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PubMed2005

The effects of unilateral muscle fatigue on bilateral physiological tremor.

The aim of this study was to examine the post-exercise effects of fatiguing the wrist extensor muscles of a single arm on postural tremor and muscle activity in both arms. Previous research has shown that, for neurologically normal subjects, the tremor seen within a single limb segment is uncorrelated to that seen contralaterally. However it has been speculated that some bilateral relation does exist, and that the nature of the relation may only become evident under conditions where the neuromuscular system is perturbed. To further investigate this potential bilateral relation, seven healthy subjects were required to adopt a bilateral postural pointing position after exercise-induced fatigue of the wrist extensor muscles of a single arm. Tremor from the forearm, hand and finger segments of each arm, surface EMG activity from extensor digitorum (ED) of each arm, and blood lactate data were collected prior to and after the exercise intervention. The main result was that fatiguing the distal muscles of one arm resulted in a bilateral increase in both the physiological tremor and ED activity. The change in tremor was confined to the index finger with no change in the tremor for the hand or forearm segments of either arm. While three peaks were seen in the frequency profile of the finger tremor, the effects of fatigue were confined to an increase in the peak power of the neurally generated 8-12 Hz tremor component. The contralateral increase in muscle activity was also reflected by a change in the frequency profile of the EMG output, with an increase in the peak power of both muscles following exercise of the wrist extensors of a single arm. The bilateral increases in physiological tremor and EMG activity of ED were only observed during the bilateral pointing task, with no changes in tremor or EMG activity seen for the non-exercised limb during the unilateral exercise protocol. The specificity of the resultant increases in the neurally generated 8-12 Hz component of finger tremor amplitude and EMG activity, coupled with the lack of any changes in tremor for the more proximal arm segments, indicate that these bilateral effects were mediated by an increase in the central neural drive to both limbs. Together this set of results challenges the general assumption of bilateral independence of tremor production, and further illustrate the task dependent nature of exercise-induced fatigue.

Adult↗
PubMed1998

Patterns of bursting occurring in thalamic cells during parkinsonian tremor.

It has been proposed that parkinsonian tremor is produced either by the activity of an intrinsic thalamic pacemaker or by the oscillation of an unstable long loop reflex arc. The former (central) hypothesis proposes that overactivity of neurons in the internal segment of the globus pallidus inhibits or hyperpolarizes thalamic neurons. When hyperpolarized, thalamic cells oscillate with bursting of the type associated with low threshold calcium spikes (low threshold spike-bursts). Low threshold spike-bursts can be identified by particular patterns of interspike intervals within the burst. The alternative (peripheral) hypothesis proposes that tremor results from oscillation of a reflex arc transmitting activity from muscle stretch receptors to thalamus, motor cortex, and back to the stretched muscle. When the gain of this reflex is increased, the arc may become unstable and oscillate. Oscillations produced by peripheral inputs may produce an acceleration-deceleration pattern within the burst which results in sinusoidal modulation of a spike train if bursting is periodic. We have assessed these two hypotheses by studying the pattern of interspike intervals occurring within bursts recorded in patients with parkinsonian tremor. The spike trains were analysed for 118 cells located in the ventral nuclear group including ventralis intermedius (thalamic cerebellar relay nucleus, n=48) and ventralis oralis posterior (thalamic pallidal relay nucleus, n=39) of patients with parkinsonian tremor. Two cells recorded in ventralis intermedius of a sleeping patient with chronic pain showed bursting activity similar to the low threshold spike-bursts recorded in sleeping animals, suggesting a common mechanism for low threshold spike-bursts across species. Forty-two cells recorded in patients with parkinsonian tremor (ventralis intermedius, n=19; ventralis oralis posterior, n=12) were classified as tremor-related cells because their activity was characterized by both a concentration of power at tremor frequency and significant correlation with tremor. Eleven tremor-related cells, 10 located in ventralis intermedius or ventralis oralis posterior and most responding to sensory inputs, had an acceleration-deceleration pattern of intraburst firing. Only one cell, a tremor-related cell in ventralis intermedius, showed the pattern expected of presumed low threshold spike-bursts. Therefore, intraburst interspike interval patterns consistent with either the central or the peripheral hypothesis were recorded in the thalamus of patients with parkinsonian tremor. Twenty-one tremor-related cells (15 cells in ventralis intermedius or ventralis oralis posterior) had bursts with intraburst interspike intervals which were independent of position of the interspike interval within the burst. Therefore, the activity of the majority of cells was not consistent with either hypothesis, suggesting that another oscillatory process may contribute to parkinsonian tremor.

