Kinetic tremor in Parkinson's disease--an underrated symptom

AiCarePWP: Deep learning-based novel research for Freezing of Gait forecasting in Parkinson

BACKGROUND AND OBJECTIVES

Episodes of Freezing of Gait (FoG) are among the most debilitating motor symptoms of Parkinson's Disease (PD), leading to falls and significantly impacting patients' quality of life. Accurate assessment of FoG by neurologists provides crucial insights into patients' conditions and disease symptoms. This proposed strategy involves utilizing a Weighted Fuzzy Logic Controller, Kalman Filter, and Kaiser-Meyer-Olkin test to detect the gait parameters while walking, resting, and standing phases. Parameters such as neuromodulation format, intensity, duration, frequency, and velocity are computed to pre-empt freezing episodes, thus aiding their prevention.

METHOD

The AiCarePWP is a wearable electronics device designed to identify instances when a patient is on the brink of experiencing a freezing episode and subsequently deliver a brief electrical impulse to the patient's shank muscles to stimulate movement. The AiCarePWP wearable device aims to identify impending freezing episodes in PD patients and deliver brief electrical impulses to stimulate movement. The study validates this innovative approach using plantar insoles with a 3D accelerometer and electrical stimulator, analysing data from the inertial measuring unit and plantar-pressure foot data to detect and predict FoG.

RESULTS

Using a Convolutional Neural Network-based model, the study evaluated 47 gait features for their ability to differentiate resting, standing, and walking conditions. Variable selection was based on sensitivity, specificity, and overall accuracy, followed by Principal Component Analysis and Varimax rotation to extract and interpret factors. Factors with eigenvalues exceeding 1.0 were retained, and 37 features were retained.

CONCLUSION

This study validates CNN's effectiveness in detecting FoG during various activities. It introduces a novel cueing method using electrical stimulation, which improves gait function and reduces FoG incidence in PD patients. Trustworthy wearable devices, based on Artificial Intelligence of Things (AIoT) and Artificial Intelligence of Medical Things (AIoMT), have been developed to support such interventions.

Action tremor features discovery for essential tremor and Parkinson's disease with explainable multilayer BiLSTM

The tremors of Parkinson's disease (PD) and essential tremor (ET) are known to have overlapping characteristics that make it complicated for clinicians to distinguish them. While deep learning is robust in detecting features unnoticeable to humans, an opaque trained model is impractical in clinical scenarios as coincidental correlations in the training data may be used by the model to make classifications, which may result in misdiagnosis. This work aims to overcome the aforementioned challenge of deep learning models by introducing a multilayer BiLSTM network with explainable AI (XAI) that can better explain tremulous characteristics and quantify the respective discovered important regions in tremor differentiation. The proposed network classifies PD, ET, and normal tremors during drinking actions and derives the contribution from tremor characteristics, (i.e., time, frequency, amplitude, and actions) utilized in the classification task. The analysis shows that the XAI-BiLSTM marks the regions with high tremor amplitude as important in classification, which is verified by a high correlation between relevance distribution and tremor displacement amplitude. The XAI-BiLSTM discovered that the transition phases from arm resting to lifting (during the drinking cycle) is the most important action to classify tremors. Additionally, the XAI-BiLSTM reveals frequency ranges that only contribute to the classification of one tremor class, which may be the potential distinctive feature to overcome the overlapping frequencies problem. By revealing critical timing and frequency patterns unique to PD and ET tremors, this proposed XAI-BiLSTM model enables clinicians to make more informed classifications, potentially reducing misclassification rates and improving treatment outcomes.

Refining the clinical diagnosis of Parkinson's disease

Our ability to define, understand, and classify Parkinson's disease (PD) has undergone significant changes since the disorder was first described in 1817. Clinical features and neuropathologic signatures can now be supplemented by in-vivo interrogation of genetic and biological substrates of disease, offering great opportunity for further refining the diagnosis of PD. In this mini-review, we discuss the historical perspectives which shaped our thinking surrounding the definition and diagnosis of PD. We highlight the clinical, genetic, pathologic and biologic diversity which underpins the condition, and proceed to discuss how recent developments in our ability to define biologic and pathologic substrates of disease might impact PD definition, diagnosis, individualised prognostication, and personalised clinical care. We argue that Parkinson's 'disease', as currently diagnosed in the clinic, is actually a syndrome. It is the outward manifestation of any array of potential dysfunctional biologic processes, neuropathological changes, and disease aetiologies, which culminate in common outward clinical features which we term PD; each person has their own unique disease, which we can now define with increasing precision. This is an exciting time in PD research and clinical care. Our ability to refine the clinical diagnosis of PD, incorporating in-vivo assessments of disease biology, neuropathology, and neurogenetics may well herald the era of biologically-based, precision medicine approaches PD management. With this however comes a number of challenges, including how to integrate these technologies into clinical practice in a way which is acceptable to patients, promotes meaningful changes to care, and minimises health economic impact.

