Freezing beyond gait in Parkinson's disease: A review of current neurobehavioral evidence

Connecting the dots: Sensory cueing enhances functional connectivity between pre-motor and supplementary motor areas in Parkinson's disease

People with Parkinson's disease often exhibit improvements in motor tasks when exposed to external sensory cues. While the effects of different types of sensory cues on motor functions in Parkinson's disease have been widely studied, the underlying neural mechanism of these effects and the potential of sensory cues to alter the motor cortical activity patterns and functional connectivity of cortical motor areas are still unclear. This study aims to compare changes in oxygenated haemoglobin, deoxygenated haemoglobin and correlations among different cortical regions of interest during wrist movement under different external stimulus conditions between people with Parkinson's disease and controls. Ten Parkinson's disease patients and 10 age- and sex-matched neurologically healthy individuals participated, performing repetitive wrist flexion and extension tasks under auditory and visual cues. Changes in oxygenated and deoxygenated haemoglobin in motor areas were measured using functional near-infrared spectroscopy, along with electromyograms from wrist muscles and wrist movement kinematics. The functional near-infrared spectroscopy data revealed significantly higher neural activity changes in the Parkinson's disease group's pre-motor area compared to controls (p = 0.006), and functional connectivity between the supplementary motor area and pre-motor area was also significantly higher in the Parkinson's disease group when external sensory cues were present (p = 0.016). These results indicate that external sensory cues' beneficial effects on motor tasks are linked to changes in the functional connectivity between motor areas responsible for planning and preparation of movements.

Grid cells: the missing link in understanding Parkinson's disease?

The mechanisms underlying Parkinson's disease (PD) are complex and not fully understood, and the box-and-arrow model among other current models present significant challenges. This paper explores the potential role of the allocentric brain and especially its grid cells in several PD motor symptoms, including bradykinesia, kinesia paradoxa, freezing of gait, the bottleneck phenomenon, and their dependency on cueing. It is argued that central hubs, like the locus coeruleus and the pedunculopontine nucleus, often narrowly interpreted in the context of PD, play an equally important role in governing the allocentric brain as the basal ganglia. Consequently, the motor and secondary motor (e.g., spatially related) symptoms of PD linked with dopamine depletion may be more closely tied to erroneous computation by grid cells than to the basal ganglia alone. Because grid cells and their associated central hubs introduce both spatial and temporal information to the brain influencing velocity perception they may cause bradykinesia or hyperkinesia as well. In summary, PD motor symptoms may primarily be an allocentric disturbance resulting from virtual faulty computation by grid cells revealed by dopamine depletion in PD.

Development and implementation of the frog-in-maze game to study upper limb movement in people with Parkinson's disease

Upper-limb bradykinesia occurs early in Parkinson's disease (PD) and bradykinesia is required for diagnosis. Our goal was to develop, implement and validate a game "walking" a frog through a maze using bimanual, alternating finger-tapping movements to provide a salient, objective, and remotely monitorable method of tracking disease progression and response to therapy in PD. Twenty-five people with PD and 16 people without PD participated. Responses on 5 different mazes were quantified and compared to spatiotemporal gait parameters and standard disease metrics in these participants. Intertap interval (ITI) on maze 2 & 3, which included turns, was strongly inversely related to stride-length and stride-velocity and directly related to motor UPDRS scores. Levodopa decreased ITI, except in maze 4. PD participants with freezing of gait had longer ITI on all mazes. The responses quantified on maze 2 & 3 were related to disease severity and gait stride-length, were levodopa responsive, and were worse in people with freezing of gait, suggesting that these mazes could be used to quantify motor dysfunction in PD. Programming our frog-in-maze game onto a remotely distributable platform could provide a tool to monitor disease progression and therapeutic response in people with PD, including during clinical trials.

Cortical Disinhibition Drives Freezing of Gait in Parkinson's Disease and an Exploratory Repetitive Transcranial Magnetic Stimulation Study

BACKGROUND

Dysfunction of the primary motor cortex, participating in regulation of posture and gait, is implicated in freezing of gait (FOG) in Parkinson's disease (PD).

OBJECTIVE

The aim was to reveal the mechanisms of "OFF-period" FOG (OFF-FOG) and "levodopa-unresponsive" FOG (ONOFF-FOG) in PD.

METHODS

We measured the transcranial magnetic stimulation (TMS) indicators and gait parameters in 21 healthy controls (HCs), 15 PD patients with ONOFF-FOG, 15 PD patients with OFF-FOG, and 15 PD patients without FOG (Non-FOG) in "ON" and "OFF" medication conditions. Difference of TMS indicators in the four groups and two conditions and its correlations with gait parameters were explored. Additionally, we explored the effect of 10 Hz repetitive TMS on gait and TMS indicators in ONOFF-FOG patients.

RESULTS

In "OFF" condition, short interval intracortical inhibition (SICI) exhibited remarkable attenuation in FOG patients (both ONOFF-FOG and OFF-FOG) compared to Non-FOG patients and HCs. The weakening of SICI correlated with impaired gait characteristics in FOG. However, in "ON" condition, SICI in ONOFF-FOG patients reduced compared to OFF-FOG patients. Pharmacological treatment significantly improved SICI and gait in OFF-FOG patients, and high-frequency repetitive TMS distinctly improved gait in ONOFF-FOG patients, accompanied by enhanced SICI.

CONCLUSIONS

Motor cortex disinhibition, represented by decreased SICI, is related to FOG in PD. Refractory freezing in ONOFF-FOG patients correlated with the their reduced SICI insensitive to dopaminergic medication. SICI can serve as an indicator of the severity of impaired gait characteristics in FOG and reflect treatments efficacy for FOG in PD patients. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Heart-rate variability as a new marker for freezing predisposition in Parkinson's disease

INTRODUCTION

Freezing of gait (FoG) is a debilitating symptom of advanced Parkinson's disease (PD) characterized by a sudden, episodic stepping arrest despite the intention to continue walking. The etiology of FoG is still unknown, but accumulating evidence unraveled physiological signatures of the autonomic nervous system (ANS) around FoG episodes. Here we aim to investigate for the first time whether detecting a predisposition for upcoming FoG events from ANS activity measured at rest is possible.

METHODS

We recorded heart-rate for 1-min while standing in 28 persons with PD with FoG (PD + FoG), while OFF, and in 21 elderly controls (EC). Then, PD + FoG participants performed walking trials containing FoG-triggering events (e.g., turns). During these trials, n = 15 did experience FoG (PD + FoG+), while n = 13 did not (PD + FoG-). Most PD participants (n = 20: 10 PD + FoG+ and 10 PD + FoG-) repeated the experiment 2-3 weeks later, while ON, and none experienced FoG. We then analyzed heart-rate variability (HRV), i.e., the fluctuations in time intervals between adjacent heartbeats, mainly generated by brain-heart interactions.

RESULTS

During OFF, HRV was significantly lower in PD + FoG + participants, reflecting imbalanced sympathetic/parasympathetic activity and disrupted self-regulatory capacity. PD + FoG- and EC participants showed comparable (higher) HRV. During ON, HRV did not differ among groups. HRV values did not correlate with age, PD duration, levodopa consumption, nor motor -symptoms severity scores.

CONCLUSIONS

Overall, these results document for the first time a relation between HRV at rest and FoG presence/absence during gait trials, expanding previous evidence regarding the involvement of ANS in FoG.

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.

Exploring the Complex Phenotypes of Impaired Finger Dexterity in Mild-to-moderate Stage Parkinson's Disease: A Time-Series Analysis

BACKGROUND

Impaired dexterity is an early motor symptom in Parkinson's disease (PD) that significantly impacts the daily activity of patients; however, what constitutes complex dexterous movements remains controversial.

