Power spectral density analysis of physiological, rest and action tremor in Parkinson’s disease patients treated with deep brain stimulation (original) (raw)
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Deep brain stimulation and medication for parkinsonian tremor during secondary tasks
Movement Disorders, 2007
This study examined the efficacy of subthalamic nucleus (STN), deep brain stimulation (DBS), and medication for resting tremor during performance of secondary tasks. Hand tremor was recorded using accelerometry and electromyography (EMG) from 10 patients with Parkinson's disease (PD) and ten matched control subjects. The PD subjects were examined off treatment, on STN DBS, on medication, and on STN DBS plus medication. In the first experiment, tremor was recorded in a quiet condition and during a cognitive task designed to enhance tremor. In the second experiment, tremor was recorded in a quiet condition and during isometric finger flexion (motor task) with the contralateral limb at 5% of the maximal voluntary contraction (MVC) that was designed to suppress tremor. Results showed that: (1) STN DBS and medication reduced tremor during a cognitive task that exacerbated tremor, (2) STN DBS normalized tremor frequency in both the quiet and cognitive task conditions, whereas tremor amplitude was only normalized in the quiet condition, (3) a secondary motor task reduced tremor in a similar manner to STN DBS. These findings demonstrate that STN DBS still suppresses tremor in the presence of a cognitive task. Furthermore, a secondary motor task of the opposite limb suppresses tremor to levels comparable to STN DBS.
Modulation of tremor amplitude during deep brain stimulation at different frequencies
Brain and Cognition, 2003
Rest tremor was quantified in the index finger tip of 16 patients with ParkinsonÕs disease (PD) receiving deep brain stimulation (DBS) of the ventro-intermediate nucleus (Vim) of the thalamus, the subthalamic nucleus (STN), or the internal part of the globus pallidus (GPi) while being off L L -dopa for 12 h. Clinically, without DBS, tremor amplitude varied from absent to high. Tremor was recorded continuously for about 5 min under three conditions of DBS repeated twice, namely, effective frequency (E), ineffective frequency (I), and no DBS (O). No changes in tremor were observed across conditions in subjects with little or no tremor. However, in subjects with moderate to large amplitude tremor, DBS decreased tremor amplitude to near normal values within a few seconds. Generally, transitions were progressive and occurred with a varying time delay. Occasionally, tremor escaped from control regardless of the stimulation condition considered. In some cases tremor amplitude in one condition appeared to depend on the preceding condition. Finally, the results were reproducible on two consecutive days. We conclude that tremor control with DBS follows specific dynamical rules, which must be compatible with the hypotheses proposed regarding the underlying mechanisms of DBS.
Characterization of subclinical tremor in Parkinson's disease
Movement Disorders, 2005
The physiological or pathological nature of subclinical tremor amplitude in Parkinson's disease (PD) is not well established. We analyzed characteristics of resting and postural tremors of subclinical amplitude in 17 patients with idiopathic PD without visible resting tremor, having a postural tremor in their least-affected hand rated 0 (12 subjects) or 1 (5 subjects) on Item 21 of the Unified Parkinson's Disease Rating Scale, compared to 17 control subjects matched for age, sex, and handedness. Tremor was recorded at the tip of the index finger using a displacement laser transducer. Overall results show that subclinical resting tremor in PD is significantly different from physiological tremor in terms of amplitude fluctuation, frequency dispersion, harmonic index, and proportional power in 4 to 6 Hz. No significant differences were found for postural tremor. These differences appear to originate mainly from patients with the mixed form of the disease. This study also confirms the preservation of physiological tremor likely originating from a distinct central oscillator in PD. The use of this method in the early and detailed characterization of PD tremors when amplitude is still within normal limits is proposed.
Re-emergent tremor in Parkinson's disease: A clinical and electromyographic study
Journal of the Neurological Sciences, 2016
Re-emergent tremor (RET) and the classical parkinsonian rest tremor were considered as two different phenomena of the same central tremor circuit. However, clinical and accelerometric characteristics of these tremors were not previously compared in a single study. We evaluated disease characteristics and accelerometric measurements of two tremor types in 42 patients with Parkinson's disease. Disease specific features and accelerometric measurements of peak frequency, amplitude at peak frequency and the root mean square (RMS) amplitude of two tremor types were compared. Eighteen patients had RET and the mean latency of the RET was 9.48 (±9.2) s. Groups of only rest tremor and RET did not differ significantly in age of disease onset, disease duration and severity and mean levodopa equivalent dose. Comparison of peak frequency and amplitude at peak frequency were not different between the groups, but RMS amplitude was significantly higher in the RET group (p = 0.03). RMS amplitude of RET was also correlated with disease severity (r = .48, p = 0.04). These results support the previous notion that rest tremor and RET are analogue, both are triggered by the same central ossilator with RET being only the suppression of the rest tremor due to arm repositioning.
Electrophysiologic characteristics of tremor in Parkinson's disease and essential tremor
Arquivos de neuro-psiquiatria, 2014
Tremor in essential tremor (ET) and Parkinson's disease (PD) usually present specific electrophysiologic profiles, however amplitude and frequency may have wide variations. To present the electrophysiologic findings in PD and ET. 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. 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. The tremor analysis alone using the methodology described here, is not sufficient to differentiate tremor in ET and PD.