Effects of upper limb vibratory stimulation training on motor symptoms in Parkinson's disease: an observational study

OBJECTIVES

Parkinson's disease is characterized by motor and non-motor symptoms. Tremor is one of the motor symptoms that can affect manual skills and have an impact on daily activities. The aim of the current study is to investigate the effect of upper limb training provided by a specific vibratory device (Armshake®, Move It GmbH - Bochum, Germany) on tremor and motor functionality in patients with Parkinson's disease. Furthermore, the training effect on global cognitive functioning is assessed.

DESIGN

An uncontrolled before-after clinical trial.

PATIENTS

Individuals with diagnosis of Parkinson's disease, motor upper limbs deficits, and absence of dementia.

METHODS

Participants underwent a 3-week programme (3 times a week) and was evaluated before, after, and at 1 month follow-up by motor (Fahn Tolosa Marin Tremor Rating Scale, Unified Parkinson's Disease Rating Scale - part III, Purdue Pegboard Test, Disability of the Arm, Shoulder and Hand Questionnaire) and cognitive (Montreal Cognitive Assessment) scales.

RESULTS

Twenty subjects are included. After treatment a statistically significant improvement in tremor, manual dexterity and activities of daily living was found. The data indicated no effects on global cognitive functioning.

CONCLUSION

These findings suggest positive effects of vibratory stimulation training on upper limb motor symptoms in Parkinson's disease.

Writing tremor in Parkinson's disease: frequency and associated clinical features

Action tremor in Parkinson's disease may present in up to 46% of patients, either as postural or kinetic tremor. How action tremor may affect handwriting has been the object of some investigations; however, clinical features of writing tremor in Parkinson's disease are still not well-characterised. One hundred consecutive patients with idiopathic Parkinson's disease were included in the study. Demographic and clinical data were collected through a standardized questionnaire. Patients were assessed for the presence of rest, action and writing tremor in on condition. The effect of a standardised sensory trick (gently touching the wrist of the upper limb manifesting tremor with the contralateral hand) was also investigated in all patients with action tremor. Writing tremor was found in 10% of patients (26% of patients with postural/kinetic tremor, either alone or in combination with rest tremor). Severity of writing tremor did not correlated with that of the other tremor variants and to the other clinical variables. Writing tremor was task-specific in 4/10 patients, no task-specific in 6/10. Sensory trick was effective on writing tremor in two patients but did not improve action tremor in any of the study patients. Results showed that writing tremor in Parkinson's disease is less common than other tremor variants, may be associated with other forms of action tremor, and may sometimes have dystonic features, including task-specificity and sensitivity to sensory trick.

Does essential tremor increase risk of cognitive impairment and dementia? Yes

Essential Tremor (ET), by definition, is a disorder of movement. Yet over the years, epidemiologic, clinical, pathologic, and neuroimaging studies have converged to reveal a cognitive side of ET. The cognitive symptoms in ET are heterogeneous and are likely to reflect heterogeneous underlying mechanisms. In this chapter, we review and synthesize a diverse set of studies from both population-based settings to cohorts with more detailed investigations into cognition to consider the various mechanisms by which cognitive symptoms may emerge in a subset of individuals with ET. As part of our analysis, we consider questions surrounding ET diagnosis and the possibility of comorbid disease as potential factors that, upon closer examination, appear to strengthen the argument in favor of ET as a risk factor for dementia. Importantly, we also consider the clinical relevance of cognitive impairment in ET. While ET is not universally characterized by significant cognitive deficits, the data from epidemiological, cognitive, neuroimaging, and postmortem neuropathologic studies converge to reveal an increased risk for cognitive impairment and dementia among individuals with ET. We conclude by offering directions for future research, and a neurocognitive framework with which to consider existing findings and to use in the design of novel studies dedicated to clarifying the basis, nature, and course of cognitive impairments in ET.

Parkinsonism and tremor syndromes

Tremor, the most common movement disorder, may occur in isolation or may co-exist with a variety of other neurologic and movement disorders including parkinsonism, dystonia, and ataxia. When associated with Parkinson's disease, tremor may be present at rest or as an action tremor overlapping in phenomenology with essential tremor. Essential tremor may be associated not only with parkinsonism but other neurological disorders, suggesting the possibility of essential tremor subtypes. Besides Parkinson's disease, tremor can be an important feature of other parkinsonian disorders, such as atypical parkinsonism and drug-induced parkinsonism. In addition, tremor can be a prominent feature in patients with other movement disorders such as fragile X-associated tremor/ataxia syndrome, and Wilson's disease in which parkinsonian features may be present. This article is part of the Special Issue "Parkinsonism across the spectrum of movement disorders and beyond" edited by Joseph Jankovic, Daniel D. Truong and Matteo Bologna.

Smartphone-Based Monitoring of Parkinson Disease: Quasi-Experimental Study to Quantify Hand Tremor Severity and Medication Effectiveness

BACKGROUND

Hand tremor typically has a negative impact on a person's ability to complete many common daily activities. Previous research has investigated how to quantify hand tremor with smartphones and wearable sensors, mainly under controlled data collection conditions. Solutions for daily real-life settings remain largely underexplored.

OBJECTIVE

Our objective was to monitor and assess hand tremor severity in patients with Parkinson disease (PD), and to better understand the effects of PD medications in a naturalistic environment.

