Motor asymmetry over time in Parkinson’s disease

Clinical asymmetry in Parkinson's disease is characterized by prevalence of subthalamic pause-burst neurons and alpha-beta oscillations

OBJECTIVE

We aimed to establish specific biomarkers of Parkinson's disease (PD) by comparing activity of more affected (MA) and less affected (LA) subthalamic nucleus (STN) of patients with prominent clinical asymmetry.

METHODS

We recorded single unit activity and local field potentials (LFP) of the STN during deep brain stimulation surgeries. Neuronal firing patterns and discharge rate, as well as oscillatory features of both single cells and LFP, were analyzed.

RESULTS

We observed notable differences in proportions of irregular-burst and pause-burst, but not tonic neurons, between the hemispheres. Oscillations of pause-burst neurons correlated significantly with the bradykinesia and rigidity scores of the corresponding hemibody. LFP derived from MA STN featured greater power in 12-15 Hz.

CONCLUSIONS

Our results provide evidence that the increased proportion of units with prolonged pauses may be associated with PD. We also speculate that some of them may gain rhythmicity in the alpha-beta range in relation to hypokinetic symptoms, long-term disease, or both.

SIGNIFICANCE

Our findings highlight the relation between specific oscillatory features of the STN, predominance of subthalamic pause-burst units and PD pathophysiology.

Lower-Limb Exoskeletons for Gait Training in Parkinson's Disease: The State of the Art and Future Perspectives

Gait dysfunction (GD) is a common impairment of Parkinson's disease (PD), which negatively impacts patients' quality of life. Among the most recent rehabilitation technologies, a lower-limb powered exoskeleton (LLEXO) arises as a useful instrument for gait training in several neurological conditions, including PD. However, some questions relating to methods of use, achievable results, and usefulness compared to traditional rehabilitation methodologies still require clear answers. Therefore, in this review, we aim to summarise and analyse all the studies that have applied an LLEXO to train gait in PD patients. Literature research on PubMed and Scopus retrieved five articles, comprising 46 PD participants stable on medications (age: 71.7 ± 3.7 years, 24 males, Hoehn and Yahr: 2.1 ± 0.6). Compared to traditional rehabilitation, low-profile lower-limb exoskeleton (lp-LLEXO) training brought major improvements towards walking capacity and gait speed, while there are no clear major benefits regarding the dual-task gait cost index and freezing of gait symptoms. Importantly, the results suggest that lp-LLEXO training is more beneficial for patients with an intermediate-to-severe level of disease severity (Hoehn and Yahr > 2.5). This review could provide a novel framework for implementing LLEXO in clinical practise, highlighting its benefits and limitations towards gait training.

Interocular asymmetry of retinal change in Parkinson's disease

PURPOSE

To investigate interocular asymmetry (IA) of retinal structure and vessel density in patients with Parkinson's disease (PD) and normal controls (NC).

METHODS

Seventy-eight subjects including 40 PD patients and 38 NC had completed optical coherence tomography angiography (OCTA) and neurological examinations for three rating scales (UPDRS-III, MMSE and MoCA). The IA was calculated by the absolute value of difference in right and left eyes. The IA of thickness in macular ganglion cell inner-plexiform layer (GCIPL), peripapillary retinal nerve fiber layer (pRNFL), and vessel density of superficial capillary plexus (SCP), deep capillary plexus (DCP), radial peripapillary capillary (RPC) were obtained from OCTA.

RESULTS

The motor-symptom-onset side of eyes showed lower vessel density in parafovea of SCP (51.09 ± 3.46 vs 49.81 ± 4.16, P = 0.03) and superior hemi of perifovea DCP (49.55 ± 5.81 vs 47.33 ± 5.71, = 0.04). The PD patients showed larger IA in thickness of superior half of pRNFL (5.27 [2.67, 10.87] vs 3.08 [1.62, 5.61], P = 0.02) and parafovea GCIPL (2.40[1.25, 6.35] vs 1.40[0.50, 2.45], P = 0.02). No significant interocular asymmetry was found in vessel density between PD and NC. A higher UPDRS-III scale was associated with larger IA in GCIPL (β = 0.093, P = 0.001) and smaller IA in DCP (β = -0.065, P = 0.037).

CONCLUSION

The motor-symptom-onset side of eyes showed more severe loss of macular vessel density than the other side of eyes. The PD patients showed asymmetrical structural change in GCIPL and pRNFL, which showed the potential as the diagnostic biomarker for PD.

Gait asymmetry and symptom laterality in Parkinson's disease: two of a kind?

BACKGROUND

The laterality of motor symptoms is considered a key feature of Parkinson's disease (PD). Here, we investigated whether gait and turning asymmetry coincided with symptom laterality as determined by the MDS-UPRDS part III and whether it was increased compared to healthy controls (HC).

METHODS

We analyzed the asymmetry of gait and turning with and without a cognitive dual task (DT) using motion capture systems and wearable sensors in 97 PD patients mostly from Hoehn & Yahr stage II and III and 36 age-matched HC. We also assessed motor symptom asymmetry using the bilateral sub-items of the MDS-UPDRS-III. Finally, we examined the strength of the association between gait asymmetry and symptom laterality.

RESULTS

Participants with PD had increased gait but not more turning asymmetry compared to HC (p < 0.05). Only 53.7% of patients had a shorter step length on the more affected body side as determined by the MDS-UPDRS-III. Also, 54% took more time and 29% more steps during turns toward the more affected side. The degree of asymmetry in the different domains did not correlate with each other and was not influenced by DT-load.

CONCLUSIONS

We found a striking mismatch between the side and the degree of asymmetry in different motor domains, i.e., in gait, turning, and distal symptom severity in individuals with PD. We speculate that motor execution in different body parts relies on different neural control mechanisms. Our findings warrant further investigation to understand the complexity of gait asymmetry in PD.

The impact of subthalamic deep-brain stimulation in restoring motor symmetry in Parkinson's disease patients: a prospective study

BACKGROUND AND OBJECTIVES

The impact of subthalamic deep-brain stimulation (STN-DBS) on motor asymmetry and its influence on both motor and non-motor outcomes remain unclear. The present study aims at assessing the role of STN-DBS on motor asymmetry and how its modulation translates into benefits in motor function, activities of daily living (ADLs) and quality of life (QoL).

