DWMHs (OR = 1.094; 95% CI, 1.001, 1.195; p = 0.047), sum scores of PVHs and DWMHs (OR = 1.080; 95% CI, 1.003, 1.164; p = 0.042), especially the DWMHs in frontal (OR = 1.263; 95% CI, 1.060, 1.505 p = 0.009), and PVHs in frontal caps (OR = 2.699; 95% CI, 1.337, 5.450; p = 0.006) were associated with FOG. Age, hypertension, and serum alkaline phosphatase (ALP) are positively correlated with scores of DWMHs in frontal and PVHs in frontal caps.

Conclusion

These results indicate that WMHs distribution areas especially in the frontal of DWMHs and PVHs play a role in PD patients with FOG.

Gait Declines Differentially in, and Improves Prediction of, People with Parkinson's Disease Converting to a Freezing of Gait Phenotype

BACKGROUND

Freezing of gait (FOG) is a debilitating, variably expressed motor symptom in people with Parkinson's disease (PwPD) with limited treatments.

OBJECTIVE

To determine if the rate of progression in spatiotemporal gait parameters in people converting from a noFOG to a FOG phenotype (FOGConv) was faster than non-convertors, and determine if gait parameters can help predict this conversion.

METHODS

PwPD were objectively monitored longitudinally, approximately every 6 months. Non-motor assessments were performed at the initial visit. Steady-state gait in the levodopa ON-state was collected using a gait mat (Protokinetics) at each visit. The rate of progression in 8 spatiotemporal gait parameters was calculated. FOG convertors (FOGConv) were classified if they did not have FOG at initial visit and developed FOG at a subsequent visit.

RESULTS

Thirty freezers (FOG) and 30 non-freezers were monitored an average of 3.5 years, with 10 non-freezers developing FOG (FOGConv). FOGConv and FOG had faster decline in mean stride-length, swing-phase-percent, and increase in mean total-double-support percent, coefficient of variability (CV) foot-strike-length and CV swing-phase-percent than the remaining non-freezers (noFOG). On univariate modeling, progression rates of mean stride-length, stride-velocity, swing-phase-percent, total-double-support-percent and of CV swing-phase-percent had high discriminative power (AUC > 0.83) for classification of the FOGConv and noFOG groups.

CONCLUSION

FOGConv had a faster temporal decline in objectively quantified gait than noFOG, and progression rates of spatiotemporal gait parameters were more predictive of FOG phenotype conversion than initial (static) parameters Objectively monitoring gait in disease prediction models may help define FOG prone groups for testing putative treatments.

Association of Depression With Early Occurrence of Postural Instability in Parkinson's Disease

OBJECTIVE

Depression in Parkinson's disease (PD) affects the quality of life of patients. Postural instability and gait disturbance are associated with the severity and prognosis of PD. We investigated the association of depression with axial involvement in early-stage PD patients.

METHODS

This study involved 95 PD patients unexposed to antiparkinsonian drugs. After a baseline assessment for depression, the subjects were divided into a depressed PD group and a nondepressed PD group. Analyses were conducted to identify an association of depression at baseline with the following outcome variables: the progression to Hoehn and Yahr scale (H-Y) stage 3, the occurrence of freezing of gait (FOG), levodopa-induced dyskinesia, and wearing-off. The follow-up period was 53.40 ± 16.79 months from baseline.

RESULTS

Kaplan-Meier survival curves for H-Y stage 3 and FOG showed more prominent progression to H-Y stage 3 and occurrences of FOG in the depressed PD group than in the nondepressed PD group (log-rank p = 0.025 and 0.003, respectively). Depression in drug-naïve, early-stage PD patients showed a significant association with the progression to H-Y stage 3 (hazard ratio = 2.55; 95% confidence interval = 1.32-4.93; p = 0.005), as analyzed by Cox regression analyses. In contrast, the occurrence of levodopa-induced dyskinesia and wearing-off did not differ between the two groups (log-rank p = 0.903 and 0.351, respectively).

CONCLUSION

Depression in drug-naïve, early-stage PD patients is associated with an earlier occurrence of postural instability. This suggests shared nondopaminergic pathogenic mechanisms and potentially enables the prediction of early development of postural instability.

The dilemma between milestones of progression versus clinical scales in Parkinson's disease

There are significant challenges in accurately documenting the progression of Parkinson's disease (PD). The disease course is highly heterogeneous, there are no validated biomarkers, and we are reliant on repeated clinical measures to assess disease state over time. Yet, the ability to chart disease progression accurately is vital in both observational and interventional study designs, where reliable measures are critical to determine whether an outcome has been met. In this chapter, we first discuss the natural history of PD, including the spectrum of clinical presentation and expected developments through the course of the disease. We then explore in detail the current strategies for measuring disease progression, which can be broadly divided into: (i) the use of quantitative clinical scales; and (ii) determination of the onset time of key milestones. We discuss the strengths and limitations of these approaches for use in clinical trials, with a particular focus on disease modification trials. The selection of outcome measures for a particular study will depend on multiple factors, but trial duration is an important determinant. Milestones are reached over a course of years rather than months, and hence clinical scales with sensitivity to change are needed for short-term studies. However, milestones represent important markers of disease stage which are not confounded by symptomatic therapies and are of critical relevance to the patient. Prolonged but low intensity follow-up beyond a limited period of treatment with a putative disease-modifying agent may allow milestones to be incorporated into evaluation of efficacy in a practical and cost-effective way.

MRI biomarkers of freezing of gait development in Parkinson’s disease

This study investigated longitudinal clinical, structural and functional brain alterations in Parkinson’s disease patients with freezing of gait (PD-FoG) and in those developing (PD-FoG-converters) and not developing FoG (PD-non-converters) over two years. Moreover, this study explored if any clinical and/or MRI metric predicts FoG development. Thirty PD-FoG, 11 PD-FoG-converters and 11 PD-non-converters were followed for two years. Thirty healthy controls were included at baseline. Participants underwent clinical and MRI visits. Cortical thickness, basal ganglia volumes and functional network graph metrics were evaluated at baseline and over time. In PD groups, correlations between baseline MRI and clinical worsening were tested. A ROC curve analysis investigated if baseline clinical and MRI measures, selected using a stepwise model procedure, could differentiate PD-FoG-converters from PD-non-converters. At baseline, PD-FoG patients had widespread cortical/subcortical atrophy, while PD-FoG-converters and non-converters showed atrophy in sensorimotor areas and basal ganglia relative to controls. Over time, PD-non-converters accumulated cortical thinning of left temporal pole and pallidum without significant clinical changes. PD-FoG-converters showed worsening of disease severity, executive functions, and mood together with an accumulation of occipital atrophy, similarly to PD-FoG. At baseline, PD-FoG-converters relative to controls and PD-FoG showed higher global and parietal clustering coefficient and global local efficiency. Over time, PD-FoG-converters showed reduced parietal clustering coefficient and sensorimotor local efficiency, PD-non-converters showed increased sensorimotor path length, while PD-FoG patients showed stable graph metrics. Stepwise prediction model including dyskinesia, postural instability and gait disorders scores and parietal clustering coefficient was the best predictor of FoG conversion. Combining clinical and MRI data, ROC curves provided the highest classification power to predict the conversion (AUC = 0.95, 95%CI: 0.86–1). Structural MRI is a useful tool to monitor PD progression, while functional MRI together with clinical features may be helpful to identify FoG conversion early.