METHODS

Using the Welch method, we generated periodograms of accelerometer data and computed signal features to compare patients with varying degrees of PD symptoms.

RESULTS

We introduced and empirically evaluated the tremor intensity parameter (TIP), an accelerometer-based metric to quantify hand tremor severity in PD using smartphones. There was a statistically significant correlation between the TIP and self-assessed Unified Parkinson Disease Rating Scale (UPDRS) II tremor scores (Kendall rank correlation test: z=30.521, P<.001, τ=0.5367379; n=11). An analysis of the "before" and "after" medication intake conditions identified a significant difference in accelerometer signal characteristics among participants with different levels of rigidity and bradykinesia (Wilcoxon rank sum test, P<.05).

CONCLUSIONS

Our work demonstrates the potential use of smartphone inertial sensors as a systematic symptom severity assessment mechanism to monitor PD symptoms and to assess medication effectiveness remotely. Our smartphone-based monitoring app may also be relevant for other conditions where hand tremor is a prevalent symptom.

STN Versus GPi Deep Brain Stimulation for Action and Rest Tremor in Parkinson's Disease

Objective

To investigate the effects of subthalamic nucleus (STN) and globus pallidus internus (GPi), deep brain stimulation (DBS) on individual action tremor/postural tremor (AT) and rest tremor (RT) in Parkinson’s disease (PD). Randomized DBS studies have reported marked benefit in tremor with both GPi and STN and DBS, however, there is a paucity of information available on AT vs RT when separated by the surgical target.

Methods

We retrospectively reviewed the 1-year clinical outcome of PD patients treated with STN and GPi DBS at the University of Florida. We specifically selected patients with moderate to severe AT. Eighty-eight patients (57 STN and 31 GPi) were evaluated at 6 and 12 months for changes in AT and RT in the OFF-medication/ON stimulation state. A comparison of “response” was performed and defined as greater than or equal to a 2-point decrease in tremor score.

Results

STN and GPi DBS both improved AT at 6- and 12-months post-implantation (p < 0.001 and p < 0.001). The STN DBS group experienced a greater improvement in AT at 6 months compared to the GPi group (p = 0.005) but not at the 12 months follow-up (p = 0.301). Both STN and GPi DBS also improved RT at 6- and 12-months post-implantation (p < 0.001 and p < 0.001). There was no difference in RT scores between the two groups at 6 months (p = 0.23) or 12 months (p = 0.74). The STN group had a larger proportion of patients who achieved a “response” in AT at 6 months (p < 0.01), however, this finding was not present at 12 months (p = 0.23). A sub-analysis revealed that in RT, the STN group had a larger percentage of “responders” when followed through 12 months (p < 0.01).

Conclusion

Both STN and GPi DBS reduced PD associated AT and RT at 12 months follow-up. There was no advantage of either brain target in the management of RT or AT. One nuance of the study was that STN DBS was more effective in suppressing AT in the early postoperative period, however, this effect diminished over time. Clinicians should be aware that it may take longer to achieve a similar tremor outcome when utilizing the GPi target.

Parkinson's Disease Exhibits Amplified Intermuscular Coherence During Dynamic Voluntary Action

Parkinson's disease (PD) is typically diagnosed and evaluated on the basis of overt motor dysfunction, however, subtle changes in the frequency spectrum of neural drive to muscles have been reported as well. During dynamic actions, coactive muscles of healthy adults often share a common source of 6-15 Hz (alpha-band) neural drive, creating synchronous alpha-band activity in their EMG signals. Individuals with PD commonly exhibit kinetic action tremor at similar frequencies, but the potential relationship between the intermuscular alpha-band neural drive seen in healthy adults and the action tremor associated with PD is not well-understood. A close relationship is most tenable during voluntary dynamic tasks where alpha-band neural drive is strongest in healthy adults, and where neural circuits affected by PD are most engaged. In this study, we characterized the frequency spectrum of EMG synchronization (intermuscular coherence) in 16 participants with PD and 15 age-matched controls during two dynamic motor tasks: (1) rotation of a dial between the thumb and index finger, and (2) dynamic scaling of isometric precision pinch force. These tasks produce different profiles of coherence between the first dorsal interosseous and abductor pollicis brevis muscles. We sought to determine if alpha-band intermuscular coherence would be amplified in participants with PD relative to controls, if such differences would be task-specific, and if they would correlate with symptom severity. We found that relative to controls, the PD group displayed amplified, but similarly task-dependent, coherence in the alpha-band. The magnitude of coherence during the rotation task correlated with overall symptom severity as per the UPDRS rating scale. Finally, we explored the potential for our coherence measures, with no additional information, to discriminate individuals with PD from controls. The area under the Receiver Operating Characteristic curve (AUC) indicated a clear separation between groups (AUC = 0.96), even though participants with PD were on their typical medication and displayed only mild-moderate symptoms. We conclude that a task-dependent, intermuscular neural drive within the alpha-band is amplified in PD. Its quantification via intermuscular coherence analysis may provide a useful tool for detecting the presence of PD, or assessing its progression.

