Freezing of gait after bilateral subthalamic nucleus stimulation for Parkinson's disease

Soft robotic apparel to avert freezing of gait in Parkinson's disease

Freezing of gait (FoG) is a profoundly disruptive gait disturbance in Parkinson's disease, causing unintended stops while walking. Therapies for FoG reveal modest and transient effects, resulting in a lack of effective treatments. Here we show proof of concept that FoG can be averted using soft robotic apparel that augments hip flexion. The wearable garment uses cable-driven actuators and sensors, generating assistive moments in concert with biological muscles. In this n-of-1 trial with five repeated measurements spanning 6 months, a 73-year-old male with Parkinson's disease and substantial FoG demonstrated a robust response to robotic apparel. With assistance, FoG was instantaneously eliminated during indoor walking (0% versus 39 ± 16% time spent freezing when unassisted), accompanied by 49 ± 11 m (+55%) farther walking compared to unassisted walking, faster speeds (+0.18 m s-1) and improved gait quality (-25% in gait variability). FoG-targeting effects were repeatable across multiple days, provoking conditions and environment contexts, demonstrating potential for community use. This study demonstrated that FoG was averted using soft robotic apparel in an individual with Parkinson's disease, serving as an impetus for technological advancements in response to this serious yet unmet need.

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.

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

Background

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

Main body

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

Conclusion

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

Three-Year Gait and Axial Outcomes of Bilateral STN and GPi Parkinson's Disease Deep Brain Stimulation

Objective: To examine the short- and long-term clinical outcomes of the bilateral subthalamic nucleus (STN) and globus pallidus internus (GPi) deep brain stimulation (DBS) on gait and axial symptoms in Parkinson's disease (PD) patients. Available data have been inconsistent and mostly short-term regarding the effect of both brain targets on gait and axial symptoms. We aimed to identify potential target specific differences at 3-year follow-up from a large single-center experience. Methods: We retrospectively reviewed short-term (6-month follow-up) and long-term (36-month follow-up) changes in the Unified Parkinson's Disease Rating Scale (UPDRS) Part II and III total scores of 72 PD patients (53 with bilateral STN-DBS and 19 with bilateral GPi-DBS). An interdisciplinary team made target-specific decisions for each DBS patient. We analyzed changes in gait and axial subscores derived from UPDRS II and III. Results: In both the STN- and GPi-DBS cohorts, we observed no significant differences in gait and axial UPDRS derived subscores in the off-med/on stimulation state at long-term follow-up when compared to baseline. On-med axial scores remained similar in the short-term but worsened in both groups (STN, 2.23 ± 3.43, p < 0.001; GPi, 2.53 ± 2.37, p < 0.01) in the long-term possibly due to disease progression. At long-term follow-up, the UPDRS III off-med/on stimulation scores worsened but were persistently improved from baseline in both groups (-9.07 ± 13.9, p < 0.001). Conclusions: The study showed that long-term both STN- and GPi-DBS had a similar effect on gait and axial symptoms in UPDRS derived subscores at 36-month follow-up despite potential baseline differences in criteria for selection of each target. More sophisticated measures of gait and balance beyond the categorical UPDRS score will be needed for future studies.

Long-term effect of subthalamic nucleus deep brain stimulation on freezing of gait in Parkinson's disease

OBJECTIVE

Subthalamic nucleus deep brain stimulation (STN DBS) is effective against freezing of gait (FOG) in Parkinson's disease (PD); however, whether this effect persists over the long term is debated. The aim of the current study was to investigate the long-term effect of STN DBS on FOG in patients with PD.

METHODS

Data on 52 cases in which PD patients received bilateral STN DBS were obtained from a prospective registry. The authors blindly analyzed FOG incidence and its severity from the videotapes of a 5-m walking task at the baseline and at the 1-, 2-, and 5- or 7-year follow-up visits. They also compared the axial score from the Unified Parkinson's Disease Rating Scale (UPDRS) part III, UPDRS part II (UPDRS-II) item 14, and the FOG questionnaire (FOG-Q). Postoperatively, video-based FOG analysis and the axial score were evaluated under 4 conditions (off-medication/off-stimulation, off-medication/on-stimulation, on-medication/off-stimulation, and on-medication/on-stimulation), and UPDRS-II item 14 and the FOG-Q score were evaluated under 2 conditions (off-medication/on-stimulation and on-medication/on-stimulation).

RESULTS

During the off-medication state, the on-stimulation condition improved FOG outcomes, except for video-based FOG severity, up to the last follow-up compared with the baseline. Video-based FOG outcomes and the axial score during the off-medication state were improved with the on-stimulation condition up to the last follow-up compared with the off-stimulation condition. During the on-medication state, the on-stimulation condition did not improve any FOG outcome compared with the baseline; however, it improved video-based FOG outcomes up to the 2-year follow-up and the axial score up to the last follow-up compared with the off-stimulation condition.

CONCLUSIONS

Our findings suggest that STN DBS has a long-term effect on FOG in the off-medication state. However, STN DBS did not show a long-term effect on FOG in the on-medication state, although it had a short-term effect until the 2-year follow-up.

Deep Brain Stimulation for Freezing of Gait in Parkinson's Disease With Early Motor Complications

BACKGROUND

Effects of DBS on freezing of gait and other axial signs in PD patients are unclear.