Associated factors and abnormal dorsal raphe nucleus connectivity patterns of freezing of gait in Parkinson's disease

BACKGROUND

Freezing of gait (FOG) is a common, disabling symptom of Parkinson's disease (PD), and its exact pathophysiological mechanism is still poorly understood. The control of gait is a complex process that may be influenced by emotions modulated by serotonergic networks. Therefore, this study aimed to determine factors associated with FOG in PD patients and to evaluate the importance of the dorsal raphe nucleus (DRN; central node in the serotoninergic system) in FOG pathophysiology.

METHODS

We combined cross-sectional survey data from 453 PD patients. According to the Freezing of Gait Questionnaire (FOGQ), patients were divided into two groups: the "PD with frozen gait (PD-FOG)" and "PD without frozen gait (PD-nFOG)" groups. Demographic characteristics, clinical features, and motor and nonmotor symptoms (NMS) assessments of PD patients were recorded. Univariate statistical analysis was performed between the two groups, and then regression analysis was performed on related factors. We also acquired resting-state functional MRI (rs-fMRI) data from 20 PD-FOG, 21 PD-nFOG, and 22 healthy controls (HCs) who were randomly chosen. We defined seeds in the DRN to evaluate functional connectivity (FC) patterns.

RESULTS

The overall frequency of FOG was 11.9% patients in the PD-FOG group were older, had a longer disease duration, had a higher levodopa equivalent daily dose, had more severe motor symptoms and worse quality of life, had a higher proportion of dyskinesia, wearing-off and postural instability/gait difficulty (PIGD) clinical phenotype, and experienced more depression and impaired sleep function than those in the PD-nFOG group. Logistic regression analysis showed that H&Ystage ≥ 3, UPDRS-III scores, PIGD clinical phenotype and excessive daytime sleepiness were associated with FOG. In addition, there was significantly lower FC between the DRN and some cortical structures, including the supplementary motor area (SMA), left superior frontal gyrus (SFG), and left median cingulated cortex (MCC) in PD-FOG patients than HCs and PD-nFOG patients.

CONCLUSIONS

These results demonstrate that the severity of PD and PIGD clinical phenotype are associated factors for freezing and that DRN dysfunction may play a key role in PD-related NMS and FOG. An abnormal cortical and brainstem networks may contribute to the mechanisms underlying FOG.

Clinical Features of Parkinson’s Disease in Patients with Early-Onset Freezing of Gait

Background. Freezing of gait (FOG) is an important symptom that can impair activities of daily living in patients with Parkinson’s disease (PD). However, its pathogenic mechanism is largely unknown. The aim of the present study was to elucidate the clinical characteristics of newly diagnosed and levodopa-naïve patients with PD who present with FOG. Methods. A total of 53 patients with untreated PD (29 men and 24 women) within 2 years of disease onset were included in the study. Using item 3 of the Freezing of Gait Questionnaire (FOG-Q), patients were classified as “freezers” and “nonfreezers” and compared for cognitive function, depressive symptoms, apathy, olfactory function, motor severity, gait parameters, and daily physical activity. We also assessed the relationship between FOG severity (total score of items 3–6 on the FOG-Q) and various clinical parameters. Results. The FOG was reported by 8 (15%) patients with PD. The Apathy Scale score ( $p=0.018$ ), Modified Hoehn and Yahr stage ( $p<0.001$ ), Unified Parkinson’s Disease Rating Scale part III score ( $p<0.001$ ), and postural instability and gait disorder score ( $p<0.001$ ) were significantly higher, and the mean gait acceleration amplitude ( $p=0.006$ ) was significantly lower in freezers compared to that in nonfreezers. However, there was no significant correlation between FOG severity and these clinical parameters. There was also no significant difference in cognitive function, depressive symptoms, and olfactory function between the two groups. Daily physical activity was significantly lower in freezers than that in nonfreezers. Conclusions. Since FOG develops soon after PD onset, the study findings suggest that the FOG might be associated with the severity of apathy, motor symptoms, and in particular, gait disturbance.

Predicting the onset of freezing of gait in Parkinson's disease

BACKGROUND

Freezing of gait is a debilitating symptom of Parkinson's disease associated with high risks of falls and poor quality of life. While productive therapy for FoG is still underway, early prediction of FoG could help high-risk PD patients to take preventive measures. In this study, we predicted the onset of FoG in de novo PD patients using a battery of risk factors from patients enrolled in PPMI cohort.

METHODS

Baseline characteristics were compared between subjects who developed FoG (68 patients, 37.2%, pre-FoG group) during the five-year follow up and subjects who did not (115 patients, 62.8%, non-FoG group). A multivariate logistic regression model was built based on backward stepwise selection of factors that were associated with FoG onset in the univariate analysis. ROC curves were used to assess sensitivity and specificity of the predictive model.

RESULTS

At baseline, age, PIGD score, cognitive functions, autonomic functions, sleep behavior, fatigue and striatal DAT uptake were significantly different in the pre-FoG group relative to the non-FoG group. However, there was no difference in genetic characteristics between the two patient sets. Univariate analysis showed several motor and non-motor factors that correlated with FoG, including PIGD score, MDS-UPDRS part II score, SDMT score, HVLT Immediate/Total Recall, MOCA, Epworth Sleepiness Scale, fatigue, SCOPA-AUT gastrointestinal score, SCOPA-AUT urinary score and CSF biomarker Abeta42. Multivariate logistic analysis stressed that high PIGD score, fatigue, worse SDMT performance and low levels of Abeta42 were independent risk factors for FoG onset in PD patients.

CONCLUSIONS

Combining motor and non-motor features including PIGD score, poor cognitive functions and CSF Abeta can identify PD patients with high risk of FoG onset.

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.

Development and validation of a nomogram for freezing of gait in patients with Parkinson's Disease

OBJECTIVES

Freezing of gait (FOG) is a common and complex disabling episodic gait disturbance in patients with Parkinson's disease (PD). Currently, the treatment of FOG remains a challenge for clinicians. The aim of our study was to develop a nomogram for FOG risk based on data collected from Chinese patients with PD.

