Measurement of rigidity in Parkinson's disease

Global Acoustic Speech Temporal Characteristics for Mandarin Speakers With Parkinson's Disease During Syllable Repetition and Passage Reading

PURPOSE

Previous research has revealed considerable variation in speech rates among English speakers with Parkinson's disease (PD) with slower, faster, or similar rates than controls. The purpose of this study was to characterize speech rates of Mandarin speakers with PD and the corresponding articulation and pause characteristics explaining the speech rates to enhance rate control therapies.

METHOD

Eighteen Mandarin speakers with PD and 18 controls produced syllable repetitions and passage reading using their typical speech style. Speech rates, articulation rates, mean pause durations (≥ 10 ms), and the number of pauses with duration between 10 ms and 300 ms and greater than 300 ms were measured and compared between groups and tasks as well as across the initial, middle, and final periods of the passage. Two-way, mixed-model analyses of variance were employed for data analysis.

RESULTS

Compared to controls, individuals with PD spoke with similar speech rates and faster articulation rates during passage reading, whereas during syllable repetitions, they produced slower speech rates and comparable articulation rates. The slower syllable repetitions produced by speakers with PD may be explained by longer pauses and more perceptual pauses, whereas faster articulation rates may explain the trend of faster speech rates during reading. Speech and articulation rates accelerated for both groups during passage reading.

CONCLUSIONS

Speech rates of Mandarin speakers with PD were characterized by faster articulation, longer pauses, and more perceptual pauses for passage reading. A descriptive model of speech rate suggested that speakers with PD and dysarthria in this study would benefit from rate reduction therapy decreasing articulation rate.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.23982282.

Quantifying Viscous Damping and Stiffness in Parkinsonism Using Data-Driven Model Estimation and Admittance Control

Rigidity of upper and lower limbs in Parkinson's disease (PD) is typically assessed via a clinical rating scale that is subject to human perception biases. Methodologies to quantify changes in rigidity associated with the angular position (stiffness) or velocity (viscous damping) are needed to enhance our understanding of PD pathophysiology and objectively assess therapies. In this proof of concept study, we developed a robotic system and a model-based approach to estimate viscous damping and stiffness of the elbow. Our methodology enables the subject to freely rotate the elbow using an admittance controller while torque perturbations tailored to identify the arm dynamics are delivered. The viscosity and stiffness are calculated based on the experimental data using least-squares estimation. We validated our technique using computer simulations and experiments with a nonhuman animal model of PD in the presence and absence of deep brain stimulation therapy. Our data show that stiffness and viscosity measurements can better differentiate rigidity changes than scores previously used for research, including the work and impulse scores, and the modified unified Parkinson's disease rating scale. Our estimation method is suitable for quantifying the effect of therapies on viscous damping and stiffness and studying the pathophysiological mechanisms underlying rigidity in PD.

Tremor and Rigidity in Patients with Parkinson's Disease: Emphasis on Epidemiology, Pathophysiology and Contributing Factors

Parkinson's disease (PD) is the second most prominent neurodegenerative movement disorder after Alzheimer's disease, involving 2-3% of the population aged above 65 years. This is mainly triggered by the depletion of dopaminergic neurons located in substantia nigra pars compacta (SNpc) in the region of basal ganglia. At present, diagnosis for symptoms of PD is clinical, contextual, unspecified and therapeutically incomprehensive. Analysis of various causes of PD is essential for an accurate examination of the disease. Among the different causes, such as tremors and rigidity, unresponsiveness to the current treatment approach contributes to mortality. In the present review article, we describe various key factors of pathogenesis and physiology associated with tremors and rigidity necessary for the treatment of PI (postural instability) in patients with PD. Additionally, several reports showing early tremor and rigidity causes, particularly age, cortex lesions, basal ganglia lesions, genetic abnormalities, weakened reflexes, nutrition, fear of fall, and altered biomechanics, have been explored. By summarizing the factors that contribute to the disease, histopathological studies can assess rigidity and tremor in PD. With a clear understanding of the contributing factors, various prospective studies can be done to assess the incidence of rigidity and tremors.

Diffuse Optical Spectroscopy Assessment of Resting Oxygen Metabolism in the Leg Musculature

We lack reliable methods to continuously assess localized, resting-state muscle activity that are comparable across individuals. Near-infrared spectroscopy (NIRS) provides a low-cost, non-invasive means to assess localized, resting-state muscle oxygen metabolism during venous or arterial occlusions (VO2VO and VO2AO, respectively). However, this technique is not suitable for continuous monitoring, and its utility is limited to those who can tolerate occlusions. Combining NIRS with diffuse correlated spectroscopy (DCS) enables continuous measurement of an index of muscle oxygen metabolism (VO2i). Despite the lack of previous validation, VO2i is employed as a measure of oxygen metabolism in the muscle. Here we characterized measurement repeatability and compared VO2i with VO2VO and VO2AO in the medial gastrocnemius (MG) in 9 healthy adults. Intra-participant repeatability of VO2i, VO2VO, and VO2AO were excellent. VO2i was not significantly correlated with VO2AO (p = 0.15) nor VO2VO (p = 0.55). This lack of correlation suggests that the variability in the calibration coefficient between VO2i and VO2AO/VO2VO in the MG is substantial across participants. Thus, it is preferable to calibrate VO2i prior to every monitoring session. Important future work is needed to compare VO2i against gold standard modalities such as positron emission tomography or magnetic resonance imaging.

Semi-automated approaches to optimize deep brain stimulation parameters in Parkinson's disease

BACKGROUND

Deep brain stimulation (DBS) is a treatment option for Parkinson's disease patients when medication does not sufficiently manage their symptoms. DBS can be a highly effect therapy, but only after a time-consuming trial-and-error stimulation parameter adjustment process that is susceptible to clinician bias. This trial-and-error process will be further prolonged with the introduction of segmented electrodes that are now commercially available. New approaches to optimizing a patient's stimulation parameters, that can also handle the increasing complexity of new electrode and stimulator designs, is needed.

METHODS

To improve DBS parameter programming, we explored two semi-automated optimization approaches: a Bayesian optimization (BayesOpt) algorithm to efficiently determine a patient's optimal stimulation parameter for minimizing rigidity, and a probit Gaussian process (pGP) to assess patient's preference. Quantified rigidity measurements were obtained using a robotic manipulandum in two participants over two visits. Rigidity was measured, in 5Hz increments, between 10-185Hz (total 30-36 frequencies) on the first visit and at eight BayesOpt algorithm-selected frequencies on the second visit. The participant was also asked their preference between the current and previous stimulation frequency. First, we compared the optimal frequency between visits with the participant's preferred frequency. Next, we evaluated the efficiency of the BayesOpt algorithm, comparing it to random and equal interval selection of frequency.

RESULTS

The BayesOpt algorithm estimated the optimal frequency to be the highest tolerable frequency, matching the optimal frequency found during the first visit. However, the participants' pGP models indicate a preference at frequencies between 70-110 Hz. Here the stimulation frequency is lowest that achieves nearly maximal suppression of rigidity. BayesOpt was efficient, estimating the rigidity response curve to stimulation that was almost indistinguishable when compared to the longer brute force method.

CONCLUSIONS

These results provide preliminary evidence of the feasibility to use BayesOpt for determining the optimal frequency, while pGP patient's preferences include more difficult to measure outcomes. Both novel approaches can shorten DBS programming and can be expanded to include multiple symptoms and parameters.

Activation-Induced Rigidity in Neurologically and Cognitively Healthy Individuals Aged 18-90 Years: A Cross-Sectional Study

BACKGROUND

Rigidity is a key clinical feature of Parkinson's disease (PD), but in a very early phase of the disease it may be absent and can be enhanced through active movements of the arm contralateral to the one being tested.