OBJECTIVE

Secondary analysis to assess whether DBS affects these symptoms within a large randomized controlled trial comparing DBS of the STN combined with best medical treatment and best medical treatment alone in patients with early motor complications (EARLYSTIM-trial).

METHODS

One hundred twenty-four patients were randomized in the stimulation group and 127 patients in the best medical treatment group. Presence of freezing of gait was assessed in the worst condition based on item-14 of the UPDRS-II at baseline and follow-up. The posture, instability, and gait-difficulty subscore of the UPDRS-III, and a gait test including quantification of freezing of gait and number of steps, were performed in both medication-off and medication-on conditions.

RESULTS

Fifty-two percent in both groups had freezing of gait at baseline based on UPDRS-II. This proportion decreased in the stimulation group to 34%, but did not change in the best medical treatment group at 24 months (P = 0.018). The steps needed to complete the gait test decreased in the stimulation group and was superior to the best medical treatment group (P = 0.016). The axial signs improved in the stimulation group compared to the best medical treatment group (P < 0.01) in both medication-off and medication-on conditions.

CONCLUSIONS

Within the first 2 years of DBS, freezing of gait and other axial signs improved in the medication-off condition compared to best medical treatment in these patients. © 2019 International Parkinson and Movement Disorder Society.

New Onset On-Medication Freezing of Gait After STN-DBS in Parkinson's Disease

Freezing of gait (FoG) is commonly observed in advanced Parkinson's disease (PD) and it is associated with reduced mobility, recurrent falls, injuries, and loss of independence. This phenomenon typically occurs as the effect of dopaminergic medications wears off (“off” FoG) but on rare occasions, it can also be observed during peak medication effect (“on” FoG). In this report, we present the case of a 65-year-old female with a 13-year history of akinetic-rigid idiopathic PD who developed recurrent episodes of “on” FoG after bilateral subthalamic nucleus deep brain stimulation (STN-DBS). She underwent STN-DBS for management of motor fluctuations, which resulted in a marked improvement in her motor symptoms. Within the next 6 months and after several programming sessions, the patient reported “on” FoG occurring regularly 1 h after taking levodopa and lasting a few hours. Accordingly, a repeated levodopa challenge showed that FoG resolved with either levodopa administration or STN stimulation alone, but the combination of both therapies induced recurrence of FoG in our patient. Subsequent management was complex requiring adjustments in levodopa dose and formulation along with advanced DBS programming.

Pre-operative obesity may influence subthalamic stimulation outcome in Parkinson's disease

BACKGROUND

Pre-operative predictive factors for optimal post-operative effect of subthalamic nucleus (STN) stimulation in Parkinson's disease (PD) have been previously reported. No study has explicitly assessed the link between excess pre-operative body weight and STN stimulation outcome.

METHODS

We retrospectively compared STN stimulation outcomes of 36 PD patients with excess pre-operative body weight (group 1) and 36 matched normal-weight pre-operative (group 2) PD patients. We focused on the post-operative outcomes in the sub-group of 12 obese (group 3) PD patients.

RESULTS

The post-operative motor improvement and the reduction of severity of levodopa-related complications were not statistically different between groups 1 and 2 (P>0.05). In the obese group (group 3), the axial sub-score significantly improved by 29.8% in the on-drug/on-stimulation conditions whereas the improvement was not significant in the off-drug/on-stimulation condition (22.4%, P=0.20). The post-operative Mattis Dementia Rating Score was significantly reduced in group 1 and group 3.

DISCUSSION

We considered that the post-operative axial impairment observed in the obese PD patients might be essentially consecutive to disease progression and/or post-operative DBS consequences, i.e. surgical procedure or electrical stimulation itself. Moreover, it could be argued that musculoskeletal disorders associated with obesity were responsible for the incomplete efficacy of STN stimulation on axial sub-scores, by increasing gait and balance impairment.

CONCLUSION

Pre-operative obesity may be regarded as a predictive clinical factor of axial and cognitive impairment after STN-DBS.

Early Use of 60 Hz Frequency Subthalamic Stimulation in Parkinson's Disease: A Case Series and Review

BACKGROUND

Deep brain stimulation (DBS) is effective in treating the segmental symptoms of Parkinson's disease (PD) as well as axial symptoms that are levodopa responsive. PD patients on chronic DBS who develop axial symptoms and gait disturbances several years later oftentimes are refractory to high frequency stimulation (HFS). Several studies report benefit produced by low frequency subthalamic nucleus (STN) stimulation in such patients, though the sustainability of the effects has been mixed.

OBJECTIVE

To report the clinical outcomes of a series of patients with Parkinson's disease and levodopa responsive axial and gait disturbances who were switched to 60 Hz stimulation within one year of their DBS surgery.

METHODS

A retrospective review of 5 patients, whose severe pre-DBS, levodopa responsive gait disorders worsened on HFS STN-DBS and were subsequently switched to 60 Hz stimulation within 1 year of their surgery.

RESULTS

The median age of this cohort was 66 years with median disease duration of 14 years. Four of 5 patients' experienced acute worsening of their axial and gait UPDRS III scores on HFS. All patients' gait disorder improved with 60 Hz along with amelioration of their segmental symptoms and reduction of their levodopa induced dyskinesia. The median time on HFS prior to switching to 60 Hz was two months. Stimulation through the ventral contacts was utilized in all patients with relatively modest changes achieved in levodopa equivalent daily dose.

