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PubMed1994

Arm tremor and precision of hand force control in a short and long term flight on the MIR-Space-Station.

To determine whether long and short time exposure of man in 0g alters normal physiological tremor patterns we recorded arm tremor using an accelerometer as well as hand forces and tremor during constant isometric contraction using a load cell. Arm tremor was decreased during both flights in amplitude and frequency. Shortly after the long term flight arm tremor amplitude was increased, indicating adaptive changes in the tonic reflex loop. Isometric hand tremor remained unchanged during the long and short time flight demonstrating that the contractile properties of hand muscles remained constant. Precision of hand force was decreased until the half duration of the long term flight.

Arm↗
PubMed1992

The prognostic value of intra-operative observations during thalamotomy for parkinsonian tremor.

Data from 27 thalamotomies were analyzed with respect to possible correlations between certain intra-operative observations and the long-term effect on parkinsonian tremor. Tremor reduction caused by mechanical impact of the electrodes in the target area was not correlated with the long-term effect on the tremor. The same was true for the threshold intensities during the intra-operative electrical stimulation of the target area, stimulation that facilitates and/or inhibits the tremor. In a minority of the patients, all with good long-term results, a combination of a pronounced tremor inhibition from the electrode insertion and a low threshold intensity was observed. Variations in other lesion parameters were not correlated with the outcome. The results are discussed within the framework of a "tremor" vs. a "tonus" mechanism underlying the thalamotomy effect.

Aged↗
PubMed2004

Effects of vision and arm position on amplitude of arm postural tremor in patients with multiple sclerosis.

OBJECTIVES: To quantify the effects of vision and arm position on arm postural tremor, comparisons were made between flexed and extended arm positions performed with the eyes open and closed. DESIGN: Case-control study. SETTING: National multiple sclerosis (MS) center in Belgium. PARTICIPANTS: Sixteen patients (32 arms) with MS who had intention tremor and 16 healthy controls (32 arms). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The amplitude of postural tremor was assessed by a magnetic position sensor attached to the index finger. RESULTS: The amplitude of postural tremor was not influenced by changes in visual condition or different arm positions. Both healthy controls and MS patients made more directional changes in the flexed, compared with the extended arm position. CONCLUSIONS: The amplitude of the arm postural tremor in MS is independent of vision and arm position. Selecting 1 arm position is sufficient to assess postural tremor amplitude.

Arm↗
PubMed2006

Upper-extremity disability in essential tremor.

OBJECTIVE: To determine the extent of disability in subjects with essential tremor (ET) using time-based, standardized measures of upper-extremity function. DESIGN: Descriptive case series. SETTING: Motor performance research laboratory. PARTICIPANTS: Thirty subjects with ET (mean age, 58.3+/-13.7 y) and 28 healthy controls (mean age, 58.4+/-12.4 y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: We assessed upper-extremity function using the Box and Block Test, Purdue Pegboard Test (PPT), and Test Evaluant la performance des Membres supérieurs des Personnes Agées (TEMPA). We measured tremor severity with laser displacement sensors. RESULTS: Subjects with ET-type tremor in 1 or both hands performed significantly worse than controls on all unilateral and bilateral tasks (P range, .038-.001) except on the PPT for the dominant side. ET subjects without ET-type tremor in the dominant hand also performed significantly worse than controls on the TEMPA unilateral tasks (P=.043). Performance on the 3 functional measures correlated moderately with tremor severity for the nondominant hand. CONCLUSIONS: Subjects with ET show measurable disability on time-based measures of upper-extremity function. However, our findings are consistent with other reports that tremor severity does not correlate well with disability, especially with regard to the dominant upper extremity.

Adult↗
PubMed2004

Citalopram, a selective serotonin reuptake inhibitor augments harmaline-induced tremor in rats.

