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At least 541 records · Page 30Linked to original sources
PubMed2004

Subdivision of essential tremor patients according to physiologic characteristics.

OBJECTIVE: To test the effect of different forearm postures on tremor characteristics. We hypothesized that changes in tremor characteristics in relation to posture can subclassify essential tremor (ET) patients. METHODS: Fourteen ET patients were tested while seated and holding a full cup in three well-defined arm postures: 15 cm above the armrest, elbow at 90 degrees flexion and when the cup was near the mouth. Hand movements were recorded using a triaxial accelerometer. Concomitantly, we recorded surface electromyogram (EMG) signals from the wrist extensor muscles. Hand acceleration and the primary tremor frequency from the power spectrum were calculated for each posture in two independent trials. The coherence at the primary tremor frequency between the EMG and the accelerometry signals was calculated. RESULTS: ET patients could be classified into two groups: ET-1 (nine patients) had position-dependent peak frequencies while ET-2 (five patients) had position-independent peak frequencies. The latter group had significantly higher coherencies between EMG and accelerometry of tremor and insignificantly higher tremor amplitudes compared with ET-1. In both groups tremor amplitude increased when the hand was near the mouth. CONCLUSION: The results suggest that ET patients can be classified based on the position dependence of frequency and other physiologic properties.

Acceleration↗
PubMed2004

Personality in essential tremor: further evidence of non-motor manifestations of the disease.

OBJECTIVE: To ascertain whether patients with essential tremor have distinct definable personality traits. METHODS: A case-control study of patients with essential tremor was carried out to look for differences in personality characteristics. The controls were derived from the same source population. Using the tridimensional personality questionnaire (TPQ), personality traits were assessed in three dimensions: harm avoidance (HA), novelty seeking (NS), and reward dependence (RD). Additional analyses were conducted to address the possibility of selection bias among the patients with essential tremor. RESULTS: There were 55 patients and 61 controls. There was a difference between patients and controls in HA subscale scores (p = 0.005) but not in NS or RD scores. The difference remained significant in analyses that adjusted for age, sex, race, and education (p = 0.005). HA subscale scores did not correlate with subjective or objective measures of disability or with indices of severity of tremor. CONCLUSIONS: Patients with essential tremor scored higher on the harm avoidance subscale scores than control subjects. HA subscale scores did not correlate with the severity of tremor or with subjective and objective scales of disability, suggesting that the personality profile observed was not entirely related to functional disability caused by the tremor. Longitudinal studies of personality in essential tremor are needed to characterise the stability and evolution of these personality traits within the natural history of the disease process.

Aged↗
PubMed1988

Visual and mechanical control of postural and kinetic tremor in cerebellar system disorders.

The influence of alterations in visual guidance and somaesthetic sensory inputs was studied in five patients with kinetic and postural tremor characteristic of cerebellar impairment. The patients performed wrist flexion-extension movements or movements about the shoulder with or without visual guidance. Different types of mechanical loads were applied to oppose the wrist movements. The tremor was greatest when the patients used visual cues to guide movements. Kinetic tremor was substantially suppressed during performance of similar movements that were not guided directly by vision. Viscous loads suppressed the tremor nearly linearly, whereas constant loads opposing extension enhanced the tremor. The postural tremor was not observed during isometric contractions. These results support the view that processing of visual information contributes to the impairment of movement in disorders with cerebellar-type tremor and that certain somaesthetic inputs can selectively influence the generation of postural tremor.

Adult↗
PubMed1990

Spectral analysis of tremor: understanding the results.

Spectral analysis of a tremor record can sometimes produce a spectrum with multiple components of significant amplitude. The problem is to determine whether the presence of several peaks represents the coexistence of separate tremor mechanisms or be a consequence of fluctuations in the frequency or amplitude of a single tremor. The spectrum of a tremor whose frequency or amplitude vary and are independent has the recognisable pattern of a central carrier frequency with sidebands of equal amplitudes distributed symmetrically around the carrier. However, if tremor amplitude and frequency fluctuate and are not independent, (frequency proportional to amplitude or frequency inversely proportional to amplitude), the spectrum has a pattern of sidebands which are asymmetrical in amplitudes and may resemble the spectrum of the combined signal from different independent oscillators. The investigation of sidebands in spectra has been neglected in tremor studies and multiple irregular peaks on a tremor spectrum have sometimes been used wrongly as evidence for the coexistence of multiple tremor mechanisms or frequency components assumed to be concurrent.