METHODS

Postoperative motor asymmetry has been assessed on the multicentric, prospective Predictive Factors and Subthalamic Stimulation in Parkinson's Disease cohort. Asymmetry was evaluated at both baseline (pre-DBS) and 1 year after STN-DBS. A patient was considered asymmetric when the right-to-left MDS-UPDRS part III difference was ≥ 5. In parallel, analyses have been carried out using the absolute right-to-left difference. The proportion of asymmetric patients at baseline was compared to that in the post-surgery evaluation across different medication/stimulation conditions.

RESULTS

537 PD patients have been included. The proportion of asymmetric patients was significantly reduced after both STN-DBS and medication administration (asymmetric patients: 50% in pre-DBS MedOFF, 35% in MedOFF/StimON, 26% in MedON/StimOFF, and 12% in MedON/StimON state). Older patients at surgery and with higher baseline UPDRS II scores were significantly less likely to benefit from STN-DBS at the level of motor asymmetry. No significant correlation between motor asymmetry and ADLs (UPDRS II) or overall QoL (PDQ-39) score was observed. Asymmetric patients had significantly higher mobility, communication, and daily living PDQ-39 sub-scores.

CONCLUSIONS

Both STN-DBS and levodopa lead to a reduction in motor asymmetry. Motor symmetry is associated with improvements in certain QoL sub-scores.

Role of HCN channels in the functions of basal ganglia and Parkinson's disease

Parkinson's disease (PD) is a motor disorder resulting from dopaminergic neuron degeneration in the substantia nigra caused by age, genetics, and environment. The disease severely impacts a patient's quality of life and can even be life-threatening. The hyperpolarization-activated cyclic nucleotide-gated (HCN) channel is a member of the HCN1-4 gene family and is widely expressed in basal ganglia nuclei. The hyperpolarization-activated current mediated by the HCN channel has a distinct impact on neuronal excitability and rhythmic activity associated with PD pathogenesis, as it affects the firing activity, including both firing rate and firing pattern, of neurons in the basal ganglia nuclei. This review aims to comprehensively understand the characteristics of HCN channels by summarizing their regulatory role in neuronal firing activity of the basal ganglia nuclei. Furthermore, the distribution and characteristics of HCN channels in each nucleus of the basal ganglia group and their effect on PD symptoms through modulating neuronal electrical activity are discussed. Since the roles of the substantia nigra pars compacta and reticulata, as well as globus pallidus externus and internus, are distinct in the basal ganglia circuit, they are individually described. Lastly, this investigation briefly highlights that the HCN channel expressed on microglia plays a role in the pathological process of PD by affecting the neuroinflammatory response.

Asymmetric Presynaptic Depletion of Dopamine Neurons in a Drosophila Model of Parkinson's Disease

Parkinson's disease (PD) often displays a strong unilateral predominance in arising symptoms. PD is correlated with dopamine neuron (DAN) degeneration in the substantia nigra pars compacta (SNPC), and in many patients, DANs appear to be affected more severely on one hemisphere than the other. The reason for this asymmetric onset is far from being understood. Drosophila melanogaster has proven its merit to model molecular and cellular aspects of the development of PD. However, the cellular hallmark of the asymmetric degeneration of DANs in PD has not yet been described in Drosophila. We ectopically express human α-synuclein (hα-syn) together with presynaptically targeted syt::HA in single DANs that innervate the Antler (ATL), a symmetric neuropil located in the dorsomedial protocerebrum. We find that expression of hα-syn in DANs innervating the ATL yields asymmetric depletion of synaptic connectivity. Our study represents the first example of unilateral predominance in an invertebrate model of PD and will pave the way to the investigation of unilateral predominance in the development of neurodegenerative diseases in the genetically versatile invertebrate model Drosophila.

Anticipatory Postural Adjustments and Compensatory Postural Responses to Multidirectional Perturbations-Effects of Medication and Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease

BACKGROUND

Postural instability is one of the most restricting motor symptoms for patients with Parkinson's disease (PD). While medication therapy only shows minor effects, it is still unclear whether medication in conjunction with deep brain stimulation (DBS) of the subthalamic nucleus (STN) improves postural stability. Hence, the aim of this study was to investigate whether PD patients treated with medication in conjunction with STN-DBS have superior postural control compared to patients treated with medication alone.

METHODS

Three study groups were tested: PD patients on medication (PD-MED), PD patients on medication and on STN-DBS (PD-MED-DBS), and healthy elderly subjects (HS) as a reference. Postural performance, including anticipatory postural adjustments (APA) prior to perturbation onset and compensatory postural responses (CPR) following multidirectional horizontal perturbations, was analyzed using force plate and electromyography data.

RESULTS

Regardless of the treatment condition, both patient groups showed inadequate APA and CPR with early and pronounced antagonistic muscle co-contractions compared to healthy elderly subjects. Comparing the treatment conditions, study group PD-MED-DBS only showed minor advantages over group PD-MED. In particular, group PD-MED-DBS showed faster postural reflexes and tended to have more physiological co-contraction ratios.

CONCLUSION

medication in conjunction with STN-DBS may have positive effects on the timing and amplitude of postural control.

Does TRODAT-1 SPECT Uptake Correlate with Cerebrospinal Fluid α-Synuclein Levels in Mid-Stage Parkinson's Disease?

BACKGROUND

Parkinson's disease (PD) is characterized by a progressive loss of nigrostriatal dopaminergic neurons with impaired motor and non-motor symptoms. It has been suggested that motor asymmetry could be caused due to an imbalance in dopamine levels, as visualized by dopamine transporter single emission computed tomography test (DAT-SPECT), which might be related to indirect measures of neurodegeneration, evaluated by the Montreal Cognitive Assessment (MOCA) and α-synuclein levels in the cerebrospinal fluid (CSF). Therefore, this study aimed to understand the correlation between disease laterality, DAT-SPECT, cognition, and α-synuclein levels in PD.

METHODS

A total of 28 patients in the moderate-advanced stage of PD were subjected to neurological evaluation, TRODAT-1-SPECT/CT imaging, MOCA, and quantification of the levels of α-synuclein.