OBJECTIVE

To explore the characteristics of finger dexterity in mild-to-moderate stage PD.

METHODS

We quantitatively assessed finger dexterity in 48 mild-to-moderate stage PD patients and 49 age-matched controls using a simple alternating two-finger typing test for 15 seconds. Time-series analyses of various kinematic parameters with machine learning were compared between sides and groups.

RESULTS

Both the more and less affected hands of patients with PD had significantly lower typing frequency and slower typing velocity than the non-dominant and the dominant hands of controls (p = 0.019, p = 0.016, p < 0.001, p < 0.001). The slope of the typing velocity decreased with time, indicating a sequence effect in the PD group. A typing duration of 6 seconds was determined sufficient to discriminate PD patients from controls. Typing error, repetition, and repetition rate were significantly higher in the more affected hands of patients with PD than in the non-dominant hand of controls (p < 0.001, p = 0.03, p < 0.001). The error rate was constant, whereas the repetition rate was steep during the initiation of typing. A predictive model of the more affected hand demonstrated an accuracy of 70% in differentiating PD patients from controls.

CONCLUSION

Our study demonstrated complex components of impaired finger dexterity in mild-to-moderate stage PD, namely bradykinesia with sequence effects, error, and repetition at the initiation of movement, suggesting that multiple neural networks may be involved in dexterity deficits in PD.

Motor cortex excitability is reduced during freezing of upper limb movement in Parkinson's disease

Whilst involvement of the motor cortex in the phenomenon of freezing in Parkinson's disease has been previously suggested, few empiric studies have been conducted to date. We investigated motor cortex (M1) excitability in eleven right-handed Parkinson's disease patients (aged 69.7 ± 9.6 years, disease duration 11.2 ± 3.9 years, akinesia-rigidity type) with verified gait freezing using a single-pulse transcranial magnetic stimulation (TMS) repetitive finger tapping paradigm. We delivered single TMS pulses at 120% of the active motor threshold at the 'ascending (contraction)' and 'descending (relaxation)' slope of the tap cycle during i) regular tapping, ii) the transition period of the three taps prior to a freeze and iii) during freezing of upper limb movement. M1 excitability was modulated along the tap cycle with greater motor evoked potentials (MEPs) during 'ascending' than 'descending'. Furthermore, MEPs during the 'ascending' phase of regular tapping, but not during the transition period, were greater compared to the MEPs recorded throughout a freeze. Neither force nor EMG activity 10-110 s before the stimulus predicted MEP size. This piloting study suggests that M1 excitability is reduced during freezing and the transition period preceding a freeze. This supports that M1 excitability is critical to freezing in Parkinson's disease.

Cortical mechanisms of movement recovery after freezing in Parkinson's disease

Involuntary interruptions of upper limb movements, referred to as "upper limb freezing" (ULF) belong to the most disabling symptoms of Parkinson's disease (PD). Our study aimed to explore the cortical neuronal mechanisms underlying the reinstation of regular movement after a freezing episode and to control them by voluntary stops. We hypothesized that this movement recovery after a freeze would be accompanied by a decrease of beta power (13-30 Hz) over the primary sensorimotor cortex (electrode "C3"). We recorded a 62-channel surface EEG in 14 PD patients during a repetitive finger tapping task. After performing time-frequency analysis of the EEG data we segmented it to i) regular finger taps, ii) ULF episodes, and iii) voluntary movement stops (VS). We analysed cortical activity during each movement modality and later focused on the last 500 ms of ULF and VS and the first half of the following regular tap. At the beginning of regular finger taps we found decreased alpha power (6-12 Hz) over C3 (P = 0.01). During ULF, there was no significant activity modulation in the alpha and beta frequency bands, whereas beta power increased over C3 during VS (P = 0.0038). When tapping was reinstated after a freeze, we found that 100 ms before movement onset beta power decreased first present over C3, followed by fronto-central electrodes and then reaching the ipsilateral right fronto-temporal electrodes when reinstating regular tapping (P = 0.0256). Initiating movement after a VS showed a different pattern with a decrease of parieto-occipital beta activity 200 ms prior to the first tap (P = 0.044). Our findings suggest that PD freezers make use of different cortical pathways when re-initiating movement after ULF or VS. This includes either fronto-central or parieto-occipital pathways. These findings may help to customize novel neuromodulation strategies to counteract freezing behaviour.

Quantitative Digitography Measures Motor Symptoms and Disease Progression in Parkinson’s Disease

Background:

Assessment of motor signs in Parkinson’s disease (PD) requires an in-person examination. However, 50% of people with PD do not have access to a neurologist. Wearable sensors can provide remote measures of some motor signs but require continuous monitoring for several days. A major unmet need is reliable metrics of all cardinal motor signs, including rigidity, from a simple short active task that can be performed remotely or in the clinic.

Objective:

Investigate whether thirty seconds of repetitive alternating finger tapping (RAFT) on a portable quantitative digitography (QDG) device, which measures amplitude and timing, produces reliable metrics of all cardinal motor signs in PD.

Methods:

Ninety-six individuals with PD and forty-two healthy controls performed a thirty-second QDG-RAFT task and clinical motor assessment. Eighteen individuals were followed longitudinally with repeated assessments for an average of three years and up to six years.

Results:

QDG-RAFT metrics showed differences between PD and controls and provided correlated metrics for total motor disability (MDS-UPDRS III) and for rigidity, bradykinesia, tremor, gait impairment, and freezing of gait (FOG). Additionally, QDG-RAFT tracked disease progression over several years off therapy and showed differences between akinetic-rigid and tremor-dominant phenotypes, as well as people with and without FOG.

Conclusions:

QDG is a reliable technology, which could be used in the clinic or remotely. This could improve access to care, allow complex remote disease management based on data received in real time, and accurate monitoring of disease progression over time in PD. QDG-RAFT also provides the comprehensive motor metrics needed for therapeutic trials.

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.

Improving Upper Extremity Bradykinesia in Parkinson’s Disease: A Randomized Clinical Trial on the Use of Gravity-Supporting Exoskeletons

Hand movements are particularly impaired in patients with Parkinson’s Disease (PD), contributing to functional disability and difficulties in activities of daily living. Growing evidence has shown that robot-assisted therapy may be considered an effective and reliable method for the delivery of the highly repetitive training that is needed to trigger neuroplasticity, as intensive, repetitive and task-oriented training could be an ideal strategy to facilitate the relearning of motor function and to minimize motor deficit. The purpose of this study is to evaluate the improvement of hand function with semi-autonomous exercises using an upper extremity exoskeleton in patients with PD. A multicenter, parallel-group, randomized clinical trial was then carried out at the IRCCS Centro Neurolesi Bonino-Pulejo (Messina, Italy). Thirty subjects with a diagnosis of PD and a Hoehn–Yahr score between 2 and 3 were enrolled in the study. Patients were 1:1 randomized into either the experimental group (ERT), receiving 45 min training daily, 6 days weekly, for 8 weeks with Armeo^®Spring (Volketswil, Switzerland) (a gravity-supporting device), or the control group (CPT), which was subjected to the same amount of conventional physical therapy. Motor abilities were assessed before and after the end of the training. The main outcomes measures were the Nine-hole peg test and the motor section of the UPDRS. All patients belonging to ERT and 9 out of 15 patients belonging to the CPT completed the trial. ERT showed a greater improvement in the primary outcome measure (nine-hole peg test) than CPT. Moreover, a statistically significant improvement was found in ERT concerning upper limb mobility, and disease burden as compared to CPT. Using an upper extremity exoskeleton (i.e., the Armeo^®Spring) for semi-autonomous training in an inpatient setting is a new perspective to train patients with PD to improve their dexterity, executive function and, potentially, quality of life.