CONCLUSION

This case series demonstrates the clinical efficacy of utilizing low frequency (60 Hz) STN stimulation early in the DBS programming course in more advanced PD patients with levodopa responsive gait disturbance and freezing of gait. Activation of a broader stimulation field likely contributed to both axial and segmental symptom improvement while possibly aiding in the reduction of dyskinesia.

Early Freezing of Gait: Atypical versus Typical Parkinson Disorders

In 18 months, 850 patients were referred to Muhammad Ali Parkinson Center (MAPC). Among them, 810 patients had typical Parkinson disease (PD) and 212 had PD for ≤5 years. Among the 212 patients with early PD, 27 (12.7%) had freezing of gait (FOG). Forty of the 850 had atypical parkinsonism. Among these 40 patients, all of whom had symptoms for ≤5 years, 12 (30.0%) had FOG. FOG improved with levodopa in 21/27 patients with typical PD but did not improve in the 12 patients with atypical parkinsonism. FOG was associated with falls in both groups of patients. We believe that FOG unresponsive to levodopa in typical PD resembles FOG in atypical parkinsonism. We thus compared the 6 typical PD patients with FOG unresponsive to levodopa plus the 12 patients with atypical parkinsonism with the 21 patients with typical PD responsive to levodopa. We compared them by tests of locomotion and postural stability. Among the patients with FOG unresponsive to levodopa, postural stability was more impaired than locomotion. This finding leads us to believe that, in these patients, postural stability, not locomotion, is the principal problem underlying FOG.

Axial disability and deep brain stimulation in patients with Parkinson disease

Axial motor signs-including gait impairment, postural instability and postural abnormalities-are common and debilitating symptoms in patients with advanced Parkinson disease. Dopamine replacement therapy and physiotherapy provide, at best, partial relief from axial motor symptoms. In carefully selected candidates, deep brain stimulation (DBS) of the subthalamic nucleus or globus pallidus internus is an established treatment for 'appendicular' motor signs (limb tremor, bradykinesia and rigidity). However, the effects of DBS on axial signs are much less clear, presumably because motor control of axial and appendicular functions is mediated by different anatomical-functional pathways. Here, we discuss the successes and failures of DBS in managing axial motor signs. We systematically address a series of common clinical questions associated with the preoperative phase, during which patients presenting with prominent axial signs are considered for DBS implantation surgery, and the postoperative phase, in particular, the management of axial motor signs that newly develop as postoperative complications, either acutely or with a delay. We also address the possible merits of new targets-including the pedunculopontine nucleus area, zona incerta and substantia nigra pars reticulata-to specifically alleviate axial symptoms. Supported by a rapidly growing body of evidence, this practically oriented Review aims to support decision-making in the management of axial symptoms.

Axial disability and deep brain stimulation in patients with Parkinson disease

Axial motor signs-including gait impairment, postural instability and postural abnormalities-are common and debilitating symptoms in patients with advanced Parkinson disease. Dopamine replacement therapy and physiotherapy provide, at best, partial relief from axial motor symptoms. In carefully selected candidates, deep brain stimulation (DBS) of the subthalamic nucleus or globus pallidus internus is an established treatment for 'appendicular' motor signs (limb tremor, bradykinesia and rigidity). However, the effects of DBS on axial signs are much less clear, presumably because motor control of axial and appendicular functions is mediated by different anatomical-functional pathways. Here, we discuss the successes and failures of DBS in managing axial motor signs. We systematically address a series of common clinical questions associated with the preoperative phase, during which patients presenting with prominent axial signs are considered for DBS implantation surgery, and the postoperative phase, in particular, the management of axial motor signs that newly develop as postoperative complications, either acutely or with a delay. We also address the possible merits of new targets-including the pedunculopontine nucleus area, zona incerta and substantia nigra pars reticulata-to specifically alleviate axial symptoms. Supported by a rapidly growing body of evidence, this practically oriented Review aims to support decision-making in the management of axial symptoms.

Impact of sub-thalamic nucleus deep brain stimulation on dual tasking gait in Parkinson's disease

Background

The beneficial effects of bilateral sub-thalamic nucleus deep brain stimulation on motor function and gait in advanced Parkinson’s disease are established. Less is known about the effect of stimulation on cognitive function and the capacity to walk while dual tasking, an ability that has been related to fall risk. Everyday walking takes place in complex environments that often require multi-tasking. Hence, dual tasking gait performance reflects everyday ambulation as well as gait automaticity. The purpose of this study was to examine the impact of sub-thalamic nucleus deep brain stimulation on dual task walking in patients with advanced Parkinson’s disease.

Methods

Gait was assessed using a performance-based test and by quantifying single-task and dual task walking conditions in 28 patients with advanced Parkinson’s disease. These tests were conducted in 4 conditions: “OFF” medication, with the stimulator turned on and off, and “ON” medication, with the stimulator turned on and off. A previously validated, computerized neuro-psychological battery assessed executive function, attention and memory “OFF” and “ON” deep brain stimulation, after subjects took their anti-Parkinsonian medications.

Results

Stimulation improved motor function and the spatiotemporal parameters of gait (e.g., gait speed) during both single-task and dual task walking conditions. Attention improved, but executive function did not. The dual task effect on gait did not change in response to stimulation. For example, during serial 3 subtractions, gait speed was reduced by -0.20 ± 0.14 m/sec while OFF DBS and OFF meds and by -0.22 ± 0.14 m/sec when the DBS was turned on (p = 0.648). Similarly, ON medication, serial 3 subtractions reduced gait speed by -0.20 ± 0.16 m/sec OFF DBS and by -0.22 ± 0.09 m/sec ON DBS (p = 0.543).