OBJECTIVE

To evaluate in a large cohort of neurologically and cognitively healthy (NCH) subjects aged 18-90 years if activation-induced rigidity (AR) is present in all age classes, and if there are biological differences between subjects showing AR (AR+) and not showing AR (AR-).

METHODS

2,228 NCH subjects categorized as young adult (18-44 years), adult (45-64 years), elderly (65-74 years), and old/oldest-old (75-90 years) were included in the analysis, and underwent brain MRI. White matter hyperintensities were assessed through two visual rating scales. Lacunes were also rated. Atrophy of the caudate nuclei and ventricular enlargement were assessed through the bicaudate ratio and the lateral ventricles to brain ratio. To elicit AR, the Froment's maneuver (FM) and the instructions of the UPDRS-ME were used.

RESULTS

Among the sample, 1,689 (75.81%) subjects showed AR, of which 1,270 (57.00%) subjects showed AR by using FM, and 419 (18.81%) showed AR by using UPDRS-ME instructions. The latter subjects also showed AR by using FM. The number of AR+ subjects significantly increased with increasing age, regardless of the activation maneuver used. In each age class, the number of AR+ subjects was significantly higher by using the FM than the UPDRS-ME instructions.

CONCLUSION

Our findings suggest that AR is likely to be one of the signs of the prodromal phase of PD.

Effect of viscoelastic properties on passive torque variations at different velocities of the knee joint extension and flexion movements

This study aimed to investigate the rate of passive torque variations of human knee joint in the different velocities of knee flexion and extension movements. Ten healthy men were invited to participate in the tests. All passive torque tests were performed for the knee joint extension and flexion on the sagittal plane in three different angular velocities of 15, 45, and 120°/s; in 5 consecutive cycles; and within 0° to 100° range of motion. The electrical activity of knee joint extensor and flexor muscles was recorded until there was no muscle activity signal. A Three-element Solid Model (SLS) was used to obtain the viscose and elastic coefficients. As the velocity increases, the stretch rate in velocity-independent tissues increases, and the stretch rate in velocity-dependent tissues decreases. By increasing the velocity, the resistance of velocity-dependent parts increases, and the velocity-independent parts are not affected by velocity. Since the first torque that resists the joint movement is passive torque, the elastic and viscous torques should be simultaneously used. It is better to perform the movement at a low velocity so that less energy is lost. The viscoelastic resistance of tissues diminishes. Graphical abstract.

New Sensor and Wearable Technologies to Aid in the Diagnosis and Treatment Monitoring of Parkinson's Disease

Parkinson's disease (PD) is a degenerative disorder of the brain characterized by the impairment of the nigrostriatal system. This impairment leads to specific motor manifestations (i.e., bradykinesia, tremor, and rigidity) that are assessed through clinical examination, scales, and patient-reported outcomes. New sensor-based and wearable technologies are progressively revolutionizing PD care by objectively measuring these manifestations and improving PD diagnosis and treatment monitoring. However, their use is still limited in clinical practice, perhaps because of the absence of external validation and standards for their continuous use at home. In the near future, these systems will progressively complement traditional tools and revolutionize the way we diagnose and monitor patients with PD.

REM sleep without atonia is associated with increased rigidity in patients with mild to moderate Parkinson's disease

OBJECTIVE

Increased muscle activity during rapid eye movement (REM) sleep (i.e. REM sleep without atonia) is common in people with Parkinson's disease (PD). This study tested the hypotheses that people with PD and REM sleep without atonia (RSWA) would present with more severe and symmetric rigidity compared to individuals with PD without RSWA and age-matched controls.

METHODS

Sixty-one individuals participated in this study (41 PD, 20 controls). An overnight sleep study was used to classify participants with PD as having either elevated (PD-RSWA+) or normal muscle activity (PD-RSWA-) during REM sleep. Quantitative measures of rigidity were obtained using a robotic manipulandum that passively pronated and supinated the forearm.

RESULTS

Quantitative measures of forearm rigidity were significantly higher in the PD-RSWA+ group compared to the control group. Rigidity was significantly more asymmetric between limbs in the PD-RSWA- group compared with controls, while there was no significant difference in symmetry between the control and PD-RSWA+ groups.

CONCLUSION

In people with mild to moderate PD, RSWA is associated with an increased and more symmetric presentation of upper limb rigidity.

SIGNIFICANCE

Dysfunction of brainstem systems that control muscle tone during REM sleep may contribute to increased rigidity during wakefulness in people with PD.

Trunk Range of Motion Is Related to Axial Rigidity, Functional Mobility and Quality of Life in Parkinson's Disease: An Exploratory Study

BACKGROUND

People with Parkinson's disease (PD) present deficits of the active range of motion (ROM), prominently in their trunk. However, if these deficits are associated with axial rigidity, the functional mobility or health related quality of life (HRQoL), remains unknown. The aim of this paper is to study the relationship between axial ROM and axial rigidity, the functional mobility and HRQoL in patients with mild to moderate PD.

METHODS

An exploratory study was conducted. Non-probabilistic sampling of consecutive cases was used. Active trunk ROM was assessed by a universal goniometer. A Biodex System isokinetic dynamometer was used to measure the rigidity of the trunk. Functional mobility was determined by the Get Up and Go (GUG) test, and HRQoL was assessed with the PDQ-39 and EuroQol-5D questionnaires.

RESULTS

Thirty-six mild to moderate patients with PD were evaluated. Significant correlations were observed between trunk extensors rigidity and trunk flexion and extension ROM. Significant correlations were observed between trunk flexion, extension and rotation ROM and GUG. Moreover, significant correlations were observed between trunk ROM for flexion, extension and rotations (both sides) and PDQ-39 total score. However, these correlations were considered poor.

CONCLUSIONS

Trunk ROM for flexion and extension movements, measured by a universal goniometer, were correlated with axial extensors rigidity, evaluated by a technological device at 30°/s and 45°/s, and functional mobility. Moreover, trunk ROM for trunk flexion, extension and rotations were correlated with HRQoL in patients with mild to moderate PD.

PDMeter: A Wrist Wearable Device for an at-Home Assessment of the Parkinson's Disease Rigidity

This work focuses on the design and the validation of a wearable mechatronic device for an at-home assessment of wrist stiffness in patients affected by Parkinson's Disease (PD). The device includes one actuated joint and four passive revolute joints with a high overall intrinsic backdriveability. In order to allow the user to freely move the wrist during activities of daily living, we implemented a transparent controller on the basis of the interaction force sensed by the embedded load cell. Conversely, in order to provide perturbations for estimating the wrist flexion-extension rigidity, we implemented a torque controller. Firstly, we report a pilot study that aimed at characterizing the device in terms of range of motion (ROM) allowed, transparency perceived and torque-tracking capability. Then, we present a case study in which we tested our device with seven PD patients in both drug-OFF and drug-ON conditions and we compared the measured stiffness with the one measured in fourteen healthy controls and with the outcome of the most used clinical scale (MDS-UPDRS). The device allowed to successfully estimate the stiffness as different depending on the movement direction. Indeed, extension stiffness was higher than the flexion one, accordingly to the literature. Moreover, the device allowed to discriminate both Healthy subjects from PD subjects, and PD subjects in OFF condition from PD subjects in ON condition. In conclusion, we demonstrate the feasibility of the device in measuring wrist rigidity, thus enabling the possibility to implement an at-home assessment of the PD rigidity.