Therapeutic Devices for Motor Symptoms in Parkinson’s Disease: Current Progress and a Systematic Review of Recent Randomized Controlled Trials

Background

Pharmacotherapy is the first-line treatment option for Parkinson’s disease, and levodopa is considered the most effective drug for managing motor symptoms. However, side effects such as motor fluctuation and dyskinesia have been associated with levodopa treatment. For these conditions, alternative therapies, including invasive and non-invasive medical devices, may be helpful. This review sheds light on current progress in the development of devices to alleviate motor symptoms in Parkinson’s disease.

Methods

We first conducted a narrative literature review to obtain an overview of current invasive and non-invasive medical devices and thereafter performed a systematic review of recent randomized controlled trials (RCTs) of these devices.

Results

Our review revealed different characteristics of each device and their effectiveness for motor symptoms. Although invasive medical devices are usually highly effective, surgical procedures can be burdensome for patients and have serious side effects. In contrast, non-pharmacological/non-surgical devices have fewer complications. RCTs of non-invasive devices, especially non-invasive brain stimulation and mechanical peripheral stimulation devices, have proven effectiveness on motor symptoms. Nearly no non-invasive devices have yet received Food and Drug Administration certification or a CE mark.

Conclusion

Invasive and non-invasive medical devices have unique characteristics, and several RCTs have been conducted for each device. Invasive devices are more effective, while non-invasive devices are less effective and have lower hurdles and risks. It is important to understand the characteristics of each device and capitalize on these.

Symmetric and asymmetric bimanual coordination and freezing of gait in Parkinsonian patients in drug phases

Freezing of gait (FOG) is a debilitating symptom in patients with Parkinson's disease (PD), which may be associated with motor control impairments in tasks other than gait. This study aimed to examine whether symmetric and asymmetric bimanual coordination is impaired in PD with FOG (PD +FOG) patients and whether dual-task and drug phases may affect bimanual coordination in these patients. Twenty PD +FOG patients, 20 PD patients without FOG (PD -FOG) performed symmetric and asymmetric functional bimanual tasks (reach to and pick up a box and open a drawer to press a pushbutton inside it, respectively) under single-task and dual-task conditions. PD patients were evaluated during on- and off-drug phases. Kinematic and coordination measures were calculated for each task. PD +FOG patients demonstrated exacerbated impairments of bimanual coordination while performing goal-directed bimanual tasks, which was more evident in the asymmetric bimanual task and under dual-task conditions, highlighting the need for rehabilitation interventions for bimanual tasks that include different cognitive loads in these patients. Interestingly, 25% and 5% of participants in the PD +FOG and -FOG groups developed upper limb freezing 2 years later, respectively. This study aimed to examine whether symmetric and asymmetric bimanual coordination is impaired in Parkinson's disease with freezing of gait (PD +FOG) patients and whether dual-task and drug phases may affect bimanual coordination in these patients. PD +FOG patients demonstrated exacerbated impairment of bimanual coordination while performing goal-directed bimanual tasks, highlighting the need for rehabilitation interventions for bimanual tasks that include different cognitive loads in these patients.

Impaired Weight-Shift Amplitude in People with Parkinson's Disease with Freezing of Gait

BACKGROUND

People with Parkinson's disease and freezing of gait (FOG; freezers) suffer from pronounced postural instability. However, the relationship between these phenomena remains unclear and has mostly been tested in paradigms requiring step generation.

OBJECTIVE

To determine if freezing-related dynamic balance deficits are present during a task without stepping and determine the influence of dopaminergic medication on dynamic balance control.

METHODS

Twenty-two freezers, 16 non-freezers, and 20 healthy age-matched controls performed mediolateral weight-shifts at increasing frequencies when following a visual target projected on a screen (MELBA task). The amplitude and phase shift differences between center of mass and target motion were measured. Balance scores (Mini-BESTest), 360° turning speed and the freezing ratio were also measured. Subjects with Parkinson's disease were tested ON and partial OFF (overnight withdrawal) dopaminergic medication.

RESULTS

Freezers had comparable turning speed and balance scores to non-freezers and took more levodopa. Freezers produced hypokinetic weight-shift amplitudes throughout the MELBA task compared to non-freezers (p = 0.002), which were already present at task onset (p < 0.001). Freezers also displayed an earlier weight-shift breakdown than controls when OFF-medication (p = 0.008). Medication improved mediolateral weight-shifting in freezers and non-freezers. Freezers decreased their freezing ratio in response to medication.

CONCLUSION

Hypokinetic weight-shifting proved a marked postural control deficit in freezers, while balance scores and turning speed were similar to non-freezers. Both weight-shift amplitudes and the freezing ratio were responsive to medication in freezers, suggesting axial motor vigor is levodopa-responsive. Future work needs to test whether weight-shifting and freezing severity can be further ameliorated through training.

Motor blocks during bilateral stepping in Parkinson's disease and effects of dopaminergic medication

INTRODUCTION

Freezing of gait (FOG) is a complex symptom in Parkinson's disease (PD) that manifests during walking as limited forward progression despite the intention to walk. It is unclear if lower limb motor blocks (LLMB) that occur independently from FOG are related to overground FOG and the effects of dopaminergic medications.

METHODS

Nineteen patients with PD were tested on two separate days in the dopaminergic medication "on" and "off" states. The patients completed a series of freezing-provoking tasks while videotaped. Raters assessed videos for FOG presence using Movement Disorders Society Unified Parkinson's Disease Rating Scale item 3.11 score greater than or equal to 1 and FOG severity using the standardized FOG score. Whilst seated in a virtual environment, patients and 20 healthy controls stepped in right-left sequence on foot pedals. Frequency and percent time in LLMB were assessed for accurate classification of FOG presence and correlation to the FOG score.

RESULTS

Frequency and percent time spent in LLMB predicted the presence of FOG in both medication states. Percent time spent in LLMB correlated with FOG severity in both medication states. LLMB frequency predicted FOG severity in the "off" state only.

CONCLUSIONS

LLMB during bilateral stepping in a virtual environment predicted the presence and severity of FOG in PD in both "on" and "off" medication states. These findings support the use of this non-walking paradigm to detect and assess FOG in PD patients unable or unsafe to walk.

Simple Smartphone-Based Assessment of Gait Characteristics in Parkinson Disease: Validation Study

Background

Parkinson disease (PD) is a common movement disorder. Patients with PD have multiple gait impairments that result in an increased risk of falls and diminished quality of life. Therefore, gait measurement is important for the management of PD.

Objective

We previously developed a smartphone-based dual-task gait assessment that was validated in healthy adults. The aim of this study was to test the validity of this gait assessment in people with PD, and to examine the association between app-derived gait metrics and the clinical and functional characteristics of PD.

Methods

Fifty-two participants with clinically diagnosed PD completed assessments of walking, Movement Disorder Society Unified Parkinson Disease Rating Scale III (UPDRS III), Montreal Cognitive Assessment (MoCA), Hamilton Anxiety (HAM-A), and Hamilton Depression (HAM-D) rating scale tests. Participants followed multimedia instructions provided by the app to complete two 20-meter trials each of walking normally (single task) and walking while performing a serial subtraction dual task (dual task). Gait data were simultaneously collected with the app and gold-standard wearable motion sensors. Stride times and stride time variability were derived from the acceleration and angular velocity signal acquired from the internal motion sensor of the phone and from the wearable sensor system.