A Multimodal Approach to the Quantification of Kinetic Tremor in Parkinson's Disease

Parkinson's disease results in motor impairment that deteriorates patients' quality of life. One of the symptoms negatively interfering with daily activities is kinetic tremor which should be measured to monitor the outcome of therapy. A new instrumented method of quantification of the kinetic tremor is proposed, based on the analysis of circles drawn on a digitizing tablet by a patient. The aim of this approach is to obtain a tremor scoring equivalent to that performed by trained clinicians. Models are trained with the least absolute shrinkage and selection operator (LASSO) method to predict the tremor scores on the basis of the parameters computed from the patients' drawings. Signal parametrization is derived from both expert knowledge and the response of an artificial neural network to the raw data, thus the approach was named multimodal. The fitted models are eventually combined into model ensembles that provide aggregated scores of the kinetic tremor captured in the drawings. The method was verified with a set of clinical data acquired from 64 Parkinson's disease patients. Automated and objective quantification of the kinetic tremor with the presented approach yielded promising results, as the Pearson's correlations between the visual ratings of tremor and the model predictions ranged from 0.839 to 0.890 in the best-performing models.

Vocal tract characteristics in Parkinson's disease

PURPOSE OF REVIEW

Voice tremor is strongly linked to the Parkinson's disease speech-voice symptom complex. Little is known about the underlying anatomic source(s) of voice tremor when it occurs. We review recent literature addressing this issue. Additionally we report findings from a study we conducted employing rating of vocal tract structures viewed using nasolaryngoscopy during vocal and nonspeech tasks.

RECENT FINDINGS

In Parkinson's disease, using laryngeal electromyography, tremor has not been identified in muscles in the vocal folds even when perceived auditorily. Preliminary findings using nasolaryngoscopy suggest that Parkinson's disease voice tremor is not associated with the vocal folds and may involve the palate, the global larynx, and the arytenoids. Tremor in the vertical larynx on /a/, and tremor in the arytenoid cartilages on /s/ differentiated patients with Parkinson's disease from neurologically healthy controls. Visual reliable detection of tremor when it is absent or borderline present, is challenging.

SUMMARY

Parkinson's disease voice tremor is likely to be related to oscillatory movement in structures across the vocal tract rather than just the vocal folds. To progress clinical practice, more refined tools for the visual rating of tremor would be beneficial. How far voice tremor represents a functionally significant factor for speakers would also add to the literature.

Diagnosing Parkinson Disease

PURPOSE OF REVIEW

While establishing the diagnosis of Parkinson disease (PD) can be straightforward, it can be challenging in some patients, even for the experienced neurologist. The misdiagnosis rate ranges from 10% to 20% or greater depending on clinician experience.

RECENT FINDINGS

Despite promise in the search for a biomarker that can establish the presence of PD and act as a marker of its progression, the diagnosis of PD continues to be based on clinical examination. Core criteria, exclusion criteria, and supportive criteria have been developed to aid the clinician in establishing the diagnosis. Nonmotor symptoms of PD are usually present at the time of diagnosis, may precede motor symptoms, and should be specifically sought during evaluation. Ancillary testing can be appropriate, but its indications and utility must be clearly understood.

SUMMARY

The diagnosis of PD requires the recognition of the core features of PD and the differentiation of its clinical presentation from other entities with similar and potentially overlapping symptoms. A careful history and examination guided by clinical diagnostic criteria will usually establish the diagnosis of PD or uncover red flags for the possibilities of other diagnoses. Appropriate selection and interpretation of ancillary testing is critical to avoid misdiagnosis and unnecessary tests.

How to use pen and paper tasks to aid tremor diagnosis in the clinic

When a patient presents with tremor, it can be useful to perform a few simple pen and paper tests. In this article, we explain how to maximise the value of handwriting and of drawing Archimedes spirals and straight lines as clinical assessments. These tasks take a matter of seconds to complete but provide a wealth of information that supplements the standard physical examination. They aid the diagnosis of a tremor disorder and can contribute to its longitudinal monitoring. Watching the patient’s upper limb while they write and draw may reveal abnormalities such as bradykinesia, dystonic posturing and distractibility. The finished script and drawings can then be evaluated for frequency, amplitude, direction and symmetry of oscillatory pen movements and for overall scale of penmanship. Essential, dystonic, functional and parkinsonian tremor each has a characteristic pattern of abnormality on these pen and paper tests.

Relationship between resting and action tremors in Parkinson's disease

OBJECTIVE

To determine the relationship between resting tremor (RT) and action tremor (AT) in Parkinson's disease (PD) patients.

METHODS

A retrospective study of RT and AT severity was conducted in 100 PD patients. The severity rating for each type of tremor in the upper extremities was assessed. The disparity in tremor severity between extremities for each tremor type was compared to that of the other two to identify commonalities in the laterality of the tremor manifestation.