MATERIALS & METHODS

A total of 379 PD patients (197 with FOG) from Kunming Medical University were recruited as a training cohort. Additionally, 339 PD patients (166 with FOG) were recruited from West China Hospital of Sichuan University, to serve as the validation cohort. The least absolute shrinkage and selection operator regression model was used to select clinical and demographic characteristics as well as blood markers, which were incorporated into a predictive model using multivariate logistic regression to predict the risk of developing FOG. The model was validated using the validation dataset, and model performance was evaluated using the C-index, calibration plot, and decision curve analyses.

RESULTS

The final predictive model included the REM Sleep Behavior Disorder Screening Questionnaire (RBDSQ) score, Parkinson's Disease Questionnaire (PDQ39), H-Y stage, and visuospatial function. The model showed good calibration and good discrimination, with a C-index value of 0.772 against the training cohort and 0.766 against the validation cohort. Decision curve analysis demonstrated the clinical utility of the nomogram.

CONCLUSION

A nomogram incorporating RBDSQ, PDQ39, H-Y stage, and visuospatial function may reliably predict the risk of FOG in PD patients.

The correlation between genetic factors and freezing of gait in patients with Parkinson's disease

BACKGROUND

Clinical-related risk factors to freezing of gait (FOG) in Parkinson's disease (PD) have been identified. Still, the influence of genetic variations on the FOG occurrence has been poorly studied thus far.

AIM

We aimed to evaluate the association of six selected polymorphisms of DRD2, ANKK1, and COMT genes with the FOG occurrence and explore the influence of ANNK1/DRD2 haplotypes on the onset of FOG in the group of PD patients.

METHOD

PD patients (n = 234), treated with levodopa for at least two years, were genotyped for the rs4680 in COMT, rs6277, rs1076560, and rs2283265 in DRD2, and rs1800497 and rs2734849 polymorphisms in ANKK1 genes. FOG was evaluated by posing a direct question. In addition, a comprehensive set of clinical scales was applied to all patients.

RESULTS

FOG occurred in 132 (56.4%) PD patients in our cohort. Freezers were younger at PD onset, had longer disease duration, used higher levodopa daily doses and dopaminergic agents, and had higher motor and non-motor scales scores than non-freezers. FOG was more frequent among AA rs4680 COMT carriers than AG and GG rs4680 COMT carriers. Independent predictors of FOG were: disease duration of more than ten years, levodopa daily dose higher than 500 mg/day, motor status, and COMT AA genotype. AGGAA and GGAAA haplotypes were revealed as protective and vulnerability factors for FOG occurrence.

CONCLUSION

In addition to previously identified disease- and therapy-related risk factors, our results suggested a possible contribution of dopamine-related genes to the FOG occurrence.

Stepping up to meet the challenge of freezing of gait in Parkinson's disease

There has been a growing appreciation for freezing of gait as a disabling symptom that causes a significant burden in Parkinson’s disease. Previous research has highlighted some of the key components that underlie the phenomenon, but these reductionist approaches have yet to lead to a paradigm shift resulting in the development of novel treatment strategies. Addressing this issue will require greater integration of multi-modal data with complex computational modeling, but there are a number of critical aspects that need to be considered before embarking on such an approach. This paper highlights where the field needs to address current gaps and shortcomings including the standardization of definitions and measurement, phenomenology and pathophysiology, as well as considering what available data exist and how future studies should be constructed to achieve the greatest potential to better understand and treat this devastating symptom.

Longitudinal Prediction of Freezing of Gait in Parkinson's Disease: A Prospective Cohort Study

Objective: Freezing of gait (FOG) is a disabling complication in Parkinson's disease (PD). Yet, studies on a validated model for the onset of FOG based on longitudinal observation are absent. This study aims to develop a risk prediction model to predict the probability of future onset of FOG from a multicenter cohort of Chinese patients with PD.

Methods: A total of 350 patients with PD without FOG were prospectively monitored for ~2 years. Demographic and clinical data were investigated. The multivariable logistic regression analysis was conducted to develop a risk prediction model for FOG.

Results: Overall, FOG was observed in 132 patients (37.70%) during the study period. At baseline, longer disease duration [odds ratio (OR) = 1.214, p = 0.008], higher total levodopa equivalent daily dose (LEDD) (OR = 1.440, p < 0.001), and higher severity of depressive symptoms (OR = 1.907, p = 0.028) were the strongest predictors of future onset of FOG in the final multivariable model. The model performed well in the development dataset (with a C-statistic = 0.820, 95% CI: 0.771–0.865), showed acceptable discrimination and calibration in internal validation, and remained stable in 5-fold cross-validation.

Conclusion: A new prediction model that quantifies the risk of future onset of FOG has been developed. It is based on clinical variables that are readily available in clinical practice and could serve as a small tool for risk counseling.

Constructing Prediction Models for Freezing of Gait by Nomogram and Machine Learning: A Longitudinal Study

Objectives: Although risk factors for freezing of gait (FOG) have been reported, there are still few prediction models based on cohorts that predict FOG. This 1-year longitudinal study was aimed to identify the clinical measurements closely linked with FOG in Chinese patients with Parkinson's disease (PD) and construct prediction models based on those clinical measurements using Cox regression and machine learning. Methods: The study enrolled 967 PD patients without FOG in the Hoehn and Yahr (H&Y) stage 1-3 at baseline. The development of FOG during follow-up was the end-point. Neurologists trained in movement disorders collected information from the patients on a PD medication regimen and their clinical characteristics. The cohort was assessed on the same clinical scales, and the baseline characteristics were recorded and compared. After the patients were divided into the training set and test set by the stratified random sampling method, prediction models were constructed using Cox regression and random forests (RF). Results: At the end of the study, 26.4% (255/967) of the patients suffered from FOG. Patients with FOG had significantly longer disease duration, greater age at baseline and H&Y stage, lower proportion in Tremor Dominant (TD) subtype, a higher proportion in wearing-off, levodopa equivalent daily dosage (LEDD), usage of L-Dopa and catechol-O-methyltransferase (COMT) inhibitors, a higher score in scales of Unified Parkinson's Disease Rate Scale (UPDRS), 39-item Parkinson's Disease Questionnaire (PDQ-39), Non-Motor Symptoms Scale (NMSS), Hamilton Depression Rating Scale (HDRS)-17, Parkinson's Fatigue Scale (PFS), rapid eye movement sleep behavior disorder questionnaire-Hong Kong (RBDQ-HK), Epworth Sleepiness Scale (ESS), and a lower score in scales of Parkinson's Disease Sleep Scale (PDSS) (P < 0.05). The risk factors associated with FOG included PD onset not being under the age of 50 years, a lower degree of tremor symptom, impaired activities of daily living (ADL), UPDRS item 30 posture instability, unexplained weight loss, and a higher degree of fatigue. The concordance index (C-index) was 0.68 for the training set (for internal validation) and 0.71 for the test set (for external validation) of the nomogram prediction model, which showed a good predictive ability for patients in different survival times. The RF model also performed well, the C-index was 0.74 for the test set, and the AUC was 0.74. Conclusions: The study found some new risk factors associated with the FOG including a lower degree of tremor symptom, unexplained weight loss, and a higher degree of fatigue through a longitudinal study, and constructed relatively acceptable prediction models.