Results

High correlations were observed between the stride time and stride time variability derived from the app and from the gold-standard system (r=0.98-0.99, P<.001), revealing excellent validity of the app-based gait assessment in PD. Compared with those from the single-task condition, the stride time (F_1,103=14.1, P<.001) and stride time variability (F_1,103=6.8, P=.008) in the dual-task condition were significantly greater. Participants who walked with greater stride time variability exhibited a greater UPDRS III total score (single task: β=.39, P<.001; dual task: β=.37, P=.01), HAM-A (single-task: β=.49, P=.007; dual-task: β=.48, P=.009), and HAM-D (single task: β=.44, P=.01; dual task: β=.49, P=.009). Moreover, those with greater dual-task stride time variability (β=.48, P=.001) or dual-task cost of stride time variability (β=.44, P=.004) exhibited lower MoCA scores.

Conclusions

A smartphone-based gait assessment can be used to provide meaningful metrics of single- and dual-task gait that are associated with disease severity and functional outcomes in individuals with PD.

Executive function network's white matter alterations relate to Parkinson's disease motor phenotype

Parkinson's disease (PD) patients with postural instability and gait disorder phenotype (PIGD) are at high risk of cognitive deficits compared to those with tremor dominant phenotype (TD). Alterations of white matter (WM) integrity can occur in patients with normal cognitive functions (PD-N). However, the alterations of WM integrity related to cognitive functions in PD-N, especially in these two motor phenotypes, remain unclear. Diffusion tensor imaging (DTI) is a non-invasive neuroimaging method to evaluate WM properties and by applying DTI tractography, one can identify WM tracts connecting functional regions. Here, we 1) compared the executive function (EF) in PIGD phenotype with normal cognitive functions (PIGD-N) and TD phenotype with normal cognitive functions (TD-N) phenotypes; 2) used DTI tractography to evaluated differences in WM alterations between these two phenotypes within a task-based functional network; and 3) examined the WM integrity alterations related to EF in a whole brain network for PD-N patients regardless of phenotypes. Thirty-four idiopathic PD-N patients were classified into two groups based on phenotypes: TD-N and PIGD-N, using an algorithm based on UPDRS part III. Neuropsychological tests were used to evaluate patients' EF, including the Trail making test part A and B, the Stroop color naming, the Stroop word naming, the Stroop color-word interference task, as well as the FAS verbal fluency task and the animal category fluency tasks. DTI measures were calculated among WM regions associated with the verbal fluency network defined from previous task fMRI studies and compared between PIGD-N and TD-N groups. In addition, the relationship of DTI measures and verbal fluency scores were evaluated for our full cohort of PD-N patients within the whole brain network. These values were also correlated with the scores of the FAS verbal fluency task. Only the FAS verbal fluency test showed significant group differences, having lower scores in PIGD-N when compared to TD-N phenotype (p < 0.05). Compared to the TD-N, PIGD-N group exhibited significantly higher MD and RD in the tracts connecting the left superior temporal gyrus and left insula, and those connecting the right pars opercularis and right insula. Moreover, compared to TD-N, PIGD-N group had significantly higher RD in the tracts connecting right pars opercularis and right pars triangularis, and the tracts connecting right inferior temporal gyrus and right middle temporal gyrus. For the entire PD-N cohort, FAS verbal fluency scores positively correlated with MD in the superior longitudinal fasciculus (SLF). This study confirmed that PIGD-N phenotype has more deficits in verbal fluency task than TD-N phenotype. Additionally, our findings suggest: (1) PIGD-N shows more microstructural changes related to FAS verbal fluency task when compared to TD-N phenotype; (2) SLF plays an important role in FAS verbal fluency task in PD-N patients regardless of motor phenotypes.

Executive Control of Walking in People With Parkinson's Disease With Freezing of Gait

BACKGROUND

Walking abnormalities in people with Parkinson's disease (PD) are characterized by a shift in locomotor control from healthy automaticity to compensatory prefrontal executive control. Indirect measures of automaticity of walking (eg, step-to-step variability and dual-task cost) suggest that freezing of gait (FoG) may be associated with reduced automaticity of walking. However, the influence of FoG status on actual prefrontal cortex (PFC) activity during walking remains unclear.

OBJECTIVE

To investigate the influence of FoG status on automaticity of walking in people with PD.

METHODS

Forty-seven people with PD were distributed into 2 groups based on FoG status, which was assessed by the New Freezing of Gait Questionnaire: PD-FoG (n = 23; UPDRS-III = 35) and PD+FoG (n = 24; UPDRS-III = 43.1). Participants walked over a 9-m straight path (with a 180° turn at each end) for 80 seconds. Two conditions were tested off medication: single- and dual-task walking (ie, with a concomitant cognitive task). A portable functional near-infrared spectroscopy system recorded PFC activity while walking (including turns). Wearable inertial sensors were used to calculate spatiotemporal gait parameters.

RESULTS

PD+FoG had greater PFC activation during both single and dual-task walking than PD-FoG (P = .031). There were no differences in gait between PD-FoG and PD+FoG. Both groups decreased gait speed (P = .029) and stride length (P < .001) during dual-task walking compared with single-task walking.

CONCLUSIONS

These findings suggest that PD+FoG have reduced automaticity of walking, even in absence of FoG episodes. PFC activity while walking seems to be more sensitive than gait measures in identifying reduction in automaticity of walking in PD+FoG.

The impact of distinct cognitive dual-tasks on gait in Parkinson's disease and the associations with the clinical features of Parkinson's disease

AIMS

To investigate the impact of distinct cognitive dual-task abilities in patients with Parkinson's disease (PD) and compare the impact of these dual-tasks in association with the severity of PD and its clinical features.

MATERIALS AND METHODS

Modified Hoehn and Yahr Scale, UPDRS, and Standardized Mini-Mental State Examination (SMMSE) were evaluated in all PD patients. The subtype of PD and the presence of freezing of gait (FOG) were also evaluated. The Timed Up and Go (TUG) test was applied under single- and dual-task conditions including the digit span-forwards, digit span-backwards, delayed recall memory, counting down the days, counting backwards from 20, and animal fluency tests.

RESULTS

Most of the cognitive dual-tasks resulted in deterioration in gait performance in our PD subjects. Remarkably, the completion time of TUG duration under single- and dual-task of counting down days was higher in the FOG (+) PD subjects (p = 0.008, p = 0.050, respectively). Besides, the TUG duration under the dual-task of counting down days was found to be positively correlated with the UPDRS-motor scores and FOG scores.

CONCLUSION

We think that the concurrent execution of the dual-task of counting down days, which requires complex attentional skills, may disturb gait via a mechanism of overloading of the attentional reserves proceeding gait which is already defective in PD subjects. The neural correlate of this domain and its significance in performing dual-tasks in PD should be investigated in future large-scale studies. The results of these studies may provide substantial perspectives regarding the pathophysiology of gait disturbance in PD.

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.

Corticomotor Excitability Changes Associated With Freezing of Gait in People With Parkinson Disease

Background and Purpose

Freezing of gait (FOG) is a debilitating gait disorder in people with Parkinson’s disease (PD). While various neuroimaging techniques have been used to investigate the pathophysiology of FOG, changes in corticomotor excitability associated with FOG have yet to be determined. Research to date has not concluded if changes in corticomotor excitability are associated with gait disturbances in this patient population. This study aimed to use transcranial magnetic stimulation (TMS) to investigate corticomotor excitability changes associated with FOG. Furthermore, the relationship between corticomotor excitability and gait performances would be determined.

