Postural instability in Parkinson’s disease: Review and bottom-up rehabilitative approaches

Acute Effects of Vibrating Insoles on Dynamic Balance and Gait Quality in Individuals With Diabetic Peripheral Neuropathy: A Randomized Crossover Study

OBJECTIVE

This study investigated the effects of vibrating insoles on dynamic balance and gait quality during level and stair walking and explored the influence of vibration type and frequency in individuals with diabetic peripheral neuropathy (DPN).

RESEARCH DESIGN AND METHODS

Twenty-two men with DPN were assessed for gait quality and postural and dynamic balance during walking and stair negotiation using a motion capture system and force plates across seven vibratory insole conditions (Vcs) versus a control (Ctrl) condition (insole without vibration). Vibration was applied during standing and walking tasks, and 15-min rest-stop periods without vibration were interposed between conditions. Repeated measures test conditions were randomized. The primary outcomes were gait speed and dynamic balance.

RESULTS

Gait speed during walking significantly improved in all Vcs compared with Ctrl (P < 0.005), with Vc2, Vc4, and Vc6 identified as the most effective. Gait speed increased (reflecting faster walking) during stair ascent and descent in Vc2 (Ctrl vs. Vc2 for ascent 0.447 ± 0.180 vs. 0.517 ± 0.127 m/s; P = 0.037 and descent 0.394 ± 0.170 vs. 0.487 ± 0.125 m/s; P = 0.016), Vc4 (Ctrl vs. Vc4 for ascent 0.447 ± 0.180 vs. 0.482 ± 0.197 m/s; P = 0.047 and descent 0.394 ± 0.170 vs. 0.438 ± 0.181 m/s; P = 0.017), and Vc6 (Ctrl vs. Vc6 for ascent 0.447 ± 0.180 vs. 0.506 ± 0.179 m/s; P = 0.043 and descent 0.394 ± 0.170 vs. 0.463 ± 0.159 m/s; P = 0.026). Postural balance improved during quiet standing with eyes closed in Vc2, Vc4, Vc6, and Vc7 (P < 0.005).

CONCLUSIONS

Vibrating insoles are an effective acute strategy for improving postural balance and gait quality during level walking and stair descent in individuals with DPN. These benefits are particularly evident when the entire plantar foot surface is stimulated.

Unraveling the threads of stability: A review of the neurophysiology of postural control in Parkinson's disease

Postural instability is a detrimental and often treatment-refractory symptom of Parkinson's disease. While many existing studies quantify the biomechanical deficits among various postural domains (static, anticipatory, and reactive) in this population, less is known regarding the neural network dysfunctions underlying these phenomena. This review will summarize current studies on the cortical and subcortical neural activities during postural responses in healthy subjects and those with Parkinson's disease. We will also review the effects of current therapies, including neuromodulation and feedback-based wearable devices, on postural instability symptoms. With recent advances in implantable devices that allow chronic, ambulatory neural data collection from patients with Parkinson's disease, combined with sensors that can quantify biomechanical measurements of postural responses, future work using these devices will enable better understanding of the neural mechanisms of postural control. Bridging this knowledge gap will be the critical first step towards developing novel neuromodulatory interventions to enhance the treatment of postural instability in Parkinson's disease.

The role of robot-assisted training on rehabilitation outcomes in Parkinson's disease: a systematic review and meta-analysis

PURPOSE

The study aims to assess the efficacy of robot-assisted rehabilitation training on upper and lower limb motor function and fatigue in Parkinson's disease (PD), and to explore the best-acting robotic rehabilitation program.

METHODS

We searched studies in seven databases and the search period was from the build to 30 June 2023. Two researchers independently screened studies and assessed the quality of the studies for data extraction.

RESULTS

A total of 21 studies were included, 18 studies related to lower limbs rehabilitation and 3 studies related to upper limbs rehabilitation, involving a total of 787 participants. The results showed that robot-assisted rehabilitation significantly improved indicators of lower limb motor function UPDRS Part III (WMD = -3.58, 95% CI = -5.91 to -1.25, p = 0.003) and BBS (WMD = 4.24, 95% CI = 2.88 to 5.54, p < 0.001), as well as non-motor symptoms of fatigue (WMD = -13.39, 95% CI = -17.92 to -8.86, p < 0.001) in PD patients. At the level of upper limb function, there was no statistically significant difference in the outcome measures of PFS (WMD = -0.25, 95% CI = -4.44 to 3.93, p = 0.9) and BBT (WMD = 1.73, 95% CI = -2.85 to 6.33, p = 0.458).