Protocol for the DeFOG trial: A randomized controlled trial on the effects of smartphone-based, on-demand cueing for freezing of gait in Parkinson's disease

Background

Freezing of gait (FOG) is a highly incapacitating symptom that affects many people with Parkinson's disease (PD). Cueing triggered upon real-time FOG detection (on-demand cueing) shows promise for FOG treatment. Yet, the feasibility of implementation and efficacy in daily life is still unknown. Therefore, this study aims to investigate the effectiveness of DeFOG: a smartphone and sensor-based on-demand cueing solution for FOG.

Methods

Sixty-two PD patients with FOG will be recruited for this single-blind, multi-center, randomized controlled phase II trial. Patients will be randomized into either the intervention group or the active control group. For four weeks, both groups will receive feedback about their physical activity using the wearable DeFOG system in daily life. In addition, the intervention group will also receive on-demand auditory cueing and instructions. Before and after the intervention, home-based assessments will be performed to evaluate the primary outcome, i.e., “percentage time frozen” during a FOG-provoking protocol. Secondary outcomes include the training effects on physical activity monitored over 7 days and the user-friendliness of the technology.

Discussion

The DeFOG trial will investigate the effectiveness of personalized on-demand cueing in a controlled design, delivered for 4 weeks in the patient's home environment. We anticipate that DeFOG will reduce FOG to a greater degree than in the control group and we will explore the impact of the intervention on physical activity levels. We expect to gain in-depth insight into whether and how patients control FOG using cueing methods in their daily lives.

Trial registration

Clinicaltrials.gov NCT03978507.

Future Therapeutic Strategies for Freezing of Gait in Parkinson's Disease

Freezing of gait (FOG) is a common and challenging clinical symptom in Parkinson’s disease. In this review, we summarise the recent insights into freezing of gait and highlight the strategies that should be considered to improve future treatment. There is a need to develop individualised and on-demand therapies, through improved detection and wearable technologies. Whilst there already exist a number of pharmacological (e.g., dopaminergic and beyond dopamine), non-pharmacological (physiotherapy and cueing, cognitive training, and non-invasive brain stimulation) and surgical approaches to freezing (i.e., dual-site deep brain stimulation, closed-loop programming), an integrated collaborative approach to future research in this complex area will be necessary to systematically investigate new therapeutic avenues. A review of the literature suggests standardising how gait freezing is measured, enriching patient cohorts for preventative studies, and harnessing the power of existing data, could help lead to more effective treatments for freezing of gait and offer relief to many patients.

Clinical features and related factors of freezing of gait in patients with Parkinson's disease

BACKGROUND

Freezing of gait (FOG) is a disabling paroxysmal gait disorder that prevents starting or resuming walking, which seriously negatively affects patients' quality of life (QOL). The diagnosis and treatment of FOG remain a huge medical challenge. The purpose of this study was to explore the clinical characteristics and related factors of FOG in patients with Parkinson's disease (PD).

METHODS

The motor and nonmotor symptoms of a total number of 77 PD patients were evaluated. Patients with or without FOG were defined as a score ≥1 in the new freezing of gait questionnaire (NFOG-Q). A comparative study between patients with and without FOG was conducted.

RESULTS

In this investigation, the prevalence of FOG was 48%. The patients with FOG had longer disease duration, higher Hoehn-Yahr stage (H-Y stage), higher dose of dopaminergic agents, and higher nonmotor and motor symptom scores. A significant positive correlation was found between the NFOG-Q score and the H-Y stage, PIGD subscore, PDQ-39, and the attention/memory in the nonmotor symptoms assessment scale (NMSS) subitem (r > 0.5, p < .05). The binary logistic regression analysis showed that the higher H-Y stage, higher rigidity subscore and Unified Parkinson's Disease Rating Scale II (UPDRS II) score, and UPDRS III score were significantly correlated with the occurrence of FOG (p < .05). In the analysis of the frequency of FOG, the prevalence of FOG in H-Y stage was higher in the middle and late stages, and the prevalence of FOG increased with the increase in PDQ-39 scores.

CONCLUSION

The severity of FOG was significantly positively correlated with the H-Y stage, PIGD subscore, PDQ-39 score, and attention/memory score. Based on our findings, we conclude that the clinical characteristics of rigidity can be used as a potential predictor of FOG.

Dream Content Predicts Motor and Cognitive Decline in Parkinson's Disease

Background

Dream content alterations in Parkinson's disease (PD) are associated with motor and cognitive dysfunction cross-sectionally. Although recent studies suggest abnormal dream content in PD might also predict cognitive decline, the relationship between dream content and motor decline in PD remains unknown.

Objective

To investigate whether abnormal dream content in PD predicts both motor and cognitive decline.

Methods

Data were obtained from the Parkinson's Progression Markers Initiative cohort study. Patients were evaluated at baseline and at the 60-month follow-up, with validated clinical scales, including the REM Sleep Behavior Disorder Screening Questionnaire (RBDSQ), Montreal Cognitive Assessment (MoCA), and the Movement Disorder Society-Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS III). Patients were dichotomized using RBDSQ item 2, which inquires whether they frequently experience aggression in their dreams. Regression analyses were used to assess whether frequent aggressive dreams at baseline predicted longitudinal changes in MDS-UPDRS III and MoCA scores as well as progression to Hoehn and Yahr stage 3 (H&Y ≥ 3) and cognitive impairment.

Results

Of the patients, 58/224 (25.9%) reported frequent aggressive dreams at baseline. Aggressive dreams predicted a faster increase in MDS-UPDRS III scores (β = 4.64; P = 0.007) and a faster decrease in MoCA scores (β = -1.49; P = 0.001). Furthermore, they conferred a 6-fold and 2-fold risk for progressing to H&Y ≥ 3 (odds ratio [OR] = 5.82; P = 0.005) and cognitive impairment (OR, 2.35; P = 0.023) within 60 months. These associations remained robust when adjusting for potential confounders.

Conclusions

This study demonstrates for the first time that frequent aggressive dreams in newly diagnosed PD may independently predict early motor and cognitive decline.

