Where Do Parkinson's Disease Patients Look while Walking?

Topography of Cholinergic Nerve Terminal Vulnerability and Balance Self-Efficacy in Parkinson's Disease

BACKGROUND

Postural instability and gait disturbances (PIGD) represent a significant cause of disability in Parkinson's disease (PD). Cholinergic system dysfunction has been implicated in falls in PD. The occurrence of falls typically results in fear of falling (FoF) that in turn may lead to poorer balance self-efficacy. Balance self-efficacy refers to one's level of confidence in their ability to balance while completing activities of daily living like getting dressed, bathing, and walking. Lower self-efficacy, or greater FoF during these activities is a function of motor, cognitive, and emotional impairments and may impact quality of life in PD. Unlike known cholinergic reduction, especially in the right lateral geniculate and caudate nuclei, little is known about the role of cholinergic transporters in FoF or mobility self-efficacy in PD.

METHODS

[18F]fluoroethoxybenzovesamicol ([18F]FEOBV) positron emission tomography (PET) studies were conducted to assess vesicular acetylcholine transporter (VAChT) expression in 126 patients with PD (male (m) = 95, female (f) = 31). Participants had a mean age of 67.3 years (standard deviation (SD) = 7.1) and median Hoehn Yahr stage of 2.5. Patients also completed the Short Falls Efficacy Scale (sFES-I) as a survey measure of concerns about falling. [18F]FEOBV data were processed in Statistical Parametric Mapping (SPM) using a voxel-wise regression model with sFES-I scores as the outcome measure.

RESULTS

Reduced [18F]FEOBV binding in tectum, metathalamic (lateral more than medial geniculate nuclei), thalamus proper, bilateral mesiotemporal (hippocampal, parahippocampal, fusiform gyri and fimbriae), and right cerebellar lobule VI significantly associated with higher sFES-I scores (p < 0.05, family-wise error (FWE) correction after Threshold-Free Cluster Enhancement (TFCE)).

CONCLUSIONS

Unlike the more limited involvement of the brainstem-thalamic complex and caudate nuclei cholinergic topography associated with falls in PD, cholinergic reductions in the extended connectivity between the thalamic complex and the temporal limbic system via the fimbriae associates with FoF. Additional cholinergic changes were seen in the cerebellum. The temporal limbic system plays a role not only in episodic memory but also in spatial navigation, scene and contextual (e.g., emotional) processing. Findings may augur novel therapeutic approaches to treat poor mobility self-efficacy in PD.

CLINICAL TRIAL REGISTRATION

No: NCT02458430. Registered 18 March, 2015, https://www.

CLINICALTRIALS

gov/study/NCT02458430; No: NCT05459753. Registered 01 July, 2022, https://www.

CLINICALTRIALS

gov/study/NCT05459753.

Effects of activity-oriented physiotherapy with and without eye movement training on dynamic balance, functional mobility, and eye movements in patients with Parkinson's disease: An assessor-blinded randomised controlled pilot trial

OBJECTIVES

To describe changes in balance, walking speed, functional mobility, and eye movements following an activity-oriented physiotherapy (AOPT) or its combination with eye movement training (AOPT-E) in patients with Parkinson's disease (PD). To explore the feasibility of a full-scale randomised controlled trial (RCT).

METHODS

Using an assessor-blinded pilot RCT, 25 patients with PD were allocated to either AOPT or AOPT-E. Supervised interventions were performed 30 minutes, 4x/weekly, for 4 weeks, alongside inpatient rehabilitation. Outcomes were assessed at baseline and post-intervention, including dynamic balance, walking speed, functional and dual-task mobility, ability to safely balance, health-related quality of life (HRQoL), depression, and eye movements (number/duration of fixations) using a mobile eye tracker. Freezing of gait (FOG), and falls-related self-efficacy were assessed at baseline, post-intervention, and 4-week follow-up. Effect sizes of 0.10 were considered weak, 0.30 moderate, and ≥0.50 strong. Feasibility was assessed using predefined criteria: recruitment, retention and adherence rates, adverse events, falls, and post-intervention acceptability using qualitative interviews.

RESULTS

Improvements were observed in dynamic balance (effect size r = 0.216-0.427), walking speed (r = 0.165), functional and dual-task mobility (r = 0.306-0.413), ability to safely balance (r = 0.247), HRQoL (r = 0.024-0.650), and depression (r = 0.403). Falls-related self-efficacy (r = 0.621) and FOG (r = 0.248) showed varied improvements, partly sustained at follow-up. Eye movement improvements were observed after AOPT-E only. Feasibility analysis revealed that recruitment was below target, with less than two patients recruited per month due to COVID-19 restrictions. Feasibility targets were met, with a retention rate of 96% (95% confidence interval [CI]: 77.68-99.79) and a 98.18% (95% CI: 96.12-99.20) adherence rate, exceeding the targets of 80% and 75%, respectively. One adverse event unrelated to the study intervention confirmed intervention safety, and interview data indicated high intervention acceptability.

