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PubMedDate not supplied

Evaluation of tremor in aluminum production workers.

A cross-sectional study of 63 current and former aluminum potroom workers and 37 comparison workers was conducted to evaluate for evidence of neurological dysfunction, including tremor from long-term exposures to aluminum using sensitive quantitative measures of arm/hand and leg tremor. Signs of upper extremity tremor were also evaluated by neurological examination and compared with the quantitative measures of arm/hand tremor. Both arm/hand and leg tremor were measured using fatiguing test conditions, but no statistically significant differences due to exposure to aluminum were present between the potroom workers and the comparison workers. The neurological examination also showed no statistically significant differences between the groups on the evaluation of signs of tremor. These results do not support the findings of Best-Pettersen et al., who reported evidence of increased tremor in aluminum workers using the static steadiness test in the Halstead-Reitan battery. Differences between the studies that may have contributed to the contrasting results are discussed. In addition, techniques are presented for using microcomputer-controlled devices to evaluate tremor in both the visible (1-6 Hz) and nonvisible (7-18 Hz) frequencies of the tremor spectrum.

Aluminum↗
PubMed1998

Quantitation of tremor in response to beta-adrenergic receptor stimulation in primates: relationship with hypokalemia.

The primary adverse effect of stimulation of beta2-adrenergic receptors is elicitation of tremor. Tremor measurements in response to beta2-adrenergic receptor stimulation were performed in a quantitative manner using a modified miniature semiconductor accelerometer in African green monkeys. The accelerometer was taped to the middle finger tip of anesthetized monkeys, and recordings of onset, duration and peak tremor responses were obtained. The selective beta2-adrenergic agonist, salbutamol (0.5 mg/kg i.v.), caused a marked increase in tremor which started within 5 min following injection and lasted for approximately 60 min. The finger tremor response was not visible, but was measurable by the accelerometer, and the increase in tremor was significantly greater from baseline within 10 min. Plasma K+ concentrations were markedly decreased within the first 15 min and remained at low steady-state concentrations during the 60-min recordings. The tremor response was abolished by the selective beta2-adrenergic receptor antagonist, ICI-118551 (0.2 mg/kg). ICI-118551 caused a significant reversal of the plasma K+ decrease but the K+ levels remained higher than control levels. These studies demonstrate that stimulation of beta2-adrenergic receptors causes tremor, most likely from entry of K+ into skeletal muscle and that there is a direct correlation between tremor and hypokalemic response.

Adrenergic beta-Agonists↗
PubMed1975

Semiology of Tremors.

Since the description by Galen in the 2nd Century, A.D., clinical neurology has acknowledged the existence of two types of tremor: that which occurs at rest and that occuring during the execution of movement. With the help of refined methods of analysis, E.M.G. and cinephotography, the authors have carried out a detailed clinical assessment in more than 400 patients. The basic criterion used to define a tremor was the classical definition of Dejerine: "An involuntary, rhythmical and symmetrical movement about an axis of equilibrium." As a result of this study, the conclusion has been reached that there are two types of tremor: postural tremor and tremor of attitude. Both are present while the limb remains immobile, whether by wilful design or when at rest in a position of posture and subject only to the action of gravity. During voluntary movement, tremor is not present. Irregular, asymmetrical and non-rhythmic oscillations may appear however - as in so-called intention tremor, of cerebellar origin - but this abnormal movement can hardly be called a real tremor. It is merely a manifestation of ataxia. As a consequence of this study, it is suggested that further understanding of the basic mechanism of tremor can be reached by the investigation of the central neural structures which are involved in the physiology of posture and attitude.

Adolescent↗
PubMed2006

Psychogenic tremor: long-term outcome.