A Heterogeneous Sensing Suite for Multisymptom Quantification of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease affecting millions worldwide. Bespoke subject-specific treatment (medication or deep brain stimulation (DBS)) is critical for management, yet depends on precise assessment cardinal PD symptoms - bradykinesia, rigidity and tremor. Clinician diagnosis is the basis of treatment, yet it allows only a cross-sectional assessment of symptoms which can vary on an hourly basis and is liable to inter- and intra-rater subjectivity across human examiners. Automated symptomatic assessment has attracted significant interest to optimise treatment regimens between clinician visits, however, no wearable has the capacity to simultaneously assess all three cardinal symptoms. Challenges in the measurement of rigidity, mapping muscle activity out-of-clinic and sensor fusion have inhibited translation. In this study, we address all through a novel wearable sensor system and machine learning algorithms. The sensor system is composed of a force-sensor, three inertial measurement units (IMUs) and four custom mechanomyography (MMG) sensors. The system was tested in its capacity to predict Unified Parkinson's Disease Rating Scale (UPDRS) scores based on quantitative assessment of bradykinesia, rigidity and tremor in PD patients. 23 PD patients were tested with the sensor system in parallel with exams conducted by treating clinicians and 10 healthy subjects were recruited as a comparison control group. Results prove the system accurately predicts UPDRS scores for all symptoms (85.4% match on average with physician assessment) and discriminates between healthy subjects and PD patients (96.6% on average). MMG features can also be used for remote monitoring of severity and fluctuations in PD symptoms out-of-clinic. This closed-loop feedback system enables individually tailored and regularly updated treatment, facilitating better outcomes for a very large patient population.

Quantitative Measurement of Rigidity in Parkinson´s Disease: A Systematic Review

Rigidity is one of the cardinal symptoms of Parkinson´s disease (PD). Present in up 89% of cases, it is typically assessed with clinical scales. However, these instruments show limitations due to their subjectivity and poor intra- and inter-rater reliability. To compile all of the objective quantitative methods used to assess rigidity in PD and to study their validity and reliability, a systematic review was conducted using the Web of Science, PubMed, and Scopus databases. Studies from January 1975 to June 2019 were included, all of which were written in English. The Strengthening the Reporting of observational studies in Epidemiology Statement (STROBE) checklist for observational studies was used to assess the methodological rigor of the included studies. Thirty-six studies were included. Rigidity was quantitatively assessed in three ways, using servomotors, inertial sensors, and biomechanical and neurophysiological study of muscles. All methods showed good validity and reliability, good correlation with clinical scales, and were useful for detecting rigidity and studying its evolution. People with PD exhibit higher values in terms of objective muscle stiffness than healthy controls. Rigidity depends on the angular velocity and articular amplitude of the mobilization applied. There are objective, valid, and reliable methods that can be used to quantitatively assess rigidity in people with PD.

Integrated robotics platform with haptic control differentiates subjects with Parkinson's disease from controls and quantifies the motor effects of levodopa

Background

The use of integrated robotic technology to quantify the spectrum of motor symptoms of Parkinson’s Disease (PD) has the potential to facilitate objective assessment that is independent of clinical ratings. The purpose of this study is to use the KINARM exoskeleton robot to (1) differentiate subjects with PD from controls and (2) quantify the motor effects of dopamine replacement therapies (DRTs).

Methods

Twenty-six subjects (Hoehn and Yahr mean 2.2; disease duration 0.5 to 15 years) were evaluated OFF (after > 12 h of their last dose) and ON their DRTs with the Unified Parkinson’s Disease Rating Scale (UPDRS) and the KINARM exoskeleton robot. Bilateral upper extremity bradykinesia, rigidity, and postural stability were quantified using a repetitive movement task to hit moving targets, a passive stretch task, and a torque unloading task, respectively. Performance was compared against healthy age-matched controls.

Results

Mean hand speed was 41% slower and 25% fewer targets were hit in subjects with PD OFF medication than in controls. Receiver operating characteristic (ROC) area for hand speed was 0.94. The torque required to stop elbow movement during the passive stretch task was 34% lower in PD subjects versus controls and resulted in an ROC area of 0.91. The torque unloading task showed a maximum displacement that was 29% shorter than controls and had an ROC area of 0.71. Laterality indices for speed and end total torque were correlated to the most affected side. Hand speed laterality index had an ROC area of 0.80 against healthy controls. DRT administration resulted in a significant reduction in a cumulative score of parameter Z-scores (a measure of global performance compared to healthy controls) in subjects with clinically effective levodopa doses. The cumulative score was also correlated to UPDRS scores for the effect of DRT.

Conclusions

Robotic assessment is able to objectively quantify parkinsonian symptoms of bradykinesia, rigidity and postural stability similar to the UPDRS. This integrated testing platform has the potential to aid clinicians in the management of PD and help assess the effects of novel therapies.

Deep brain stimulation for Parkinson's disease modulates high-frequency evoked and spontaneous neural activity

Deep brain stimulation is an established therapy for Parkinson's disease; however, its effectiveness is hindered by limited understanding of therapeutic mechanisms and the lack of a robust feedback signal for tailoring stimulation. We recently reported that subthalamic nucleus deep brain stimulation evokes a neural response resembling a decaying high-frequency (200-500 Hz) oscillation that typically has a duration of at least 10 ms and is localizable to the dorsal sub-region. As the morphology of this response suggests a propensity for the underlying neural circuitry to oscillate at a particular frequency, we have named it evoked resonant neural activity. Here, we determine whether this evoked activity is modulated by therapeutic stimulation - a critical attribute of a feedback signal. Furthermore, we investigated whether any related changes occurred in spontaneous local field potentials. Evoked and spontaneous neural activity was intraoperatively recorded from 19 subthalamic nuclei in patients with Parkinson's disease. Recordings were obtained before therapeutic stimulation and during 130 Hz stimulation at increasing amplitudes (0.67-3.38 mA), 'washout' of therapeutic effects, and non-therapeutic 20 Hz stimulation. Therapeutic efficacy was assessed using clinical bradykinesia and rigidity scores. The frequency and amplitude of evoked resonant neural activity varied with the level of 130 Hz stimulation (p < .001). This modulation coincided with improvement in bradykinesia and rigidity (p < .001), and correlated with spontaneous beta band suppression (p < .001). Evoked neural activity occupied a similar frequency band to spontaneous high-frequency oscillations (200-400 Hz), both of which decreased to around twice the 130 Hz stimulation rate. Non-therapeutic stimulation at 20 Hz evoked, but did not modulate, resonant activity. These results indicate that therapeutic deep brain stimulation alters the frequency of evoked and spontaneous oscillations recorded in the subthalamic nucleus that are likely generated by loops within the cortico-basal ganglia-thalamo-cortical network. Evoked resonant neural activity therefore has potential as a tool for providing insight into brain network function and has key attributes of a dynamic feedback signal for optimizing therapy.

Lower Limb Rigidity Is Associated with Frequent Falls in Parkinson's Disease

BACKGROUND AND OBJECTIVE

The role of muscle rigidity as an etiological factor of falls in Parkinson's disease (PD) is poorly understood. Our objective was to determine whether lower leg rigidity was differentially associated with frequent falls in PD compared to upper limb, neck, and total rigidity measures.

METHODS

We examined the associations between Unified Parkinson's Disease Rating Scale-Part III (motor) rigidity subscores and the history of monthly or more frequent falls in 216 individuals with PD (age, 66 ± 10 years; 36% female; disease duration, 7 ± 5 years) with logistic regression.