RESULTS

Overall, RT is predictive of AT on the same side, but not the opposing side of the body. Patients with less intense resting right upper limb (RRU) tremor and moderately intense RRU tremor were significantly more likely to have an action right upper limb (ARU) tremor (-1.53, P = 0.020; -1.88, P = 0.005, respectively). Similarly, patients with less intense resting left upper limb (RLU) tremor and moderately intense RLU tremors were significantly more likely to have an action left upper limb (ALU) tremor (-3.49, P = 0.000; -1.86, P = 0.017, respectively). In addition, RRU and ALU tremors were associated with an increase in RLU and ARU tremors, respectively.

CONCLUSION

Tremors are common findings in PD patients, and often impair quality of life. By identifying and classifying the relationship between resting and ATs in PD patients, our study sheds light onto the importance of better understanding and future management of this debilitating symptomology.

Comparison of VIM and STN DBS for Parkinsonian Resting and Postural/Action Tremor

Background

Resting tremor is common in Parkinson’s disease (PD), but up to 47% of PD patients have action tremor, which is sometimes resistant to medications. Deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) of the thalamus or subthalamic nucleus (STN) is effective for medication-refractory tremor in PD, though it remains unclear whether STN DBS is as effective as VIM DBS for postural/action tremor related to PD.

Methods

We carried out a single-center retrospective review of patients with medication-refractory resting, postural, and action PD tremor, treated with either VIM or STN DBS between August 2004 and March 2014. We assessed the degree of improvement using items 20 and 21 of the Unified Parkinson’s Disease Rating Scale (UPDRS) motor scale and examined the proportion of patients achieving tremor arrest.

Results

A total of 18 patients were analyzed, 10 treated with STN and eight treated with VIM, with similar off-medication motor UPDRS scores. There was no significant difference in improvement in tremor scores or in the proportion of patients experiencing tremor arrest between the two stimulation sites. Overall, 56% and 72% of patients experienced complete absence of postural/action tremor and resting tremor, respectively, at last follow-up.

Discussion

This study demonstrated excellent outcomes on both resting and postural/action tremor after either VIM or STN DBS. Resting tremor improved to a greater degree than postural/action tremor in both groups. These results suggest that a large randomized controlled trial is needed to show a superior effect of one target on PD tremor.

Distal motor deficit contributions to postural instability and gait disorder in Parkinson's disease

Clinical subtypes in Parkinson's disease (PD) are often based on the presence of clustered motor symptoms. In contrast to the tremor dominant (TD) subtype, the postural instability and gait disorder (PIGD) subtype is characterized by predominantly axial motor involvement and increased cognitive impairment. It is, however, unclear if subtypes represent distinct underlying neuropathological mechanisms or reflect more severe disease progression. We aimed to clarify the validity of PD subtypes by investigating behavioral outcomes at multiple levels. Therefore, spatiotemporal kinematics of gait, upper and lower limb repetitive movements in combination with a balance and cognitive assessment were recorded in 73 patients with PD. We classified patients as PIGD (n=43), TD (n=22) or indeterminate (n=8) while 'off' medication and recruited 20 age-matched controls. Surprisingly, differences between PIGD and TD were more prominent during repetitive distal motor tasks than during gait. Gait impairment in PIGD was only shown by reduced step length and gait speed. However, motor scaling and coordination of distal movements were more affected in PIGD than in TD patients. PIGD patients also had impaired postural control compared to TD patients as shown by lower mini-BESTest scores. There were no cognitive differences between patient subgroups. Distal movement was not significantly different in TD patients from controls, except for greater movement asymmetry. The results indicate a widespread impairment within PIGD with more pronounced distal than axial motor deficits. This suggests involvement of different neurotransmitter systems in the neuropathology of PD subtypes, which are at least partially independent of disease progression.

Effective Management of Upper Limb Parkinsonian Tremor by IncobotulinumtoxinA Injections Using Sensor-based Biomechanical Patterns

BACKGROUND

Focal treatment of Parkinson's disease tremor by botulinum toxin type A incobotulinumtoxinA (BoNT-A) injections has been inadequately investigated and at best provides modest relief with significant muscle weakness. Complexity of multi-joint tremulous movements results in non-individualized dosing regimens. This 38-week open-label study used kinematic technology to guide muscle selection and improve efficacy of incobotulinumtoxinA (BoNT-A) injections for Parkinson's disease tremor.

METHODS

Participants (n=28) attended study visits at weeks 0, 6, 16, 22, 32, and 38, and were injected with BoNT-A at weeks 0, 16, and 32. During each visit, clinical tremor scales, the Unified Parkinson's Disease Rating Scale (UPDRS) and the Fahn-Tolosa-Marin (FTM), and kinematic assessments were conducted. Participants performed rest and postural scripted tasks with motion sensors placed over the wrist, elbow, and shoulder joints where tremor was quantified by angular root mean square (RMS) amplitude in multiple degrees of freedom at each joint. Injection parameters were determined using the clinician's interpretation of which muscles would contribute to the upper limb tremor biomechanics analyzed kinematically.

RESULTS

Kinematic measures of tremor amplitude allowed detailed segmentation of tremor into directional components at each arm joint permitting a statistically significant decrease in mean UPDRS item 20 (rest tremor) at week 16 (p=0.006) and at week 32 (p=0.014), and in FTM tremor severity scores at week 6 (p=0.024). Ten participants perceived mild muscle weakness following the third treatment, which did not interfere with performing activities of daily living.