Citalopram, a serotonin reuptake inhibitor (SSRI) is one of the widely used antidepressants. Apart from its antidepressant activity citalopram is also used for anxiety, panic disorders, obsessive-compulsive disorder and behavioral disturbances of dementia. Tremor is the second most common neurological adverse effect in patients receiving treatment with SSRIs. Use of these agents in depressed patients with essential tremor has not been studied. The present study was undertaken to investigate the effect of chronic citalopram treatment on harmaline-induced tremors in rats. Female Sprague-Dawley rats weighing 70+/-2 g were given citalopram in doses of 0, 10, 20 and 40 mg/kg by gavage for 2 weeks. On the 15th day, the rats were given harmaline (10 mg/kg, i.p.) 30 min after the last dose of citalopram. The latency of onset, intensity and duration of tremor and EMG were recorded. Serotonin (5HT) and 5-hydroxy indole acetic acid (5HIAA) were measured in brain stem. Citalopram dose dependently exacerbated the duration, intensity and amplitude of EMG of harmaline-induced tremor. A significant decrease in 5HT turnover (5HIAA/5HT ratio) in the brain stem was observed suggesting a possible role of serotoninergic impairment in citalopram-induced augmentation of harmaline-induced tremor. Clinical implications of these observations warrant further investigation.

Analysis of Variance↗
PubMed2006

Delayed beta synchronization after movement of the more affected hand in essential tremor.

To investigate the pathomechanism of parkinsonian tremor (PT) and essential tremor (ET) by studying the correlation between tremor asymmetry and post-movement beta synchronization (PMBS) of the human EEG. We recorded the EEG of 10 patients with ET, 10 patients with Parkinson's disease and 10 controls. Subjects pressed an on-off switch in a self-paced manner with the thumb of their less (T+) and more (T++) tremulous hand. After digitalization of the EEG from the Cz, C3, C4 electrodes the movement reactive beta frequency, its maximum peak power value and its latency triggered to movement offset were determined. In ET tremor intensity did not influence the power of PMBS, however it was significantly delayed after the movement of the more tremulous hand. In Parkinson's disease after the movement of the more tremulous hand PMBS power was decreased, but it was not delayed. In controls the side of movement had no effect on the power and latency of the PMBS. The neuronal mechanisms underlying PMBS generation are differently affected in essential tremor and Parkinson's disease. The increase of PMBS latency after movement of the more affected hand in ET indicates possible cortical mechanisms in essential tremor generation.

Adult↗
PubMed2006

Organochlorine pesticide exposure in essential tremor: a case-control study using biological and occupational exposure assessments.

Essential tremor (ET) is a common neurological disorder. Its etiology and pathogenesis are not well understood and several environmental factors (i.e., toxicants) have been studied. Organochlorine pesticides (OCPs) are potent tremor-producing chemicals. These pervasive environmental contaminants have been linked with other tremor disorders (e.g., Parkinson's disease) but they have not been assessed in ET cases. Our objective was to test the hypothesis that ET is associated with OCP exposure. Serum OCP concentrations and lifetime occupational histories were assessed in ET cases and control subjects. Six serum OCP concentrations (p,p'-DDE, p,p'-DDT, beta-hexachlorocyclo-hexane, oxychlordane, trans-nonachlor, and dieldrin) were assessed. Data from a lifetime occupational history were reviewed by a blinded industrial hygienist. The six serum OCP concentrations were similar in 136 ET cases and 144 control subjects. There was no association in ET cases between the six serum OCP concentrations and total tremor score. Three (2.2%) ET cases versus 9 (6.3%) controls had past occupational exposure to OCPs (OR=0.34, 95% CI=0.09-1.28, p=0.10). Although OCPs have been associated with other tremor disorders, we were not able to find an association between the six most tremorogenic OCPs and ET. Our data suggest that these tremor-producing chemicals are not of major etiological importance in our patients with ET.

Aged↗
PubMed2003

Essential tremor: differential diagnosis and current therapy.