RESULTS

A total of 35 individuals were frequent fallers. Significant associations were identified between lower limb rigidity and frequent falls (P = 0.01) after controlling for age, sex, PD duration, total Unified Parkinson's Disease Rating Scale- Part III score, and presence of freezing of gait. No significant associations (P ≥ 0.14) were identified for total, arm, or neck rigidity.

CONCLUSION

Lower limb rigidity is related to frequent falls in people with PD. Further investigation may be warranted into how parkinsonian rigidity could cause falls.

A palm-worn device to quantify rigidity in Parkinson's disease

BACKGROUND

Parkinsonian rigidity is identified on clinical examination as resistance to passive movement. Measurement of rigidity commonly relies on ordinal rating scales (MDS-UPDRS), however instrumented objective measures may provide greater mechanistic insight.

NEW METHOD

We present a palm-worn instrument to objectively quantify rigidity on a continuous scale. The device employs a miniature motor to flex the third digit of the hand about the metacarpophalangeal joint whilst transducers record flexion/extension forces. We aim to determine congruence with the MDS-UPDRS, investigate sensitivity to the impact of deep brain stimulation (DBS) and contralateral movement, and make comparisons with healthy individuals. Eight participants with Parkinson's disease underwent evaluation during conditions: on and off DBS, and with and without contralateral limb movement to activate rigidity. During each DBS condition, wash-in/out effects were tracked using both our instrument and two blinded clinical raters. Sixteen healthy volunteers (age-matched/young) served as controls.

RESULTS

Rigidity measured using our instrument had moderate agreement with the MDS-UPDRS and showed differences between therapeutic state, activation conditions, and disease/healthy cohorts. Rigidity gradually worsened over a one-hour period after DBS cessation, but improved more rapidly with DBS resumption.

COMPARISON WITH EXISTING METHODS

Previous attempts to quantify rigidity include manual approaches where a clinician is required to manipulate limbs while sensors passively gather information, or large automated instruments to move the wrist or elbow.

CONCLUSION

Given its ability to track changes in rigidity due to therapeutic intervention, our technique could have applications where continuous measurement is required or where a suitably qualified rater is absent.

Spasticity in adults with cerebral palsy and multiple sclerosis measured by objective clinically applicable technique

OBJECTIVE

The present study evaluated ankle stiffness in adults with and without neurological disorders and investigated the accuracy and reproducibility of a clinically applicable method using a dynamometer.

METHODS

Measurements were obtained from 8 healthy subjects (age 39.3), 9 subjects with spastic cerebral palsy (CP) (age 39.8) and 8 subjects with multiple sclerosis (MS) (age 49.9). Slow and fast dorsiflexion stretches of the ankle joint were performed to evaluate passive muscle-tendon-joint stiffness, reflex mediated stiffness and range of movement (ROM), respectively. Intra/inter-rater reliability for passive and reflex mediated ankle muscle stiffness was assessed for all groups.

RESULTS

Subjects with CP and MS showed significantly larger values of passive stiffness in the triceps surae muscle tendon complex and smaller ROM compared to healthy individuals, while no significant difference in reflex mediated stiffness. Measurements of passive muscle-tendon-joint stiffness and reflex mediated stiffness showed good to excellent inter- and intra-rater reliability (ICC: 0.62-0.91) in all groups.

CONCLUSION

Increased stiffness was found in subjects with CP and MS with a clinically applicable method that provides valid and reproducible measurement of passive ankle muscle-tendon-joint stiffness and reflex mediated stiffness.

SIGNIFICANCE

The present technique may provide important supplementary information for the clinician.

Combined Vision and Wearable Sensors-based System for Movement Analysis in Rehabilitation

Background: Traditional rehabilitation sessions are often a slow, tedious, disempowering and non-motivational process, supported by clinical assessment tools, i.e. evaluation scales that are prone to subjective rating and imprecise interpretation of patient’s performance. Poor patient motivation and insufficient accuracy are thus critical factors that can be improved by new sensing/processing technologies.

Objectives: We aim to develop a portable and affordable system, suitable for home rehabilitation, which combines vision-based and wearable sensors. We introduce a novel approach for examining and characterizing the rehabilitation movements, using quantitative descriptors. We propose new Movement Performance Indicators (MPIs) that are extracted directly from sensor data and quantify the symmetry, velocity, and acceleration of the movement of different body/hand parts, and that can potentially be used by therapists for diagnosis and progress assessment.

Methods: First, a set of rehabilitation exercises is defined, with the supervision of neurologists and therapists for the specific case of Parkinson’s disease. It comprises full-body movements measured with a Kinect device and fine hand movements, acquired with a data glove. Then, the sensor data is used to compute 25 Movement Performance Indicators, to assist the diagnosis and progress monitoring (assessing the disease stage) in Parkinson’s disease. A kinematic hand model is developed for data verification and as an additional resource for extracting supplementary movement information.

Results: Our results show that the proposed Movement Performance Indicators are relevant for the Parkinson’s disease assessment. This is further confirmed by correlation of the proposed indicators with clinical tapping test and UPDRS clinical scale. Classification results showed the potential of these indicators to discriminate between the patients and controls, as well as between the stages that characterize the evolution of the disease.

Conclusions: The proposed sensor system, along with the developed approach for rehabilitation movement analysis have a significant potential to support and advance traditional rehabilitation therapy. The main impact of our work is two-fold: (i) the proposition of an approach for supporting the therapists during the diagnosis and monitoring evaluations by reducing subjectivity and imprecision, and (ii) offering the possibility of the system to be used at home for rehabilitation exercises in between sessions with doctors and therapists.

Thalamic GABA levels and occupational manganese neurotoxicity: Association with exposure levels and brain MRI

Excessive occupational exposure to Manganese (Mn) has been associated with clinical symptoms resembling idiopathic Parkinson's disease (IPD), impairing cognitive and motor functions. Several studies point towards an involvement of the brain neurotransmitter system in Mn intoxication, which is hypothesized to be disturbed prior to onset of symptoms. Edited Magnetic Resonance Spectroscopy (MRS) offers the unique possibility to measure γ-amminobutyric acid (GABA) and other neurometabolites in vivo non-invasively in workers exposed to Mn. In addition, the property of Mn as Magnetic Resonance Imaging (MRI) contrast agent may be used to study Mn deposition in the human brain. In this study, using MRI, MRS, personal air sampling at the working place, work history questionnaires, and neurological assessment (UPDRS-III), the effects of chronic Mn exposure on the thalamic GABAergic system was studied in a group of welders (N=39) with exposure to Mn fumes in a typical occupational setting. Two subgroups of welders with different exposure levels (Low: N=26; mean air Mn=0.13±0.1mg/m3; High: N=13; mean air Mn=0.23±0.18mg/m3), as well as unexposed control workers (N=22, mean air Mn=0.002±0.001mg/m3) were recruited. The group of welders with higher exposure showed a significant increase of thalamic GABA levels by 45% (p<0.01, F(1,33)=9.55), as well as significantly worse performance in general motor function (p<0.01, F(1,33)=11.35). However, welders with lower exposure did not differ from the controls in GABA levels or motor performance. Further, in welders the thalamic GABA levels were best predicted by past-12-months exposure levels and were influenced by the Mn deposition in the substantia nigra and globus pallidus. Importantly, both thalamic GABA levels and motor function displayed a non-linear pattern of response to Mn exposure, suggesting a threshold effect.