Methods

Eighteen participants with PD and FOG (PD + FOG), 15 without FOG (PD − FOG), and 15 non-disabled adults (Control) were recruited for this study. Single and paired-pulse TMS paradigms were used to assess corticospinal and intracortical excitability, respectively. Gait performance was measured by the 10-Meter-Walk test. Correlation analysis was performed to evaluate relationships between TMS outcomes and gait parameters.

Results

Compared with the Control group, the PD + FOG group showed a significantly lower resting motor threshold and reduced short intracortical inhibition (SICI). Correlation analysis revealed a relationship between resting motor evoked potential and step length, and between SICI and walking velocity in the Control group. While the silent period correlated with step length in the PD − FOG group, no significant relationship was observed in the PD + FOG group.

Discussion and Conclusion

Compared to the Control group, the PD + FOG group exhibited reduced corticomotor inhibition. Distinct correlations observed among the three groups suggest that the function of the corticomotor system plays an important role in mediating walking ability in non-disabled adults and people with PD − FOG, while people with PD + FOG may rely on neural networks other than the corticomotor system to control gait.

Freezing of Speech Single Questionnaire as a Screening Tool for Cognitive Dysfunction in Patients With Dementia With Lewy Bodies

Introduction

Freezing phenomenon is a striking feature of Parkinson's disease. However, it has never been studied in people with dementia with Lewy bodies (DLB). We designed a freezing of speech single questionnaire (FOSSQ) and investigated the frequency and association of freezing of speech (FOS) in patients with DLB and other types of dementia.

Methods

This is a retrospective analysis of data from the project of history-based artificial intelligent computerized dementia diagnostic system. We compared the frequencies of FOS among non-demented (ND) participants, patients with Alzheimer's disease (AD), vascular dementia (VaD), and DLB. Further, we explored the association factors of FOS in all the participants.

Results

We enrolled 666 individuals with the following disease distribution: 190, ND; 230, AD; 183, VaD; and 63, DLB. Compared to individuals with ND (2.1%), patients with AD (6.1%), or VaD (18.0%), DLB (54.0%) showed a significantly higher frequency of positive FOS (all p < 0.001). The association factors of FOS were older age, more severe dementia, more severe motor dysfunction, fluctuating cognition, visual hallucinations, parkinsonism, rapid eye movement sleep behavior disorder, attention, mental manipulation, and language.

Conclusion

Our study showed that the informant-based FOSSQ may be a practical screening tool for discriminating DLB from individuals with ND or other forms of dementia. The FOSSQ can be applied in clinical practice as well as on the artificial intelligent platform.

Functional Connectivity Changes of Key Regions for Motor Initiation in Parkinson's Disease

Akinesia, a cardinal symptom of Parkinson's disease, has been linked to abnormal activation in putamen and posterior medial frontal cortex (pMFC). However, little is known whether clinical severity of akinesia is linked to dysfunctional connectivity of these regions. Using a seed-based approach, we here investigated resting-state functional connectivity (RSFC) of putamen, pMFC and primary motor cortex (M1) in 60 patients with Parkinson's disease on regular medication and 72 healthy controls. We found that in patients putamen featured decreases of connectivity for a number of cortical and subcortical areas engaged in sensorimotor and cognitive processing. In contrast, the pMFC showed reduced connectivity with a more focal cortical network involved in higher-level motor-cognition. Finally, M1 featured a selective disruption of connectivity in a network specifically connected with M1. Correlating clinical impairment with connectivity changes revealed a relationship between akinesia and reduced RSFC between pMFC and left intraparietal lobule (IPL). Together, the present study demonstrated RSFC decreases in networks for motor initiation and execution in Parkinson's disease. Moreover, results suggest a relationship between pMFC-IPL decoupling and the manifestation of akinetic symptoms.

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.

Frontal theta and beta oscillations during lower-limb movement in Parkinson's disease

OBJECTIVES

Patients with Parkinson's disease (PD) have deficits in lower-limb functions such as gait, which involves both cognitive and motor dysfunction. In PD, theta and beta brain rhythms are associated with cognitive and motor functions, respectively. We tested the hypothesis that PD patients with lower-limb abnormalities would exhibit abnormal theta and beta rhythms in the mid-frontal cortical region during lower-limb action.

METHODS

This study included thirty-nine participants; 13 PD patients with FOG (PDFOG+), 13 without FOG (PDFOG-), and 13 demographically-matched controls. We recorded scalp electroencephalograms (EEG) during a lower-limb pedaling motor task, which required intentional initiation and stopping of a motor movement.

RESULTS

FOG scores were correlated with disease severity and cognition. PDFOG+ patients pedaled with reduced speed and decreased acceleration compared to PDFOG- patients and controls. PDFOG+ patients exhibited attenuated theta-band (4-8 Hz) power and increased beta-band (13-30 Hz) power at mid-frontal electrode Cz during pedaling. Frontal theta- and beta-band oscillations also correlated with motor and cognitive deficits.

CONCLUSION

Frontal theta and beta oscillations are predictors of lower-limb motor symptoms in PD and could be used to design neuromodulation for PD-related lower-limb abnormalities.

SIGNIFICANCE

These data provide insight into mechanisms of lower-limb dysfunction in PD with FOG.

How Cognition and Motivation "Freeze" the Motor Behavior in Parkinson's Disease

Objective

Freezing of gait (FoG) is a debilitating problem in patients with PD. The multifactorial pathogenesis of FoG remains poorly understood. We aimed to find which factors are most strongly associated with the occurrence of FoG.

Methods

Three hundred five PD patients were enrolled and subdivided according to the presence (FoG +, n = 128) or absence (FoG-, n = 177) of FoG. Several clinical, functional, and neuropsychological data were collected and compared between groups. The association between the probability of presence of FoG and possible explanatory variables was assessed by logistic regression analysis.

Results

FoG + patients were younger at the diagnosis (p = 0.04), and their mean daily dose of dopaminergic drugs (p < 0.0001) was higher in comparison with FoG- patients. FoG + patients get worse in Frontal Assessment Battery (p = 0.005), had higher scores in Apathy Evaluation Scale (p = 0.03), and were much more impaired on Wisconsin Card Sorting Test (WCST) (p = 0.018), Trail Making Test A (p = 0.0013), and Ray Auditory Verbal Learning Test (p = 0.012). Levodopa equivalent dose, age (direct), age at disease onset (inverse), and WCST were significant predictors of FoG (p = 0.01, p = 0.0025, p = 0.0016, and p = 0.029, respectively).

Conclusion

FoG + patients show more deficits in executive functions and in motivation. The main explanatory variables of FoG occurrence are levodopa equivalent dose, age, age at disease onset, and WCST. These data suggest that a specific involvement of frontal cortical circuits in PD is responsible for certain cognitive–behavioral alterations related to the occurrence of FoG.

Context-Dependent Behavior in Parkinson’s Disease With Freezing of Gait

Background. Context-dependent behavior is a phenomenon in which people demonstrate superior performance in the context where a motor task was originally learned, but show poorer performance in an unfamiliar context. Previous studies found that people with Parkinson’s disease (PD) demonstrated greater context-dependency than nondisabled adults. Moreover, the frontostriatal circuit appeared to play a role in mediating context-dependent behavior. Neuroimaging studies showed that people with PD and freezing of gait (FoG) had difficulty recruiting the frontostriatal circuit when performing a set-shifting task, known to be mediated by this neural network. Objective. This study aimed to investigate whether individuals with PD and FoG (PD + FoG) would be more context-dependent than those without FoG (PD − FoG). Furthermore, the association between context-dependent behavior and set-shifting ability would be determined. Methods. Sixteen individuals with PD + FoG, 15 participants with PD − FoG, and 15 nondisabled adults (Control) were recruited. The participants practiced 3 numerical sequences, each associated with a specific context. One day following practice, the participants were tested under 2 conditions: the sequence-context associations remained the same as practice or were changed. Set-shifting ability was measured by the Trail Making Test (TMT). Results. Compared to the PD − FoG group, the PD + FoG group showed a greater decrement in normalized motor performance when the sequence-context associations were changed. Context-dependency correlated with the TMT in the PD − FoG group but not in the PD + FoG or Control groups. Conclusion. While people with PD + FoG appeared to be more context-dependent than individuals without FoG, a relationship between context-dependent behavior and set-shifting existed only in those without FoG.