Essential tremor is a common movement disorder that affects between 5 and 10 million persons in the United States. It is characterized primarily by an action and postural tremor most often affecting the arms, but it can also affect other body parts. Essential tremor is a progressive neurologic disorder and can cause substantial disability in some patients. Although there is no cure for essential tremor, pharmacologic and surgical treatments can provide some benefit. Primidone and propranolol are first-line treatments. Other medications with potential efficacy include benzodiazepines, gabapentin, topiramate, and botulinum toxin. Patients with medication-resistant tremor may benefit from thalamotomy or deep brain stimulation of the thalamus. The use of medical and surgical therapies can provide benefit in up to 80% of patients with essential tremor.

Acetates↗
PubMed2002

2-deoxy-D-glucose attenuates harmaline induced tremors in rats.

Neuronal hyperactivity in essential tremor is accompanied by high energy demand in cerebellum, medulla and the thalamus. It has been suggested that brain regions that have increased metabolic demands are highly vulnerable to interruptions in glucose metabolism. In the present investigation attempt was made to study the effect of 2-deoxyglucose (2DG) a glycolytic pathway inhibitor on harmaline induced tremor in rats. Wistar rats of either sex weighing 100+/-3 g were given harmaline (10 mg/kg, i.p.) alone or along with 2DG (15 min before harmaline) in doses of 300, 600 and 900 mg/kg, respectively. The latency of onset, intensity and duration of tremor following harmaline administration were recorded. Neurobehavioral responses, electromyography (EMG) and levels of blood glucose and cerebellar serotonin (5HT) were determined after 40 min of harmaline administration. 2DG significantly and dose dependently attenuated severity of harmaline induced tremors and amplitude of EMG. Treatment of rats with 2DG alone reduced the locomotor activity, however, no significant change was observed in grip strength, landing foot splay, air righting reflex and response to tactile stimuli. Harmaline alone and along with 2DG had no effect on behavioral parameters except a decrease in landing foot splay. 2DG produced a dose-dependent hyperglycemia and attenuated harmaline induced increase in cerebellar 5HT levels. Our results clearly suggest the protective effect of 2DG in harmaline induced tremor. Further studies are warranted to assess the role of glucoprivation in the suppression of neuronal excitability in tremors.

Animals↗
PubMed2000

Involvement of 5-hydroxytryptamine(1A) receptors in nicotine-induced tail tremor in rats.

Involvement of the serotonergic system in tail tremor induced by repeated administration of nicotine was investigated in rats. Tail tremor induced by nicotine (0.5 mg/kg, s.c.) was suppressed by a 5-HT(1A) receptor antagonist, N-¿2-[4-(2-methoxyphenyl)-1-piperazinyl-]ethyl¿-N-(2-pyridinyl)cycloh exanecarboxamide trihydrochloride (WAY-100635; 0.3-3 mg/kg, i.p.), but not by a 5-HT(2) receptor antagonist, ketanserin (0.1-0.3 mg/kg, i.p). The 5-HT(1A) receptor agonists, buspirone (1-20 mg/kg, i.p.), gepirone (1-10 mg/kg, i.p.), tandospirone (1-10 mg/kg, i.p.) and (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT; 0.01-0.1 mg/kg, s.c.), enhanced the tail tremor. The enhancement of tail tremor by buspirone (10 mg/kg, i.p.) was blocked by WAY-100635 (0.3-3 mg/kg, i.p.). These findings suggest that nicotine-induced tail tremor is mediated by 5-HT(1A) receptors and that 5-HT(1A) receptor antagonists are effective in the treatment of tremor.

Animals↗
PubMed2004

[A surgical approach to Holmes' tremor associated with high-frequency synchronous bursts].