Quantitative Assessment of the Arm/Hand Movements in Parkinson's Disease Using a Wireless Armband Device

We present an approach for quantitative assessment of the arm/hand movements in patients with Parkinson’s disease (PD), from sensor data acquired with a wearable, wireless armband device (Myo sensor). We propose new Movement Performance Indicators that can be adopted by practitioners for the quantitative evaluation of motor performance and support their clinical evaluations. In addition, specific Movement Performance Indicators can indicate the presence of the bradykinesia symptom. The study includes seventeen PD patients and sixteen age-matched controls. A set of representative arm/hand movements is defined under the supervision of movement disorder specialist. In order to assist the evaluations, and for progress monitoring purposes, as well as for assessing the amount of bradykinesia in PD, a total set of 84 Movement Performance Indicators are computed from the sensor readings. Subsequently, we investigate whether wireless armband device, with the use of the proposed Movement Performance Indicators can be utilized: (1) for objective and precise quantitative evaluation of the arm/hand movements of Parkinson’s patients, (2) for assessment of the bradykinesia motor symptom, and (3) as an adequate low-cost alternative for the sensor glove. We conducted extensive analysis of proposed Movement Performance Indicators and results are indicating following clinically relevant characteristics: (i) adequate reliability as measured by ICC; (ii) high accuracy in discrimination between the patients and controls, and between the disease stages (support to disease diagnosis and progress monitoring, respectively); (iii) substantial difference in comparison between the left-hand and the right-hand movements across controls and patients, as well as between disease stage groups; (iv) statistically significant correlation with clinical scales (tapping test and UPDRS-III Motor Score); and (v) quantitative evaluation of bradykinesia symptom. Results suggest that the proposed approach has a potential to be adopted by physicians, to afford them with quantitative, objective and precise methods and data during clinical evaluations and support the assessment of bradykinesia.

Impaired bed mobility: quantitative torque analysis with axial inertial sensors

Difficulty in turning in bed is rated as the most troublesome night-time symptom among Parkinson’s disease (PD) patients. Aim: To develop a practical objective method for home assessment of a patient’s ability to turn in bed. Methods: Nocturnal parameters and torque of self-turning in bed from 17 PD couples were assessed and compared using a wearable axial sensor for two nights in their homes. Results: The torque of axial rotation which indicates the ability of PD patients to turn in bed was significantly less than their spouses (p < 0.001). Significant correlations were observed between the torque of turning in bed and total unified Parkinson’s Disease Rating Scale score (r = 0.71; p = 0.001), and total Nocturnal Akinesia Dystonia and Cramp score (r = 0.634; p = 0.006). Conclusion: Our study confirms a decreased ability in turning in PD.

Quantification of Hand Motor Symptoms in Parkinson's Disease: A Proof-of-Principle Study Using Inertial and Force Sensors

This proof-of-principle study describes the methodology and explores and demonstrates the applicability of a system, existing of miniature inertial sensors on the hand and a separate force sensor, to objectively quantify hand motor symptoms in patients with Parkinson’s disease (PD) in a clinical setting (off- and on-medication condition). Four PD patients were measured in off- and on- dopaminergic medication condition. Finger tapping, rapid hand opening/closing, hand pro/supination, tremor during rest, mental task and kinetic task, and wrist rigidity movements were measured with the system (called the PowerGlove). To demonstrate applicability, various outcome parameters of measured hand motor symptoms of the patients in off- vs. on-medication condition are presented. The methodology described and results presented show applicability of the PowerGlove in a clinical research setting, to objectively quantify hand bradykinesia, tremor and rigidity in PD patients, using a single system. The PowerGlove measured a difference in off- vs. on-medication condition in all tasks in the presented patients with most of its outcome parameters. Further study into the validity and reliability of the outcome parameters is required in a larger cohort of patients, to arrive at an optimal set of parameters that can assist in clinical evaluation and decision-making.

Automated assessment of symptom severity changes during deep brain stimulation (DBS) therapy for Parkinson's disease

Deep brain stimulation (DBS) is currently being used as a treatment for symptoms of Parkinson's disease (PD). Tracking symptom severity progression and deciding the optimal stimulation parameters for people with PD is extremely difficult. This study presents a sensor system that can quantify the three cardinal motor symptoms of PD - rigidity, bradykinesia and tremor. The first phase of this study assesses whether data recorded from the system during physical examinations can be used to correlate to clinician's severity score using supervised machine learning (ML) models. The second phase concludes whether the sensor system can distinguish differences before and after DBS optimisation by a clinician when Unified Parkinson's Disease Rating Scale (UPDRS) scores did not change. An average accuracy of 90.9 % was achieved by the best ML models in the first phase, when correlating sensor data to clinician's scores. Adding on to this, in the second phase of the study, the sensor system was able to pick up discernible differences before and after DBS optimisation sessions in instances where UPDRS scores did not change.

The effect of subthalamic stimulation on viscoelastic stiffness of skeletal muscles in patients with Parkinson's disease

BACKGROUND

Myotonometric evaluation of viscoelastic stiffness of skeletal muscles has been proposed to document the effect of surgical or pharmacological treatment on rigidity in patients with Parkinson's disease. The aim of the study was to analyze the changes of viscoelastic stiffness induced by deep brain stimulation.

METHODS

Fifteen patients in an advanced stage of Parkinson's disease participated in the study. The study took place in the off-medication conditions after one night of drug withdrawal. The Unified Parkinson's Disease Rating Scale was used for clinical assessment of the disease. Myotonometry was used to measure viscoelastic stiffness in the resting muscles before and directly after passive wrist movements, commonly used for clinical evaluation of rigidity. The measurements were repeated during the stimulation-on and stimulation-off periods and compared with fifteen healthy control persons.

FINDINGS

The clinical scores for wrist rigidity improved from 3.0 (1-4) to 0.93 (0-2) (P<0.05) due to brain stimulation. The mean values of viscoelastic stiffness were similar before and after passive wrist movements, but the differences between the patients with high vs. low rigidity values (354.9 vs 310.2N/m; P<0.05) and in stimulation-off vs. stimulation-on conditions (342.7 vs 310.5N/m; P<0.05) were significant only if the measurements had been performed after passive wrist movements.

INTERPRETATION

Effective deep brain stimulation and increased rigidity can significantly change viscoelastic stiffness in the resting muscles in patients with Parkinson's disease, especially if evaluated after passive wrist movements. This paper supports the use of myotonometry for objective quantification of parkinsonian rigidity at rest.

The Phenomenology of Parkinson's Disease

The motor symptoms of Parkinson's disease are not limited to the cardinal symptoms of bradykinesia, rigidity, and resting tremor, but also include a variety of interrelated motor phenomena such as deficits in spatiotemporal planning and movement sequencing, scaling and timing of movements, and intermuscular coordination that can be clinically observed. Although many of these phenomena overlap, a review of the full breadth of the motor phenomenon can aid in the diagnosis and monitoring of disease progression.