The CuePed Trial: How Does Environmental Complexity Impact Cue Effectiveness? A Comparison of Tonic and Phasic Visual Cueing in Simple and Complex Environments in a Parkinson's Disease Population with Freezing of Gait

Background

The optimal prescription of cueing for the treatment of freezing of gait (FoG) in Parkinson's disease (PD) is currently a difficult problem for clinicians due to the heterogeneity of cueing modalities, devices, and the limited comparative trial evidence. There has been a rise in the development of motion-sensitive, wearable cueing devices for the treatment of FoG in PD. These devices generally produce cues after signature gait or electroencephalographic antecedents of FoG episodes are detected (phasic cues). It is not known whether these devices offer benefit over simple (tonic) cueing devices.

Methods

We assembled 20 participants with PD and FoG and familiarized them with a belt-worn, laser-light cueing device (Agilitas™). The device was designed with 2 cueing modalities—gait-dependent or “phasic” cueing and gait-independent or “tonic” cueing. Participants used the device sequentially in the off, phasic, or tonic modes, across 2 tasks—a 2-minute walk and an obstacle course.

Results

A significant improvement in mean distance walked during the 2-minute walk test was observed for the tonic mode (127.3 m) compared with the off (111.4 m) and phasic (116.1 m) conditions. In contrast, there was a nonsignificant trend toward improvement in FoG frequency, duration, and course time when the device was switched from off to tonic and to phasic modes for the obstacle course.

Conclusions

Parkinson's disease patients with FoG demonstrated an improvement in distance walked during the two-minute walk test when a cueing device was switched from off to phasic and to tonic modes of operation. However, this benefit was lost when patients negotiated an obstacle course.

When motor control gets out of hand: Speeding up triggers freezing in the upper limb in Parkinson's disease

INTRODUCTION

Patients with Parkinson's disease (PD) can suffer from sudden movement arrests during upper limb tasks. The current study investigated a test to assess freezing of the upper limbs (FOUL) at two speed conditions to improve the sensitivity of FOUL detection.

METHODS

Forty-nine patients with PD and 10 age-matched controls (HC) performed a freezing-provoking writing task, requiring up- and down-stroke writing at varying sizes in-between visual target zones indicating funnel-shapes on a touch-sensitive tablet. They performed five trials at their preferred speed, referred to as the Normal Funnel Task (NFT) and five trials at maximum speed, referred to as the Fast Funnel Task (FFT), in a random order.

RESULTS

Based on a combination of kinematic criteria and video analysis, 183 FOUL episodes were detected in 24 participants (23 PD, 1 HC). The number of patients with FOUL, number of FOUL episodes and percentage time frozen were significantly higher during FFT than NFT. Most FOUL episodes occurred during writing at small (51.6%) and decreasing size (36.3%). Additionally, FOUL outcomes significantly correlated with the Montreal Cognitive Assessment and New Freezing of Gait Questionnaire.

CONCLUSION

As FOUL is more prevalent under higher task demands, these data offer support for the "threshold model", previously proposed to provide insight in freezing of gait (FOG) and underscoring the presupposed link between FOG and FOUL. As well, this study may provide a novel paradigm to assess FOUL in both laboratory and clinical settings.

A new method based on quiet stance baseline is more effective in identifying freezing in Parkinson's disease

Freezing, an episodic movement breakdown that goes from disrupted gait patterns to complete arrest, is a disabling symptom in Parkinson’s disease. Several efforts have been made to objectively identify freezing episodes (FEs), although a standardized methodology to discriminate freezing from normal movement is lacking. Novel mathematical approaches that provide information in the temporal and frequency domains, such as the continuous wavelet transform, have demonstrated promising results detecting freezing, although still with limited effectiveness. We aimed to determine whether a computerized algorithm using the continuous wavelet transform based on baseline (i.e. no movement) rather than on amplitude decrease is more effective detecting freezing. Twenty-six individuals with Parkinson’s disease performed two trials of a repetitive stepping-in-place task while they were filmed by a video camera and tracked by a motion capture system. The number of FEs and their total duration were determined from a visual inspection of the videos and from three different computed algorithms. Differences in the number and total duration of the FEs between the video inspection and each of the three methods were obtained. The accuracy to identify the time of occurrence of a FE by each method was also calculated. A significant effect of Method was found for the number (p = 0.016) and total duration (p = 0.013) of the FEs, with the method based on baseline being the closest one to the values reported from the videos. Moreover, the same method was the most accurate in detecting the time of occurrence, and the one reaching the highest sensitivity (88.2%). Findings suggest that threshold detection methods based on baseline and movement amplitude decreases capture different characteristics of Parkinsonian gait, with the first one being more effective at detecting FEs. Moreover, robust approaches that consider both time and frequency characteristics are more sensitive in identifying freezing.

Depressive symptoms may increase the risk of the future development of freezing of gait in patients with Parkinson's disease: Findings from a 5-year prospective study

INTRODUCTION

Prospective studies identifying predictors of freezing of gait (FOG) in Parkinson's disease (PD) are limited. We aim to explore which symptoms are associated with future development of FOG in non-freezers.

METHODS

Fifty-seven PD patients without FOG at baseline were re-evaluated after a mean of five years. At baseline, disease severity [Unified Parkinson's Disease Rating Scale (MDS-UPDRS)], gait under single and dual-tasking, balance, cognition and other non-motor symptoms were assessed. The new-FOG-questionnaire (NFOG-Q) determined FOG. Multivariate binary logistic regression determined independent predictors of FOG.

RESULTS

At follow-up, 26 subjects (46%) had FOG while 31 remained non-freezers. At baseline, non-freezers (FOG-) and future freezers (FOG+) were similar (p > 0.10) with respect to age, gender, disease duration, dopaminergic medications, and cognitive function. However, FOG + had significantly worse scores on the Geriatric Depression Scale (GDS) (FOG+:5.2 ± 3.7; FOG-:2.4 ± 2.0, p = 0.005), PDQ-39, the NMS-questionnaire, UPDRS-part I, UPDRS-part III (off), and the Berg Balance Scale. In binary logistic regression, GDS, gait speed and UPDRS-III (on vs. off) were the only significant independent predictors of future FOG (GDS: OR = 10.93, p = 0.003, ΔUPDRS-III: OR = 1.34, p = 0.006). Moreover, 80% of the subjects who had marked depressive symptoms at baseline (GDS≥5) developed FOG at follow-up. In contrast, only 27% of those with few depressive symptoms at baseline became freezers (p < 0.001).

CONCLUSIONS

Depressive symptoms apparently precede the development of FOG. While elucidation of the relationship between depression and FOG needs further study, our findings offer another perspective regarding the pathophysiology of FOG and may help clinicians to estimate the risk of developing this debilitating phenomenon.

Relationships between gait and emotion in Parkinson's disease: A narrative review

BACKGROUND

Disturbance of gait is a key feature of Parkinson's disease (PD) and has a negative impact on quality of life. Deficits in cognition and sensorimotor processing impair the ability of people with PD to walk quickly, efficiently and safely. Recent evidence suggests that emotional disturbances may also affect gait in PD.