INTRODUCTION: Psychogenic disorders, also referred to as somatoform, conversion, somatization, hysteria, and medically unexplained symptoms, are among the most challenging disorders to diagnose and treat. Psychogenic movement disorders are increasingly encountered in specialized clinics, and represent approximately 15% of all patients evaluated in the Baylor College of Medicine Movement Disorders Clinic. OBJECTIVE: To characterize psychogenic tremor and provide data on prognosis and long-term outcome in a large group of patients with psychogenic tremor followed in a movement disorders clinic. METHODS: Patients evaluated at the Baylor College of Medicine Movement Disorders Clinic in Houston, Texas, between 1990 and 2003 with the diagnosis of psychogenic movement disorder (PMD), who consented to be interviewed, were administered a structured questionnaire designed to assess current motor and psychological function. RESULTS: psychogenic tremor is the most common PMD, accounting for 4.1% of all patients evaluated in our clinic. We were able to obtain clinical information on a total of 228 of 517 (44.1%) patients with PMD, followed for a mean of 3.4+/-2.8 years. Among the 127 patients diagnosed with psychogenic tremor, 92 (72.4%) were female, the mean age at initial evaluation was 43.7+/-14.1 years, and the mean duration of symptoms was 4.6+/-7.6 years. The following clinical features were considered to be characteristic of psychogenic tremor: abrupt onset (78.7%), distractibility (72.4%), variable amplitude and frequency (62.2%), intermittent occurrence (35.4%), inconsistent movement (29.9%), and variable direction (17.3%). Assessment of long-term outcome showed that 56.6% of patients reported improvement in their tremor. Factors predictable of a favorable outcome were elimination of stressors and patient's perception of effective treatment by the physician. CONCLUSION: This largest longitudinal study of patients with psychogenic tremor provides data on the clinical characteristics and natural history of this most common PMD. The accurate diagnosis of psychogenic tremor is based not only on exclusion of other causes but is also dependent on positive clinical criteria, the presence of which should avoid unnecessary investigation. The prognosis of psychogenic tremor may be improved with appropriate behavioral and pharmacologic management.

Adolescent↗
PubMed1983

Effects of cigarette smoking and oral nicotine on hand tremor.

The effect of nicotine on hand tremor was assessed by measuring the current induced in a coil by a magnet attached to the finger. Experiment 1 assessed the amplitude of tremor induced by smoking two cigarettes in a group of 33 subjects drawn from two age groups. Smoking increased tremor significantly. Age, sex, and anxiety levels had no effect. Experiment 2 assessed the effect of smoking on tremor frequency. Analog recordings of tremor in 10 subjects were processed to yield the total power in 20 1-Hz bands from 1 to 20 Hz. The log amplitude showed a strong linear relationship to the log frequency, but this relationship was not affected by smoking. Smoking also had no effect on peak frequency in the frequency spectrum. Experiment 3 confirmed that the effects of smoking on tremor were attributable to nicotine. Twelve subjects were tested before and after smoking a cigarette and before and after chewing gum containing 4 mg nicotine. The two conditions induced comparable increases in tremor. A 2-mg nicotine preparation tested in eight subjects had no effect on tremor. Tremor may be a useful index of the central activity of nicotine and may help illuminate its mechanism of action.

Administration, Oral↗
PubMed2003

Tremor-related activity of neurons in the 'motor' thalamus: changes in firing rate and pattern in the MPTP vervet model of parkinsonism.

The pathophysiology of parkinsonian tremor remains a matter of debate with two opposing hypotheses proposing a peripheral and a central origin, respectively. A central origin of tremor could arise either from a rhythmic activity of the internal segment of the globus pallidus (GPi) or from a structure such as the thalamus, outside the basal ganglia. In this study, single-unit recordings were performed in three 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated monkeys within the GPi and within three territories of the motor thalamus (delimited by their afferent inputs from the GPi, the substantia nigra and the cerebellum, respectively). For each recorded neuron, we compared the variations in firing rate and pattern in tremor and no tremor periods. Tremor either occurred spontaneously or was induced by external stimulation. When the animals entered into a tremor period we observed: (i) an increase in the mean firing rate in about half of the recorded neurons of the motor thalamus; and (ii), a change from an irregular to a rhythmic discharge within the range of tremor frequency (5-7 Hz) in about 10% of the recorded neurons of the motor thalamus (pallidal and cerebellar territories) and the GPi. Most of the thalamic neurons that exhibited a rhythmic discharge during tremor were found to be sensitive to external stimulation. Because the changes in firing rate occurred predominantly in the motor thalamus and not in the GPi, and because a fast rhythmic discharge of 10-15 Hz was frequently observed in the GPi and not in the motor thalamus, we conclude that thalamic activity is not a simple reproduction of basal ganglia output. Moreover, we suggest that thalamic processing of basal ganglia outputs could participate in the genesis of tremor, and that this thalamic processing could be influenced by sensory inputs and/or changes in attentional level elicited by external stimulation.