Electromyography↗
PubMedDate not supplied

Fuzzy methods in tremor assessment, prediction, and rehabilitation.

Tremor is a disabling condition for a large segment of population, mainly elderly. To the present date, there are no adequate tools to diagnose and help rehabilitation of subjects with tremor, but recently there is a tremendous surge of interest in the research in the field. We report on the use of fuzzy methods in applications for rehabilitation, namely in tremor diagnosing and control. We synthesize our results regarding the characterization of the tremor by means of nonlinear dynamics techniques and fuzzy logic, and the prediction of tremor movements in view of rehabilitation purposes. Based on linear and nonlinear analysis of tremor, and using fuzzy aggregation, the fusing of tremor parameters in global functional disabling factors is proposed. Nonlinear dynamic parameters, namely correlation dimension and Lyapunov exponent is used in order to improve the assessment of tremor. The benefits of the fuzzy fused tremor parameters rely on more complete and accurate assessment of the functional impairment and on improved feedback for rehabilitation, based on the fused parameters of the tremor. Further steps in rehabilitation may require external muscular control. In turn, the control of tremor by electrical stimulation requires movement prediction. Several neural and neuro-fuzzy predictors are compared and a neuro-fuzzy predictor is presented, allowing us five-step ahead prediction, with an RMS error of the order of 10%. The benefits of the neuro-fuzzy predictor are good prediction capability, versatility, and apparently a high robustness to individual variations of the tremor. The reported research, which extended over several years and included development of sensors, equipment, and software, has been aimed to development of products. The results may also open new ways in tremor rehabilitation.

Aged↗
PubMed2002

Clinical and electromyographic assessment of essential tremor treatment.

It is a matter of debate whether beta-blockers or primidone have a better influence on essential tremor. It is also controversial whether essential tremor with synchronous electromyographic activity is influenced by the administration beta-blockers, while tremor with alternating electromyographic activity is influenced by primidone. The aim of this study was to reevaluate the effects of beta-blockers and primidone on essential tremor. We also aimed to evaluate the differential effects of beta-blockers and primidone on tremor with synchronous or alternating electromyographic activity and on tremor in different limb positions. One hundred patients (57 female, 43 male) with essential tremor were included in this study. According to the electromyographic pattern recorded from the antagonistic muscles, the patients were subdivided into group with synchronous (SYN) and group with alternating (ALT) activity. After the initial clinical and electromyographic examinations the patients were randomly assigned first to treatment with propranolol (180 mg daily), or to treatment with primidone (500 mg daily) for 30 days. After a washout period of 20 days the patients were assigned to the other treatment. Our results revealed that the effects of propranolol and primidone on essential tremor and on SYN or ALT tremor were similar. Differences between both drugs existed as regards to better primidone influence on the kinetic and intention tremors and to tremor localized outside the limbs. In conclusion it is better to treat patients with kinetic and intention essential tremor and tremor localized outside the limbs with primidone.

Adrenergic beta-Antagonists↗
PubMed2000

Postural and resting tremor in the upper limb.

OBJECTIVE: Tremor from multiple segments of the upper limb was recorded under postural and resting conditions. The aims of this study were to examine the nature of tremor within a single limb segment, intra- and inter-limb co-ordination of tremor, and the influence of cardiac mechanical events on physiological tremor. METHODS: Tremor was recorded from eight healthy adult subjects during a postural pointing task where the level of support for the upper limb segments was successively increased. The dynamics of tremor within a single segment were examined using power spectral, ApEn and amplitude analyses. Inter-segment tremor relations were determined using coherence and Cross-correlation analyses. RESULTS: Single segment analysis demonstrated that each (unsupported) limb segment contained two major frequency peaks (at 1-4 Hz and 8-12 Hz). Both peaks were still evident in the distal segments when the proximal segments were supported. External support of the more proximal limb segments also resulted in decreased finger tremor, but these changes were not simply additive over segments within a limb or equal across fingers. There were significant relations between adjacent proximal and distal limb segment pairs but no correlations between contralateral limb segments or between heart rate and limb tremor. CONCLUSIONS: These findings imply that: the low frequency component (1-4 Hz) of physiological tremor in the hand and finger could not be attributed to passive transmission of oscillations from the upper arm and forearm; and the contribution of proximal segments on tremor in the index finger tremor could not be predicted from mechanical principles alone. The minimization of finger tremor involved compensatory coupling of segments of the upper arm with particular emphasis upon active control of the wrist joint.