Brain network topology and future development of freezing of gait in Parkinson's disease: a longitudinal study

BACKGROUND

Freezing of gait (FOG) is a common disabling gait disturbance in Parkinson's disease (PD). The objectives of this study were to explore alterations in the topological organization of whole-brain functional networks in patients with PD who will develop FOG.

METHODS

We recruited 20 patients with PD who developed FOG (PD-FOGt) during a 5-year follow-up period, 20 patients with PD who did not developed FOG (PD-FOGn) within the follow-up period, and 20 healthy control subjects. Using graph theory approaches, we performed a comparative analysis of the topological organization of whole-brain functional networks among the groups, and further explored their potential relationships with latency to develop FOG.

RESULTS

At baseline, the global topological properties of functional brain networks in PD-FOGt and PD-FOGn showed no abnormalities. Additionally, regarding regional topological properties, compared with PD-FOGn patients, PD-FOGt patients exhibited decreased nodal centrality in the left middle frontal gyrus (MFG). Although there were no significant differences compared with PD-FOGn patients, the PD-FOGt group exhibited the lowest nodal centrality values in the frontal cortex (left gyrus rectus), and visual cortex (bilateral inferior occipital gyrus and left fusiform gyrus), and the highest nodal centrality values in the cerebellum (vermis_6) among the three groups. However, no relationship was found between the nodal centrality in above brain regions and latency to develop FOG.

CONCLUSION

This study demonstrates the disrupted regional topological organization might contribute to the future development of FOG in PD patients, especially associated with damage to the left MFG.

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.

Neuropsychiatric Burden Is a Predictor of Early Freezing and Motor Progression in Drug-Naïve Parkinson's Disease

BACKGROUND

Neuropsychiatric symptoms (NPS) are the most common non-motor symptom in Parkinson's disease (PD).

OBJECTIVE

To investigate the association between the burden of NPS and motor prognosis in patients with PD.

METHODS

We enrolled 329 drug-naïve patients with PD, who was non-demented and followed-up≥2 years after their first visit to the clinic with baseline dopamine transporter (DAT) imaging and neuropsychiatric inventory (NPI) scores. We performed a survival analysis and a linear mixed model analysis to assess longitudinal motor outcomes according to the NPI total score.

RESULTS

The Kaplan-Meier analysis showed no difference in the development of levodopa-induced dyskinesia and wearing-off according to the NPI total score. However, higher burden of NPI total score was associated with earlier freezing of gait (FOG) development in the time-dependent Cox regression models after adjusting for age at symptom onset, sex, disease duration, Unified PD Rating Scale motor score, baseline Mini-Mental State Examination score, DAT activity in the posterior putamen and levodopa-equivalent daily dose (LEDD) (Hazard ratio 1.047, p = 0.002). A linear mixed model analysis revealed that patients with a higher NPI total score had a more rapid LEDD increment (NPI×time, p = 0.003). Among 52 patients with PD who eventually developed FOG during the follow-up period, there was a significant correlation between the NPI total score and time with FOG development (γ= -0.472; p = 0.001) after adjusting for confounding factors.

CONCLUSION

The present study demonstrated that the severity of NPS is a predictor of early freezing and motor progression in patients with PD.

Antisaccade, a predictive marker for freezing of gait in Parkinson's disease and gait/gaze network connectivity

Freezing of gait is a challenging sign of Parkinson's disease associated with disease severity and progression and involving the mesencephalic locomotor region. No predictive factor of freezing has been reported so far. The primary objective of this study was to identify predictors of freezing occurrence at 5 years. In addition, we tested whether functional connectivity of the mesencephalic locomotor region could explain the oculomotor factors at baseline that were predictive of freezing onset. We performed a prospective study investigating markers (parkinsonian signs, cognitive status and oculomotor recordings, with a particular focus on the antisaccade latencies) of disease progression at baseline and at 5 years. We identified two groups of patients defined by the onset of freezing at 5 years of follow-up; the 'Freezer' group was defined by the onset of freezing in the ON medication condition during follow-up (n = 17), while the 'non-Freezer' group did not (n = 8). Whole brain resting-state functional MRI was recorded at baseline to determine how antisaccade latencies were associated with connectivity of the mesencephalic locomotor region networks in patients compared to 25 age-matched healthy volunteers. Results showed that, at baseline and compared to the non-Freezer group, the Freezer group had equivalent motor or cognitive signs, but increased antisaccade latencies (P = 0.008). The 5-year course of freezing of gait was correlated with worsening antisaccade latencies (P = 0.0007). Baseline antisaccade latencies was also predictive of the freezing onset (χ2 = 0.008). Resting state connectivity of mesencephalic locomotor region networks correlated with (i) antisaccade latency differently in patients and healthy volunteers at baseline; and (ii) the further increase of antisaccade latency at 5 years. We concluded that antisaccade latency is a predictive marker of the 5-year onset of freezing of gait. Our study suggests that functional networks associated with gait and gaze control are concurrently altered during the course of the disease.

Prevalence and Clinical Features of FOG in Chinese PD Patients, a Multicenter and Cross-Sectional Clinical Study

Objectives: Freezing of gait (FOG) is generally considered as an independent symptom of Parkinson's disease (PD) with a complex pathophysiology. There is a wide range of associated clinical features of FOG reported from different studies without consistent conclusion. Thus, a multicenter, cross-sectional study was designed to investigate the prevalence and clinical features of FOG together with its unique contribution quality of life in Chinese PD patients.

Methods: Eight hundred and thirty eight PD patients were consecutively recruited into this study from 12 hospital centers in six provinces in China. Clinical information, including motor and neuropsychological features as well as pharmacological details, was collected.

Results: Of 827 PD patients, 245 (29.63%) reported FOG. The prevalence of FOG was strongly correlated with modified H-Y stages and symptomatic duration (p < 0.01). 84.90% freezers experienced FOG during turning and 88.98% experienced when initiating the first step. Compared with non-freezers, freezers reported longer disease duration (7.73 ± 5.44 vs. 4.69 ± 3.94, p < 0.000), higher frequent PIGD phenotype (61.22 vs. 35.91%, p < 0.000), higher scores of UPDRS III (32.85 ± 15.47 vs. 22.38 ± 12.89, p < 0.000), HAMA (10.99 ± 7.41 vs. 7.59 ± 6.47, p < 0.000), HAMD (15.29 ± 10.29 vs. 10.58 ± 8.97, p < 0.000) and lower MMSE score (25.12 ± 5.27 vs. 26.63 ± 3.97, p < 0.000), and higher daily levodopa dosage (432.65 ± 264.31 vs. 319.19 ± 229.15, p < 0.000) with less frequent initial use of dopaminergic agonist (8.57 vs. 14.78%, p < 0.05). Using binary logistic regression, the associated factors of FOG might be non-tremor dominant onset (OR = 3.817, p < 0.000), the presence of anxiety (OR = 2.048, p < 0.000) and imbalance (OR = 4.320, p = 0.012). Freezers had poorer quality of life than non-freezers and FOG impacted PDQ-8 independently.