Regularity of force tremor in Parkinson's disease
Clinical Neurophysiology, 2001
The study examines the time-dependent structure of force tremor to investigate two hypotheses: (1), the regularity of tremor can help in discriminating normal aging from that of Parkinson's disease (PD); and (2), there is increased tremor regularity with increases in the severity of PD.
Voluntary Tremor Suppression in Parkinson's Disease
2013
Parkinson's disease (PD) is a common degenerative neurological disorder, and resting tremor is one of the main symptoms of this disease. It has been observed that some patients with Parkinsonian rest tremor are able to suppress their tremor voluntarily with mental concentration or by focusing attention on the affected limb. This process is not well understood and this study aims to describe and assess voluntary tremor suppression in patients with PD, as well as to identify the critical cortical or subcortical regions activated during this process. Methods: Nine participants with tremor-dominant PD were recruited for this study. These patients had unilateral rest tremors of the upper limb and were able to consciously stop their tremor for a period of time. Each patient was assessed using the Unified Parkinson's Disease Rating Scale (UPDRS), movement tracking and functional imaging. Physical characteristics of the tremor such as amplitude and frequency were measured using a 3-D Polhemus Liberty electromagnetic movement tracking in the MoVELab. Functional imaging was undertaken using functional magnetic resonance imaging (fMRI) in a 3.0 Tesla scanner, with functional data collected with a standard T2 weighted MRI sequence along with T1 weighted 3-D anatomical data. Results: The extent of voluntary tremor suppression differed between the participants with some being able to suppress reliably for long periods of time, and others unable to do so consistently. Participants had slight to moderate tremors according to the UPDRS. The majority of participants described their method of suppression as concentrating on the affected limb and/or focusing on relaxing the limb. Movement tracking confirmed what was observed, with variation in tremor amplitude, and the extent of suppression. FMRI showed differing areas of activation involved in tremor suppression amongst the participants. Activated areas were generally contralateral to the tremor, and were widespread, including parts of the primary motor cortex, superior parietal lobule, supramarginal gyrus and middle frontal gyrus. Conclusion: This study was the first attempt at describing the process of voluntary tremor suppression in PD. The differing methods the participants used to suppress iii their tremor were recorded and described, and objective measures of the suppression taken. Functional imaging revealed a number of areas involved in tremor suppression. iv Preface This thesis is the result of an eventful period of research and study and is submitted for consideration for a Bachelor of Medical Science with Honours. Beginning in 2010, this has been an intensive undertaking and I have found myself gathering skills in many areas I never thought I would have in the past. With the help of many at the Van der Veer Institute (now the New Zealand Brain Research Institute), I have learnt how to independently manage participants, perform focused clinical histories and examinations, apply Parkinson's disease rating scales, gather three dimensional movement data, and explore functional magnetic resonance imaging. Aspects of this research project have been presented at NZBRI discussion groups and at the Australasian Winter Conference on Brain Research in 2010. Feedback at such meetings has been invaluable in improving this project. v Acknowledgements I would like to express my sincere thanks to my supervisors, Professor Tim Anderson and Dr Michael MacAskill, for their support, patience and guidance throughout my research year. I am also indebted to the wealth of expertise of Leslie
Journal of NeuroEngineering and Rehabilitation, 2020
Background Tremor is a cardinal symptom of Parkinson’s disease (PD) that may cause severe disability. As such, objective methods to determine the exact characteristics of the tremor may improve the evaluation of therapy. This methodology study aims to validate the utility of two objective technical methods of recording Parkinsonian tremor and evaluate their ability to determine the effects of Deep Brain Stimulation (DBS) of the subthalamic nucleus and of vision. Methods We studied 10 patients with idiopathic PD, who were responsive to L-Dopa and had more than 1 year use of bilateral subthalamic nucleus stimulation. The patients did not have to display visible tremor to be included in the study. Tremor was recorded with two objective methods, a force platform and a 3 dimensional (3D) motion capture system that tracked movements in four key proximal sections of the body (knee, hip, shoulder and head). They were assessed after an overnight withdrawal of anti-PD medications with DBS ON ...
Brain, 2004
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) and antiparkinsonian medication have proved to be effective treatments for tremor in Parkinson's disease. To date it is not known how and to what extent STN DBS alone and in combination with antiparkinsonian medication alters the pathophysiology of resting and postural tremor in idiopathic Parkinson's disease. The purpose of this study was to examine the effects of STN DBS and antiparkinsonian medication on the neurophysiological characteristics of resting and postural hand tremor in Parkinson's disease. Resting and postural hand tremor were recorded using accelerometry and surface electromyography (EMG) from 10 Parkinson's disease patients and 10 matched control subjects. The Parkinson's disease subjects were examined under four treatment conditions: (i) off treatment; (ii) STN DBS; (iii) medication; and (iv) medication plus STN DBS. The amplitude, EMG frequency, regularity, and 1-8 Hz tremor-EMG coherence were analysed. Both STN DBS and medication reduced the amplitude, regularity and tremor-EMG coherence, and increased the EMG frequency of resting and postural tremor in Parkinson's disease. STN DBS was more effective than medication in reducing the amplitude and increasing the frequency of resting and postural tremor to healthy physiological levels. These findings provide strong evidence that effective STN DBS normalizes the amplitude and frequency of tremor. The findings suggest that neural activity in the STN is an important modulator of the neural network(s) responsible for both resting and postural tremor genesis in Parkinson's disease.