Acceleration↗
PubMed1993

Significance of parkinsonian manifestations in essential tremor.

Parkinsonian features, notably resting tremor may be seen in some essential tremor patients but the significance of those is unknown. The reported risk of parkinsonism in essential tremor patients varies from being unchanged to 35 times higher than expected. We studied 9 patients with essential tremor who had autopsies. In 6 of the 9 (66%) resting tremor was noted and in 3 (33%) cases fully developed parkinsonism was noted. The parkinsonism was consequent to neuroleptic usage in 2 and to basal ganglia status lacunaris and cribrosus in one case but no consistent abnormalities were noted in 3 essential tremor only and 3 essential tremor plus resting tremor cases. We conclude that resting tremor is an age-related natural evolution in some essential tremor patients. We recommend that the additional diagnosis of parkinsonism in the essential tremor be made only when resting tremor, bradykinesia and rigidity are all evident. The risk of ideopathic Parkinson's disease in essential tremor cases is similar to the general population.

Aged↗
PubMed2003

The cerebral oscillatory network of parkinsonian resting tremor.

Data from experiments in MPTP monkeys as well as from invasive and non-invasive recordings in patients with Parkinson's disease suggest an abnormal synchronization of neuronal activity in the generation of resting tremor in Parkinson's disease. In six patients with tremor-dominant idiopathic Parkinson's disease, we recorded simultaneously surface electromyograms (EMGs) of hand muscles, and brain activity with a whole-head magnetoencephalography (MEG) system. Using a recently developed analysis tool (Dynamic Imaging of Coherent Sources; DICS), we determined cerebro-muscular and cerebro-cerebral coherence as well as the partial coherence between cerebral areas and muscle, and localized coherent sources within the individual MRI scans. The phase lag between the EMG and cerebral activity was determined by means of a Hilbert transform of both signals. After overnight withdrawal from medication, patients showed typical Parkinson's disease resting tremor (4-6 Hz). This tremor was associated with strong coherence between the EMG of forearm muscles and activity in the contralateral primary motor cortex (M1) at tremor frequency but also at double tremor frequency. Phase lags between M1 activity and EMG were between 15 and 25 ms (M1 activity leading) at single, but also at double tremor frequency, corresponding well to the corticomuscular conduction time. Furthermore, significant coherence was observed between M1 and medial wall areas (cingulate/supplementary motor area; CMA/SMA), lateral premotor cortex (PM), diencephalon, secondary somatosensory cortex (SII), posterior parietal cortex (PPC) and the contralateral cerebellum at single tremor and, even stronger at double tremor frequency. Spectra of coherence between thalamic activity and cerebellum as well as several brain areas revealed additional broad peaks around 20 Hz. Power spectral analysis of activity in all central areas indicated the strongest frequency components at double tremor frequency. Partial coherence analysis and the calculation of phase shifts revealed a strong bidirectional coupling between the EMG and diencephalic activity and a direct afferent coupling between the EMG and SII and the PPC. In contrast, the cerebellum, SMA/CMA and PM show little evidence for direct coupling with the peripheral EMG but seem to be connected with the periphery via other cerebral areas (e.g. M1). In summary, our results demonstrate tremor-related oscillatory activity within a cerebral network, with abnormal coupling in a cerebello-diencephalic-cortical loop and cortical motor (M1, SMA/CMA, PM) and sensory (SII, PPC) areas contralateral to the tremor hand. The main frequency of cerebro-cerebral coupling corresponds to double the tremor frequency.

Adult↗
PubMed1995

Levodopa does not aggravate postural tremor in Parkinson's disease.