DISCUSSION

Kinematics is a simple method for standardizing assessments and treatment of upper limb Parkinson's disease tremor, thereby personalizing tremor therapy and optimizing the effect of BoNT-A injections for Parkinson's disease tremor.

Effects of STN DBS and auditory cueing on the performance of sequential movements and the occurrence of action tremor in Parkinson's disease

Background

Parkinson’s disease (PD) patients show a higher ability to perform repetitive movements when they are cued by external stimuli, suggesting that rhythmic synchronization with an auditory timekeeper can be achieved in the absence of intact basal ganglia function. Deep brain stimulation (DBS) is another therapeutic method that improves movement performance in PD and may suppress or enhance action tremor. However, the combined effect of these therapies on action tremor has not been studied yet. In this pilot study, we thus test the effect of both DBS in the subthalamic nucleus (STN) and auditory cueing on movement performance and action tremor.

Methods

7 PD patients treated with (bilateral) STN DBS were asked to move one hand or foot between two dots, separated by 30 cm as indicated on the table or the floor. The movement frequency was dictated by a metronome with a frequency in the range of 1.6 to 4.8 Hz. Each test was repeated three times for each extremity, with different stimulation settings applied during each repetition. The power spectral density patterns of recorded movements were studied. Tremor intermittency was taken into account by classifying each 2-second window of the recorded angular velocity signals as a tremor or non-tremor window. By determining the phase locking value it was tested whether movement or tremor was synchronized with the auditory cue.

Results

While action tremor presence or absence did not affect the level of synchronization of the movement signal with the auditory cue for the different metronome frequencies, the number of extremities showing action tremor was significantly reduced under external cueing conditions in combination with DBS. In this respect the cueing frequencies of 1.6 and 4.8 Hz showed similar effects, suggesting that the frequency of the cueing signal is not that critical.

Conclusion

The combination of deep brain stimulation and auditory cueing, which both are proposed to involve the activation of cerebellar circuits, shows an enhanced action tremor reduction in Parkinson’s disease.

Electronic supplementary material

The online version of this article (doi:10.1186/1743-0003-11-135) contains supplementary material, which is available to authorized users.

Electrophysiologic characteristics of tremor in Parkinson's disease and essential tremor

Tremor in essential tremor (ET) and Parkinson's disease (PD) usually present specific electrophysiologic profiles, however amplitude and frequency may have wide variations.

OBJECTIVE

To present the electrophysiologic findings in PD and ET.

METHOD

Patients were assessed at rest, with posture and action. Seventeen patients with ET and 62 with PD were included. PD cases were clustered into three groups: predominant rest tremor; tremor with similar intensity at rest, posture and during kinetic task; and predominant kinetic tremor.

RESULTS

Patients with PD presented tremors with average frequency of 5.29±1.18 Hz at rest, 5.79±1.39 Hz with posture and 6.48±1.34 Hz with the kinetic task. Tremor in ET presented with an average frequency of 5.97±1.1 Hz at rest, 6.18±1 Hz with posture and 6.53±1.2 Hz with kinetic task. Seven (41.2%) also showed rest tremor.

CONCLUSION

The tremor analysis alone using the methodology described here, is not sufficient to differentiate tremor in ET and PD.

Medical treatment of essential tremor

Essential tremor (ET) is the most common pathological tremor characterized by upper limb action-postural tremor (PT)/kinetic tremor (KT). There are no specific neuropathological or biochemical abnormalities in ET. The disability is consequent to amplitude of KT, which may remain mild without handicap or may become disabling. The most effective drugs for sustained tremor control are propranolol and primidone. Symptomatic drug treatment must be individualized depending on the circumstances that provoke the tremor-related disability. Broad guidelines for treatment are discussed in this review. Patients may be treated intermittently only on stressful occasions with propranolol, clonazepam, or primidone monotherapy, or an alcoholic drink. Those with persistently disabling tremor need continued treatment.

Effectiveness of BoNT A in Parkinson's disease upper limb tremor management

OBJECTIVE

One the greatest challenges of BoNT A therapy for tremor lies in the complexity and variation of components involved in tremor movement, and the lack of objective measures to determine these components. This 3 month open-label single injection study aims to couple clinician best judgment with kinematics to improve effect of BoNT A (incobotulinumtoxinA) injection in 7 patients with upper limb Parkinson's disease (PD) tremor.

METHODS

Injection was guided with clinical and kinematic assessment of tremor using angular wrist position in 3 degrees of freedom: flexion/extension, pronation/supination, and radial/ulnar deviation. Overall tremor severity and change were measured by linear finger acceleration.

RESULTS

Kinematic data from static and functional tasks demonstrate no improvement at one month post-injection, but significant improvement at two and three months. Clinical scales across UPDRS Items 20 (1, 2, 3 months post) and 21 (2 months), and spiral drawings (3 months) showed significant improvement from baseline, while line drawings did not.

