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At least 865 records · Page 48Linked to original sources
PubMed1986

Computer simulation of parkinsonian tremor.

A computer simulation of tremor using a mathematical model is presented, which integrates the traditional two theories; 'peripheral feedback theory' for physiological tremor and central oscillator theory' for Parkinsonian tremor. The model includes a basic stretch-reflex loop, which is modulated by the central nervous system through the gamma fibres. Fatigue of intrafusal fibres, which results from chronic stimulation by the gamma system, is assumed to be the main cause of Parkinsonian tremor. A computer simulation using the model shows that both physiological tremor and Parkinsonian tremor can be caused by the varying contractivity of the intrafusal fibres.

Computers↗
PubMed2004

Blockade of adenosine A2A receptors antagonizes parkinsonian tremor in the rat tacrine model by an action on specific striatal regions.

Acute administration of the acetylcholinesterase inhibitor tacrine to rats induces tremulous jaw movements which can be used as a valuable model of parkinsonian tremor. In the present study, the number of tremor episodes and jaw movements were evaluated to assess the effects of the selective A2A antagonists SCH 58261 and SCH BT2 on tremorgenesis. SCH 58261 dose-dependently, and maximally at 5 mg/kg, reduced the number of both tremor episodes (-35%) and jaw movements (-50%), induced in rats by tacrine (2.5 mg/kg ip). Since adenosine A2A receptors are largely expressed throughout the striatum, chronic cannulae were implanted in the rat dorsomedial (DMS) and ventrolateral striatum (VLS) to investigate whether A2A antagonists could act at this level. Infusion of SCH BT2 (5 microg/microl), a water-soluble analogue of SCH 58261, in VLS antagonized both tremor episodes (-68%) and jaw movements (-76%) elicited by tacrine (2.5 mg/kg ip), whereas SCH BT2 infusion in DMS was less effective in blocking jaw movements (-50%) and did not significantly affect the number of tremor episodes. Taken together, the results of this study indicate that A2A antagonists effectively reduce the magnitude of tremulous jaw movements induced in rats by acute tacrine, mainly by an action in VLS and suggest that A2A antagonists might be used as specific agents against parkinsonian tremor.

Adenosine A2 Receptor Antagonists↗
PubMed2006

Successful treatment of rubral tremor by high-dose trihexyphenidyl: a case report.

A 24-year-old male suffered from acute-onset right-sided hemiparesis, dysarthria, and ophthalmoplegia in February 2001. Brain magnetic resonance imaging revealed a cavernous angioma with hemorrhage over the left thalamus. Moreover, some rhythmic, coarse, low-frequency (2-3 Hz) oscillation over the right wrist and elbow was noted 1 month later. Action tremor was more predominant than resting tremor. Rubral tremor was diagnosed on the basis of the clinical presentation and tremography analysis. Rubral tremor is not unusual, and pharmacotherapy is nearly always ineffective in clinical practice. Deep brain stimulation, thalamotomy, and pallidotomy are all considered effective according to recent research. However, they are either very expensive or invasive, and involve surgical risks. In our patient, we tried valproate, clonazepam, and verapamil one after another, but all in vain. Finally, titration of trihexyphenidyl provided significant benefit. The tremor was successfully controlled by a single high daily dose of trihexyphenidyl (38 mg) without severe or uncomfortable side effects. Here, we report a case of successful monotherapy of rubral tremor with high-dose trihexyphenidyl.

Adult↗
PubMed2002

The influence of pitch and loudness changes on the acoustics of vocal tremor.

The effect of tremor on phonation is to modulate an otherwise steady sound source in its amplitude, fundamental frequency, or both. The severity of untreated vocal tremor has been reported to change under certain conditions that may be related to muscle tension. In order to better understand the phenomenon of vocal tremor, its acoustic properties were examined as individuals volitionally altered their pitch and loudness. These voice conditions were anticipated to alter the tension of the intrinsic laryngeal muscles. The voices of 10 individuals with a diagnosis of vocal tremor were recorded before participating in a longitudinal treatment study. They produced vowels at low and high pitch and loudness levels as well as in a comfortable voice condition. Acoustic analyses quantified the amplitude and frequency modulations of the speakers' voices across the various conditions. Individual speakers varied in the way the pitch and loudness changes affected their tremor, but the following statistically significant effects for the speakers as a group were observed: Higher pitch phonation was associated with a more rapid rate for both amplitude and frequency modulations. Amplitude modulation become faster for louder phonation. Low-pitched phonotion led to decreases in the extent of amplitude tremor. Varying pitch led to dramatic changes in the phase relationship between amplitude and frequency modulation in some of the speakers, whereas this effect was not apparent in other speakers.