RESEARCH QUESTION

We explored if there were relationships between walking ability, emotion and cognitive impairment in people with PD.

METHODS

The literature was firstly reviewed for unimpaired individuals. The recent experimental evidence for the influence of emotion on gait in people with PD was then explored. The contribution of affective disorders to continuous gait disorders was investigated, particularly for bradykinetic and hypokinetic gait. In addition, we investigated the influence of emotional processing on episodic gait disturbances, such as freezing of gait. Potential effects of pharmacological, surgical and physical therapy interventions were also considered.

RESULTS

Emerging evidence showed that emotional disturbances arising from affective disorders such as anxiety and depression, in addition to cognitive impairment, could contribute to gait disorders in some people with PD. An analysis of the literature indicated mixed evidence that improvements in affective disorders induced by physical therapy, pharmacological management or surgery improve locomotion in PD.

SIGNIFICANCE

When assessing and treating gait disorders in people with PD, it is important to take into the account non-motor symptoms such as anxiety, depression and cognitive impairment, in addition to the motor sequalae of this progressive neurological condition.

Quantitative Analysis of Relationship Between Hypokinetic Dysarthria and the Freezing of Gait in Parkinson's Disease

Hypokinetic dysarthria (HD) and freezing of gait (FOG) are both axial symptoms that occur in patients with Parkinson's disease (PD). It is assumed they have some common pathophysiological mechanisms and therefore that speech disorders in PD can predict FOG deficits within the horizon of some years. The aim of this study is to employ a complex quantitative analysis of the phonation, articulation and prosody in PD patients in order to identify the relationship between HD and FOG, and establish a mathematical model that would predict FOG deficits using acoustic analysis at baseline. We enrolled 75 PD patients who were assessed by 6 clinical scales including the Freezing of Gait Questionnaire (FOG-Q). We subsequently extracted 19 acoustic measures quantifying speech disorders in the fields of phonation, articulation and prosody. To identify the relationship between HD and FOG, we performed a partial correlation analysis. Finally, based on the selected acoustic measures, we trained regression models to predict the change in FOG during a 2-year follow-up. We identified significant correlations between FOG-Q scores and the acoustic measures based on formant frequencies (quantifying the movement of the tongue and jaw) and speech rate. Using the regression models, we were able to predict a change in particular FOG-Q scores with an error of between 7.4 and 17.0 %. This study is suggesting that FOG in patients with PD is mainly linked to improper articulation, a disturbed speech rate and to intelligibility. We have also proved that the acoustic analysis of HD at the baseline can be used as a predictor of the FOG deficit during 2 years of follow-up. This knowledge enables researchers to introduce new cognitive systems that predict gait difficulties in PD patients.

Inhibiting Basal Ganglia Regions Reduces Syllable Sequencing Errors in Parkinson's Disease: A Computer Simulation Study

Background: Parkinson's disease affects many motor processes including speech. Besides drug treatment, deep brain stimulation (DBS) in the subthalamic nucleus (STN) and globus pallidus internus (GPi) has developed as an effective therapy.

Goal: We present a neural model that simulates a syllable repetition task and evaluate its performance when varying the level of dopamine in the striatum, and the level of activity reduction in the STN or GPi.

Method: The Neural Engineering Framework (NEF) is used to build a model of syllable sequencing through a cortico-basal ganglia-thalamus-cortex circuit. The model is able to simulate a failing substantia nigra pars compacta (SNc), as occurs in Parkinson's patients. We simulate syllable sequencing parameterized by (i) the tonic dopamine level in the striatum and (ii) average neural activity in STN or GPi.

Results: With decreased dopamine levels, the model produces syllable sequencing errors in the form of skipping and swapping syllables, repeating the same syllable, breaking and restarting in the middle of a sequence, and cessation (“freezing”) of sequences. We also find that reducing (inhibiting) activity in either STN or GPi reduces the occurrence of syllable sequencing errors.

Conclusion: The model predicts that inhibiting activity in STN or GPi can reduce syllable sequencing errors in Parkinson's patients. Since DBS also reduces syllable sequencing errors in Parkinson's patients, we therefore suggest that STN or GPi inhibition is one mechanism through which DBS reduces syllable sequencing errors in Parkinson's patients.

Multitarget transcranial direct current stimulation for freezing of gait in Parkinson's disease

BACKGROUND

Recent findings suggest that transcranial direct current stimulation of the primary motor cortex may ameliorate freezing of gait. However, the effects of multitarget simultaneous stimulation of motor and cognitive networks are mostly unknown. The objective of this study was to evaluate the effects of multitarget transcranial direct current stimulation of the primary motor cortex and left dorsolateral prefrontal cortex on freezing of gait and related outcomes.

METHODS

Twenty patients with Parkinson's disease and freezing of gait received 20 minutes of transcranial direct current stimulation on 3 separate visits. Transcranial direct current stimulation targeted the primary motor cortex and left dorsolateral prefrontal cortex simultaneously, primary motor cortex only, or sham stimulation (order randomized and double-blinded assessments). Participants completed a freezing of gait-provoking test, the Timed Up and Go, and the Stroop test before and after each transcranial direct current stimulation session.

RESULTS

Performance on the freezing of gait-provoking test (P = 0.010), Timed Up and Go (P = 0.006), and the Stroop test (P = 0.016) improved after simultaneous stimulation of the primary motor cortex and left dorsolateral prefrontal cortex, but not after primary motor cortex only or sham stimulation.

CONCLUSIONS

Transcranial direct current stimulation designed to simultaneously target motor and cognitive regions apparently induces immediate aftereffects in the brain that translate into reduced freezing of gait and improvements in executive function and mobility. © 2018 International Parkinson and Movement Disorder Society.

Gait initiation is influenced by emotion processing in Parkinson's disease patients with freezing

BACKGROUND

Freezing of gait is a symptom that affects more than 50% of Parkinson's disease (PD) patients and increasing evidence suggests that nonmotor systems (i.e., limbic system) are involved in its underlying mechanisms.

OBJECTIVE

The objective of this study was to investigate whether gait initiation characteristics are influenced by emotional stimuli in patients with PD, with or without freezing of gait.

METHODS

A total of 44 participants, divided into 3 groups (15 PD patients with and 15 PD patients without freezing of gait and 14 controls), stood on a sensorized mat and were asked to take a step forward in response to a pleasant image and a step backward in response to an unpleasant one (congruent task, low cognitive load) or to take a step backward in response to a pleasant image and a step forward in response to an unpleasant one (incongruent task, high cognitive load). Reaction time, step size, anticipatory postural adjustments, and sway path were measured.

RESULTS

In PD with freezing of gait, the reaction time was longer and the step size was shorter than in the other groups when they took a step forward in response to an unpleasant image (incongruent task). Changes in reaction time performance in response to unpleasant images remained significant after having adjusted for executive dysfunction and positively correlated with the "frequency" of freezing episodes.

CONCLUSIONS

This study demonstrates that gait initiation was influenced by the emotional valence of visual stimuli in addition to the cognitive load of the task suggesting that the limbic system may be involved in freezing of gait. © 2018 International Parkinson and Movement Disorder Society.

Cerebellar Volume and Executive Function in Parkinson Disease with and without Freezing of Gait

BACKGROUND

Freezing of gait (FOG) affects approximately 50% of people with Parkinson Disease (PD), impacting quality of life and placing financial and emotional strain on the individual and caregivers. People with PD and FOG have similar deficits in motor adaptation and cognition as individuals with cerebellar lesions, indicating the cerebellum may play a role in FOG.