Conclusions

Bilateral sub-thalamic nucleus deep brain stimulation improves motor symptoms, certain features of gait and even some aspects of cognitive function. However, stimulation apparently fails to reduce the negative impact of a dual task on walking abilities. These findings provide new insight into the effects of deep brain stimulation on gait during cognitively challenging conditions and everyday walking.

Exploring the cortical and subcortical functional magnetic resonance imaging changes associated with freezing in Parkinson's disease

Freezing of gait is a devastating symptom of advanced Parkinson's disease yet the neural correlates of this phenomenon remain poorly understood. In this study, severity of freezing of gait was assessed in 18 patients with Parkinson's disease on a series of timed 'up and go' tasks, in which all patients suffered from episodes of clinical freezing of gait. The same patients also underwent functional magnetic resonance imaging with a virtual reality gait paradigm, performance on which has recently been shown to correlate with actual episodes of freezing of gait. Statistical parametric maps were created that compared the blood oxygen level-dependent response associated with paroxysmal motor arrests (freezing) to periods of normal motor output. The results of a random effects analysis revealed that these events were associated with a decreased blood oxygen level-dependent response in sensorimotor regions and an increased response within frontoparietal cortical regions. These signal changes were inversely correlated with the severity of clinical freezing of gait. Motor arrests were also associated with decreased blood oxygen level-dependent signal bilaterally in the head of caudate nucleus, the thalamus and the globus pallidus internus. Utilizing a mixed event-related/block design, we found that the decreased blood oxygen level-dependent response in the globus pallidus and the subthalamic nucleus persisted even after controlling for the effects of cognitive load, a finding which supports the notion that paroxysmal increases in basal ganglia outflow are associated with the freezing phenomenon. This method also revealed a decrease in the blood oxygen level-dependent response within the mesencephalic locomotor region during motor arrests, the magnitude of which was positively correlated with the severity of clinical freezing of gait. These results provide novel insights into the pathophysiology underlying freezing of gait and lend support to models of freezing of gait that implicate dysfunction across coordinated neural networks.

Review: management of Parkinson's disease

Parkinson's disease (PD) is one of the most frequent neurological diseases. Despite the modern imaging and nuclear techniques which help to diagnose it in a very early stage and lead to a better discrimination of similar diseases, PD has remained a clinical diagnosis. The increasing number of available treatment options makes the disease management often complicated even when the presence of PD seems undoubted. In addition, nonmotor symptoms and side effects of some therapies constitute some pitfalls already in the preclinical state or at the beginnings of the disease, especially with the progressive effect on patients. Therefore, this review aimed to summarize study results and depict recommended medical treatments for the most common motor and nonmotor symptoms in PD. Additionally, emerging new therapeutic options such as continuous pump therapies, eg, with apomorphine or parenteral levodopa, or the implantation of electrodes for deep brain stimulation were also considered.

Long-term evaluation of gait initiation in six Parkinson's disease patients with bilateral subthalamic stimulation

Defined as the transient state between standing and walking, gait initiation is negatively affected in Parkinson's disease (PD), which often results in significant disability. Although deep brain stimulation (DBS) is the most common surgical procedure for PD, the long-term effects of DBS on gait initiation are not well studied. The present study evaluated the long-term effects of subthalamic nucleus (STN) DBS on the preparation phase of gait initiation using principal component (PC) analysis. Six patients with PD who had undergone STN DBS and 24 healthy control subjects were evaluated. PD subjects were assessed 11.3±10.3 (P1) and 78.9±10.6 (P2) months after surgery. PD subjects were tested with STN DBS in two conditions: without medication and with medication. PC analysis was applied separately for the vertical, anterior-posterior and medial-lateral components of ground reaction force (GRF) recorded during gait initiation. Three PC scores were chosen by the scree test for each GRF component and all these PC scores were used for calculating a standard distance between healthy controls and PD subjects. The Friedman test showed a significant difference in standard distance among conditions (P=0.004), with the post-hoc test recognizing differences among P1 conditions and P2 medication-on condition. The eigenvector loading factors pointed to major differences between PD conditions surrounding the maximum amplitude of vertical and anterior-posterior GRF. For the studied sample, all distances increased in the follow-up evaluation (P2) with and without medications, indicating a worsening in gait initiation after seven years.

Movement orientation switching with the eyes and lower limb in Parkinson disease

Difficulty switching between motor programs is a proposed cause of motor blocks in Parkinson disease (PD). Switching from one movement to another has been studied in the upper extremity and during postural control tasks, but not yet in the eyes and lower limb in PD. The purpose of this study was to compare movement orientation switching ability between people with PD and age-matched controls (CON) and to determine if switching ability is correlated between the eyes and lower limb. Twenty-six persons with PD and 19 age-matched controls participated. Movement orientation switching was studied in a seated position with the head fixed in a chinrest. In response to a randomly generated tone, participants switched from a continuous back-and-forth movement in either the horizontal or vertical orientation to the opposite orientation as quickly as possible. Lower limb movements were performed with the great toe pointing back and forth between targets positioned on a 45° angled floor platform. Eye movements were back and forth between the same targets. Eye and lower limb switch time was reduced in PD (p<0.01), but after normalizing switch time to movement velocity, no differences existed between PD and CON. Eye and lower limb switch times were correlated in PD (r=0.513, p<0.01) but not in CON. In PD, switch time and movement velocity of the lower limb, but not the eyes, correlated with bradykinesia and postural instability/gait. Our results suggest that individuals with PD experience movement-switching deficits with both the eyes and lower limb, perhaps driven by overall bradykinesia.