A novel assistive method for rigidity evaluation during deep brain stimulation surgery using acceleration sensors

OBJECTIVE Despite the widespread use of deep brain stimulation (DBS) for movement disorders such as Parkinson's disease (PD), the exact anatomical target responsible for the therapeutic effect is still a subject of research. Intraoperative stimulation tests by experts consist of performing passive movements of the patient's arm or wrist while the amplitude of the stimulation current is increased. At each position, the amplitude that best alleviates rigidity is identified. Intrarater and interrater variations due to the subjective and semiquantitative nature of such evaluations have been reported. The aim of the present study was to evaluate the use of an acceleration sensor attached to the evaluator's wrist to assess the change in rigidity, hypothesizing that such a change will alter the speed of the passive movements. Furthermore, the combined analysis of such quantitative results with anatomy would generate a more reproducible description of the most effective stimulation sites. METHODS To test the reliability of the method, it was applied during postoperative follow-up examinations of 3 patients. To study the feasibility of intraoperative use, it was used during 9 bilateral DBS operations in patients suffering from PD. Changes in rigidity were calculated by extracting relevant outcome measures from the accelerometer data. These values were used to identify rigidity-suppressing stimulation current amplitudes, which were statistically compared with the amplitudes identified by the neurologist. Positions for the chronic DBS lead implantation that would have been chosen based on the acceleration data were compared with clinical choices. The data were also analyzed with respect to the anatomical location of the stimulating electrode. RESULTS Outcome measures extracted from the accelerometer data were reproducible for the same evaluator, thus providing a reliable assessment of rigidity changes during intraoperative stimulation tests. Of the 188 stimulation sites analyzed, the number of sites where rigidity-suppressing amplitudes were found increased from 144 to 170 when the accelerometer evaluations were considered. In general, rigidity release could be observed at significantly lower amplitudes with accelerometer evaluation (mean 0.9 ± 0.6 mA) than with subjective evaluation (mean 1.4 ± 0.6 mA) (p < 0.001). Of 14 choices for the implant location of the DBS lead, only 2 were the same for acceleration-based and subjective evaluations. The comparison across anatomical locations showed that stimulation in the fields of Forel ameliorates rigidity at similar amplitudes as stimulation in the subthalamic nucleus, but with fewer side effects. CONCLUSIONS This article describes and validates a new assistive method for assessing rigidity with acceleration sensors during intraoperative stimulation tests in DBS procedures. The initial results indicate that the proposed method may be a clinically useful aid for optimal DBS lead placement as well as a new tool in the ongoing scientific search for the optimal DBS target for PD.

Quantification of neural reflex and muscular intrinsic contributions to parkinsonian rigidity

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by rigidity, bradykinesia, resting tremor, and postural instability. Rigidity, defined as an increased resistance to passive movement of a joint, progresses faster than other motor signs in PD. Rigidity is attributable to both exaggerated neural reflex and altered muscle mechanical properties. However, little is known about the contributions of individual components to rigidity. Further, there is no evidence regarding the effects of dopaminergic medication on individual components. Objectives of this study were to quantify the contributions of neural reflexes and intrinsic muscle properties to rigidity and investigate the effects of medication on each contributing component. Joint torque and muscle activities of the wrist in 14 patients and 14 controls were measured during externally induced movements. Each subject with PD was tested in Off- and On-medication states. A system identification technique was applied to differentiate and quantify the neural reflex and intrinsic mechanical components. A mixed model of ANOVA was performed to compare the differences between the two components of rigidity for both groups, and to compare between the Off- and On-medication states for patients. The results showed that reflex and intrinsic components are comparable (p > 0.05), and both are enhanced in subjects with PD than in the controls (p < 0.05). Medication decreased the reflex component of rigidity (p < 0.01). It is concluded that both reflex and intrinsic factors are responsible for rigidity. Present findings are clinically significant as they may provide guidance in development of effective therapeutic interventions.

A portable system for quantitative assessment of parkinsonian rigidity

Rigidity is one of the primary symptoms of Parkinson's disease. Passive flexion and extension of the elbow is used to assess rigidity in this study. An examiner flexes and extends the subject's elbow joint through a rigidity assessment cuff attached around the wrist. Each assessment lasts for 10 seconds. Two force sensor boxes and an inertial measurement unit are used to measure the applied force and the state of the elbow movement. Elastic and viscous values will be obtained through a least squares estimation with all the data. 9 healthy subjects were tested with this system in two experimental conditions: 1) normal state (relaxed); 2) imitated rigidity state. Also the subjects were performed the assessment task with different frequencies and elbow movement ranges. The imitated rigidity action increases viscosity and elasticity. The effect sizes (Cohen's d) of the viscosity and elasticity between normal state and imitated state are 1.61 and 1.36 respectively, which means the difference is significant. Thus, this system can detect the on-off fluctuations of parkinsonian rigidity. Both wrist movement angle and frequency have small effect on the viscosity, but have elevated effect on the elasticity.

Neural and nonneural contributions to wrist rigidity in Parkinson's disease: an explorative study using the NeuroFlexor

Objective. The NeuroFlexor is a novel method incorporating a biomechanical model for the measurement of neural and nonneural contributions to resistance induced by passive stretch. In this study, we used the NeuroFlexor method to explore components of passive movement resistance in the wrist and finger muscles in subjects with Parkinson's disease (PD). Methods. A cross-sectional comparison was performed in twenty-five subjects with PD with clinically identified rigidity and 14 controls. Neural (NC), elastic (EC), and viscous (VC) components of the resistance to passive extension of the wrist were calculated using the NeuroFlexor. Measurements were repeated during a contralateral activation maneuver. Results. PD subjects showed greater total resistance (P < 0.001) and NC (P = 0.002) compared to controls. EC and VC did not differ significantly between groups. Contralateral activation maneuver resulted in increased NC in the PD group but this increase was due to increased resting tension. Total resistance and NC correlated with clinical ratings of rigidity and with bradykinesia. Conclusions. The findings suggest that stretch induced reflex activity, but not nonneural resistance, is the major contributor to rigidity in wrist muscles in PD. The NeuroFlexor is a potentially valuable clinical and research tool for quantification of rigidity.

Parkinson's disease rigidity: relation to brain connectivity and motor performance

OBJECTIVE

(1) To determine the brain connectivity pattern associated with clinical rigidity scores in Parkinson's disease (PD) and (2) to determine the relation between clinically assessed rigidity and quantitative metrics of motor performance.

BACKGROUND

Rigidity, the resistance to passive movement, is exacerbated in PD by asking the subject to move the contralateral limb, implying that rigidity involves a distributed brain network. Rigidity mainly affects subjects when they attempt to move; yet the relation between clinical rigidity scores and quantitative aspects of motor performance are unknown.

METHODS

Ten clinically diagnosed PD patients (off-medication) and 10 controls were recruited to perform an fMRI squeeze-bulb tracking task that included both visually guided and internally guided features. The direct functional connectivity between anatomically defined regions of interest was assessed with Dynamic Bayesian Networks (DBNs). Tracking performance was assessed by fitting Linear Dynamical System (LDS) models to the motor performance, and was compared to the clinical rigidity scores. A cross-validated Least Absolute Shrinkage and Selection Operator (LASSO) regression method was used to determine the brain connectivity network that best predicted clinical rigidity scores.

RESULTS

The damping ratio of the LDS models significantly correlated with clinical rigidity scores (p = 0.014). An fMRI connectivity network in subcortical and primary and premotor cortical regions accurately predicted clinical rigidity scores (p < 10(-5)).

CONCLUSION

A widely distributed cortical/subcortical network is associated with rigidity observed in PD patients, which reinforces the importance of altered functional connectivity in the pathophysiology of PD. PD subjects with higher rigidity scores tend to have less overshoot in their tracking performance, and damping ratio may represent a robust, quantitative marker of the motoric effects of increasing rigidity.

Stretch reflex spatial threshold measure discriminates between spasticity and rigidity

OBJECTIVE

Muscle spasticity following stroke has been shown to result from limitations in the range of regulation of the tonic reflex spatial threshold (ST), i.e., the joint angle at which the stretch reflex begins to act due to descending and segmental influences on motoneurons. The purpose of this study was to determine whether spasticity due to stroke and rigidity due to parkinsonism can be discriminated based on the ST measure.

METHODS

Elbow muscles were stretched at different velocities in healthy, stroke (spasticity) and parkinsonism (rigidity) subjects. The elbow angle at which muscle activation began for each stretch velocity (dynamic ST) and the velocity sensitivity of the ST were measured. Dynamic ST values extrapolated to zero velocity defined the tonic ST.