CONCLUSION

Robot-assisted rehabilitation significantly improved motor function, fatigue, and balance confidence in PD patients, but current evidence doesn't show that intelligent rehabilitation systems improve upper limb function. In particular, robotics combined with virtual reality worked best.

The 'Postural Rhythm' of the Ground Reaction Force during Upright Stance and Its Conversion to Body Sway-The Effect of Vision, Support Surface and Adaptation to Repeated Trials

The ground reaction force (GRF) recorded by a platform when a person stands upright lies at the interface between the neural networks controlling stance and the body sway deduced from centre of pressure (CoP) displacement. It can be decomposed into vertical (VGRF) and horizontal (HGRF) vectors. Few studies have addressed the modulation of the GRFs by the sensory conditions and their relationship with body sway. We reconsidered the features of the GRFs oscillations in healthy young subjects (n = 24) standing for 90 s, with the aim of characterising the possible effects of vision, support surface and adaptation to repeated trials, and the correspondence between HGRF and CoP time-series. We compared the frequency spectra of these variables with eyes open or closed on solid support surface (EOS, ECS) and on foam (EOF, ECF). All stance trials were repeated in a sequence of eight. Conditions were randomised across different days. The oscillations of the VGRF, HGRF and CoP differed between each other, as per the dominant frequency of their spectra (around 4 Hz, 0.8 Hz and <0.4 Hz, respectively) featuring a low-pass filter effect from VGRF to HGRF to CoP. GRF frequencies hardly changed as a function of the experimental conditions, including adaptation. CoP frequencies diminished to <0.2 Hz when vision was available on hard support surface. Amplitudes of both GRFs and CoP oscillations decreased in the order ECF > EOF > ECS ≈ EOS. Adaptation had no effect except in ECF condition. Specific rhythms of the GRFs do not transfer to the CoP frequency, whereas the magnitude of the forces acting on the ground ultimately determines body sway. The discrepancies in the time-series of the HGRF and CoP oscillations confirm that the body's oscillation mode cannot be dictated by the inverted pendulum model in any experimental conditions. The findings emphasise the robustness of the VGRF "postural rhythm" and its correspondence with the cortical theta rhythm, shed new insight on current principles of balance control and on understanding of upright stance in healthy and elderly people as well as on injury prevention and rehabilitation.

Postural stability in early Parkinson’s disease: effect of cognitive dual-tasking

Purpose: The primary aim of this study is to evaluate postural stability by using a static posturography in patients with early Parkinson’s disease (PD). Secondly, this paper addresses the need for illustrating the effect of dual-tasking on postural stability in early PD patients. Materials and Methods: Twenty-nine early PD patients with maximum 5 years of disease duration were included in this study. The selected group had no clinical PI while their age- and sex-matched healthy controls were carried out. Neurological examination and mini-mental state examination (MMSE) were performed in all subjects. Unified Parkinson Disease Rating Scale (UPDRS) and modified Hoehn and Yahr (H&Y) scores were recorded in PD patients. Postural stability was assessed in all subjects on a static posturography platform under three different conditions: eyes open, eyes closed and a cognitive task of producing words with given letters. Results: The mean age of the PD was 59.2±10.5 whereas the control groups mean age was 56.3±7.6 (p>0.05). The female-male ratio was 9/20 in the PD and 12/17 in the control group. There was no important difference between the two groups in terms of demographic characteristics. In the PD group, the mean UPDRS was 12.8±4.9. The patients were mostly receiving polytherapy. Eye closure and cognitive task caused an increase in most sway parameters in both groups. Conclusion: Early PD patients on medication, postural stability is preserved and cognitive dual-tasking does not affect postural stability in these patients in the early stage.