Pathophysiology of freezing of gait and some possible treatments for it

Freezing of gait (FOG) is a disabling symptom of Parkinson's disease (PD). In this study, we used the model of PD gait behavior for comparing normal and PD persons in order to simulate FOG and find its pathophysiology and probable treatments. We observed in the adapted model that the dopaminergic weights were reduced and the amount of dopaminergic bias was increased. These findings show that the aggravation of the disease and severe resistance of neurons to dopamine agonists may be the main cause of the FOG. Based on our model three therapeutic strategies may be proposed: decreasing the cortex signal to basal ganglia, using high dose glutamate antagonist, and using less glutamate antagonist with some amounts of gabapentin.

Freezing of gait: moving forward on a mysterious clinical phenomenon

Freezing of gait (FoG) is a unique and disabling clinical phenomenon characterised by brief episodes of inability to step or by extremely short steps that typically occur on initiating gait or on turning while walking. Patients with FoG, which is a feature of parkinsonian syndromes, show variability in gait metrics between FoG episodes and a substantial reduction in step length with frequent trembling of the legs during FoG episodes. Physiological, functional imaging, and clinical-pathological studies point to disturbances in frontal cortical regions, the basal ganglia, and the midbrain locomotor region as the probable origins of FoG. Medications, deep brain stimulation, and rehabilitation techniques can alleviate symptoms of FoG in some patients, but these treatments lack efficacy in patients with advanced FoG. A better understanding of the phenomenon is needed to aid the development of effective therapeutic strategies.

Repetitive stepping in place identifies and measures freezing episodes in subjects with Parkinson's disease

Freezing of gait (FOG) in Parkinson's disease (PD) is challenging to measure. We asked whether a repetitive stepping in place (SIP) task on force plates could identify freezing episodes (FEs) in PD subjects, self-classified as "freezers", using the validated FOG questionnaire (FOG-Q) and whether a computerized algorithm could provide automatic detection of FEs during SIP. Thirty PD subjects and nine age-matched controls completed the SIP task. PD subjects were assessed using the Unified Parkinson's Disease Rating motor Scale (UPDRS-III) and the FOG-Q. The identification of "freezers" using the SIP task correlated with the FOG-Q (r=0.80, P<0.001). The specificity and sensitivity of identifying freezers using the SIP task reached 93% and 87%. The number and duration of FEs detected by the algorithm correlated with visual inspection (r=0.97, r=0.998, P<0.001). Freezers had larger SIP asymmetry compared to controls (P=0.02) and non-freezers (P=0.03) as well as larger arhythmicity (P=0.003 and P<0.001, respectively). UPDRS subscores were higher in freezers compared to non-freezers (P<0.05). These results suggest that the SIP task is a useful tool to detect freezing in PD and is correlated with FOG-Q. SIP cycle asymmetry and stride time variability were worse in freezers, similar to that shown in FOG studies. Detection of the number and duration of FEs using a computerized algorithm correlated with independent visual inspection of records.

Quantitative evaluation of the effects of subthalamic stimulation on gait in Parkinson's disease patients using principal component analysis

BACKGROUND

Principal component analysis (PCA) was applied to the ground reaction force (GRF) for evaluating the deep brain stimulation of the subthalamic nucleus (DBS-STN) effects in Parkinson's disease (PD) subjects with and without medication.

METHODS

Ten subjects who underwent DBS-STN were evaluated under the following four conditions: without treatment (mof-sof), with stimulation (mof-son), with medication (mon-sof), and with both treatments (mon-son). A control group of 30 subjects was also evaluated. PCA was applied separately on each GRF component. Broken stick criterion selected eight principal components (PC) from vertical GRF and one from each horizontal GRF. A standard distance was calculated using these 10 PCs and the gait speed to measure how far the PD group's gait was from the normal pattern.

RESULTS

The standard distance allowed classifying normal and PD subjects in the mof-sof condition with 100% accuracy, sensitivity, and specificity. The same distance was calculated for mon-sof, mof-son, and mon-son conditions. The smallest mean standard distance was found in the mon-son condition, which was significantly different from mof-sof (Friedman test with Dunn post-hoc, p < .05).

CONCLUSION

PCA allowed the quantitative evaluation of treatment effects, indicating that DBS-STN improves the GRF pattern in PD subjects, primarily in the medication on state.

Assessment of the effects of subthalamic stimulation in Parkinson disease patients by artificial neural network

This study aims at using a probabilistic neural network (PNN) for discriminating between normal and Parkinson disease (PD) subjects using as input the principal components (PCs) derived from vertical component of the ground reaction force (vGRF). The trained PNN was further used for evaluating the effects of deep brain stimulation of the subthalamic nucleus (STN DBS) on PD, with and without medication. A sample of 45 subjects (30 normal and 15 PD subjects who underwent STN DBS) was evaluated by gait analysis. PD subjects were assessed under four test conditions: without treatment (mof-sof), only with stimulation (mof-son) or medication (mon-sof), and with combined treatments (mon-son). PC analysis was applied on vGRF, where six PC scores were chosen by the broken stick test. Using a bootstrap approach for the PNN model, and the area under the receiver operating characteristic curve (AUC) as performance measurement, the first three and fifth PCs were selected as input variables. The PNN presented AUC = 0.995 for classifying controls and PD subjects in the mof-sof condition. When applied to classify the PD subjects under treatment, the PNN indicated that STN DBS alone is more effective than medication, and further vGRF enhancement is obtained with combined therapies.