Action Potentials↗
PubMed1993

Worsening of postural tremor in patients with levodopa-induced dyskinesia: a quantitative analysis.

Some investigators have proposed that Parkinson's disease (PD) patients often exhibit a worsening of tremor before the emergence of levodopa-induced dyskinesia (LDD). It is not clear, however, whether the presence of tremor depends on the severity of dyskinesia, nor is the precise time course of tremor relative to dyskinesia well understood. This report describes an objective study of the relationship between postural tremor and dyskinesia in eight PD patients who showed signs of choreoathetoid hand movements after a single dose of levodopa. Spectral analysis of sustained hand force provided an objective and sensitive method of detecting worsening of tremor in patients with LDD. Severity of clinical symptoms was highly correlated with severity of dyskinesia. Six of the patients exhibited increased tremor amplitude within 45 min of exposure to levodopa, with two of the six patients experiencing bilateral and four of the six having unilateral worsening of postural tremor. Tremor was more severe on the side with the more severe dyskinesia. These findings provide objective support for the notion that dyskinesia and postural tremor may stem from a common pathophysiologic mechanism.

Aged↗
PubMed2001

Tremor in otosurgery: influence of physical strain on hand steadiness.

BACKGROUND: The microscopically small middle ear structures require the otosurgeon to have a steady hand because instrument stability is a critical factor for a successful microsurgical procedure. Hand steadiness is mainly influenced by the tremor movements of the hand. The aim of this study was to measure hand tremor under simulated microsurgical conditions and to estimate the influence of different kinds of physical strain (e.g., physical exertion and hand exercise), as well as food abstinence and coffee consumption. Further, the effect of one-or two-handed manipulation and microsurgical experience was investigated. METHODS: The hand movements of 16 adult subjects were assessed during a defined manual manipulation using a stapes model to simulate microsurgical procedures. A laserinterferometric-based displacement technique was developed to measure tremor amplitude and frequency, as well as maximum displacement, to evaluate the subjects' fine motor skills. RESULTS: The mean tremor frequency across all measurements was 8.1 Hz and did not show any dependence on different kinds of physical strain. Two-handed manipulations showed significantly lower tremor amplitudes than one-handed performances. Tremor amplitude and maximum displacement did not change after hand exercise, food abstinence, and coffee consumption. However, after physical exertion, a significant increase in the tremor amplitude was found. Subjects with advanced microsurgical experience showed smaller tremor amplitudes for one-handed runs. CONCLUSION: The tremor data are interpreted as a recommendation to avoid physical exertion before microsurgery. In cases of absolute necessity for hand steadiness, two-handed manipulations are preferable. Further, hand steadiness might be improved by microsurgical training and experience.

Adult↗
PubMed2004

Essential tremor. Epidemiology, diagnosis, and treatment.

BACKGROUND: Essential tremor (ET) is the most common adult tremor disorder and is characterized by postural and kinetic tremor. Symptoms are typically progressive and potentially disabling, often forcing patients to change jobs or seek early retirement. Proper treatment is contingent on a correct diagnosis, and other possible causes of tremor must be excluded. REVIEW SUMMARY: Although primidone and propranolol have been regarded as the mainstays of pharmacologic therapy for ET, additional agents may be useful in reducing tremor. Surgical procedures are available that effectively ameliorate tremor that is refractory to medical management. This article reviews the epidemiology, pathophysiology, and treatment options for ET. CONCLUSIONS: Despite a range of treatment options currently available, further research is necessary to manage this syndrome most effectively. Double-blind, controlled trials are needed to determine whether primidone, propranolol, or a combination of these medications is superior in the initial management of ET. Other pharmacologic agents have shown potential to reduce tremor and should be investigated further. Additional studies are also needed to determine the best treatment of head and voice tremor with pharmacologic and surgical interventions. With proper treatment, tremor is sufficiently reduced in the majority of patients.