INTRODUCTION: The effectiveness of thalamic stimulation is now clearly demonstrated for essential tremor, but remains to be demonstrated for other types of tremor. OBSERVATION: A young woman presented Holmes' tremor resulting from a pontine tegmental hemorrhage related to an arteriovenous malformation. A surgical approach was considered when major functional impairment persisted at 2-year follow-up despite drug therapy. The patient underwent unilateral thalamic deep brain stimulation (Vim); major improvement persisted at eighteen months follow-up. CONCLUSION: This observation is in line with previous reports suggesting that thalamic surgery can be one of the best options for treating medically intractable Holmes' tremor. The mechanism underlying the tremor, implying dentate-rubro-thalamic pathways is discussed. Moreover, the patient exhibited short periods of 16Hz tremor when her arms were maintained outstretched. Thalamic stimulation also appears to be effective for these high-frequency synchronous cerebellar bursts.

Adult↗
PubMed1998

Deep brain stimulation is preferable to thalamotomy for tremor suppression.

BACKGROUND: The use of deep brain stimulation (DBS) at a site identical to that of thalamotomy is becoming increasingly popular for the control of tremor. It therefore seemed reasonable to compare the two operations. METHODS: A retrospective comparison was made of 19 DBS implants--16 for Parkinson's disease (PD), 3 for essential tremor (ET)--and 26 thalamotomies--23 for PD and 3 for ET--performed by the author with similar techniques between November 1, 1990 and July 1, 1996 and followed for at least 3 months. RESULTS: Complete tremor abolition occurred in 42% of both groups, near abolition in 79% and 69% respectively, recurrence in 5% and 15%, respectively. To achieve these results, 15% of thalamotomies, but no DBS implant, had to be repeated. Thus tremor recurrence after DBS can be controlled by stimulation parameter adjustment rather than by re-operation. A "microthalamotomy" effect from merely implanting an electrode, seen in 53% of cases and persisting for more than 1 year in five cases, prognosticated a good result and underlined the need for precision in target site selection. Ataxia, dysarthria, and gait disturbance were more common after thalamotomy (42%) than DBS (26%), but when they occurred after DBS they could nearly always be controlled by adjusting stimulation parameters. CONCLUSIONS: Thus, the flexibility of DBS for tremor control and complication avoidance makes it superior to thalamotomy for tremor control at the expense of equipment cost and continual management.

Ataxia↗
PubMed1997

Adaptive Fourier modeling for quantification of tremor.

A new computational method for quantification of tremor, the weighted frequency Fourier linear combiner (WFLC), is presented. This technique rapidly determines the frequency and amplitude of tremor by adjusting its filter weights according to a gradient search method. It provides continual tracking of frequency and amplitude modulations over the course of a test. By quantifying time-varying characteristics, the WFLC assists in correctly interpreting the results of spectral analysis, particularly for recordings exhibiting multiple spectral peaks. It therefore supplements spectral analysis, providing a more accurate picture of tremor than spectral analysis alone. The method has been incorporated into a desktop tremor measurement system to provide clinically useful analysis of tremor recorded during handwriting and drawing using a digitizing tablet. Simulated data clearly demonstrate tracking of variations in frequency and amplitude. Clinical recordings then show specific examples of quantification of time-varying aspects of tremor.

Algorithms↗
PubMed2003

Serotonin synthesis inhibition in olivo-cerebellar system attenuates harmaline-induced tremor in Swiss albino mice.

Recent experimental evidences point to the active role of central serotonin (5-HT) elicited mechanisms in the pathogenesis of tremor. The present study was undertaken to investigate the effects of p-chlorophenylalanine (pCPA), a specific tryptophan hydroxylase inhibitor and a central 5-HT depletor, on the neurochemical processes that occur synchronously in olivary nucleus (ON) and cerebellum during harmaline-induced tremor in mice. Tremor appeared by 3-4 min following harmaline administration, and reached its peak by 25 min for the doses (10-30 mg/kg) studied. Peak of harmaline-tremor coincided with increases in 5-HT in ON and cerebellum, as assayed employing HPLC-electrochemistry. Administration of pCPA caused significant depletion in 5-HT level in both the regions analyzed, and also significantly inhibited harmaline-induced tremor. Our present results support the earlier electrophysiological evidences that harmaline-induced tremor originates from ON, and confirm the role of 5-HT in the genesis of this motor neuronal dysfunction.