Conclusion: Nearly one third of the PD patients experienced FOG. Its frequency increased with PD progression and FOG reduced independently the quality of life. Non-tremor dominant, disease progression, and anxiety were risk factors of FOG.

The Relationship Between Anxiety Disorders and Parkinson's Disease: Clinical and Therapeutic Issues

PURPOSE OF REVIEW

This paper seeks to describe anxiety's different symptomatologic presentations in Parkinson's disease (PD), its longitudinal course and predictors, as well as its motor and non-motor correlates. It also reviews the available screening tools and different treatment modalities.

RECENT FINDINGS

In PD, longitudinal predictors of anxiety are mostly non-motor non-dopaminergic symptoms. The longitudinal course of anxiety is mainly a stable one. The Parkinson Anxiety Scale and the Geriatric Anxiety Scale are the 2 recommended screening tools. A third of PD patients suffer from an anxiety disorder at any time point. It can precede or follow PD motor symptoms. Anxiety is associated with demographic, disease-related motor and non-motor features. There is a lack of studies evaluating psychotropic treatment of anxiety in PD. Adjustment of dopaminergic treatment is indicated when anxiety is associated with motor fluctuations. DBS can be useful as well as CBT and body-mind interventions.

Thalamic morphology predicts the onset of freezing of gait in Parkinson's disease

The onset of freezing of gait (FOG) in Parkinson's disease (PD) is a critical milestone, marked by a higher risk of falls and reduced quality of life. FOG is associated with alterations in subcortical neural circuits, yet no study has assessed whether subcortical morphology can predict the onset of clinical FOG. In this prospective multimodal neuroimaging cohort study, we performed vertex-based analysis of grey matter morphology in fifty-seven individuals with PD at study entry and two years later. We also explored the behavioral correlates and resting-state functional connectivity related to these local volume differences. At study entry, we found that freezers (N = 12) and persons who developed FOG during the course of the study (converters) (N = 9) showed local inflations in bilateral thalamus in contrast to persons who did not (non-converters) (N = 36). Longitudinally, converters (N = 7) also showed local inflation in the left thalamus, as compared to non-converters (N = 36). A model including sex, daily levodopa equivalent dose, and local thalamic inflation predicted conversion with good accuracy (AUC: 0.87, sensitivity: 88.9%, specificity: 77.8%). Exploratory analyses showed that local thalamic inflations were associated with larger medial thalamic sub-nuclei volumes and better cognitive performance. Resting-state analyses further revealed that converters had stronger thalamo-cortical coupling with limbic and cognitive regions pre-conversion, with a marked reduction in coupling over the two years. Finally, validation using the PPMI cohort suggested FOG-specific non-linear evolution of thalamic local volume. These findings provide markers of, and deeper insights into conversion to FOG, which may foster earlier intervention and better mobility for persons with PD.

Poor sleep quality is associated with cognitive, mobility, and anxiety disability that underlie freezing of gait in Parkinson's disease

BACKGROUND

Individuals with Parkinson's disease (PD) who report freezing of gait (FOG) have poorer sleep quality than those without FOG. Cognitive, anxiety, and mobility disability are components of the FOG phenotype, however, no study has investigated if poor sleep quality is associated with all three components that underlie FOG in PD.

RESEARCH QUESTION

Are there associations among sleep quality and all three components of the FOG phenotype?

METHODS

Forty and 39 individuals with and without FOG (PD + FOG and PD-FOG), respectively, and 31 age-matched healthy controls (HC) participated in this study. Self-reported FOG (new-FOG questionnaire-NFOGQ), sleep quality (Pittsburgh Sleep Quality Index-PSQI), cognitive function (Montreal Cognitive Assessment-MoCA), anxiety (subscale from Hospital Anxiety and Depression Scale-HADS-A), and mobility (timed-up-and-go test-TUG) were assessed.

RESULTS AND SIGNIFICANCE

PSQI scores were correlated with the scores of NFOGQ, MoCA, HADS-A, and TUG time in PD + FOG (P ≤ 0.0038). The multiple regression analysis identified the PSQI scores as the only predictor of the variance of the NFOGQ scores (R² = 0.46, P < .0001). The variance in the PSQI scores were explained (69 %) by MoCA scores, NFOGQ scores, TUG time, and HADS-A scores (P ≤ 0.05). Although PD + FOG had a higher disease severity compared to PD-FOG (P < 0.001), disease severity did not enter in the regression model to explain PSQI scores and NFOGQ scores. We also observed associations of PSQI scores with the MoCA scores and TUG time for HC (P ≤ 0.0038), whereas there was no association between PSQI scores and any variable in PD-FOG (P > 0.05). Finally, PD + FOG presented worse scores of PSQI, MoCA, HADS-A, and TUG time than PD-FOG and HC (P < 0.05). Thus, poor sleep quality is associated with FOG and all three components that underlie FOG, regardless of the disease severity. Therefore, treatments useful to decrease FOG should be targeted to ameliorate sleep quality, cognition, anxiety, and mobility.

Association of freezing of gait and clinical features in patients with Parkinson's disease

Freezing of gait (FOG) is a disabling symptom that affects the quality of life of patients with Parkinson's disease (PD) and its pathophysiology is not fully understood yet. The aim of the present study is to evaluate the relationship between FOG and other clinical characteristics in patients with PD. The clinical characteristics, modified Hoehn and Yahr (mHY) stages, Unified Parkinson's Disease Rating Scale (UPDRS) scores, and total Freezing of Gait Questionnaire (FOG-Q) scores of the patients with PD were recorded. FOG-Q item 1.3 was used to evaluate patients with or without FOG. A total of 65 patients with PD (32 with FOG and 33 without FOG) were included to the study. Disease duration was longer, mHY stages were higher, bradykinesia and dyskinesia were more common in patients with FOG compared to patients without (p = 0.001, p = 0.036, p = 0.019 and p = 0.021; respectively). Patients with FOG had lower UPDRS part III tremor subscores (p = 0.020), although gait, postural balance subscores and part IV motor fluctuations scores were higher (p = 0.003, p = 0.023 and p < 0.001; respectively). A positive correlation was found between FOG-Q scores and mHY stages (p < 0.001), UPDRS part II and III total scores (p = 0.020 and p = 0.001) and part III bradykinesia, and gait and postural balance subscores (p = 0.003, p = 0.036 and p = 0.003, respectively), and part IV motor fluctuation scores (p = 0.006). The results of the present study point to an association between FOG and bradykinesia rather than tremor, prolonged disease duration and advanced disease stage reflecting its association with more severe and extensive neurodegenerative processes.