RESULTS

We found that α-synuclein in the CSF was correlated with global cognition (positive correlation, r² = 0.3, p = 0.05) and DAT-SPECT concentration in the putamen (positive correlation, r² = 0.4, p = 0.005), and striatum (positive correlation, r² = 0.2, p = 0.03), thus working as a neurodegenerative biomarker. No other correlations were found between DAT-SPECT, CSF α-synuclein, and cognition, thus suggesting that they may be lost with disease progression.

CONCLUSIONS

Our data highlight the importance of understanding the dysfunction of the dopaminergic system in the basal ganglia and its complex interactions in modulating cognition.

Step-Counting Accuracy of a Commercial Smartwatch in Mild-to-Moderate PD Patients and Effect of Spatiotemporal Gait Parameters, Laterality of Symptoms, Pharmacological State, and Clinical Variables

Commercial smartwatches could be useful for step counting and monitoring ambulatory activity. However, in Parkinson's disease (PD) patients, an altered gait, pharmacological condition, and symptoms lateralization may affect their accuracy and potential usefulness in research and clinical routine. Steps were counted during a 6 min walk in 47 patients with PD and 47 healthy subjects (HS) wearing a Garmin Vivosmart 4 (GV4) on each wrist. Manual step counting was used as a reference. An inertial sensor (BTS G-Walk), placed on the lower back, was used to compute spatial-temporal gait parameters. Intraclass correlation coefficient (ICC) and mean absolute percentage error (MAPE) were used for accuracy evaluation and the Spearman test was used to assess the correlations between variables. The GV4 overestimated steps in PD patients with only a poor-to-moderate agreement. The OFF pharmacological state and wearing the device on the most-affected body side led to an unacceptable accuracy. The GV4 showed an excellent agreement and MAPE in HS at a self-selected speed, but an unacceptable performance at a slow speed. In PD patients, MAPE was not associated with gait parameters and clinical variables. The accuracy of commercial smartwatches for monitoring step counting might be reduced in PD patients and further influenced by the pharmacological condition and placement of the device.

Longitudinal assessment of motor function following the unilateral intrastriatal 6-hydroxydopamine lesion model in mice

Introduction

Despite the widespread use of the unilateral striatal 6-hydroxydopamine (6-OHDA) lesion model in mice in recent years, the stability of behavioral deficits in the 6-OHDA striatal mouse model over time is not yet clear, raising concerns about using this model to evaluate a compound's long-term therapeutic effects.

Materials and methods

In the current study, mice were tested at regular intervals in the cylinder test and gait analysis beginning 3 days after 6-OHDA injection of 4 and 8 μg and lasting until 56 days post-lesion. Apomorphine-induced rotational test and rotarod test were also performed on Day 23 and 43 post-lesion, respectively. Immunohistochemistry for dopaminergic neurons stained by tyrosine hydroxylase (TH) was also performed.

Results

Our results showed that both the 4 and 8 μg 6-OHDA lesion groups exhibited forelimb use asymmetry with a preference for the ipsilateral (injection) side on Day 3 and until Day 21 post-lesion, but did not show forelimb asymmetry on Day 28 to 56 post-lesion. The 8 μg 6-OHDA lesion group still exhibited forelimb asymmetry on Day 28 and 42 post-lesion, but not on Day 56. The gait analysis showed that the contralateral front and hind step cycles increased from Day 3 to 42 post-lesion and recovered on Day 56 post-lesion. In addition, our results displayed a dose-dependent reduction in TH⁺ cells and TH⁺ fibers, as well as dose-dependent apomorphine-induced rotations. In the rotarod test, the 8 μg 6-OHDA lesion group, but not the 4 μg group, decreased the latency to fall on the rotarod on Day 43 post-lesion.

Conclusion

In summary, unilateral striatal 6-OHDA injections of 4 and 8 μg induced spontaneous motor impairment in mice, which partially recovered starting on Day 28 post-lesion. Forced motor deficits were observed in the 8 g 6-OHDA lesion group, which remained stable on Day 43 post-lesion. In addition, the rotarod test and apomorphine-induced rotational test can distinguish between lesions of different extents and are useful tools for the assessment of functional recovery in studies screening novel potential therapies.

Association of Total Bilirubin with Motor Signs in Early Parkinson's Disease in LRRK2 Variant Carriers

Oxidative stress is considered a possible mechanism in Parkinson's disease (PD) progression. Bilirubin has been recognized as a powerful antioxidant that increases due to heme-oxygenase activity. We aimed to investigate the association of total bilirubin (TB) with motor signs and asymmetry in different stages of early PD. A case-control study was performed to investigate the differences in TB levels in PD patients and healthy controls (HC) both carrying LRRK2 variants. We compared TB levels in HC and Hoehn and Yahr (HY) I and II cohorts separately, followed by multiple linear regression analysis to evaluate the association between TB and motor dysfunction in each stage. We used Movement Disorder Society-Sponsored Revision of the Unified Parkinson's Disease Rating Scale (UPDRS) part III scores and asymmetry scores to address motor disability. Asymmetry scores were calculated from the corresponding UPDRS III tasks. TB was significantly increased in HY II compared to HC (P < 0.001). Positive correlations with TB were found for UPDRS III total score (ρ = 0.303, P = 0.034) and asymmetry score (ρ = 0.418, P = 0.003) in HY I. Multiple linear regression found a significant relationship between TB and asymmetry scores in HY I (R² = 0.261, P = 0.037), but no relationship was achieved with UPDRS III total scores. Increased TB serves as an important diagnostic marker in earlier stages of PD. A significant relationship was found between TB and motor asymmetry in HY I patients. According to our findings, bilirubin mainly exhibits its protective effects in HY I population.

Serial changes of I-123 FP-CIT SPECT binding asymmetry in Parkinson's disease: Analysis of the PPMI data

Background

Dopaminergic denervation and motor symptoms are usually asymmetric at the onset of Parkinson's disease (PD). In this study, we estimated the asymmetry of specific binding ratio (SBR) of I-123 FP-CIT SPECT images during 4-years of follow up, to demonstrate the pattern of serial changes of asymmetry.

Methods

Clinical and I-123 FP-CIT SPECT image data of 301 PD patients and 141 normal controls were reviewed from the Parkinson's Progression Markers Initiative cohort. I-123 FP-CIT SPECT images were taken at baseline, 1-, 2-, and 4-year follow up periods for PD patients, and at baseline for normal controls. Asymmetry index were calculated by two methods. Method 1, by using the ratio of absolute difference of right and left SBRs to the average SBR. Method 2, by using the ratio of absolute difference of right and left SBRs to the SBR values of age-matched normal controls.