CONCLUSIONS

This study suggests injection of BoNT A as a viable focal management option for upper limb PD tremor. In addition to clinical judgment, objective quantification of tremor dynamics by kinematics may be a feasible assessment and guidance tool which can be used to optimize injection conditions for focal tremor therapy. Kinematic analysis of tremor across a variety of joints in all degrees of movement may provide important insight into tremor dynamics, allowing optimized, targeted focal therapy.

Is action tremor in Parkinson's disease related to resting tremor?

OBJECTIVE

Action tremor (AT) and resting tremor (RT) have been widely cited in many studies with Parkinson's disease (PD) patients, but studies looking at the association between the two tremor types are few and show inconsistent results. This study will look at the prevalence and association of AT and RT in a large sample of idiopathic PD patients, and will put the results into context with the literature.

METHODS

A retrospective chart review analysis of 332 patients with idiopathic PD was performed. Prevalence rates of particular tremor types were noted. The presence of AT was analyzed relative to the presence and severity of RT.

RESULTS

Nearly all individuals with AT also had RT. The concurrence of the two tremor types was found to be highly significant by statistical analysis (P < 0.0001). The severity of RT, measured by its laterality, may also be of importance, albeit to a much smaller extent if at all. Neither presence of tremor nor type of tremor present was influenced by patient gender, age, or Hoehn and Yahr stage of PD.

CONCLUSIONS

The results indicate that AT has extensive presence in PD. This and its seemingly close relationship to RT suggest that AT may be considered a variant of RT, particularly in PD patients. The degree of association between RT and AT needs to be further analyzed in PD, as well as in essential tremor (ET) and ET-PD.

Power spectral density analysis of physiological, rest and action tremor in Parkinson's disease patients treated with deep brain stimulation

Background

Observation of the signals recorded from the extremities of Parkinson’s disease patients showing rest and/or action tremor reveal a distinct high power resonance peak in the frequency band corresponding to tremor. The aim of the study was to investigate, using quantitative measures, how clinically effective and less effective deep brain stimulation protocols redistribute movement power over the frequency bands associated with movement, pathological and physiological tremor, and whether normal physiological tremor may reappear during those periods that tremor is absent.

Methods

The power spectral density patterns of rest and action tremor were studied in 7 Parkinson’s disease patients treated with (bilateral) deep brain stimulation of the subthalamic nucleus. Two tests were carried out: 1) the patient was sitting at rest; 2) the patient performed a hand or foot tapping movement. Each test was repeated four times for each extremity with different stimulation settings applied during each repetition. Tremor intermittency was taken into account by classifying each 3-second window of the recorded angular velocity signals as a tremor or non-tremor window.

Results

The distribution of power over the low frequency band (<3.5 Hz – voluntary movement), tremor band (3.5-7.5 Hz) and high frequency band (>7.5 Hz – normal physiological tremor) revealed that rest and action tremor show a similar power-frequency shift related to tremor absence and presence: when tremor is present most power is contained in the tremor frequency band; when tremor is absent lower frequencies dominate. Even under resting conditions a relatively large low frequency component became prominent, which seemed to compensate for tremor. Tremor absence did not result in the reappearance of normal physiological tremor.

Conclusion

Parkinson’s disease patients continuously balance between tremor and tremor suppression or compensation expressed by power shifts between the low frequency band and the tremor frequency band during rest and voluntary motor actions. This balance shows that the pathological tremor is either on or off, with the latter state not resembling that of a healthy subject. Deep brain stimulation can reverse the balance thereby either switching tremor on or off.

Distinguishing essential tremor from Parkinson's disease: bedside tests and laboratory evaluations

Distinguishing essential tremor from Parkinson's disease can be challenging, both in the early stages of these diseases and as these diseases progress. Various tremor types (rest, postural, kinetic and intention) may be seen in both essential tremor and Parkinson's disease. Furthermore, with time, the two diseases may coexist within a single patient. Detailed clinical examination with attention to specific features of tremor (frequency, amplitude, pattern and distribution) and associated neurological findings may help distinguish patients with the two diseases. Laboratory testing may provide information that further aids in differentiating the two diseases. These tests include accelerometry and surface electromyography, spiral analysis, dopamine transporter imaging, olfactory testing and, eventually, postmortem histopathology. These tests have limitations and their diagnostic utility requires additional study.

How to tackle tremor - systematic review of the literature and diagnostic work-up

Background: Tremor is the most prevalent movement disorder in clinical practice. It is defined as involuntary, rhythmic, oscillatory movements. The diagnostic process of patients with tremor can be laborious and challenging, and a clear, systematic overview of available diagnostic techniques is lacking. Tremor can be a symptom of many diseases, but can also represent a distinct disease entity. Objective: The objective of this review is to give a clear, systematic and step-wise overview of the diagnostic work-up of a patient with tremor. The clinical relevance and value of available laboratory tests in patients with tremor will be explored. Methods: We systematically searched through EMBASE. The retrieved articles were supplemented by articles containing relevant data or provided important background information. Studies that were included investigated the value and/or usability of diagnostic tests for tremor. Results: In most patients, history and clinical examination by an experienced movement disorders neurologist are sufficient to establish a correct diagnosis, and further ancillary examinations will not be needed. Ancillary investigation should always be guided by tremor type(s) present and other associated signs and symptoms. The main ancillary examination techniques currently are electromyography and SPECT imaging. Unfortunately, many techniques have not been studied in large prospective, diagnostic studies to be able to determine important variables like sensitivity and specificity. Conclusion: When encountering a patient with tremor, history, and careful clinical examination should guide the diagnostic process. Adherence to the diagnostic work-up provided in this review will help the diagnostic process of these patients.