Hypomimia in Parkinson's Disease: What Is It Telling Us?

Introduction: Amimia is one of the most typical features of Parkinson's disease (PD). However, its significance and correlation with motor and nonmotor symptoms is unknown. The aim of this study is to evaluate the association between amimia and motor and nonmotor symptoms, including cognitive status, depression, and quality of life in PD patients. We also tested the blink rate as a potential tool for objectively measuring upper facial bradykinesia. Methods: We prospectively studied amimia in PD patients. Clinical evaluation was performed using the Unified Parkinson's Disease Rating Scale (UPDRS) and timed tests. Cognitive status, depression, and quality of life were assessed using the Parkinson's Disease Cognitive Rating Scale (PD-CRS), the 16-Item Quick Inventory of Depressive Symptomatology (QIDS-SR16), and the PDQ-39, respectively. Amimia was clinically evaluated according to item 19 of UPDRS III. Finally, we studied upper facial amimia by measuring resting blink frequency and blink rate during spontaneous conversation. Results: We included 75 patients. Amimia (item 19 UPDRS III) correlated with motor and total UPDRS (r: 0.529 and 0.551 Spearman), and its rigidity, distal bradykinesia, and motor axial subscores (r: 0.472; r: 0.252, and r: 0.508, respectively); Hoehn and Yahr scale (r: 0.392), timed tests, gait freezing, cognitive status (r: 0.29), and quality of life (r: 0.268) correlated with amimia. Blinking frequency correlated with amimia (measured with item 19 UPDRS), motor and total UPDRS. Conclusion: Amimia correlates with motor (especially axial symptoms) and cognitive situations in PD. Amimia could be a useful global marker of overall disease severity, including cognitive decline.

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.

Current Perspectives on the Assessment and Management of Gait Disorders in Parkinson's Disease

Gait dysfunction is a key defining feature of Parkinson's disease (PD), and is associated with symptoms of freezing and an increased risk of falls. In this narrative review, we cover the putative mechanisms of gait dysfunction in PD, the assessment of gait abnormalities, and the management of symptoms caused by the inherent difficulty in walking. Our understanding of the causes of gait problems in PD has progressed in recent times, moving from neurocognitive theory to correlates of affected neuronal pathways. In particular, this can be shown to correspond with abnormalities in responses to dual-task paradigms and dysfunction in cholinergic signaling. Great progress has been made in the sophistication and precision of gait assessment; however, it has firmly remained in the research domain. There is significant momentum behind wearable technologies that can be used by patients in their own environment, acting as digital biomarkers that can not only reflect progression but also independently discriminate PD from non-PD individuals. The treatment of gait dysfunction has historically relied on physical therapies and training combined with a view to mitigating the impact of such consequences as falls. Pharmacological therapies that are the mainstay of treatment in PD have tended to address symptoms like bradykinesia; however, optimization of dopaminergic therapies likely has a positive effect on quality of gait. Other targets have been assessed with the goal of improving gait, of which medications that improve cholinergic signaling appear most promising. Neuromodulation techniques are increasingly used in the form of deep-brain stimulation; however, standard targets, such as the globus pallidus interna, have a modest effect on gait. Considerable benefit has been seen through targeting the pedunculopontine nucleus, and a dual-target approach may be warranted. Stimulation of the spinal cord and brain through direct or magnetic approaches has been assessed, but requires further evidence.

Instrumental Assessment of Stepping in Place Captures Clinically Relevant Motor Symptoms of Parkinson's Disease

Fluctuations of motor symptoms make clinical assessment in Parkinson's disease a complex task. New technologies aim to quantify motor symptoms, and their remote application holds potential for a closer monitoring of treatment effects. The focus of this study was to explore the potential of a stepping in place task using RGB-Depth (RGBD) camera technology to assess motor symptoms of people with Parkinson's disease. In total, 25 persons performed a 40 s stepping in place task in front of a single RGBD camera (Kinect for Xbox One) in up to two different therapeutic states. Eight kinematic parameters were derived from knee movements to describe features of hypokinesia, asymmetry, and arrhythmicity of stepping. To explore their potential clinical utility, these parameters were analyzed for their Spearman's Rho rank correlation to clinical ratings, and for intraindividual changes between treatment conditions using standard response mean and paired t-test. Test performance not only differed between ON and OFF treatment conditions, but showed moderate correlations to clinical ratings, specifically ratings of postural instability (pull test). Furthermore, the test elicited freezing in some subjects. Results suggest that this single standardized motor task is a promising candidate to assess an array of relevant motor symptoms of Parkinson's disease. The simple technical test setup would allow future use by patients themselves.

The Adapted Resistance Training with Instability Randomized Controlled Trial for Gait Automaticity

BACKGROUND

Deficits in the cerebellar locomotor region (CLR) have been associated with loss of gait automaticity in individuals with freezing of gait in Parkinson's disease (freezers); however, exercise interventions that restore gait automaticity in freezers are lacking. We evaluated the effects of the adapted resistance training with instability ([ARTI] complex exercises) compared with traditional motor rehabilitation (without complex exercises) on gait automaticity and attentional set-shifting. We also verified associations between gait automaticity change and CLR activation change previously published.

METHODS

Freezers were randomized either to the experimental group (ARTI, n = 17) or to the active control group (traditional motor rehabilitation, n = 15). Both training groups performed exercises 3 times a week for 12 weeks. Gait automaticity (dual-task and dual-task cost [DTC] on gait speed and stride length), single-task gait speed and stride length, attentional set-shifting (time between Trail Making Test parts B and A), and CLR activation during a functional magnetic resonance imaging protocol of simulated step initiation task were evaluated before and after interventions.

RESULTS

Both training groups improved gait parameters in single task (P < 0.05), but ARTI was more effective than traditional motor rehabilitation in improving DTC on gait speed, DTC on stride length, dual-task stride length, and CLR activation (P < 0.05). Changes in CLR activation were associated with changes in DTC on stride length (r = 0.68, P = 0.002) following ARTI. Only ARTI improved attentional set-shifting at posttraining (P < 0.05).

CONCLUSIONS

ARTI restores gait automaticity and improves attentional set-shifting in freezers attributed to the usage of exercises with high motor complexity. © 2020 International Parkinson and Movement Disorder Society.

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.