Results

Asymmetry index by method 2 revealed a more significant decrease during the 4-year follow up period, compared with method 1. The baseline asymmetry index of the putamen by method 2 showed significant correlation with the non-dominant putamen SBRs. However, there were no significant correlation with the baseline asymmetry index by method 2 and motor symptoms, cognition, nor autonomic symptoms.

Conclusion

We suggest a novel asymmetry index in association to age-matched normal SBR values. This novel index could be adopted in predicting and evaluating the natural course of PD.

Impaired Hand Function and Its Association With Self-Perceived Hand Functional Ability and Quality of Life in Parkinson Disease

OBJECTIVE

Comprehensive hand function in people with Parkinson disease (PD) has been underevaluated. The objectives were to compare self-perceived and objective hand functions of PD and controls, compare outcomes between more and less affected hand subgroups, and evaluate relationship between self-perceived and objective outcomes in subgroups.

DESIGN

A total of 165 PD and 82 healthy participants completed the Jebsen-Taylor Hand Function Test, Purdue Pegboard Test, grip strength test, and Manual Ability Measure-16 in a cross-sectional study. PD participants completed the Parkinson Disease Questionnaire-39. Associations between objective and self-perceived/quality of life outcomes in PD groups were analyzed, and nondominant and dominant more affected subgroups performance was compared.

RESULTS

PD participants had significantly worse performance in most Jebsen-Taylor Hand Function Test and all Purdue Pegboard Test items, lower Manual Ability Measure-16 scores, and poorer handgrip strength. Weak associations were found between dexterity, but not grip strength, and self-perceived functional hand ability and Parkinson Disease Questionnaire-39 scores in PD subgroups. For nondominant more affected subgroup, poorer dexterity was associated with better Parkinson Disease Questionnaire-39 Activity of Daily Living domain scores.

CONCLUSION

People with mild to moderate PD were shown to have poorer manual dexterity, reduced grip strength, and lower self-perceived functional hand ability than controls. Associations between dexterity and self-perceived outcomes highlight the importance of unimanual and bimanual training.

Gray and white matter alterations in different predominant side and type of motor symptom in Parkinson's disease

Background

Parkinson's disease (PD) is highly heterogeneous reflected by different affected side of body and type of motor symptom. We aim to explore clinical characteristics and underlying brain structure alterations in PD with different predominant sides and motor types.

Methods

We recruited 161 PD patients and 50 healthy controls (HC). Patients were classified into four subtypes according to their predominant side and motor type: left akinetic/rigid‐dominant (LAR), left tremor‐dominant (LTD), right akinetic/rigid‐dominant (RAR), and right tremor‐dominant (RTD). All participants assessed motor and cognitive performances, then underwent T1‐weighted and diffusion tensor imaging scanning. A general linear model was used to compare neuroimaging parameters among five groups.

Results

Among four PD subtypes, patients of LAR subtype experienced the worst motor impairment, and only this subtype showed worse cognitive performance compared with HC. Compared with HC and other subtypes, LAR subtype showed a significant reduction in cortical thickness of the right caudal‐anterior‐cingulate gyrus and fractional anisotropy of the right cingulum bundle.

Conclusions

We demonstrated that LAR subtype had the worst clinical performance, which the severer damage in the right cingulate region might be the underlying mechanism. This study underscores the importance of classifying PD subtypes based on both the side and type of motor symptom for clinical intervention and research to optimize behavioral outcomes in the future.

Prediction of Freezing of Gait in Parkinson's Disease Using Unilateral and Bilateral Plantar-Pressure Data

Background

Freezing of gait (FOG) is an intermittent walking disturbance experienced by people with Parkinson's disease (PD). FOG has been linked to falling, injury, and overall reduced mobility. Wearable sensor-based devices can detect freezes already in progress and provide a cue to help the person resume walking. While this is helpful, predicting FOG episodes before onset and providing a timely cue may prevent the freeze from occurring. Wearable sensors mounted on various body parts have been used to develop FOG prediction systems. Despite the known asymmetry of PD motor symptom manifestation, the difference between the most affected side (MAS) and least affected side (LAS) is rarely considered in FOG detection and prediction studies.

Methods

To examine the effect of using data from the MAS, LAS, or both limbs for FOG prediction, plantar pressure data were collected during a series of walking trials and used to extract time and frequency-based features. Three datasets were created using plantar pressure data from the MAS, LAS, and both sides together. ReliefF feature selection was performed. FOG prediction models were trained using the top 5, 10, 15, 20, 25, or 30 features for each dataset.

Results

The best models were the MAS model with 15 features and the LAS and bilateral models with 5 features. The LAS model had the highest sensitivity (79.5%) and identified the highest percentage of FOG episodes (94.9%). The MAS model achieved the highest specificity (84.9%) and lowest false positive rate (1.9 false positives/walking trial). Overall, the bilateral model was best with 77.3% sensitivity and 82.9% specificity. In addition, the bilateral model identified 94.2% of FOG episodes an average of 0.8 s before FOG onset. Compared to the bilateral model, the LAS model had a higher false positive rate; however, the bilateral and LAS models were similar in all the other evaluation metrics.

Conclusion

The LAS model would have similar FOG prediction performance to the bilateral model at the cost of slightly more false positives. Given the advantages of single sensor systems, the increased false positive rate may be acceptable to people with PD. Therefore, a single plantar pressure sensor placed on the LAS could be used to develop a FOG prediction system and produce performance similar to a bilateral system.