Improvement in sagittal alignment and mechanical low-back pain following deep brain stimulation for Parkinson's disease: illustrative case

BACKGROUND

Parkinson's disease (PD) is a common neurogenerative disease marked by the characteristic triad of bradykinesia, rigidity, and tremor. A significant percentage of patients with PD also demonstrate postural abnormalities (camptocormia) that limit ambulation and accelerate degenerative pathologies of the spine. Although deep brain stimulation (DBS) is a well-established treatment for the motor fluctuations and tremor seen in PD, the efficacy of DBS on postural abnormalities in these patients is less clear.

OBSERVATIONS

The authors present a patient with a history of PD and prior lumbosacral fusion who underwent bilateral subthalamic nucleus DBS and experienced immediate improvement in sagittal alignment and subjective relief of mechanical low-back pain.

LESSONS

DBS may improve postural abnormalities seen in PD and potentially delay or reduce the need for spinal deformity surgery.

Cognitive Function and Postural Control Strategies in Relation to Disease Progression in Patients with Parkinson's Disease

AIM

This study assessed the influence of performing an additional cognitive task on center of pressure (COP) displacement in the early and advanced stages of patients with Parkinson's disease (PD) compared to age-matched healthy controls (HCs).

METHODS

The study included 40 HCs and 62 patients with PD: early PD (n = 38) and advanced PD (n = 24). COP parameters were determined by static posturography during quiet standing with open eyes (ST, single task) and simultaneous performance of a cognitive task (DT, dual task). Cognitive functioning was examined with a Mini Mental State Examination, number-counting-backward test, and number of enunciated words during DT.

RESULTS

In the advanced-PD group, DT significantly reduced the sway radius (p = 0.009), area of stabilogram (p = 0.034), medio-lateral length (p = 0.027), and velocity (p = 0.033) compared to ST. In HCs, DT showed a significant increase in the sway radius (p = 0.006), total length (p = 0.039), sway velocity (p = 0.037), anterior-posterior length, and sway velocity. Both PD groups showed worse cognitive performance compared to HCs.

CONCLUSIONS

Both early and advanced patients with PD showed significant delay in cognitive performance associated with executive function compared to the HCs. During additional cognitive tasks, patients with advanced stages of PD may reduce stabilographic parameters in medio-lateral direction, and this is probably an adaptive strategy to restore balance.

Initial Vestibular Function May Be Associated with Future Postural Instability in Parkinson’s Disease

Backgrounds: We aimed to understand the association between initial vestibular function examination and postural instability (PI) development in Parkinson’s disease (PD). Methods: After screening 51 PD patients, we divided 31 patients into 2 groups based on the presence of PI at the follow-up visit and compared the clinical features and vestibular-evoked myogenic potential (VEMP) variables. Results: The mean values of Hoehn and Yahr stage, Unified Parkinson’s Disease Rating Scale (UPDRS) part III, and item 30 (postural stability) of UPDRS were larger in patients with PI at a follow-up visit (p = 0.000, 0.006, 0.048, respectively). In VEMP analyses, the onset latencies of left and right cervical VEMPs were significantly reduced in patients with PI (p = 0.013, 0.040, respectively). Conclusion: We found that the initial VEMP test may be associated with later postural imbalance in PD, suggesting the baseline evaluation may help predict future PI occurrence. A more significant number of patients and more long-term follow-ups are likely to be required for confirmation.

LA-ICP-MS bioimaging demonstrated disturbance of metal ions in the brain of Parkinson's disease model mouse undergoing manganese-enhanced MRI

Manganese-enhanced MRI (MEMRI) is a powerful tool to study neuronal activity and microarchitecture in vivo. Yet the influence of exogenous manganese on the brain of the Parkinson's disease (PD) model mouse is poorly understood. Laser ablation connected to inductively coupled plasma mass spectrometry (LA-ICP-MS) imaging for tissue section is an ideal tool to simultaneously analyze the metabolism of endogenous metal ions. In this study, DJ-1 knockout PD model mice were subjected to an MnCl₂ saline treatment and the distribution of Mn and several other endogenous metal ions in brain regions was assessed by MEMRI and LA-ICP-MS imaging. The results demonstrated that Mn mainly deposited in subcortical regions, such as ventricles, hippocampus (HC), medial preoptic nucleus (MPO), lateral septal nucleus (LS), and ventromedial hypothalamic nucleus (VMH). The enhanced signal-to-noise ratio (S/N) determined by MEMRI for Mn is closely related to the signal in LA-ICP-MS imaging. Significantly, the treatment of MnCl₂ disturbs the homeostasis of iron, zinc, copper, and calcium in the DJ-1 mouse, which could result in more severe symptoms of PD. Therefore, the application of MEMRI in the study of neurological disease must be made with caution.