Adrenergic beta-Agonists↗
PubMed1998

Adaptive canceling of physiological tremor for improved precision in microsurgery.

Physiological hand tremor impedes microsurgery. We present both a novel adaptive algorithm for tremor estimation and a new technique for active real-time canceling of physiological tremor. Tremor is modeled online using the weighted-frequency Fourier linear combiner (WFLC). This adaptive algorithm models tremor as a modulating sinusoid, and tracks its frequency, amplitude, and phase. Piezoelectric actuators move the surgical instrument tip in opposition to the motion of tremor, effectively subtracting the tremor from the total motion. We demonstrate the technique in one dimension using a cantilever apparatus as a benchtop simulation of the surgical instrument. Actual hand motion, prerecorded during simulated surgery, is used as input. In 25 tests, WFLC tremor compensation reduces the rms tip motion in the 6-16 Hz tremor band by 67%, and reduces the rms error with respect to an a posteriori estimate of voluntary motion by 30%. The technique can be implemented in a hand-held microsurgical instrument.

Algorithms↗
PubMed1989

Tremor in progressive supranuclear palsy.

Reports of tremor in progressive supranuclear palsy (PSP) have been infrequent; some authors indicate that tremor is never seen in PSP. Five patients with PSP and tremor are presented. Our series of cases and those reviewed in the literature suggest that tremor occurs in 12-16% of PSP cases. The rest tremor observed in 3 of our cases differed from the "pill-rolling" and "parkinsonian tremor" described in previously reported cases by being slower in rate (3 per second or less). This slow rest tremor is rarely seen in Parkinson's disease (4-6 per second). Our experience suggests that, contrary to previous opinions, tremor may be the presenting complaint and a prominent finding in PSP and the presence or absence of tremor is of no value in the differential diagnosis of PSP from Parkinson's disease.

Aged↗
PubMed2003

Case study of a young man with tremor.

PURPOSE: To provide the clinician with an opportunity to review the most common causes of tremor in young adults. DATA SOURCES: Extensive review of international scientific literature on tremors and other movement disorders, supplemented by a recent case study. CONCLUSIONS: Essential tremor (ET) is the most common tremor disorder in the world. In contrast to common expectations, the 2nd decade of life represents a period of peak incidence. The early presentation may be so mild that the tremor goes unnoticed by patients and clinicians for many years. The most important movement disorder to rule out in the workup of patients with tremors is Parkinson's disease. IMPLICATIONS FOR PRACTICE: The diagnosis of ET is generally made on clinical grounds. A comprehensive history and careful physical examination that rules out cerebellar or extrapyramidal disease is required. The clinician must distinguish between resting tremors and action tremors. If the appropriate diagnosis is unclear, a tremor recording (electromyogram) may assist in this distinction. Referral to a neurologist may be warranted.

Adult↗
PubMed2005

Effects of peripheral cooling on intention tremor in multiple sclerosis.