A Study on Lower Limb Asymmetries in Parkinson’s Disease during Gait Assessed through Kinematic-Derived Parameters

Unilaterality of motor symptoms is a distinctive feature of Parkinson’s Disease (PD) and represents an important co-factor involved in motor deficits and limitations of functional abilities including postural instability and asymmetrical gait. In recent times, an increasing number of studies focused on the characterization of such alterations, which have been associated with increased metabolic cost and risk of falls and may severely compromise their quality of life. Although a large number of studies investigated the gait alterations in people with PD (pwPD), few focused on kinematic parameters and even less investigated interlimb asymmetry under a kinematic point of view. This retrospective study aimed to characterize such aspects in a cohort of 61 pwPD (aged 68.9 ± 9.3 years) and 47 unaffected individuals age- and sex-matched (66.0 ± 8.3 years), by means of computerized 3D gait analysis performed using an optical motion-capture system. The angular trends at hip, knee and ankle joints of pwPD during the gait cycle were extracted and compared with those of unaffected individuals on a point-by-point basis. Interlimb asymmetry was assessed using angle–angle diagrams (cyclograms); in particular, we analyzed area, orientation, trend symmetry and range offset. The results showed that pwPD are characterized by a modified gait pattern particularly at the terminal stance/early swing phase of the gait cycle. Significant alterations of interlimb coordination were detected at the ankle joint (cyclogram orientation and trend symmetry) and at the hip joint (range offset). Such findings might be useful in clinical routine to characterize asymmetry during gait and thus support physicians in the early diagnosis and in the evaluation of the disease progression.

Deficient Interhemispheric Connectivity Underlies Movement Irregularities in Parkinson's Disease

BACKGROUND

Movement execution is impaired in patients with Parkinson's disease. Evolving neurodegeneration leads to altered connectivity between distinct regions of the brain and altered activity at interconnected areas. How connectivity alterations influence complex movements like drawing spirals in Parkinson's disease patients remains largely unexplored.

OBJECTIVE

We investigated whether deteriorations in interregional connectivity relate to impaired execution of drawing.

METHODS

Twenty-nine patients and 31 age-matched healthy control participants drew spirals with both hands on a digital graphics tablet, and the regularity of drawing execution was evaluated by sample entropy. We recorded resting-state fMRI and task-related EEG, and calculated the time-resolved partial directed coherence to estimate effective connectivity for both imaging modalities to determine the extent and directionality of interregional interactions.

RESULTS

Movement performance in Parkinson's disease patients was characterized by increased sample entropy, corresponding to enhanced irregularities in task execution. Effective connectivity between the motor cortices of both hemispheres, derived from resting-state fMRI, was significantly reduced in Parkinson's disease patients in comparison to controls. The connectivity strength in the nondominant to dominant hemisphere direction in both modalities was inversely correlated with irregularities during drawing, but not with the clinical state.

CONCLUSION

Our findings suggest that interhemispheric connections are affected both at rest and during drawing movements by Parkinson's disease. This provides novel evidence that disruptions of interhemispheric information exchange play a pivotal role for impairments of complex movement execution in Parkinson's disease patients.

Aberrant Changes in Cortical Complexity in Right-Onset Versus Left-Onset Parkinson's Disease in Early-Stage

There is increasing evidence to show that motor symptom lateralization in Parkinson’s disease (PD) is linked to non-motor features, progression, and prognosis of the disease. However, few studies have reported the difference in cortical complexity between patients with left-onset of PD (LPD) and right-onset of PD (RPD). This study aimed to investigate the differences in the cortical complexity between early-stage LPD and RPD. High-resolution T1-weighted magnetic resonance images of the brain were acquired in 24 patients with LPD, 34 patients with RPD, and 37 age- and sex-matched healthy controls (HCs). Cortical complexity including gyrification index, fractal dimension (FD), and sulcal depth was analyzed using surface-based morphometry via CAT12/SPM12. Familywise error (FWE) peak-level correction at p < 0.05 was performed for significance testing. In patients with RPD, we found decreased mean FD and mean sulcal depth in the banks of the left superior temporal sulcus (STS) compared with LPD and HCs. The mean FD in the left superior temporal gyrus (STG) was decreased in RPD compared with HCs. However, in patients with LPD, we did not identify significantly abnormal cortical complex change compared with HCs. Moreover, we observed that the mean FD in STG was negatively correlated with the 17-item Hamilton Depression Scale (HAMD) among the three groups. Our findings support the specific influence of asymmetrical motor symptoms in cortical complexity in early-stage PD and reveal that the banks of left STS and left STG might play a crucial role in RPD.

Does Subthalamic Deep Brain Stimulation Impact Asymmetry and Dyscoordination of Gait in Parkinson's Disease?

Background. Subthalamic deep brain stimulation (STN-DBS) is an effective treatment for selected Parkinson's disease (PD) patients. Gait characteristics are often altered after surgery, but quantitative therapeutic effects are poorly described. Objective. The goal of this study was to systematically investigate modifications in asymmetry and dyscoordination of gait 6 months postoperatively in patients with PD and compare the outcomes with preoperative baseline and to asymptomatic controls without PD. Methods. A convenience sample of thirty-two patients with PD (19 with postural instability and gait disorder (PIGD) type and 13 with tremor dominant disease) and 51 asymptomatic controls participated. Parkinson patients were tested prior to the surgery in both OFF and ON medication states, and 6-months postoperatively in the ON stimulation condition. Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) I to IV and medication were compared to preoperative conditions. Asymmetry ratios, phase coordination index, and walking speed were assessed. Results. MDS-UPDRS I to IV at 6 months improved significantly, and levodopa equivalent daily dosages significantly decreased. STN-DBS increased step time asymmetry (hedges' g effect sizes [95% confidence interval] between pre- and post-surgery: .27 [-.13, .73]) and phase coordination index (.29 [-.08, .67]). These effects were higher in the PIGD subgroup than the tremor dominant (step time asymmetry: .38 [-.06, .90] vs .09 [-.83, 1.0] and phase coordination index: .39 [-.04, .84] vs .13 [-.76, .96]). Conclusions. This study provides objective evidence of how STN-DBS increases asymmetry and dyscoordination of gait in patients with PD and suggests motor subtypes-associated differences in the treatment response.

Effects of Motor Symptom Laterality on Clinical Manifestations and Quality of Life in Parkinson's Disease

BACKGROUND

The asymmetry of motor manifestations present in Parkinson's disease (PD) suggests the existence of differences between both hemispheres. As a consequence, this asymmetry might contribute to different PD clinical phenotypes.

OBJECTIVE

To study the relationship between motor symptom laterality with motor, non-motor symptoms (NMS), freezing of gait (FOG), and quality of life (QoL) impairment in PD.