Characterization of postural tremor in Parkinson's disease (PD) is incomplete. It was suggested to be an exaggerated physiological tremor and to be enhanced by the action of levodopa. We compared the magnitude of postural tremor to the magnitude of rest tremor and to plasma levodopa levels in 20 PD patients, 10 with stable motor response to oral levodopa, and 10 with the wearing-off phenomenon. Tremor assessment included motor scores of the Unified Parkinson's Disease Rating Scale and accelerometric measurements. Accelerometric data showed that the absolute power of both rest and postural basal dominant tremor frequencies significantly diminished with the increase in plasma levodopa levels and increased with their decrease. Tremor frequencies were also significantly changed by levodopa, which slowed rest tremor and increased postural tremor dominant frequency. This latter, however, did not reach the 8- to 12-Hz frequency band said to be typical of exaggerated physiological tremor. No significant differences between groups were found in their tremor response to levodopa. This study shows that the net postural tremor exhibited by PD patients is improved by levodopa, that levodopa does not augment tremor in the 8- to 12-Hz range, and that this effect is independent of the patient's motor response pattern of oral levodopa.

Aged↗
PubMed2000

Using time domain characteristics to discriminate physiologic and parkinsonian tremors.

Tremor amplitude and frequency do not always clearly differentiate subjects with particular pathologies from control subjects or from subjects with other pathologies, especially in early stages of a disease. For patients with early stages of Parkinson's disease (PD) the discriminative power of amplitude was compared with that of other time domain characteristics of tremor recordings that are probably not evident clinically. Postural tremor with and without visual feedback and rest tremor were recorded in both hands of a group of patients with Parkinson's disease (n = 21) and a group of healthy control subjects (n = 30) using displacement lasers. Velocity and acceleration data were derived from displacement data. Twelve time domain characteristics were calculated on each recording and the discriminating power of each was evaluated using the worse hand in each case. Postural tremor with no visual feedback separates the two groups of subjects most efficiently, especially in velocity and acceleration. Tremor in Parkinson's disease (in comparison to normal physiologic tremor) has a specific morphology, has a distinctive histogram, is more periodic, and contains indications of nonlinearity in the underlying dynamics. There may also be greater difference in amplitude between the two hands and time asymmetry in tremor of patients with PD. A series of finger flexions seems to enhance normal tremor but not tremor in PD and may thus aid in discrimination. Discrimination of tremor attributable to PD from normal physiologic tremor can be enhanced by measuring time domain characteristics subtler than amplitude, particularly when amplitude itself is not large. Tremor measurement should not be limited to acceleration data because some information is more visible in other variables.

Aged↗
PubMed1998

Clinico-tremorgraphic features of neuroleptic-induced tremor.

Instrumental tremorgrams have been used to improve the diagnostic accuracy of various movement disorders, including tardive akathisia. The aim of the present work was to evaluate their place in the diagnosis of neuroleptic-induced tremor and to determine whether they can help to differentiate this disorder from other neuroleptic-induced movement disorders and from other types of tremor. Fourteen psychiatric patients treated with various neuroleptic medications were diagnosed as having neuroleptic-induced tremor on the basis of clinical criteria. They underwent accelerometric recordings following diagnosis. All patients demonstrated upper-limb tremor; four also had involvement of the lower limbs, jaw or tongue. Most demonstrated both resting and postural tremor, the latter being the more prominent. The tremor was mainly rhythmic, regular and sinusoidal. It did not significantly interfere with activities of daily living in the majority of patients, but four did exhibit some degree of impairment. Repeated accelerometric recordings showed constant and regular waveforms and frequencies (between 4 and 7 Hz) in each patient. We conclude that the presence of repeated constant waveforms and frequencies on accelerometric tracings may serve as confirmation of the diagnosis of neuroleptic-induced tremor. In light of the findings of this and other studies, we suggest that tremorgrams may be helpful in differentiating neuroleptic-induced tremor from other neuroleptic-induced movement disorders (e.g., tardive dyskinesia and tardive akathisia) and from psychogenic tremor. Although these techniques may also assist in the differentiation of neuroleptic-induced tremor from some tremor disorders (e.g., asterixis or ataxic tremor), their overall potential to distinguish it from other types of organic tremor is more limited.

Adult↗
PubMed1999

Distal versus proximal arm tremor in multiple sclerosis assessed by visually guided tracking tasks.