[Deep brain stimulation and gait disorders in Parkinson disease]

INTRODUCTION

Gait disorders and freezing of gait (FOG) are seen in most patients with advanced Parkinson disease. Response to levodopa and deep brain stimulation is variable across patients.

STATE OF ART

Thalamic stimulation is ineffective on gait and can even worsen balance when bilaterally applied. Pallidal stimulation moderately improves gait disorders and FOG although this effect tends to wane after three to five years. Stimulation of the subthalamic nucleus (STN) improves levodopa-responsive gait disorders and FOG. However, some patients worsen after STN stimulation and others are better improved under levodopa than under STN stimulation. Synergistic effects of the two treatments have been reported. As for pallidal stimulation, there is a failure of long-term STN stimulation to improve gait, probably due to the involvement of non-dopaminergic pathways as the disease progresses. Levodopa-resistant gait disorders and FOG do not usually benefit from STN stimulation. In the rare cases of levodopa-induced FOG, STN stimulation may be indirectly effective, as it enables reduction or arrest of the levodopa treatment.

PERSPECTIVES

Pedunculopontine nucleus stimulation has recently been performed in small groups of patients with disabling gait disorders and FOG. Although encouraging, the first results need to be confirmed by controlled studies involving larger series of patients.

CONCLUSIONS

Overall, gait disorders remain a motor PD symptom that is little improved, or only temporarily, by current pharmacological and surgical treatments. Patient management is complex.

A decision tool to support appropriate referral for deep brain stimulation in Parkinson's disease

BACKGROUND AND OBJECTIVE

Although Deep Brain Stimulation (DBS) has been proven to be an effective treatment for patients with advanced Parkinson's disease (PD), it may be difficult for general neurologists to identify appropriate candidates for this procedure. We developed an electronic decision tool that can assist neurologists in deciding which PD patients should be referred for DBS consideration.

METHODS

Using the RAND/UCLA Appropriateness Method, an international expert panel assessed the appropriateness of referral for 972 theoretical patient profiles. Panel results were embedded in an electronic decision support tool which displays the panel statement on referral (appropriate, inappropriate and uncertain) after completion of the patient profile.

RESULTS

Referral was considered appropriate for 33% of the theoretical profiles. Logistic regression showed excellent internal consistency of the ratings (predictive value 92%). Symptom severity (OFF-symptoms, dyskinesias, refractory tremor) and PD duration were positively associated with the panel judgment that referral is appropriate. Presence of levodopa-resistant axial symptoms, age >or= 70 years and presence of cognitive impairment showed the strongest negative impact.

CONCLUSIONS

The RAND/UCLA method proved to be useful in determining the appropriate criteria for DBS referral. Validity and applicability of the decision tool (accessible via http://test.stimulus-dbs.org) in clinical practice need to be further determined.

Deep brain stimulation effect on freezing of gait

The majority of patients with Parkinson's disease suffer from freezing of gait (FOG), which responds more or less to levodopa. Thalamic stimulation, mainly used in the treatment of tremor dominant Parkinson's disease is ineffective in FOG. GPi stimulation moderately improves FOG, but this effect may abate in the long term. STN stimulation was reported to improve levodopa-responsive FOG. In some patients, the benefit from levodopa is greater than that from STN stimulation, and levodopa and STN stimulation can have additive effects. On the contrary, STN stimulation is ineffective on levodopa-resistant FOG. In the few cases of levodopa-induced FOG, STN stimulation can indirectly be effective, thanks to a great decrease or arrest of levodopa. Stimulation of the pedunculopontine nucleus has recently been performed in small groups of patients suffering from both off- and on-levodopa gait impairments. The first results appear encouraging, but they need to be confirmed by controlled studies in larger series of patients.

Clinical and cerebral activity changes induced by subthalamic nucleus stimulation in advanced Parkinson's disease: a prospective case-control study

BACKGROUND

High-frequency stimulation of the subthalamic nucleus (STN-DBS) improves motor symptoms in advanced Parkinson's disease (PD), but the mechanisms are still unclear. Functional imaging evidenced pathological overactivity in motor cortical areas in advanced PD that can be normalized by effective therapies.

PATIENTS AND METHODS

We studied resting state cerebral blood flow pre-operatively and 12 months after surgery in 40 patients with advanced PD using ECD-SPECT. SPECT scans were also acquired 1 year apart in 21 matched PD controls who did not undergo surgery. Statistical analysis was performed using statistical parametric mapping (SPM2) software. In addition, we correlated brain perfusion changes after surgery with clinical improvement, assessed using the unified PD rating scale motor score (UPDRS-III).

RESULTS

Patients showed marked motor improvement and medication reduction after surgery. Stimulated PD patients revealed bilateral rCBF decrements in motor cortical areas and prefrontal cortex bilaterally compared to pre-surgical condition as well as versus PD controls (p<.01 FDR corrected). Perfusion increases were found in cerebellum, temporal and occipital lobes. Clinical improvement was associated with perfusion decrements in primary motor and premotor cortices.