Clinical and Oculomotor Correlates With Freezing of Gait in a Chinese Cohort of Parkinson's Disease Patients

Accumulating evidence suggests that freezing of gait (FOG) is a unique gait disturbance in Parkinson’s disease (PD), and its pathophysiology is not fully elucidated. The present study aims to investigate the clinical and oculomotor associations with FOG in Chinese PD patients. From Jan 2017 to Dec 2019, a total of 210 PD patients were consecutively registered for FOG evaluation based on item-3 of the Freezing of Gait Questionnaire (FOGQ). We explored the demographic, motor, and non-motor symptom differences in FOG positive (PD+FOG, n = 45) vs. negative (PD-FOG, n = 165) group. In addition, 40 PD patients and 37 healthy controls (HC) also underwent oculomotor test via videonystagmography (VNG). Visually guided saccade (VGS) latency, saccade accuracy and gain in smooth pursuit eye movement (SPEM) at three frequencies of horizontal axis were compared among PD+FOG (n = 20), PD-FOG (n = 20), and HC (n = 37). Compared with PD-FOG, PD+FOG had longer disease duration, more severe motor symptoms, lower cognitive scores, more severe depressive and autonomic impairments, as well as higher daily levodopa equivalent dosage. FOG occurred more frequently in patients with wearing-off. VNG subgroup analysis demonstrated that PD+FOG had prolonged saccade latency and decreased saccade accuracy relative to PD-FOG or HC. SPEM gain at 0.1 and 0.2 Hz was also decreased in PD+FOG compared with HC. Furthermore, prolonged saccade latency was correlated with higher FOGQ scores in PD patients. Our results verify that PD with FOG patients suffer from more severe motor and non-motor symptoms, indicating more extensive neurodegeneration. Prolonged saccade latency could be a practical oculomotor parameter both for identification and progression of FOG in PD.

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.

The prevalence of freezing of gait in Parkinson's disease and in patients with different disease durations and severities

Background

The prevalence rates of freezing of gait (FOG) in Parkinson’s disease (PD) vary widely, ranging from 14.0 to 55.1%. Our aim is to calculate the overall prevalence of FOG in all PD patients with different disease durations and severities.

Methods

Using Medline/PubMed/Embase, we carried out a systematic literature search for studies reporting the PD and clinically relevant FOG.

Results

After primary screening, a total of 35 studies were identified and further analyzed for inclusion into the analysis, and 29 studies fulfilled the quality criteria and included in this meta-analysis. The overall prevalence of FOG in PD was 39.9% (95% CI 35.3-44.5%). The FOG identified by the freezing of gait questionnaire item 3 may be more prevalent (43.8%, 95% CI 38.5-49.1%) than the FOG identified by the Unified Parkinson’s Disease Rating Scale item 14 (36.0%, 95% CI 29.0-43.1%). Disease duration and severity are both the clinical features associated with the FOG. The highest FOG prevalence rate in PD patients was seen in patients with disease durations ≥ 10 years, at 70.8%, followed that of PD patients with disease durations ≥ 5 years (53.3%), and PD patients with disease durations < 5 years (22.4%). FOG presented in 28.4% of PD patients with Hoehn and Yahr staging (H&Y) score ≤ 2.5, and in 68.4% of PD patients with H&Y score ≥ 2.5.

Conclusion

This meta-analysis confirms that the prevalence of FOG in PD is considerable, and highlights the need for accurate identification of FOG in PD.

Freezing of gait in Parkinson's disease: pathophysiology, risk factors and treatments

Background

Freezing of gait (FOG) is a common, disabling symptom of Parkinson's disease (PD), but the mechanisms and treatments of FOG remain great challenges for clinicians and researchers. The main focus of this review is to summarize the possible mechanisms underlying FOG, the risk factors for screening and predicting the onset of FOG, and the clinical trials involving various therapeutic strategies. In addition, the limitations and recommendations for future research design are also discussed.

Main body

In the mechanism section, we briefly introduced the physiological process of gait control and hypotheses about the mechanism of FOG. In the risk factor section, gait disorders, PIGD phenotype, lower striatal DAT uptake were found to be independent risk factors of FOG with consistent evidence. In the treatment section, we summarized the clinical trials of pharmacological and non-pharmacological treatments. Despite the limited effectiveness of current medications for FOG, especially levodopa resistant FOG, there were some drugs that showed promise such as istradefylline and rasagiline. Non-pharmacological treatments encompass invasive brain and spinal cord stimulation, noninvasive repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) and vagus nerve stimulation (VNS), and physiotherapeutic approaches including cues and other training strategies. Several novel therapeutic strategies seem to be effective, such as rTMS over supplementary motor area (SMA), dual-site DBS, spinal cord stimulation (SCS) and VNS. Of physiotherapy, wearable cueing devices seem to be generally effective and promising.

Conclusion

FOG model hypotheses are helpful for better understanding and characterizing FOG and they provide clues for further research exploration. Several risk factors of FOG have been identified, but need combinatorial optimization for predicting FOG more precisely. Although firm conclusions cannot be drawn on therapeutic efficacy, the literature suggested that some therapeutic strategies showed promise.

Repetitive Motor Control Deficits Most Consistent Predictors of Conversion to Freezing of Gait in Parkinson's Disease: A Prospective Cohort Study

BACKGROUND

The onset of freezing of gait (FOG) represents a turning point in the lives of patients with Parkinson's disease (PD). FOG increases fall risk and is associated with worse physical and mental health related quality of life, thus increasing disease burden. Moreover, therapeutic studies aiming to ameliorate freezing have had limited success. In a step towards pre-emptive therapy to delay or prevent the onset of FOG, this prospective cohort study set out to uncover clinical markers of conversion to FOG.

OBJECTIVE

Investigate clinical markers of conversion to FOG.

METHODS

Sixty PD patients without FOG were followed up for two years and underwent extensive clinical testing each year. FOG classification was made with the New Freezing of Gait Questionnaire. Clinical predictors of conversion to FOG were investigated using univariate analysis and through building a multivariable model using all measured components.

RESULTS

Twelve patients developed FOG during the study (Incidence: 11.5% per year). Due to the large number of predictors, univariate analyses did not survive multiple comparison correction, precluding strong inference on any one predictor. Overall, the effect sizes suggested that motor deficits including difficulties with repetitive movement scaling (AUC: 0.71), coordination (AUC: 0.73) and consistency (AUC: 0.76) as well as gait asymmetry (AUC: 0.79) and variability (AUC: 0.71) were most predictive of conversion. Further, converters reported more subjective cognitive difficulty (AUC: 0.74), although their measured performance was similar to non-converters. Multivariable analyses further showed that the two components most consistently selected in the predictive model were: 1) an MDS-UPDRS component with worse axial motor, hand use and non-motor symptoms; and 2) finger tapping abnormalities.

CONCLUSION

Conversion to FOG was predicted mainly by objective and clinical measures of motor dyscontrol, as non-motor disturbances were surfacing. Although based on a small cohort with limited converters, this novel finding informs future studies aimed at FOG prevention.