CONCLUSIONS

AOPT-E and AOPT appeared to be effective in patients with PD. Feasibility of a larger RCT was confirmed and is needed to validate results.

Low and high-order topological disruption of functional networks in multiple system atrophy with freezing of gait: A resting-state study

OBJECTIVE

Freezing of gait (FOG), a specific survival-threatening gait impairment, needs to be urgently explored in patients with multiple system atrophy (MSA), which is characterized by rapid progression and death within 10 years of symptom onset. The objective of this study was to explore the topological organisation of both low- and high-order functional networks in patients with MAS and FOG.

METHOD

Low-order functional connectivity (LOFC) and high-order functional connectivity FC (HOFC) networks were calculated and further analysed using the graph theory approach in 24 patients with MSA without FOG, 20 patients with FOG, and 25 healthy controls. The relationship between brain activity and the severity of freezing symptoms was investigated in patients with FOG.

RESULTS

Regarding global topological properties, patients with FOG exhibited alterations in the whole-brain network, dorsal attention network (DAN), frontoparietal network (FPN), and default network (DMN), compared with patients without FOG. At the node level, patients with FOG showed decreased nodal centralities in sensorimotor network (SMN), DAN, ventral attention network (VAN), FPN, limbic regions, hippocampal network and basal ganglia network (BG), and increased nodal centralities in the FPN, DMN, visual network (VIN) and, cerebellar network. The nodal centralities of the right inferior frontal sulcus, left lateral amygdala and left nucleus accumbens (NAC) were negatively correlated with the FOG severity.

CONCLUSION

This study identified a disrupted topology of functional interactions at both low and high levels with extensive alterations in topological properties in MSA patients with FOG, especially those associated with damage to the FPN. These findings offer new insights into the dysfunctional mechanisms of complex networks and suggest potential neuroimaging biomarkers for FOG in patients with MSA.

Physiological measures and anatomical correlates of subthalamic deep brain stimulation effect on gait in Parkinson's disease

We examined whether conflicting visual and non-visual information leads to gait abnormalities and how the subthalamic deep brain stimulation (STN DBS) influences gait dysfunction in Parkinson's disease (PD). We used a motion capture system to measure the kinematics of the lower limbs during treadmill walking in immersive virtual reality. The visual information provided in the virtual reality paradigm was modulated to create a mismatch between the optic-flow velocity of the visual scene and the walking speed on the treadmill. In each mismatched condition, we calculated the step duration, step length, step phase, step height, and asymmetries. The key finding of our study was that mismatch between treadmill walking speed and the optic-flow velocity did not consistently alter gait parameters in PD. We also found that STN DBS improved the PD gait pattern by changing the stride length and step height. The effects on phase and left/right asymmetry were not statistically significant. The DBS parameters and location also determined its effects on gait. Statistical effects on stride length and step height were noted when the DBS volume of activated tissue (VTA) was in the dorsal aspect of the subthalamus. The statistically significant effects of STN DBS was present when VTA significantly overlapped with MR tractogrphically measured motor and pre-motor hyperdirect pathways. In summary, our results provide novel insight into ways for controlling walking behavior in PD using STN DBS.

Alterations of structure and functional connectivity of visual brain network in patients with freezing of gait in Parkinson’s disease

Freezing of gait (FOG) is a disabling gait disorder common in advanced stage of Parkinson’s disease (PD). The gait performance of PD-FOG patients is closely linked with visual processing. Here, we aimed to investigate the structural and functional change of visual network in PD-FOG patients. Seventy-eight PD patients (25 with FOG, 53 without FOG) and 29 healthy controls (HCs) were included. All the participants underwent structural 3D T1-weighted magnetic resonance imaging (MRI) and resting state functional MRI scan. Our results demonstrated a significant decrease of right superior occipital gyrus gray matter density in PD-FOG relative to non-FOG (NFOG) patients and healthy controls (PD-FOG vs. PD-NFOG: 0.33 ± 0.04 vs. 0.37 ± 0.05, p = 0.005; PD-FOG vs. HC: 0.37 ± 0.05 vs. 0.39 ± 0.06, p = 0.002). Functional MRI revealed a significant decrease of connectivity between right superior occipital gyrus and right paracentral lobule in PD-FOG compared to PD-NFOG (p = 0.045). In addition, the connectivity strength was positively correlated with gray matter density of right superior occipital gyrus (r = 0.471, p = 0.027) and negatively associated with freezing of gait questionnaire (FOGQ) score (r = -0.562, p = 0.004). Our study suggests that the structural and functional impairment of visual-motor network might underlie the neural mechanism of FOG in PD.