CONCLUSIONS

Effective STN-DBS is associated with neuronal activity changes in brain regions implicated in movement programming and performance. We hypothesize that clinical benefit might be associated with stimulation-induced normalization of the abnormal overactivity within the cortico-basal ganglia-thalamo-cortical motor loop in advanced PD.

Externally provoked freezing of gait in open runways in advanced Parkinson's disease results from motor and mental collapse

Freezing of gait (FOG) in Parkinson's disease (PD) is defined as a sudden inability to maintain effective stepping movements. However, its pathophysiology remains unclear. The objectives are: (1) To assess the contribution of both spatial (walking speed, stride length) and temporal parameters (cadence, stride time) and their coefficients of variation to the genesis of FOG in PD. (2) To evaluate whether and how externally imposed modifications of self-determined gait would elicit FOG. We included ten patients with advanced PD, and with daily off drug FOG episodes. We focused on walking in an open runway. For each subject, we manipulated gait by externally imposing four changes in walking speed and four changes in cadence. FOG episodes, often with a long duration of more than 5-s, were observed mostly under conditions with a high imposed cadence. The steps that immediately preceded these episodes were mainly characterized by an increase in cadence and an increase in stride length variability. The results also underscore that FOG can be elicited in a laboratory setting when patients are placed under considerable strain, at least in advanced stages of PD. Patients were unable to adequately negotiate the extreme imposed cadence condition, and this resulted in frequent FOG episodes, even while walking in an open runway. Placing advanced PD patients into extreme imposed conditions leads to a motor wise and mental collapse response, culminating in FOG. Future work should establish the relevance of these findings for the more common forms of FOG, including brief episodes during turning or gait initiation.

Rasagiline improves freezing in a patient with primary progressive freezing gait

We herein report the case of a 84-year-old man with a 4-year history of freezing of gait (FOG) consistent with the diagnosis of primary progressive freezing gait. Single photon emission tomography (SPECT) with a radiolabeled ligand of the dopamine transporter (DAT-SPECT) showed integrity of striatal dopaminergic terminals, whereas brain perfusion SPECT disclosed multiple areas of decreased perfusion in frontal and parietal lobes, as well as in the subcortical gray nuclei of both sides. Treatment with the new irreversible monoamine oxidase B inhibitor rasagiline at standard doses resulted in a rapid, dramatic, and sustained improvement of the frequency and duration of FOG episodes. In addition, brain perfusion SPECT after treatment showed a marked increase of the activity in all cortical areas as well as in the basal ganglia and thalamus. Rasagiline may prove to be an effective and safe treatment for this disabling condition.

A model-based approach for assessing parkinsonian gait and effects of levodopa and deep brain stimulation

Gait and balance disturbances are amongst the most disabling features of Parkinson's disease (PD), and are not adequately controlled with currently available medical and surgical therapies. Development of objective quantitative measures of these abnormalities would greatly help in the assessment and the development of therapeutic interventions. Recently, we developed a methodology, using dynamical system theory, for testing gait with a state-of-the-art motion-detection system (OPTOTRAK 3020, Northern Digital, Inc.). We also developed a model of the dynamics of the foot that predicts the stance and swing phase dynamics of normal walking. In the present study, we determined whether model parameters were altered in subjects with PD when they were tested on/off levodopa (LD) and on/off deep brain stimulation (DBS) in a 2 x 2 matrix.

Assessment of the effects of subthalamic stimulation in Parkinson disease patients by artificial neural network

This study aims at applying an artificial neural network for the evaluation of the effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN) on Parkinson disease (PD) patients with and without medication. A sample of 15 PD patients who have undergone STN DBS were evaluated under four test conditions: medication off and stimulation off (mof-sof), medication off and stimulation on (mof-son), medication on and stimulation off (mon-sof) and medication on and stimulation on (mon-son). A control group with 30 subjects was also evaluated. Principal component analysis (PCA) was applied on vertical ground reaction force (vGRF) and the first six principal component scores (PC score) were obtained in both groups. Those PCs scores were used as input in a probabilistic neural network (PNN). PNN presented satisfactory classification performance in the separation of controls and PD with 90.1% accuracy, 69.2% sensitivity and 100% specificity. The stimulation mof-son and mon-son conditions presented better results compared to mon-sof. In the mof-son condition, 41.7% were classified as normal, while further enhancement (63.3%) was given by the mon-son condition. These results indicated the potentiality of PNN to quantitatively evaluate treatment effects. Furthermore, STN DBS shows improvement on vGRF pattern in PD patients, most substantially when used with medication.