Animals↗
PubMedDate not supplied

Vim thalamic stimulation for tremor.

Chronic stimulation of the ventral intermediate nucleus (Vim) of the thalamus is highly effective for the treatment of tremor. Patients with tremor associated with Parkinson's disease and essential tremor appear to respond best. Patients with cerebellar tremors may also respond but to a lesser extent. Although tremor is improved, Vim DBS does not substantially improve the daily living activities of patients with Parkinson's disease. This is related to the lack of effect on rigidity, bradykinesia, and gait and postural disturbances associated with Parkinson's. For this reason, the majority of patients with Parkinson's disease who require surgery are better treated with interventions in the globus pallidus or subthalamic nucleus, targets that allow improvement in all cardinal features of Parkinson's disease. In contrast, Vim DBS has unequivocal functional benefit in patients with essential tremor, this is likely to remain the major indication of this form of therapy. The mechanism of action of thalamic DBS is not understood and remains a research priority.

Electric Stimulation Therapy↗
PubMed2002

Effect of acute caffeine on severity of harmaline induced tremor in rats.

Recent studies suggest an association between caffeine consumption and tremor. However, the available literature is scanty and inconclusive. The present study was undertaken to investigate the effect of acute caffeine treatment on harmaline induced tremors in the rat. Four groups of male Sprague-Dawley rats (six animals in each group) weighing 88+/-2 g were administered harmaline (10 mg/kg, intraperitoneally (i.p.)) for inducing experimental tremors. The rats in group 1 served as controls and received normal saline, whereas the animals in groups 2, 3 and 4 were given caffeine (i.p.) at doses of 50, 100 and 150 mg/kg, respectively 60 min after harmaline administration. The latency of onset, intensity and duration of tremor and electromyographic (EMG) responses were recorded. Treatment of rats with caffeine resulted in a significant increase in the intensity and duration of harmaline induced tremors. Caffeine also enhanced the EMG amplitude in harmaline treated animals. In conclusion, the results of this study suggest that acute treatment with caffeine significantly potentiates the severity of harmaline induced tremors in rats.

Animals↗
PubMed1997

Scopolamine reversal of tremor produced by low doses of physostigmine in rats: evidence for a cholinergic mechanism.

In order to provide evidence for the involvement of cholinergic mechanisms in a low-dose physostigmine-induced tremor, a novel technique for measuring forelimb tremor in rats was used. Rats that were administered physostigmine (0.05 and 0.1 mg/kg, s.c.), scopolamine (0.1 and 0.2 mg/kg, s.c.), and combinations of the two drugs, pressed a force-sensing operandum while a computer measured force output and performed Fourier analyses on resulting force-time waveforms. When given alone, both drugs decreased task engagement but mutually antagonized this effect when given together. Physostigmine increased tremors as well as peak force. Scopolamine decreased tremor and force when administered alone and reversed physostigmine-induced increases in force and tremor. Physostigmine's low-dose induction of increased tremor during rats' skilled forelimb use appears to have a prominent cholinergic component.

Animals↗
PubMed1999

Tremor-frequency (3-6 Hz) activity in the sensorimotor arm representation of the internal segment of the globus pallidus in patients with Parkinson's disease.

Neurons in the internal segment of the globus pallidus (GPi) oscillate at approximately the frequency of parkinsonian tremor. However, the correlation of that activity with tremor has not previously been studied. We now describe the relationship between single neuron activity in the arm sensorimotor portion of GPi and upper extremity tremor in patients with Parkinson's disease. There was a significant concentration of power in the tremor-frequency range (3-6 Hz) for 11/44 GPi neurons. However, pallidal tremor-frequency activity correlated significantly with electromyogram (EMG) activity during tremor for only a single GPi neuron. These data are most consistent with the hypothesis that the output of neurons in GPi is transformed in thalamus by a non-linear mechanism, before transmission via the cortex to the spinal motorneurons that drive movement.

Brain Mapping↗