METHODS

In this cross-sectional study, we measured motor symptoms severity and complications with the Unified Parkinsons' disease Rating Scale (UPDRS), FOG with the FOG questionnaire, QoL with the 39-item PD Quality of Life Questionnaire Summary Index, and NMS with the NMS, Visual Analogue Scales for Pain and Fatigue, Beck Depression Inventory-II, Impulsive-Compulsive Disorders, and PD Sleep and Cognitive Rating scales. We defined left and right motor laterality using the UPDRS part III. We used comparative, regression, and effect size analyses to evaluate the impact of asymmetry on motor and NMS, FOG, and QoL.

RESULTS

342 left (LPD) and 310 right (RPD) patients, with a mean age of 62.0±8.8 years, were included. In multivariate regression analysis, LPD was associated with a greater motor (OR = 1,50, 95% CI 1.02-2.21), FOG (OR = 1.56, 95% CI 1.01-2.41), and overall NMS impairment (OR = 1.43, 95% CI 1.001-2.06), and better QoL (OR = 0.52 95% CI 0.32-0.85). Overall, only a mild effect size was found for all comparisons in which significant differences were present.

CONCLUSION

In this large multicenter study, motor symptom laterality seems to carry a mild but significant impact on PD clinical manifestations, and QoL.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Asymmetry at Disease Onset Is Not a Predictor of Parkinson's Disease Progression

BACKGROUND

Even though a significant fraction of Parkinson's disease (PD) patients presents with only minor or no motor asymmetry, the motor symptoms in PD typically start on one side of the body and worse symptoms on the side of the disease onset usually persist long after the disease has become clinically bilateral. The asymmetric presentation of PD has been studied over the years, with some studies showing slower progression in PD subjects with asymmetric disease presentation. In other studies, however, it was not possible to relate the asymmetry to disease progression.

OBJECTIVE

The main objective of the present study was to assess the effect of asymmetry at disease onset on disease progression.

METHODS

Using the data available in the Parkinson's Progression Markers Initiative (PPMI) database, at baseline, 423 subjects with de-novo PD were included in the study. Instead of dichotomizing the subjects in asymmetric and symmetric, we kept the asymmetry index and the non-motor, disability, and motor progression at one-, three-, and five-year follow-up continuous. Linear regression was used to correlate asymmetry indices and disease progression.

RESULTS

There was no correlation between neither clinically, nor DatSCAN defined asymmetry and non-motor, motor, and disability progression in the de-novo PD subjects with a 5-year follow-up.

CONCLUSION

Asymmetry does not predict progression of PD. Further studies are needed to investigate whether early detection of asymmetry on clinical grounds could successfully distinguish between PD and symmetric types of atypical parkinsonism in the early stages of the disease.

Asymmetric Dopamine Transporter Loss Affects Cognitive and Motor Progression in Parkinson's Disease

Background

Asymmetric hemispheric loss of dopaminergic neurons is one of the characteristic features of Parkinson's disease (PD). However, it is still debated if right or left asymmetry differently affects cognitive and motor progression.

Objectives

The objective of this study was to investigate, for the first time, the relevance of dopamine transporter (DAT) asymmetry on cognitive and motor manifestations at onset and at 4‐year progression in drug‐naïve PD.

Methods

From the Parkinson's Progression Markers Initiative multicenter cohort, we identified 249 right‐handed patients with PD with baseline asymmetry greater than 20% in putamen DAT binding at single‐photon emission computed tomography. A predominant putamen asymmetry was found on the left in 143 patients (PD‐left), and on the right side in 106 patients (PD‐right); we compared them with 196 healthy controls. Patients were followed longitudinally (2‐year and 4‐year visits), examining their clinical, cognitive, and imaging data.

Results

At baseline, the PD‐left group showed worse performance on the Symbol Digit Modality Test, an attention and processing‐speed test, and lower cerebrospinal fluid β‐amyloid levels than the PD‐right group. These differences were maintained at follow‐up, declining over time in both groups. By contrast, the PD‐right group showed greater motor impairment at baseline, which increased over 4 years. Striatal DAT binding decreased over time in both groups, but the PD‐right group showed a steeper decline, particularly during the first 2‐year follow‐up. Putaminal asymmetry assessed at baseline was maintained over time.

Conclusions

These findings suggest that hemispheric asymmetric dopaminergic denervation influences PD cognitive and motor performance as well as progression. Predominant right hemisphere nigrostriatal dopaminergic loss is associated with greater motor severity, whereas more pronounced left hemisphere denervation affects cognitive manifestations at onset and their progression. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Motor Symptom Lateralization Influences Cortico-Striatal Functional Connectivity in Parkinson's Disease

Objective: The striatum is unevenly impaired bilaterally in Parkinson's disease (PD). Because the striatum plays a key role in cortico-striatal circuits, we assume that lateralization affects cortico-striatal functional connectivity in PD. The present study sought to evaluate the effect of lateralization on various cortico-striatal circuits through resting-state functional magnetic resonance imaging (fMRI). Methods: Thirty left-onset Parkinson's disease (LPD) patients, 27 right-onset Parkinson's disease (RPD) patients, and 32 normal controls with satisfactory data were recruited. Their demographic, clinical, and neuropsychological information was collected. Resting-state fMRI was performed, and functional connectivity changes of seven subdivisions of the striatum were explored in the two PD groups. In addition, the associations between altered functional connectivity and various clinical and neuropsychological characteristics were analyzed by Pearson's or Spearman's correlation. Results: Directly comparing the LPD and RPD patients demonstrated that the LPD patients had lower FC between the left dorsal rostral putamen and the left orbitofrontal cortex than the RPD patients. In addition, the LPD patients showed aberrant functional connectivity involving several striatal subdivisions in the right hemisphere. The right dorsal caudate, ventral rostral putamen, and superior ventral striatum had decreased functional connectivity with the cerebellum and parietal and occipital lobes relative to the normal control group. The comparison between RPD patients and the controls did not obtain significant difference in functional connectivity. The functional connectivity between the left dorsal rostral putamen and the left orbitofrontal cortex was associated with contralateral motor symptom severity in PD patients. Conclusions: Our findings provide new insights into the distinct characteristics of cortico-striatal circuits in LPD and RPD patients. Lateralization of motor symptoms is associated with lateralized striatal functional connectivity.