OBJECTIVE: To investigate the effect of peripheral sustained cooling on intention tremor in patients with multiple sclerosis (MS). MS induced upper limb intention tremor affects many functional activities and is extremely difficult to treat.Materials/ METHODS: Deep (18 degrees C) and moderate (25 degrees C) cooling interventions were applied for 15 minutes to 23 and 11 tremor arms of patients with MS, respectively. Deep and moderate cooling reduced skin temperature at the elbow by 13.5 degrees C and 7 degrees C, respectively. Evaluations of physiological variables, the finger tapping test, and a wrist step tracking task were performed before and up to 30 minutes after cooling. RESULTS: The heart rate and the central body temperature remained unchanged throughout. Both cooling interventions reduced overall tremor amplitude and frequency proportional to cooling intensity. Tremor reduction persisted during the 30 minute post cooling evaluation period. Nerve conduction velocity was decreased after deep cooling, but this does not fully explain the reduction in tremor amplitude or the effects of moderate cooling. Cooling did not substantially hamper voluntary movement control required for accurate performance of the step tracking task. However, changes in the mechanical properties of muscles may have contributed to the tremor amplitude reduction. CONCLUSIONS: Cooling induced tremor reduction is probably caused by a combination of decreased nerve conduction velocity, changed muscle properties, and reduced muscle spindle activity. Tremor reduction is thought to relate to decreased long loop stretch reflexes, because muscle spindle discharge is temperature dependent. These findings are clinically important because applying peripheral cooling might enable patients to perform functional activities more efficiently.

Activities of Daily Living↗
PubMed1976

Physiological and pharmacological aids in the differential diagnosis of tremor.

Physiological and pharmacological studies of more than 150 patients with movement disorders are reported. Particular attention is paid to the differentiation of various types of tremor on the basis of rate, rhythm, and pattern of EMG activity in antagonistic muscles. The typical 'tremor-at-rest' of Parkinson's disease--3-7 Hz activity which alternates between antagonistic muscles--is suppressed, at least briefly, during voluntary activity, at which time typical 8--12 Hz 'physiological tremor' may be seen. Essential tremor and its familial or senile variants also have a characteristic EMG pattern during voluntary activity--5-8 Hz bursts of activity which are synchronous in antagonistic muscles. This type of tremor may also be present in patients with Parkinson's disease and in certain kinships with a Charcot-Marie-Tooth polyneuropathy. Other tremors in association with polyneuropathy ('neuropathic tremor') have different physiological characteristics. Myoclonus is of essentially two types ('positive' with EMG bursts and 'negative' with brief pauses in ongoing activity, as with asterixis) and may, at times, mimic tremor. Certain specific tremors respond predictably to specific pharmacological therapy.

Ataxia↗
PubMed2001

Amitriptyline enhances the central component of physiological tremor.

OBJECTIVES: Postural tremor is a regularly encountered side effect of amitriptyline which can be strong enough to cause discontinuation of therapy. The aim was to characterise amitriptyline induced tremor and to assess if the central or reflex component of physiological tremor was modulated by this drug. METHODS: The postural hand tremor was measured in 15 patients on a clinical rating scale, by power spectral analysis of accelerometer, forearm flexor, and extensor EMG before and after the beginning of amitriptyline treatment for major depression or chronic pain syndrome. A coherence analysis between flexor and extensor muscles on the same side was performed. RESULTS: There was a clinically visible increase in postural tremor in a third of these patients. The tremor amplitude measured by accelerometer total power increased in every patient under amitriptyline. The EMG synchronisation as reflected by significant peaks in the flexor or extensor spectrum generally occurring at higher frequencies (8-18 Hz) than the accelerometric tremor frequencies (6-11 Hz) did not change. The number of patients with a significant flexor-extensor coherence in the 7-15 Hz range increased significantly under amitriptyline, the frequency bands of significant coherence corresponded with the EMG frequencies, and both were independent of changes to the hand's resonant frequency by added inertia. CONCLUSIONS: An enhancement of postural tremor under amitriptyline is a common phenomenon although not always clinically apparent. The increase in EMG-EMG coherence indicates an increased common central drive to the motor units as its frequency is not influenced by peripheral resonance or reflex mechanisms. This is the first account of a drug induced enhancement of the central component of physiological tremor.

Amitriptyline↗
PubMed1976

Frequency and displacement amplitude relations for normal hand tremor.