OBJECTIVES: To compare action tremor (AT) during manual tracking in normal subjects and patients with multiple sclerosis with tremor (MS-tremor group) and without tremor (MS-no tremor group), and to differentiate tremor occurring predominantly around the distal joint from that involving the proximal joints of the arm. METHODS: Subjects performed both a visually guided ramp tracking task using wrist flexion/extension and a whole arm circle tracking task using shoulder movement. Action tremor at the wrist or shoulder was computed as the SD of the tracking velocity. The ratio of wrist:arm tremor was then calculated to differentiate distal from proximal tremor in the tested arm. Frequency spectra of the records were also examined. RESULTS: During wrist tracking, AT in patients with multiple sclerosis contained a major frequency component at 4-5 Hz; the frequency was slightly lower during whole arm tracking. The ratio of wrist:arm tremor was significantly higher in the MS-tremor group. Of 12 tested arms, eight had tremor significantly weighted towards the distal joint, only one towards the proximal joint, and three had a ratio inside the control range. CONCLUSIONS: AT in the arms of patients with multiple sclerosis can be effectively differentiated into proximal or distal using these two different tracking tasks. Despite the variability of the effects of multiple sclerosis, most of the AT was distal rather than proximal in this group of patients. Possibly conduction block along the corticocerebellocortical pathways caused this distal tremor.

Adult↗
PubMed1982

Objective and subjective tremor responses to oral beta 2 agents on first exposure. A comparison of metaproterenol and terbutaline.

Objective and subjective postural tremor responses at 60 and 120 min after drug treatment were studied in 24 veterans with chronic obstructive pulmonary disease who received either 5 mg terbutaline, 20 mg metaproterenol, or a placebo in random order. Subjects were fasting, and had not taken theophylline for 15 to 24 h or any oral sympathomimetics for 2 wk. The mean tremor response to terbutaline and metaproterenol was equal at 60 min, but the 120-min response to metaproterenol was less. When the 60- and 120-min responses were averaged, tremor response to terbutaline was significantly greater than that to metaproterenol in a 5 : 4 ratio. Subjective awareness was also greater. These results are consistent with the difference in bronchodilatory potency of the two preparations. That the drug producing the greater tremor could usually be identified by the patient, even at low tremor intensities, is consistent with the hypothesis that perception of tremor is a function of relative rather than absolute increase over basal tremor unless the tremor becomes physically disabling. In general, the individual tremor response was proportional to the extent by which a patient's basal tremor exceeded the minimal basal tremor for the group as a whole. These results fit a model in which the postural tremor derives from beta-sensitive and beta-insensitive cardioballistic and skeletal muscle forces. Variability in tremor response resides principally at the peripheral skeletal beta 2-receptor and its control system.

Administration, Oral↗
PubMed2005

Practice parameter: therapies for essential tremor [RETIRED]: report of the Quality Standards Subcommittee of the American Academy of Neurology.

BACKGROUND: Essential tremor (ET) is one of the most common tremor disorders in adults and is characterized by kinetic and postural tremor. To develop this practice parameter, the authors reviewed available evidence regarding initiation of pharmacologic and surgical therapies, duration of their effect, their relative benefits and risks, and the strength of evidence supporting their use. METHODS: A literature review using MEDLINE, EMBASE, Science Citation Index, and CINAHL was performed to identify clinical trials in patients with ET published between 1966 and August 2004. Articles were classified according to a four-tiered level of evidence scheme and recommendations were based on the level of evidence. RESULTS AND CONCLUSIONS: Propranolol and primidone reduce limb tremor (Level A). Alprazolam, atenolol, gabapentin (monotherapy), sotalol, and topiramate are probably effective in reducing limb tremor (Level B). Limited studies suggest that propranolol reduces head tremor (Level B). Clonazepam, clozapine, nadolol, and nimodipine possibly reduce limb tremor (Level C). Botulinum toxin A may reduce hand tremor but is associated with dose-dependent hand weakness (Level C). Botulinum toxin A may reduce head tremor (Level C) and voice tremor (Level C), but breathiness, hoarseness, and swallowing difficulties may occur in the treatment of voice tremor. Chronic deep brain stimulation (DBS) (Level C) and thalamotomy (Level C) are highly efficacious in reducing tremor. Each procedure carries a small risk of major complications. Some adverse events from DBS may resolve with time or with adjustment of stimulator settings. There is insufficient evidence regarding the surgical treatment of head and voice tremor and the use of gamma knife thalamotomy (Level U). Additional prospective, double-blind, placebo-controlled trials are needed to better determine the efficacy and side effects of pharmacologic and surgical treatments of ET.