Wrist Position Sense in Two Dimensions: Between-Hand Symmetry and Anisotropic Accuracy Across the Space

A deep investigation of proprioceptive processes is necessary to understand the relationship between sensory afferent inputs and motor outcomes. In this work, we investigate whether and how perception of wrist position is influenced by the direction along which the movement occurs. Most previous studies have tested Joint Position Sense (JPS) through 1 degree of freedom (DoF) wrist movements, such as flexion/extension (FE) or radial/ulnar deviation (RUD). However, the wrist joint has 3-DoF and many activities of daily living produce combined movements, requiring at least 2-DoF wrist coordination. For this reason, in this study, target positions involved movement directions that combined wrist flexion or extension with radial or ulnar deviation. The chosen task was a robot-aided Joint Position Matching (JPM), in which blindfolded participants actively reproduced a previously passively assumed target joint configuration. The JPM performance of 20 healthy participants was quantified through measures of accuracy and precision, in terms of both perceived target direction and distance along each direction of movement. Twelve different directions of movement were selected and both hands tested. The left and right hand led to comparable results, both target extents and directions were differently perceived according to the target direction on the FE/RUD space. Moreover, during 2-DoF combined movements, subjects' perception of directions was impaired when compared to 1-DoF target movements. In summary, our results showed that human perception of wrist position on the FE/RUD space is symmetric between hands but not isotropic among movement directions.

Limb and trunk accelerometer data collected with wearable sensors from subjects with Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by motor and non-motor symptoms. Dyskinesia and motor fluctuations are complications of PD medications. An objective measure of on/off time with/without dyskinesia has been sought for some time because it would facilitate the titration of medications. The objective of the dataset herein presented is to assess if wearable sensor data can be used to generate accurate estimates of limb-specific symptom severity. Nineteen subjects with PD experiencing motor fluctuations were asked to wear a total of five wearable sensors on both forearms and shanks, as well as on the lower back. Accelerometer data was collected for four days, including two laboratory visits lasting 3 to 4 hours each while the remainder of the time was spent at home and in the community. During the laboratory visits, subjects performed a battery of motor tasks while clinicians rated limb-specific symptom severity. At home, subjects were instructed to use a smartphone app that guided the periodic performance of a set of motor tasks.

Parkinson's disease laterality: a 11C-PE2I PET imaging study

Asymmetry of striatal dopaminergic deficits and motor symptoms is a typical characteristic of idiopathic Parkinson's disease (PD). This study aims to characterise the trend of asymmetry in moderate-stage PD. We performed a 19-month longitudinal study in 27 patients with PET-CT imaging and appropriate clinical assessments. 11C-PE2I non-displaceable binding potential (BPND) was calculated bilaterally for the striatum at baseline and follow-up to estimate the in vivo density of striatal dopamine transporters (DAT). Changes in striatal 11C-PE2I BPND over time were more prominent in the ipsilateral as compared to contralateral side. Changes in MDS-UPDRS-III (motor component of the Movement Disorders Society Unified PD Rating Scale) were not different between the clinically most and least affected body sides. Our data support that the asymmetry in striatal dopaminergic degeneration becomes less prominent in moderate-stage PD. In contrast, during the above period, the asymmetry of motor symptoms was maintained between the clinically most and least affected body sides.

Predictors of second-sided deep brain stimulation for Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) is a progressive neurological movement disorder that is commonly treated with deep brain stimulation (DBS) surgery in advanced stages. The purpose of this study was to investigate factors that affect time to placement of a second-sided DBS lead for PD when a unilateral lead is initially placed for asymmetrical presentation. The decision whether to initially perform unilateral or bilateral DBS is largely based on physician and/or patient preference.

METHODS

This study was a retrospective cohort analysis of patients with PD undergoing initial unilateral DBS for asymmetrical disease between January 1999 and December 2017 at the authors' institution. Patients treated with DBS for essential tremor or other conditions were excluded. Variables collected included demographics at surgery, time since diagnosis, Unified Parkinson's Disease Rating Scale motor scores (UPDRS-III), patient-reported quality-of-life outcomes, side of operation, DBS target, intraoperative complications, and date of follow-up. Paired t-tests were used to assess mean changes in UPDRS-III. Cox proportional hazards analysis and the Kaplan-Meier method were used to determine factors associated with time to second lead insertion over 5 years.

RESULTS

The final cohort included 105 patients who underwent initial unilateral DBS for asymmetrical PD; 59% of patients had a second-sided lead placed within 5 years with a median time of 34 months. Factors found to be significantly associated with early second-sided DBS included patient age 65 years or younger, globus pallidus internus (GPi) target, and greater off-medication reduction in UPDRS-III score following initial surgery. Older age was also found to be associated with a smaller preoperative UPDRS-III levodopa responsiveness score and with a smaller preoperative to postoperative medication-off UPDRS-III change.

CONCLUSIONS

Younger patients, those undergoing GPi-targeted unilateral DBS, and patients who responded better to the initial DBS were more likely to undergo early second-sided lead placement. Therefore, these patients, and patients who are more responsive to medication preoperatively (as a proxy for DBS responsiveness), may benefit from consideration of initial bilateral DBS.

Asymmetrical nigral iron accumulation in Parkinson's disease with motor asymmetry: an explorative, longitudinal and test-retest study

Parkinson's disease (PD) is commonly characterized by asymmetrical motor impairment. This study aimed to clarify the iron distributions in PD patients with significant motor asymmetry and their longitudinal alterations. This study included 123 PD patients and 121 normal controls. Thirty-eight PD patients were revisited. PD patients with significant motor asymmetry were identified by using an objective criterion. Inter-group, inter-hemisphere and inter-visit differences of regional tissue susceptibility were analyzed. Iron accumulation in dominantly and non-dominantly affected substantia nigra (SN) were observed in PD patients with motor asymmetry compared with normal controls (p < 0.005, Bonferroni corrected). Iron accumulation in the dominantly affected SN was significantly higher than that in the non-dominantly affected SN (p < 0.01, Bonferroni corrected). After follow-up, time effect on the iron content in SN was observed, directing to decrease in PD patients with motor asymmetry without hemispherical difference (p < 0.05). In conclusion, asymmetrical iron accumulation in SN was associated with the motor asymmetry in PD at baseline, while along the disease evolution iron content in SN became longitudinally decreased. All these findings provide new evidence for PD pathogenesis that the abnormal iron metabolism in SN is complicated and not always unidirectional.