Aged↗
PubMed1995

Variations on tremor parameters.

This paper describes our analysis procedure for long-term tremor EMG recordings, as well as three examples of applications. The description of the method focuses on how characteristics of the tremor (e.g. frequency, intensity, agonist-antagonist interaction) can be defined and calculated based on surface EMG data. The resulting quantitative characteristics are called "tremor parameters." We discuss sinusoidally modulated, band-limited white noise as a model for pathological tremor-EMG, and show how the basic parameters can be extracted from this class of signals. The method is then applied to (1) estimate tremor severity in clinical studies, (2) quantify agonist-antagonist interaction, and (3) investigate the variations of the tremor parameters using simple methods from time-series analysis. (c) 1995 American Institute of Physics.

Journal Article↗
PubMed1995

Shooting performance is related to forearm temperature and hand tremor size.

The changes in postural tremor of the hand and the subsequent effect on shooting performance produced by moderate cooling and heating of the forearm were studied in six subjects. Cooling produced a large decrease in tremor size of the ipsilateral hand, whereas warming the limb produced an increase in tremor size. Cooling or warming the forearm did not change the peak frequency of tremor significantly, which was quite stable for each subject. The improvement in shooting performance after cooling the forearm, as measured by grouping pattern of the shots, reached statistical significance and warming caused a significant worsening. This measure of performance was shown to correlate (r = 0.776) inversely with tremor size. The causes and implications of these changes are discussed. It is suggested that local cooling may be useful for people who wish temporarily to reduce tremor in order to improve dexterity for shooting and for other purposes.

Adult↗
PubMed1988

Scrapie agent proteins do not accumulate in grey tremor mice.

The grey tremor mouse is an autosomal recessive mutant characterized by a phenotype of unusual pigmentation, neurological abnormalities and early death. These mice have a spongiform encephalopathy similar to scrapie and Creutzfeldt-Jakob disease. Although the disease is clearly heritable, the grey tremor mouse spongiform pathology has also been transmitted by inoculation of genetically normal mice with diseased brain homogenates. The possibility that a scrapie-like agent is involved has been proposed. We examined brain homogenates from grey tremor mice, scrapie-affected mice and normal mice for the presence of the mouse scrapie agent protein (MoSp33-37) and its normal cellular homologue. All untreated homogenates contained one or both isoforms of this protein as detected on immunoblots. Grey tremor mouse brain homogenates, when protease-treated, showed no evidence of MoSp33-37. A purification method for MoSp33-37 concentrated it in samples from scrapie-affected mice, but this protein was not detected in grey tremor or normal mice. These results suggest that it is unlikely that the scrapie agent is involved in grey tremor disease.

Animals↗
PubMed1981

Motor unit firing and its relation to tremor in the tonic vibration reflex of the decerebrate cat.

1. The discharge of single motor units has been recorded from the soleus muscle of the decerebrate cat during the tonic vibration reflex elicited isometrically, to further understanding of the tremor that is seen in the reflex contraction. The reflex was elicited by pulses of vibration of 50 micrometers amplitude at 150 Hz, and up to four units were studied concurrently. 2. Individual units fired rather regularly and at a low frequency (range 4-14 Hz). The rate of firing of any unit normally fell within the frequency band of the tremor recorded at the same time. On comparing different preparations a higher frequency of tremor was associated with a higher frequency of motor firing. 3. The responses of pairs of motor units recorded concurrently during repeated production of the reflex were compared by cross-correlation analysis; over 1000 spikes from each train were normally used for this. The major of the cross-correlograms were flat with no overt sign of any synchronization between the units other than that due to the vibration. 4. Clear indications of correlated motor unit firing could be produced deliberately by modulating the amplitude of vibration at a frequency comparable to that of the normal tremor and thereby introducing a rhythmic component into the tonic vibration reflex. 5. About 20% of the cross-correlograms obtained during normal tremor showed varying amounts of an irregular 'waviness' suggesting a possible correlation between the times of firing of a pair of units. But such waves never developed steadily throughout the period of analysis, in contrast to the comparable waves produced on modulating the vibration. Similar waves were seen on cross-correlating a motor unit with an electronic oscillator, confirming that their occurrence does not necessarily demonstrate the existence of active neural interactions. 6. It is concluded that there is no strong and widespread neural synchronizing mechanism active during the tonic vibration reflex, although the possibility of some weak neural interactions has not been excluded. The findings favour the idea that the tremor in this preparation is simply the inevitable result of motor units discharging asynchronously, but at closely similar subtetanic frequencies.