RESULTS

Compared to healthy subjects, spasticity and rigidity were associated with a decrease in the range of central regulation of tonic STs. STs were hypersensitive in spastic muscles and either hypo- or inversely sensitive to stretch velocity in rigid muscles.

CONCLUSIONS

ST characteristics discriminate between neurological deficits of muscle tone.

SIGNIFICANCE

Results suggest that spasticity and rigidity result from deficits in descending facilitatory control combined with deficits in dynamic fusimotor or/and presynaptic control of Ia inputs to motoneurons.

The food reaching test: a sensitive test of behavioral improvements by deep brain stimulation in MPTP-treated monkey

We modified an objective behavioral test, namely the food reaching test (FRT), for quantitative assessment of motor performance improved by deep brain stimulation (DBS) of the subthalamic nucleus (STN) in the Parkinsonian monkeys. The symptomatic features and their severity in 3 monkeys treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were evaluated with a subjective monkey Parkinson's disease rating scale (PDRS). We then performed STN-DBS with the minimum current intensity that stopped the tremor. The time required for the monkeys to pick up all 5 pieces of potato (FRT time) was measured as a major index to evaluate bradykinesia. The success rate was adopted as another index for assessing overall motor impairments. Although both FRT time and PDRS score were similarly improved by STN-DBS, change of FRT time appeared more sensitive than that of PDRS scores. FRT is an easily trained behavioral test with high objectivity and sensitivity that can be applied for assessing motor performance in MPTP-treated monkeys during experiments in a restrained condition such as functional imaging of the brain.

What brain signals are suitable for feedback control of deep brain stimulation in Parkinson's disease?

Feedback control of deep brain stimulation (DBS) in Parkinson's disease has great potential to improve efficacy, reduce side effects, and decrease the cost of treatment. In this, the timing and intensity of stimulation are titrated according to biomarkers that capture current clinical state. Stimulation may be at standard high frequency or intelligently patterned to directly modify specific pathological rhythms. The search for and validation of appropriate feedback signals are therefore crucial. Signals recorded from the DBS electrode currently appear to be the most promising source of feedback. In particular, beta-frequency band oscillations in the local field potential recorded at the stimulation target may capture variation in bradykinesia and rigidity across patients, but this remains to be confirmed within patients. Biomarkers that reliably reflect other impairments, such as tremor, also need to be established. Finally, whether brain signals are causally important needs to be established before stimulation can be specifically patterned rather than delivered at empirically defined high frequency.

A torque-based method demonstrates increased rigidity in Parkinson's disease during low-frequency stimulation

Low-frequency oscillations in the basal ganglia are prominent in patients with Parkinson’s disease off medication. Correlative and more recent interventional studies potentially implicate these rhythms in the pathophysiology of Parkinson’s disease. However, effect sizes have generally been small and limited to bradykinesia. In this study, we investigate whether these effects extend to rigidity and are maintained in the on-medication state. We studied 24 sides in 12 patients on levodopa during bilateral stimulation of the STN at 5, 10, 20, 50, 130 Hz and in the off-stimulation state. Passive rigidity at the wrist was assessed clinically and with a torque-based mechanical device. Low-frequency stimulation at ≤20 Hz increased rigidity by 24 % overall (p = 0.035), whereas high-frequency stimulation (130 Hz) reduced rigidity by 18 % (p = 0.033). The effects of low-frequency stimulation (5, 10 and 20 Hz) were well correlated with each other for both flexion and extension (r = 0.725 ± SEM 0.016 and 0.568 ± 0.009, respectively). Clinical assessments were unable to show an effect of low-frequency stimulation but did show a significant effect at 130 Hz (p = 0.002). This study provides evidence consistent with a mechanistic link between oscillatory activity at low frequency and Parkinsonian rigidity and, in addition, validates a new method for rigidity quantification at the wrist.

Neural tension technique is no different from random passive movements in reducing spasticity in patients with traumatic brain injury

PURPOSE

Neural tension technique (NTT) is a therapy believed to reduce spasticity and to increase range of motion (ROM). This study compared the ability of NTT and random passive movements (RPMs) to reduce spasticity in the knee flexors in 10 spastic patients with brain injury.

METHODS

An RCT study with crossover design evaluated muscle tone measured by: 1) hand-held dynamometer; 2) Modified Ashworth Scale (MAS); 3) and ROM by; 4) angles of resistance onset "catch" (R1) compensatory movement (R2); and 5) 'subjectively perceived reduction in muscle tone'. Outcome measures were recorded by three raters before and after a single treatment session.

RESULTS

Objective stiffness measured with the hand-held device showed no significant changes for the NTT or RPM (p ≥ 0.09-0.79). The subjective measures showed significant changes after the NTT for the non-blinded rater (MAS: p < 0.05: R1: p < 0.05; R2: p < 0.05), but for the blinded rater a significant reduction was found only for R1 (p < 0.05) and R2 (p < 0.05). For the non-blinded rater intervention effects were found for R1 (p < 0.01), R2 (p < 0.01) and subjectively perceived tone reduction (p < 0.01). For the blinded rater no intervention effect was found.

CONCLUSIONS

An objective evaluation of NTT demonstrates that it does not reduce spasticity. However, it does increase ROM with the same effect as RPM.

IMPLICATIONS FOR REHABILITATION

• Neural tension techniques does not reduce spasticity in patients with traumatic brain injury when evaluated with objective biomechanical evaluation methods. • Neural tension techniques may improve range of motion with the same effect as random passive movements.

Assessment of a portable device for the quantitative measurement of ankle joint stiffness in spastic individuals

OBJECTIVE

Spasticity is a common complication with neurological diseases and CNS lesions. Instrumented systems to evaluate spasticity often cannot provide an immediate result, thus limiting their clinical usefulness. In this study we investigated the accuracy and reliability of the portable Neurokinetics RA1 Ridgidity Analyzer to measure stiffness of the ankle joint in 46 controls, 14 spinal cord injured (SCI) and 23 multiple sclerosis (MS) participants.

METHODS

Ankle stiffness measures were made twice by two raters, at speeds above and below the expected stretch reflex threshold. Ankle torque was measured with the portable device and a stationary torque motor. Inter- and intra-rater reliability was assessed with the intra-class correlation coefficient (ICC).

RESULTS

Stiffness measures with the portable and stationary devices were significantly correlated for controls and MS participants (p < 0.01). Intra-rater reliability for the portable device ranged from 0.60-0.89 (SCI) and 0.63-0.67 (control) and inter-rater reliability ranged from 0.70-0.73 (SCI) and 0.61-0.77 (control). Ankle stiffness measures in SCI and MS participants were significantly larger than in controls for both slow (p < 0.05) and fast movements (p < 0.01), with stiffness being larger for fast compared to slow movements in SCI and MS participants (p < 0.05), but not in controls (p = 0.5).

CONCLUSION

The portable device correlated well with measures obtained by a torque motor in both controls and MS participants, showed high intra- and inter-rater reliability for the SCI participants, and could easily distinguish between stiff and control ankle joints. However, the device, in its current form, may be less accurate during rapid movements when inertia contributes to stiffness and the shape of the air-filled pads did not provide a good interface with the foot.

SIGNIFICANCE

This study demonstrates that a portable device can potentially be a useful diagnostic tool to obtain reliable information of stiffness for the ankle joint.

Amplitude- and velocity-dependency of rigidity measured at the wrist in Parkinson's disease

OBJECTIVE

Quantify the effects of increased amplitude and rate of muscle stretch on parkinsonian rigidity.