Effect of Parkinson's disease and two therapeutic interventions on muscle activity during walking: a systematic review

Gait deficits are a common feature of Parkinson’s disease (PD) and predictors of future motor and cognitive impairment. Understanding how muscle activity contributes to gait impairment and effects of therapeutic interventions on motor behaviour is crucial for identifying potential biomarkers and developing rehabilitation strategies. This article reviews sixteen studies that investigate the electromyographic (EMG) activity of lower limb muscles in people with PD during walking and reports on their quality. The weight of evidence establishing differences in motor activity between people with PD and healthy older adults (HOAs) is considered. Additionally, the effect of dopaminergic medication and deep brain stimulation (DBS) on modifying motor activity is assessed. Results indicated greater proximal and decreased distal activity of lower limb muscles during walking in individuals with PD compared to HOA. Dopaminergic medication was associated with increased distal lower limb muscle activity whereas subthalamic nucleus DBS increased activity of both proximal and distal lower limb muscles. Tibialis anterior was impacted most by the interventions. Quality of the studies was not strong, with a median score of 61%. Most studies investigated only distal muscles, involved small sample sizes, extracted limited EMG features and lacked rigorous signal processing. Few studies related changes in motor activity with functional gait measures. Understanding mechanisms underpinning gait impairment in PD is essential for development of personalised rehabilitative interventions. Recommendations for future studies include greater participant numbers, recording more functionally diverse muscles, applying multi-muscle analyses, and relating EMG to functional gait measures.

Abnormal Spontaneous Brain Activity in Left-Onset Parkinson Disease: A Resting-State Functional MRI Study

Objective: Motor asymmetry is characteristic in Parkinson disease (PD). This phenomenon is originated from uneven degeneration of bilateral substantia nigra. However, this asymmetry may not restrict to substantia nigra or striatum. We aimed to determine the effect of asymmetry on spontaneous brain activity across the whole brain. Methods: We consecutively recruited 71 patients with PD, as well as 35 healthy controls, and collected relevant demographic, clinical, and neuropsychological information. The PD patients were divided into two groups according to the side of motor symptom onset. All the participants underwent resting-state functional magnetic resonance imaging, and spontaneous brain activity was assessed using amplitude of low-frequency fluctuation (ALFF). The associations between areas showing significant group differences and various clinical and neuropsychological measures were analyzed. Results: Finally, the data of 30 PD patients with left-onset (LPD), 27 PD patients with right-onset (RPD), and 32 healthy controls were obtained. The three groups had similar age and gender ratios. Our results demonstrated that LPD patients had increased ALFF in the left inferior temporal gyrus and decreased ALFF in bilateral thalamus and cerebellum anterior lobes than the control group. The value of ALFF of the left inferior temporal gyrus was correlated with motor function, and ALFF value of the thalamus was associated with cognition. Comparisons between LPD and RPD patients and between RPD patients and the controls did not yield significant difference. Conclusions: The present study provides new insights into the distinct characteristics of spontaneous brain activity in LPD, which may be associated with motor and cognitive function.

The Relationship between Side of Onset and Cerebral Regional Homogeneity in Parkinson's Disease: A Resting-State fMRI Study

OBJECTIVE

Motor symptoms are usually asymmetric in Parkinson's disease (PD), and asymmetry in PD may involve widespread brain areas. We sought to evaluate the effect of asymmetry on the whole brain spontaneous activity using the measure regional homogeneity (ReHo) through resting-state functional MRI.

METHODS

We recruited 30 PD patients with left onset (LPD), 27 with right side (RPD), and 32 controls with satisfactory data. Their demographic, clinical, and neuropsychological information were obtained. Resting-state functional MRI was performed, and ReHo was used to determine the brain activity. ANCOVA was utilized to analyze between-group differences in ReHo and the associations between abnormal ReHo, and various clinical and neuropsychological variables were explored by Spearman's correlation.

RESULTS

LPD patients had higher ReHo in the right temporal pole than the controls. RPD patients had increased ReHo in the right temporal pole and decreased ReHo in the primary motor cortex and premotor area, compared with the controls. Directly comparing LPD and RPD patients did not show a significant difference in ReHo. ReHo of the right temporal pole was significantly correlated with depression and anxiety in RPD patients.

CONCLUSIONS

Both LPD and RPD have increased brain activity synchronization in the right temporal pole, and only RPD has decreased brain activity synchronization in the right frontal motor areas. The changed brain activity in the right temporal pole may play a compensatory role for depression and anxiety in PD, and the altered cerebral function in the right frontal motor area in RPD may represent the reorganization of the motor system in RPD.

Cueing Paradigms to Improve Gait and Posture in Parkinson's Disease: A Narrative Review

Progressive gait dysfunction is one of the primary motor symptoms in people with Parkinson’s disease (PD). It is generally expressed as reduced step length and gait speed and as increased variability in step time and step length. People with PD also exhibit stooped posture which disrupts gait and impedes social interaction. The gait and posture impairments are usually resistant to the pharmacological treatment, worsen as the disease progresses, increase the likelihood of falls, and result in higher rates of hospitalization and mortality. These impairments may be caused by perceptual deficiencies (poor spatial awareness and loss of temporal rhythmicity) due to the disruptions in processing intrinsic information related to movement initiation and execution which can result in misperceptions of the actual effort required to perform a desired movement and maintain a stable posture. Consequently, people with PD often depend on external cues during execution of motor tasks. Numerous studies involving open-loop cues have shown improvements in gait and freezing of gait (FoG) in people with PD. However, the benefits of cueing may be limited, since cues are provided in a consistent/rhythmic manner irrespective of how well a person follows them. This limitation can be addressed by providing feedback in real-time to the user about performance (closed-loop cueing) which may help to improve movement patterns. Some studies that used closed-loop cueing observed improvements in gait and posture in PD, but the treadmill-based setup in a laboratory would not be accessible outside of a research setting, and the skills learned may not readily and completely transfer to overground locomotion in the community. Technologies suitable for cueing outside of laboratory environments could facilitate movement practice during daily activities at home or in the community and could strongly reinforce movement patterns and improve clinical outcomes. This narrative review presents an overview of cueing paradigms that have been utilized to improve gait and posture in people with PD and recommends development of closed-loop wearable systems that can be used at home or in the community to improve gait and posture in PD.