Adrenergic beta-Antagonists↗
PubMed1995

[Clinical and physiological studies on senile tremor].

We examined 6 male and 10 female patients with senile tremor which started at 60 years of age or older. The patients' age on examination ranged from 66 to 82 years (mean: 73.4; SD: 5.4 years). The surface electromyogram (EMG) was recorded from the bilateral biceps brachii, triceps brachii, forearm flexor and forearm extensor muscles. The frequency of the tremor was counted and patterns of grouping discharges were analysed. The effect of mechanical perturbation to the affected muscle on tremor rhythm was also examined. The same investigations were performed in 15 male and 7 female patients with essential tremor with onset age before 60 years as control patients. The mean frequency was 6.2 Hz (SD: 1.3 Hz) in senile tremor and 7.3 Hz (SD: 1.5 Hz) in essential tremor. There was a significant difference between the two groups. The mean frequency in control patients whose age on examination was 60 years or over was, however, 6.0 Hz (SD: 0.8 Hz), and there was no difference from the mean frequency in senile tremor. The frequency in both groups was inversely correlated to the patient's age on examination. The antagonist muscles were reciprocally discharged in 15 patients in the senile tremor group and in 7 in the controls. Mechanical perturbation of the affected muscle re-set the tremor rhythm in all patients examined. Thus, senile tremor had characteristics resembling tremor in the control patients, suggesting that senile tremor may be a subtype of essential tremor.

Aged↗
PubMedDate not supplied

Judgment of disability stages in Parkinson disease patients due to pathological tremor of index finger.

The purpose of this study is to investigate the disability stages of Parkinson disease (PD) patients by wave analysis of parkinsonian pathological tremor. Physiological tremor and pathological tremor for the index finger are detected by accelerator sensor. The power spectrum is calculated by an auto-regressive model (AR model). The peak frequency and the peak power of the tremor for the index finger are evaluated under two conditions: (1) maintaining the index finger in a horizontal position using visual feedback with or without a weight load of 50 g, in which tremor is referred to as postural tremor, (2) resting the index finger with eyes closed, in which the tremor is referred to as resting tremor. The physiological tremor and the pathological tremor for the finger are characterized by two peak frequency components in which the first peak frequency component is 8-12 Hz, and the second is 20-25 Hz under the two conditions stated above. The peak frequency and the peak power for the PD patients at the two peak frequency components show the characteristics for the disability level of the PD patients. The first peak power especially around 8-12 Hz in the postural tremor without and with the weight load significantly increases as the disability stage determined by the Hoehn-Yahr method worsens, and there is significant difference of the peak powers for the stages. These results suggest that the first peak power around 8-12 Hz for the postural tremor without and with the weight load is a useful index to judge PD disability stage. It is found that postural tremor without and with the weight load gives the significant peak frequency and peak power compared with those for normal persons. It is pointed out that the first peak frequency component of 8-12 Hz originates from the central nervous system, and the first peak power reflects the degrees of disorder in the central nervous system, since PD is caused by the functional lowering of the central nervous system.

Adult↗
PubMedDate not supplied

[Gabapentin in the treatment of tremor].