METHODS

Eighteen subjects with Parkinson's disease participated in this study. Subjects' tested hand was passively displaced through 60° and 90° ranges of wrist flexion and extension at velocities of 50°/s and 280°/s in both treated and untreated conditions. Joint angular position, resistance torque, and surface electromyography (EMG) of the wrist flexors and extensors were recorded. Rigidity was quantified by normalized work scores and normalized angular impulses for flexion and extension, separately. Reflex responses of stretched and shortened muscles were quantified by mean EMG and EMG ratio. A series of ANOVAs was performed to determine the effect of amplitude, velocity and medication on selected variables.

RESULTS

Both work scores and angular impulses revealed that the larger displacement amplitude and the higher velocity were associated with significantly greater rigidity, increased EMG ratio and mean EMG of stretched muscles. Dopaminergic medication was not associated with a reduction in rigidity.

CONCLUSIONS

Parkinsonian rigidity is modulated by the amplitude and rate of muscle stretch.

SIGNIFICANCE

These findings shed light on the biomechanical underpinnings and physiological characteristics of rigidity and may inform clinical rigidity assessment in Parkinson's disease.

Acute effects of passive leg cycling on upper extremity tremor and bradykinesia in Parkinson's disease

BACKGROUND

Previous studies have shown that single bouts of high-rate active cycling (> 80 rpm) improve upper extremity motor function in individuals with Parkinson's disease (PD). It is unknown if passive leg cycling produces a similar effect on upper extremity function. This article examines whether passive leg cycling can promote immediate changes in upper tremor and bradykinesia in PD and if pedaling rates have variable effects.

METHODS

Twenty individuals with mild-to-moderate idiopathic PD completed 4 sessions, with each session taking place 1 week apart. In the second to fourth sessions, a motorized bicycle was set to passively rotate the subjects' legs at rates of 60, 70, or 80 rpm for 30 minutes. Quantitative upper extremity motor assessments were completed immediately before and after each session.

RESULTS

Passive leg cycling was shown to reduce tremor and bradykinesia in PD. However, the rate of passive cycling did not affect the degree of improvement in bradykinesia or tremor.

CONCLUSION

These findings suggest that lower extremity passive cycling can promote changes in upper extremity motor function in individuals with PD.

An EMG-based system for continuous monitoring of clinical efficacy of Parkinson's disease treatments

Current methods for assessing the efficacy of treatments for Parkinson's disease (PD) rely on physician rated scores. These methods pose three major shortcomings: 1) the subjectivity of the assessments, 2) the lack of precision on the rating scale (6 discrete levels), and 3) the inability to assess symptoms except under very specific conditions and/or for very specific tasks. To address these shortcomings, a portable system was developed to continuously monitor Parkinsonian symptoms with quantitative measures based on electrical signals from muscle activity (EMG). Here, we present the system design and the implementation of methods for system validation. This system was designed to provide continuous measures of tremor, rigidity, and bradykinesia which are related to the neurophysiological source without the need for multiple bulky experimental apparatuses, thus allowing more precise, quantitative indicators of the symptoms which can be measured during practical daily living tasks. This measurement system has the potential to improve the diagnosis of PD as well as the evaluation of PD treatments, which is an important step in the path to improving PD treatments.

Changes in viscoelastic properties of skeletal muscles induced by subthalamic stimulation in patients with Parkinson's disease

BACKGROUND

Objective measurements would be useful to document the effect of deep brain stimulation in alleviating rigidity in patients with Parkinson's disease. The aim of the study was to examine the changes of viscoelastic properties in skeletal muscles as indicators of rigidity.

METHODS

Six patients in an advanced stage of Parkinson's disease participated in the study. The study took place in the off-medication conditions after one night of drug withdrawal. The wrist rigidity was examined according to the Unified Parkinson's Disease Rating Scale in both sides. Myotonometry (Myoton) was used to determine stiffness and elasticity in extensor digitorum muscles bilaterally. The measurements were repeated and compared during the stimulation-on and stimulation-off periods.

FINDINGS

A comparison of mean clinical motor scores revealed a significant improvement of parkinsonian symptoms due to brain stimulation. In particular, arm rigidity improved on average from 2.83 (1-4) in stimulation-off phase to 1.17 (0-2) in stimulation-on phase (P<0.05). The mean values of elasticity and stiffness were not significantly different in stimulation-on and stimulation-off conditions. The patients with elevated clinical rigidity scores had higher mean values of stiffness (262.5 vs 211.0; P<0.05) but the differences in elasticity were not significant.

INTERPRETATION

Increased rigidity is associated with increased values of viscoelastic stiffness. This paper supports the use of myotonometry for objective quantification of rigidity and in the future, this tool could prove helpful for optimizing deep brain stimulation settings in patients with Parkinson's disease.

Blood oxygenation level-dependent activation in basal ganglia nuclei relates to specific symptoms in de novo Parkinson's disease

To aid the development of symptomatic and disease modifying therapies in Parkinson's disease (PD), there is a strong need to identify noninvasive measures of basal ganglia (BG) function that are sensitive to disease severity. This study examines the relation between blood oxygenation level-dependent (BOLD) activation in every nucleus of the BG and symptom-specific disease severity in early stage de novo PD. BOLD activation measured at 3 T was compared between 20 early stage de novo PD patients and 20 controls during an established precision grip force task. In addition to the BG nuclei, activation in specific thalamic and cortical regions was examined. There were three novel findings. First, there were significant negative correlations between total motor Unified PD Rating Scale and BOLD activation in bilateral caudate, bilateral putamen, contralateral external segment of the globus pallidus, bilateral subthalamic nucleus, contralateral substantia nigra, and thalamus. Second, bradykinesia was the symptom that most consistently predicted BOLD activation in the BG and thalamus. Also, BOLD activation in the contralateral internal globus pallidus was related to tremor. Third, the reduced cortical activity in primary motor cortex and supplementary motor area in de novo PD did not relate to motor symptoms. These findings demonstrate that BOLD activity in nuclei of the BG relates most consistently to bradykinesia and functional magnetic resonance imaging has strong potential to serve as a noninvasive marker for the state of BG function in de novo PD.

Analysis of viscoelastic properties of wrist joint for quantification of parkinsonian rigidity

This study aims to analyze viscoelastic properties of the wrist in patients with Parkinson's disease (PD) in comparison with the clinical score of severity. Forty-five patients with PD and 12 healthy volunteers participated in this study. Severity of rigidity at the wrist was rated by a neurologist just before the experiment. Wrist joint torque resistive to the imposed movement was measured. Three different models, (identical in structure, only different in the number of parameters for extension and flexion phases) were used in identification of viscoelastic properties: 1) one damping constant and one spring constant throughout all phases, 2) two damping constants for each phase and one spring constant throughout all phases, and 3) two damping constants and two spring constants for each phase. Normalized work and impulse suggested in the literature were also calculated. Spring constants of different models and phases showed comparable correlation with rigidity score ( r=0.68-0.73). In terms of the correlation of damping constant with clinical rigidity score, model 1 ( r = 0.90) was better than models 2 and 3 ( r=0.59 - 0.71). These results suggest that the clinical rigidity score is better represented by the mean viscosity during both flexion and extension. In models with two dampers (model 2 and 3), the damping constant was greater during extension than flexion in patients , in contrast that there was no phase difference in normal subjects. This suggests that in contrast with normal subjects, phase-dependent viscosity may be an inherent feature of PD. Although work and impulse were correlated with clinical rigidity score ( r = 0.11 - 0.84), they could not represent the phase-dependent rigidity inherent in PD. In conclusion, the viscosity of model 1 would be appropriate for quantification of clinical ratings of rigidity and that of model 2 for distinction of PD and also for investigation of phase-dependent characteristics in parkinsonian rigidity.