Spectral analysis of hand tremor records obtained from normal subjects during continuous extension of the hand for 15-45 min revealed that the root-mean-square (rms) displacement amplitude of the tremor increased from control levels of about 30 mum to levels on the order of 100-1,000 times control. Associated with this increase in the displacement was a systematic decrease in the hand tremor frequency from control values of 8-9 Hz to values of 4-6 Hz. Spectral analysis of demodulated extensor EMG records indicated a consistent relation between EMG modulation amplitude at the tremor frequency and the tremor displacement amplitude for tremor records with rms displacement above about 100 mum. No consistent relation was found between these two variables for tremor records with displacements below 100 mum. Consideration of both mechanical and neural reflex effects indicated that a viscoelastic-mass mechanism primarily determined the small-amplitude (less than 100 mum) tremors, while the large displacement tremors may have involved both mechanical and neural feed back factors.

Computers↗
PubMed1995

EMG analysis of harmaline-induced tremor in normal and three strains of mutant mice with Purkinje cell degeneration and the role of the inferior olive.

1. The effects of intraperitoneal injections of 10 mg/kg harmaline were tested in normal mice and three strains of cerebellar mutant mice with Purkinje cell degeneration. Ten normal (wild-type) mice (+/+), as well as five lurcher (lc/+), six nervous (nr/nr), and eight Purkinje cell degeneration (pcd/pcd) mutants were implanted with chronic electromyogram (EMG) electrodes in the hamstring and quadriceps muscle groups of the right hindlimb. 2. EMGs were recorded in each of the mice during spontaneous activity before and after intraperitoneal injections of 0.3 ml harmaline (10 mg/kg). Spectral analysis was used to quantify the amplitude and frequency of tremor found in the EMGs after harmaline administration. Normal mice responded to harmaline with strong, continuous 11- to 14-Hz tremor. Mutants from the pcd/pcd strain also reacted with continuous tremor, but of lower amplitude and frequency. In contrast, nr/nr mutants exhibited intermittent paroxysmal tremor lasting for only a few seconds, and lc/+ mutants showed no evidence of tremor whatsoever. 3. In order to detect covert tremor that was possibly not revealed by focal intramuscular EMG recordings, several mutant and normal mice were also tested on a suspended platform to which an accelerometer was attached. The results confirmed the findings from EMG recordings. 4. An incidental observation made during the course of this study was that harmaline tremor disappeared from the normal mouse during swimming and reappeared when the animal was withdrawn from the water. 5. Although Purkinje cells appeared to increase both the depth of modulation and the frequency of tremor, the inhibitory action of the cerebellar cortex does not seem to be essential for the generation of tremor. 6. Parasagittal cerebellar sections of the normal, wild-type mice and the three strains of cerebellar mutant mice of various ages were stained with cresyl violet and examined for Purkinje cell degeneration. Purkinje cell degeneration was found to be complete in the pcd/pcd and lc/+ strains. Although an initial examination of parasagittal sections of the nr/nr strain failed to find any surviving Purkinje cells, further examination of sections cut in the coronal plane revealed small clusters of Purkinje cells in the vermal area of the posterior lobe. 7. The retrograde transport of wheat-germ-agglutinin-conjugated horseradish peroxidase (WGA-HRP) pressure-injected into the cerebellar cortex was used to study the olivocerebellar projections in the wild-type mice and the three strains of cerebellar mutant mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Thalamotomy for essential and cerebellar tremor.

Thalamotomy significantly suppressed essential tremor in 86% of patients and restored the ability to hold a glass to drink in 81% in the long term, but tremor recurred in 5/21 patients up to 5 years postoperatively, unlike parkinsonian patients whose tremor seldom recurs after 3 months. In multiple sclerosis (MS), 67% of those followed showed sustained significant suppression of tremor, 67% sustained improvement in dexterity, 50% in drinking; tremor recurred up to 5 years postoperatively. In other cerebellar tremors, 52% of those followed enjoyed lasting significant relief of tremor, 55% in dexterity, 45% in drinking, tremor relief being best in poststroke cases. Chronic thalamic stimulation may be the preferred therapy in MS and other cerebellar tremors.

Adult↗