PATIENTS AND METHODS: We evaluated the efficacy of gabapentin added to basal tremor treatment by means of a 16 month non randomized open study conducted at our Unit on treated and monitored patients. Efficacy was evaluated by means of the following scales: Tremor Scale (TS), Global Disability Examiner Scale (GDE) and Global Disability Patient Scale (GDP). For the GDE and GDP scales we constructed a dichotomic result evaluation variable (improvement vs. non improvement) and adjusted a logistic regression model (independent variables: age, gender, tremor duration and number of antitremor drugs associated with gabapentin). Two multiregression models were adjusted for the TS (12 month score result variable). Model 1: TS (items 1 14) and model 2: TS (items 15 21). INDEPENDENT VARIABLES: age, gender, tremor duration, initial test score and number of antitremor drugs associated with gabapentin. We studied 63 patients aged 59.4 years (SD, 16 years): 34 essential tremor, 16 Parkinson s disease tremor, 10 multiple sclerosis tremor, 4 writing tremor and 3 orthostatic tremor. RESULTS: At 12 months gabapentin improved the clinical results. The largest decrease (absolute terms) was observed in multiple sclerosis tremor, and in percentage terms the largest decrease was in orthostatic tremor. Logistic regression showed that masculine gender and a shorter tremor duration predicted a better result. Multiregression showed association between end and basal score, on the one hand, and a better result in males and shorter tremor duration, on the other

Acetates↗
PubMedDate not supplied

Clinical and surface EMG characteristics of valproate induced tremors.

PURPOSE: To describe the Clinical and Surface EMG characteristics of Valproate induced Tremors. Sodium Valproate is known to produce tremors as a side effect. We analyzed clinical and surface electromyographic characteristics of tremors in epileptic subjects who presented with tremors while on sodium valproate. METHODS: Neurological examination and surface electromyographic recordings were performed on 20 subjects with sodium valproate induced tremors. Surface electromyographic tremerogram was correlated with clinical presentation of tremors. RESULTS: This study revealed sodium valproate induced tremors involving primarily upper limbs symmetrically. In the present study, all patients presented with action postural tremors except two, who had tremors in the resting position as well. None of these patients had tremors in goal-directed position. The tremors typically were of high frequency (mean 10 Hz), low amplitude, short burst duration and synchronous burst pattern (Synchronous EMG activity in the agonist and antagonistic muscles). CONCLUSIONS: Frequency, amplitude, burst duration and burst pattern of sodium valproate induced tremors resembles benign essential tremors on surface electromyographic recordings.

Adolescent↗
PubMed1999

Contribution of motor unit activity enhanced by acute fatigue to physiological tremor of finger.

The contribution of motor unit activity to a physiological tremor (hereafter called as tremor) in a middle finger is studied by both a power spectrum and a correlation analysis in which the correlation coefficient and the coherence spectrum are obtained when five kinds of loads, 0, 50, 100, 150, and 200 g, are added to the middle finger for two minutes in a loading experiment on twelve male subjects. A weight of 200 g is applied to the subjects for ten minutes in a fatigue experiment. Throughout both experiments, the middle finger remains stretched from the load of the weight. The tremor is measured by an accelerometer (MT-3T, Nihon Kohden, Japan) attached to the middle finger, and the surface electromyogram (EMG) is measured by bipolar electrodes placed on m. extensor digitorum communis. A power spectrum analysis is carried out on the tremor and EMG, and a correlation analysis is performed on the relationship between the tremor and the demodulated EMG. It is found in the loading experiment that when the weight on the finger increases, the amplitude of the tremor oscillation increases since the activity of the motor units of the muscle is enhanced by the phenomenon of recruitment. Two frequency components of the tremor spectra at 10 Hz and 25 Hz under a no load condition reflect the components of the activity of the motor units of the muscle because the tremor shows a significant correlation in the frequency zone of 10 Hz and 25 Hz with the demodulated EMG. The lower frequency component of the tremor spectrum at 10 Hz results in synchronized activity of the motor units, while the higher frequency at 25 Hz occurs from the stretch reflex loop via the motoneurons of the spinal cord. The shift of the higher frequency component to the lower frequency domain due to the load of the weight originates from the prolongation of the response time of the finger mechanical system because the lag time at the peak of the correlation coefficient increases with the load of the weight. It is found in the fatigue experiment that the amplitude of the tremor oscillation increases with the progress of fatigue. The increase is caused by the recruitment of the motor unit activity of the muscle holding the finger as well as by the synchronization of the firings of the motoneurons. The progress of the synchronization is verified by the fact that the mean power frequency (MPF) of the EMG spectrum decreases and the correlation between the tremor and the demodulated EMG increases with the progress of fatigue. The mechanisms of the increase of the amplitude of the tremor oscillation under the load of the weight to the finger and under the state of fatigue of the finger are elucidated by the analysis of the tremor and EMG.

Adult↗