Action Potentials↗
PubMed2002

Nonvolcanic deep tremor associated with subduction in southwest Japan.

Deep long-period tremors were recognized and located in a nonvolcanic region in southwest Japan. Epicenters of the tremors were distributed along the strike of the subducting Philippine Sea plate over a length of 600 kilometers. The depth of the tremors averaged about 30 kilometers, near the Mohorovic discontinuity. Each tremor lasted for at most a few weeks. The location of the tremors within the subduction zone indicates that the tremors may have been caused by fluid generated by dehydration processes from the slab.

Journal Article↗
PubMed1975

Genetical components of physiological tremor.

Pysiological tremor was measured in 14 pairs of monozygotic twins, 14 pairs of dizygotic twins, and 14 pairs of control subjects matched for age and sex. Postural finger tremor was measured in each pair using a sub-miniature accelerometer and subjecting the amplified signals to power spectral analysis. Significant genetical influences were found for the proportion of tremore at frequencies near the peak frequency of 9-10 Hz. No genetical effects were found at other frequencies or for the absolute amount of tremore. The results suggest that physiological tremor between 8 and 13 Hz is genetically influenced and that tremor at these frequencies is determined by different mechanisms than those at other frequencies.

Adolescent↗
PubMed1970

Effect of speed of muscle contraction on physiological tremor in normal subjects and in patients with thyrotoxicosis and myxoedema.

The speed of the ankle jerk and physiological finger tremor in patients with thyrotoxicosis and myxoedema have been compared with those in age-matched control subjects. Tremor amplitude depends on the speed of muscle contraction; the faster muscle contracts the greater is the amplitude of tremor, and vice versa. The frequency of the dominant tremor peak is not affected by the speed of contraction but its size increases as muscle contracts faster. Muscle dynamics is clearly one of many factors influencing physiological tremor but is not responsible for the dominant frequency of tremor at round 9 c/sec.

Ankle↗
PubMed2003

Chronic deep brain stimulation for the treatment of tremor in multiple sclerosis: review and case reports.

BACKGROUND: Deep brain stimulation (DBS) offers a non-ablative alternative to thalamotomy for the surgical treatment of medically refractory tremor in multiple sclerosis. However, relatively few outcomes have been reported. OBJECTIVE: To provide a systematic review of the published cases of DBS use in multiple sclerosis and to present four additional patients. METHODS: Quantitative and qualitative review of the published reports and description of a case series from one centre. RESULTS: In the majority of reported cases (n=75), the surgical target for DBS implantation was the ventrointeromedial nucleus of the thalamus. Tremor reduction and improvement in daily functioning were achieved in most patients, with 87.7% experiencing at least some sustained improvement in tremor control postsurgery. Effects on daily functioning were less consistently assessed across studies; in papers reporting relevant data, 76.0% of patients experienced improvement in daily functioning. Adverse effects were similar to those reported for DBS in other patient populations. CONCLUSIONS: Few of the studies reviewed used highly standardised quantitative outcome measures, and follow up periods were generally one year or less. Nonetheless, the data suggest that chronic DBS often produces improved tremor control in multiple sclerosis. Complete cessation of tremor is not necessarily achieved, there are cases in which tremor control decreases over time, and frequent reprogramming appears to be necessary.

Adult↗
PubMed1999

Stereotactic ventral intermedial thalamotomy for the treatment of essential tremor: results of a series of 37 patients.