Freezing of gait in Parkinson's disease

Freezing of Gait (FOG) is one of the most disabling and least understood symptoms in Parkinson's disease (PD), and is usually observed in the advanced stage of the disease. FOG can be experienced on turning, in narrow spaces, whilst reaching a destination, and in stressful situations. FOG is commonly observed in the "off" state, but it can also be observed in the "on" state. Dual tasking (cognitive load) aggravates FOG. Visual or auditory cues often resolve FOG. Analysis of gait revealed that the rhythm of stepping suddenly jumps into high frequency (4-5 Hz) in FOG (hastening), and that floor reaction forces are disregulated. Stride-to-stride variability is increased in FOG. Hastening phenomenon was reported not only in PD patients but also in patients with striatal lesions. The basal ganglia and its frontal projections may be one of the essential lesion sites for FOG.A recent study using single-photon emission tomography (SPECT) revealed enhanced lateral premotor cortex (PMC) activity during paradoxical gait in PD, suggesting that PMC can compensate for the impaired function of the medial frontal cortex when cued by visual input. Treatment of FOG includes behavioural, medical, and surgical approaches. Tricks of all kinds (including external cues) are effective therapeutic approaches. If FOG occurs predominantly in the "off" state, dopaminergic therapy can be increased. For "on" freezing or if "on" response is otherwise optimised, the dose of the dopaminergic agent may be manipulated, but it could lead to the deterioration of parkinsonism. Deep brain stimulation of the STN often alleviates FOG in the "off" state.

Botulinum toxin in the treatment of tremors, dystonias, sialorrhea and other symptoms associated with Parkinson's disease

Botulinum toxins are an effective treatment modality for a growing number of neurologic conditions. Although there has been varied interest and success in their use, they have been studied for a variety of conditions associated with Parkinson's disease. Conditions reviewed in this paper include hand and jaw tremor, dystonia, blepharospasm and apraxia of eyelid opening, bruxism, camptocormia, freezing of gait, sialorrhea and constipation. We will make comments when applicable on our unique experience with botulinum toxin in these conditions. Other conditions associated with Parkinson's disease, which will not be reviewed here, but may benefit from botulinum toxin treatment include anterocollis (also known as dropped head syndrome), hyperhidrosis, seborrhea and overactive bladder.

Freezing and hypokinesia of gait induced by stimulation of the subthalamic region

We report a case of a Parkinson's disease patient treated by bilateral deep brain stimulation of the subthalamic nucleus, who developed freezing and hypokinesia of gait induced by stimulation through a left-side misplaced electrode which was more antero-medial than the planned trajectory. Subsequently, correct repositioning of the left electrode afforded complete relief of gait disturbances. Freezing and hypokinesia of gait may be side effects of deep brain stimulation of the subthalamic region due to current spreading antero-medially to the subthalamic nucleus. These side effects are not subject to habituation and restrict any increase in stimulation parameters. We hypothesize that pallidal projections to the pedunculopontine nucleus could be responsible for these gait disturbances in our patient.

Does freezing in Parkinson’s disease change limb coordination?

The aim of this study was to analyse the kinematic characteristics of the strides before freezing and compare this with a voluntary stop and ongoing gait. Also, we investigated whether gait profiles were different as a function of the side of the body. Ten patients were included with a mean age of 64.8 years (SD 5.1). Within a Vicon 3D gait laboratory, patients performed several trials of normal walking and voluntary stops or were exposed to circumstances, which provoked freezing in the off-phase of the medication cycle. Spatiotemporal and key kinematic data of the four strides prior to freezing were compared between body sides and walking conditions using multiple regression models for repeated measures. Prior to freezing patients had severely decreased movement ranges in the sagittal plane (ranging between 31% and 61.5%), most notably in the ankle and hip joints. The general shape of movement remained in the pre-freezing profiles with largely intact dissociation of knee and hip movement in stance but reduced dissociation in swing. Also present were reduced push-off movements in the ankle with fixed dorsiflexion, increased flexion in hip and knee and anterior tilt of the pelvis. During both voluntary (stopping) and involuntary deceleration (freezing), the body side with the last complete stride before the freeze, showed significantly smaller joint ranges (p < .01). Body side differences were larger than sequential deterioration of consecutive steps within each side. Freezing is distinct from normal deceleration of gait in that the reduction of propulsive movement is much greater. Despite hastening of steps, timing deficits did not affect overall movement shapes, except for the tendency to have a flexed walking pattern. The side of the body where gait terminated before freezing was in most cases the side of symptom-dominance, but not consistently so.

Different cerebral cortical areas influence the effect of subthalamic nucleus stimulation on parkinsonian motor deficits and freezing of gait

Inconsistent response in freezing of gait (FOG) with levodopa treatment or STN DBS makes the pathogenesis difficult to understand. We studied brain areas associated with the expression of STN DBS effect on parkinsonian motor deficits and FOG. Ten Parkinson's disease patients with typical FOG were included. One month before STN DBS, we performed [(18)F]-deoxyglucose PET scans and measured the UPDRS motor and modified FOG (mFOG) scores during levodopa off and on periods. At two months after STN DBS, same rating scores were measured. The percentage improvement of mFOG and UPDRS motor scores by STN DBS during levodopa off period was calculated. We searched for brain areas in which glucose metabolism correlated with the improvement of mFOG and UPDRS motor scores by DBS. During levodopa off period, STN DBS improved the UPDRS motor scores by 32.3% and the mFOG scores by 56.6%. There was no correlation between the improvements of both scores. The improvement of UPDRS motor score by DBS correlated with the metabolic activities of rostral supplementary motor area (Brodmann's area 8; BA8), anterior cingulate cortex (BA32), and prefrontal cortex (BA9). On the other hand, there was a positive correlation between the improvement of mFOG score by DBS and the metabolic activity of the parietal, occipital, and temporal sensory association cortices. In conclusion, dysfunction of different cerebral cortical areas limits the beneficial effects of DBS on parkinsonian motor deficits and FOG.