Deep brain stimulation in the subthalamic nuclei alters postural alignment and adaptation in Parkinson's disease

Parkinson’s disease (PD) can produce postural abnormalities of the standing body position such as kyphosis. We investigated the effects of PD, deep brain stimulation (DBS) in the subthalamic nucleus (STN), vision and adaptation on body position in a well-defined group of patients with PD in quiet standing and during balance perturbations. Ten patients with PD and 25 young and 17 old control participants were recruited. Body position was measured with 3D motion tracking of the ankle, knee, hip, shoulder and head. By taking the ankle as reference, we mapped the position of the joints during quiet standing and balance perturbations through repeated calf muscle vibration. We did this to explore the effect of PD, DBS in the STN, and vision on the motor learning process of adaptation in response to the repeated stimulus. We found that patients with PD adopt a different body position with DBS ON vs. DBS OFF, to young and old controls, and with eyes open vs. eyes closed. There was an altered body position in PD with greater flexion of the head, shoulder and knee (p≤0.042) and a posterior position of the hip with DBS OFF (p≤0.014). With DBS ON, body position was brought more in line with the position taken by control participants but there was still evidence of greater flexion at the head, shoulder and knee. The amplitude of movement during the vibration period decreased in controls at all measured sites with eyes open and closed (except at the head in old controls with eyes open) showing adaptation which contrasted the weaker adaptive responses in patients with PD. Our findings suggest that alterations of posture and greater forward leaning with repeated calf vibration, are independent from reduced movement amplitude changes. DBS in the STN can significantly improve body position in PD although the effects are not completely reversed. Patients with PD maintain adaptive capabilities by leaning further forward and reducing movement amplitude despite their kyphotic posture.

Effects of robot-assisted gait training on postural instability in Parkinson's disease: a systematic review

INTRODUCTION

Postural instability is a cardinal feature of Parkinson's disease, together with rest tremor, rigidity and bradykinesia. It is a highly disabling symptom that becomes increasingly common with disease progression and represents a major source of reduced quality of life in patients with Parkinson's disease. Rehabilitation aims to enable patients with Parkinson's disease to maintain their maximum level of mobility, activity and independence. To date, a wide range of rehabilitation approaches has been employed to treat postural instability in Parkinson's disease, including robotic training. Our main aim was to conduct a systematic review of current literature about the effects of robot-assisted gait training on postural instability in patients with Parkinson's disease.

EVIDENCE ACQUISITION

A systematic search using the following MeSH terms "Parkinson disease," "postural balance," "robotics," "rehabilitation" AND string "robotics [mh]" OR "robot-assisted" OR "electromechanical" AND "rehabilitation [mh]" OR "training" AND "postural balance [mh]" was conducted on PubMed, Cochrane Library and Pedro electronic databases. Full text articles in English published up to December 2020 were included. Data about patient characteristics, robotic devices, treatment procedures and outcome measures were considered. Every included article got checked for quality. Level of evidence was defined for all studies.

EVIDENCE SYNTHESIS

Three authors independently extracted and verified data. In total, 18 articles (2 systematic reviews, 9 randomized controlled trials, 4 uncontrolled studies and 3 case series/case reports) were included. Both end-effector and exoskeleton devices were investigated as to robot-assisted gait training modalities. No clear relationship between treatment parameters and clinical conditions was observed. We found a high level of evidence about the effects of robot-assisted gait training on balance and freezing of gait in patients with Parkinson's disease.

CONCLUSIONS

This systematic review provides to the reader a complete overview of current literature and levels of evidence about the effects of robot-assisted gait training on postural instability issues (static and dynamic balance, freezing of gait, falls, confidence in activities of daily living and gait parameters related to balance skills) in patients with Parkinson's disease.