Telemonitoring System of Neurological Signs in a Health Telematique Network

The paper presents a new, experimental, wireless tremor telemonitoring system composed of an optional variable number of portable devices integrating three-axis acceleration mini-sensors which are connected to very small dimensions acquisition systems with Wi-Fi transmission capabilities. The main advantages of the design system consist of the possibilities to monitor simultaneously many body parts of one or multiple subjects on local or more extended areas both for scheduled assessments and in an everyday life environment. Possible applications of the presented experimental system, considered as a part of a health telematic network, consist of delivering supplementary, consistent sets of data to clinicians in order to reliably assess patients’ state in home and community settings, over longer periods of time. This system consists of delivering new data necessary for differential diagnosis of different types of tremors, or to precise different stages of illness in a health telematic network. The multiple simultaneous measuring capabilities and the extended observation time period could cover eventually neglected aspects related to occasional, temporary, or an intermittent tremor. The Wi-Fi DAQ proposed system’s novelty, in contrast with existing Wi-Fi solutions, is its ultra low power Wi-Fi capability, which makes it suitable for sensing applications where battery power management is critical.

Ambulatory monitoring of activities and motor symptoms in Parkinson's disease

Ambulatory monitoring of motor symptoms in Parkinsons disease (PD) can improve our therapeutic strategies, especially in patients with motor fluctuations. Previously published monitors usually assess only one or a few basic aspects of the cardinal motor symptoms in a laboratory setting. We developed a novel ambulatory monitoring system that provides a complete motor assessment by simultaneously analyzing current motor activity of the patient (e.g. sitting, walking) and the severity of many aspects related to tremor, bradykinesia, and hypokinesia. The monitor consists of a set of four inertial sensors. Validity of our monitor was established in seven healthy controls and six PD patients treated with deep brain stimulation (DBS) of the subthalamic nucleus. Patients were tested at three different levels of DBS treatment. Subjects were monitored while performing different tasks, including motor tests of the Unified Parkinsons Disease Rating Scale (UPDRS). Output of the monitor was compared to simultaneously recorded videos. The monitor proved very accurate in discriminating between several motor activities. Monitor output correlated well with blinded UPDRS ratings during different DBS levels. The combined analysis of motor activity and symptom severity by our PD monitor brings true ambulatory monitoring of a wide variety of motor symptoms one step closer..

Clinically deployable Kinesia technology for automated tremor assessment

The objective was to design, build, and assess Kinesia, a wireless system for automated assessment of Parkinson's disease (PD) tremor. The current standard in evaluating PD is the Unified Parkinson's Disease Rating Scale (UPDRS), a qualitative ranking system typically completed during an office visit. Kinesia integrates accelerometers and gyroscopes in a compact patient-worn unit to capture kinematic movement disorder features. Objectively quantifying PD manifestations with increased time resolution should aid in evaluating efficacy of treatment protocols and improve patient management. In this study, PD subjects performed the tremor subset of the UPDRS motor section while wearing Kinesia. Quantitative kinematic features were processed and highly correlated to clinician scores for rest tremor (r(2) = 0.89), postural tremor (r(2) = 0.90), and kinetic tremor (r(2) = 0.69). The quantitative features were used to develop a mathematical model that predicted tremor severity scores for new data with low errors. Finally, PD subjects indicated high clinical acceptance.

Atypical task-invariant organization of multi-segment tremors in patients with Parkinson's disease during manual tracking

The objective of the study was to investigate the interplay between involuntary tremulous activities and task performance under volitional control for patients with Parkinson's disease (PD) during position tracking. A volunteer sample of nine untreated patients and nine age-matched healthy subjects participated in this study. They performed a sinusoidal tracking maneuver with a shoulder and a static pointing task; meanwhile, a position trace of the index and accelerometer data in the upper limb were recorded to characterize tracking performance and postural-kinetic tremors. In reference to postural tremor, the kinetic tremor of control subjects during tracking was considerably modulated, leading to a lower regularity and greater spectral deviation. In contrast, patients with PD demonstrated greater postural and kinetic tremors than control subjects, and tremulous movements of the patients were comparatively task-invariant. The prominent coherence peak, which occurred at 8-12 Hz in control subjects, was atypically presented at 5-8 Hz for PD patients with poorer tracking performance. Functionally, congruency of position tracking was related to amplitude of kinetic tremor after subtracting from amplitude of postural tremor. In conclusion, task-dependent organization of tremulous movements was impaired in patients with PD. The inferior tracking performance of the patients correlated implicitly with kinetic tremor, signifying some sharing of neural substrates for manual tracking and tremor generation.