OBJECTIVE

To examine potential differences in cerebellar volumes and their relationships with cognition between PD with (FOG+) and without FOG (FOG-).

METHODS

Sixty-three participants were divided into two groups, FOG+ (n = 25) and FOG- (n = 38), based on the New Freezing of Gait Questionnaire. Cognitive assessment included Trail Making, Stroop, Verbal Fluency, and Go-NoGo executive function tasks. All participants completed structural T1- and T2-weighted MRI scans. Imaging data were processed with FreeSurfer and the Spatially Unbiased Infratentorial toolbox to segment the cerebellum into individual lobules.

RESULTS

FOG+ performed significantly worse on phonemic verbal fluency (F(1, 22)  =  7.06, p = 0.01) as well as the Go-NoGo task (F(1, 22)  =  9.00, p = 0.004). We found no differences in cerebellar volumes between groups (F(4, 55)  = 1.42, p = 0.24), but there were significant relationships between verbal fluency measures and lobule volumes in FOG-.

CONCLUSIONS

These findings underscore the need for longitudinal studies to better characterize potential changes in cerebellar volume, cognitive function, and functional connectivity between people with PD with and without FOG.

The Practicalities of Assessing Freezing of Gait

Background: Freezing of gait (FOG) is a mysterious, complex and debilitating phenomenon in Parkinson’s disease. Adequate assessment is a pre-requisite for managing FOG, as well as for assigning participants in FOG research. The episodic nature of FOG, as well as its multiple clinical expressions make its assessment challenging.

Objective: To highlight the available assessment tools and to provide practical, experience-based recommendations for reliable assessment of FOG.

Methods: We reviewed FOG assessment from history taking, questionnaires, lab and home-based measurements and examined how these methods account for presence and severity of FOG, their limits and advantages. The practicalities for their use in clinical and research practice are highlighted.

Results: According to the available assessment tools severity of FOG is marked by one or a combination of multiple clinical expressions including frequency, duration, triggering circumstances, response to levodopa, association with falls and fear of falling, or need for assistance to avoid falls.

Conclusions: To date, a unique methodological tool that encompasses the entire complexity of FOG is lacking. Combining methods should give a better picture of FOG severity, in accordance with the precise clinical or research context. Further development of any future assessment tool requires understanding and thorough analysis of the specific clinical expressions of FOG.

Pure akinesia with gait freezing: a clinicopathologic study

Background

Pure akinesia with gait freezing is a rare syndrome with few autopsied cases. Severe freezing of gait occurs in the absence of bradykinesia and rigidity. Most autopsies have revealed progressive supranuclear palsy. We report the clinical and postmortem findings of two patients with pure akinesia with gait freezing, provide video recordings of these patients, and review the literature describing similar cases. We also discuss bradykinesia, hypokinesia and akinesia in the context of this clinical syndrome.

Case presentation

Two patients with the syndrome of pure akinesia with gait freezing were examined by the same movement disorder specialist at least annually for 9 and 18 years. Both patients initially exhibited freezing, tachyphemia, micrographia and festination without bradykinesia and rigidity. Both autopsies revealed characteristic tau pathology of progressive supranuclear palsy, with nearly total neuronal loss and gliosis in the subthalamus and severe neuronal loss and gliosis in the globus pallidus and substantia nigra. Previously published postmortem studies revealed that most patients with this syndrome had progressive supranuclear palsy or pallidonigroluysian atrophy.

Conclusions

Pallidonigroluysian degeneration produces freezing and festination in the absence of generalized slowing (bradykinesia). Freezing and festination are commonly regarded as features of akinesia. Akinesia literally means absence of movement, and akinesia is commonly viewed as an extreme of bradykinesia. The pure akinesia with gait freezing phenotype illustrates that bradykinesia and akinesia should be viewed as separate phenomena.

Electronic supplementary material

The online version of this article (doi:10.1186/s40734-017-0063-1) contains supplementary material, which is available to authorized users.

Freezing during tapping tasks in patients with advanced Parkinson's disease and freezing of gait

Introduction

Parkinson’s disease patients with freezing of gait also experience sudden motor blocks (freezing) during other repetitive motor tasks. We assessed the proportion of patients with advanced PD and freezing of gait who also displayed segmental “freezing” in tapping tasks.

Methods

Fifteen Parkinson’s disease patients with freezing of gait were assessed. Freezing of gait was evaluated using a standardized gait trajectory with the usual triggers. Patients performed repetitive tapping movements (as described in the MDS-UPDRS task) with the hands or the feet in the presence or absence of a metronome set to 4 Hz. Movements were recorded with a video motion system. The primary endpoint was the occurrence of segmental freezing in these tapping tasks. The secondary endpoints were (i) the relationship between segmental episodic phenomena and FoG severity, and (ii) the reliability of the measurements.

Results

For the upper limbs, freezing was observed more frequently with a metronome (21% of trials) than without a metronome (5%). For the lower limbs, the incidence of freezing was higher than for the upper limbs, and was again observed more frequently in the presence of an auditory cue (47%) than in its absence (14%).

Conclusion

Although freezing of the lower limbs was easily assessed during an MDS-UPDRS task with a metronome, it was not correlated with the severity of freezing of gait (as evaluated during a standardized gait trajectory). Only this latter was a reliable measurement in patients with advanced Parkinson’s disease.

Cueing for people with Parkinson's disease with freezing of gait: A narrative review of the state-of-the-art and novel perspectives

Freezing, which manifests during gait and other movements, is an incapacitating motor symptom experienced by many patients with Parkinson's disease (PD). In rehabilitation, auditory and visual cueing methods are commonly applied to evoke a more goal-directed type of motor control and, as such, reduce freezing severity in patients with PD. In this narrative review, we summarize the current evidence regarding the effects of external cueing in patients with PD with freezing of gait (FOG) and provide suggestions on how to further improve cueing effectiveness with emerging technological developments. For this paper, we reviewed 24 articles describing the assessment of the effects of cues in patients with FOG (n=354). Because these studies mostly involved quasi-experimental designs, no methodological analysis was undertaken. In general, the evidence suggests that cue-augmented training can reduce FOG severity, improve gait parameters and improve upper-limb movements immediately after training. However, findings were not univocal, and long-term consolidation and transfer of the effects appear to be hampered specifically in this subgroup. With the increasing use of wearable technology, new possibilities are allowing for adapting the cue type, cue content and dose of cues to the needs of individual patients, which may boost the clinical use and efficiency of cued training in PD patients with FOG.

A Case of Apparent Upper-Body Freezing in Parkinsonism while Using a Wheelchair

Freezing of gait (FOG) is a common, disabling gait disturbance in Parkinson’s disease (PD) and other Parkinsonian syndromes. Freezing also occurs during non-gait movements involving the upper limbs. The mechanisms underlying freezing are complex, likely involving motor, cognitive, and sensory systems that contribute to the episodes. Here, we reported a 60-year-old female with a 24-year history of parkinsonism who experienced significant FOG when ambulatory. Disease progression resulted in her permanent use of a powered wheelchair. While using the power chair, the patient experiences apparent paroxysmal freezing in the hand and arm used to steer and propel the chair. These episodes, some lasting up to several minutes, occur only in circumstances (e.g., entering and leaving an elevator) that are similar to environments known to elicit and exacerbate FOG. Episodes are transient and can be volitionally interrupted by the patient but sometimes require external assistance. Therapeutic intervention for this type of potential freezing has yet to be determined. This case may provide insight into the complex nature of freezing behavior and suggests a need for new approaches to treating non-traditional freezing behavior.