We have analyzed 43 ventral intermediate thalamotomies performed in our center for treatment of medically intractable essential tremor (ET) in 37 patients. The mean age of patients was 70.9 years (range 42-84), duration of symptoms 33.3 years (1-65). The surgery in all cases was performed with stereotactic technique using MRI or CT localization. Intraoperative neurophysiological confirmation of the target location was obtained using a macrostimulation technique. All patients experienced either complete abolition of the contralateral tremor or significant improvement in tremor intensity immediately after the surgery. At follow-up examination 1-13 months after the operation, 60.5% of patients had no tremor, and 13.9% had mild residual tremor without interference with daily life. Tremor recurrence was observed in 5 patients, all of whom underwent repeat ventral intermedial (VIM) thalamotomy with excellent results. Transient problems with speech and motor functions were observed after 15 thalamotomies, permanent hemiparesis and speech difficulties were seen in 6 patients. We conclude that VIM thalamotomy is a highly effective procedure for medically intractable ET and may be performed with no mortality and low morbidity rate.

Adolescent↗
PubMed2000

Deep brain stimulation of the Vim nucleus of the thalamus for the treatment of tremor.

The surgical treatment of tremor has evolved considerably in the past few years. Of the several conditions associated with severe tremor, the most common are Parkinson's disease (PD) and essential tremor (ET). Levodopa therapy reduced drastically the number of patients with PD who require surgery because of inadequate control. However, there remains a small number of "tremor dominant" PD patients for whom surgical treatment is often the best option. The ventralis intermediate nucleus (Vim) of the thalamus has been the preferred surgical target for the treatment of parkinsonian tremor for many years, but this is now challenged by the subthalamic nucleus (STN). Deep brain stimulation (DBS) of either target possesses high therapeutic efficacy against tremor in PD. ET may be difficult to treat pharmacologically. Thalamotomy is an effective surgical procedure for ameliorating ET but may be associated with persistent neurologic deficits. DBS of the thalamus is also a highly effective means of reducing ET. DBS appears to be safer than thalamotomy and is now the recommended surgical procedure.

Electric Stimulation Therapy↗
PubMed2004

Analysis of amplitude and frequency variations of essential and Parkinsonian tremors.

Variations in the amplitude and period of essential and Parkinsonian tremors were studied. It was found that the variations in frequency (or period) were mostly similar to the white noise, with the standard deviation typically less than 10% of the mean, whereas the variations in amplitude were much larger, with standard deviations greater than 30% of the mean, and so could not be effectively smoothed by running means. It is conjectured that variations in frequency reflect the stable nature of the neural network that generates the rhythmicity responsible for the tremor. The variations in amplitude, however, reflect more the fluctuations in the firing of individual neurons in the network. It is further discussed that the oscillator behind pathological tremor has a stochastic nature and can be characterised as a diffusional process. The latter suggests that it is sometimes possible for tremors to be described as chaotic processes on certain scales in phase space. It is further discussed how the stochastic nature of tremors determines the lack of correlation between different tremulous parts of the body.

Biological Clocks↗
PubMed2003

Tremor in children.

Tremor in childhood, beginning in the neonatal period, is more common than generally appreciated. Although some tremor disorders in children (eg, essential tremor) also affect adults, others (eg, shuddering, jitteriness, spasmus nutans, and vitamin B12-deficiency tremor) are seen exclusively in children. This review covers the etiology, clinical features, and treatment of the major tremor syndromes in children, and when appropriate, makes comparisons with similar disorders in adults.

Child↗
PubMed2003

Tremor--easily seen but difficult to describe and treat.

Tremor is a common movement disorder yet many physicians struggle with its terminology as well as with its treatment. Attempts have been made to develop standard terminology and criteria for tremors but this process continues to evolve. In this review, a summary of the currently-proposed phenomenology and syndromic classification of all types of tremor is presented. The diagnosis and management of essential tremor is presented in more detail, as it is the most commonly encountered tremor.

Adrenergic beta-Antagonists↗
PubMed2003

Long-term follow-up of thalamic deep brain stimulation for essential and parkinsonian tremor.

Thirteen consecutive patients with thalamic deep brain stimulation (DBS) were examined serially for 3 to 5 years. Initially, all demonstrated at least 50% improvement in contralateral tremor. At last follow-up, three of eight patients with Parkinson disease no longer used DBS because tremor had markedly improved, and for two, motor fluctuations and levodopa-induced dyskinesias became the major disability, with tremor less troublesome. Two of five patients with essential tremor had contralateral tremor improvement after ongoing stimulation for 2 years; two developed marked tolerance to DBS.

Adult↗