Computer Simulation↗
PubMed1994

Limb temperature and human tremors.

The changes in postural tremor of the hand produced by moderate cooling of the muscles of one forearm have been investigated in 16 normal subjects and in 16 patients with essential tremor. In both groups, cooling produced a profound long lasting decrease in tremor level of the ipsilateral hand. In normal subjects, although cooling reduced the tremor size, the EMG of the active muscle clearly increased. Warming the limb in normal subjects produced an increase in tremor level and decrease in EMG. Cooling or warming the limb did not, however, significantly change the peak frequency which was quite stable for each subject. The results of cooling were compared with a brief period of ischaemia, which also reduces tremor size. Local cooling may be a useful manoeuvre for patients with essential tremor, and for others who wish to reduce their tremor temporarily in order to improve dexterity.

Adult↗
PubMed1998

Thalamic neuronal activity correlated with essential tremor.

Animal studies suggest that an olivocerebello-bulbospinal pathway mediates harmaline induced tremor, which resembles essential tremor in humans. However, recent evidence suggests that thalamocortical pathways participate in essential tremor. Thalamic single neuron activity has been analysed during thalamotomy for essential tremor. It has been shown by spectral cross correlation analysis that thalamic activity has a significant, linear relation to forearm EMG activity during tremor. The presence of this tremor related activity at the site where a lesion abolishes essential tremor suggests that the thalamus has an important role in the mechanism of essential tremor.

Adult↗
PubMed1999

Levodopa may improve orthostatic tremor: case report and trial of treatment.

Primary orthostatic tremor is a regular fast lower limb tremor causing unsteadiness on standing. Treatment is generally unsatisfactory. A patient with primary orthostatic tremor who 9 years later developed levodopa responsive idiopathic Parkinson's disease is described. The patient exhibited the classic features of primary orthostatic tremor with relief of the tremor by walking or sitting while treated with levodopa. However, in the "off" state, when the benefits of levodopa disappeared, this orthostatic tremor was continuous and severely compromised the patient's gait. On the basis of this finding eight patients with primary orthostatic tremor were treated with levodopa. Five patients experienced benefit and elected to remain on long term treatment. This study is the first trial of therapy in primary orthostatic tremor and suggests that levodopa can lead to good symptomatic relief in this potentially disabling condition.

Aged↗
PubMed2002

Peripheral mechanisms in tremor after traumatic neck injury.

Tremor is a rare manifestation after neck injury, and its physiological mechanism has not been elucidated. We studied the effects of torque loading and ischaemic nerve block on coarse postural tremor in the right upper extremity, which had developed in association with a C7-C8 radiculopathy after traumatic neck injury in a 55 year old man. Loading reduced the tremor frequency from 6.1 Hz to 4.2 Hz with corresponding electromyography (EMG) bursts at the same frequencies as the tremor. Ischaemic nerve block also reduced the tremor frequency from 6.2 Hz to 2.8 Hz, and the time course of the frequency was not in parallel with that of the size of the maximal M wave. A significant reduction of the tremor frequency by loading and ischaemic nerve block indicates a mechanical reflex mechanism underlying the tremor, and association of synchronous EMG bursts suggests an increase in gain in the stretch reflex loop. The stretch reflex loop plays an important role in generation of oscillation in tremor after neck injury.

Cervical Vertebrae↗
PubMed1976

A mechanical-reflex oscillator hypothesis for parkinsonian hand tremor.

Spectral analysis was performed on postural hand tremor records obtained from 22 parkinsonian subjects. Of these 22 subjects, 18 had postural hand tremor that occurred primarily at a single frequency during any one 16-s period. In general, this tremor occurred at different steady-state frequencies (each calculated over 16 s) between about 4 Hz and 8-9 Hz. This frequency decreased approximately 1 Hz for each 10-fold increase in displacement amplitude (root-mean-square, rms, amplitude determined at 16 cm from the wrist), decreasing from 8-9 Hz at about 30 mum to 3.75-4.0 Hz at about 30,000 mum. The major finding was that the frequency of parkinsonian hand tremor was nearly the same as that for hand tremor from normal subjects when these frequenceis were compared at similar rms displacement levels. This comparison, plus a comparison between other aspects of these two kinds of tremor, indicate that the mechanism for parkinsonian hand tremor is similar to that for large-displacement (greater than 100 mum) hand tremor of normal subjects, i.e., a mechanical-reflex oscillator mechanism.

Hand↗
PubMed1976

Motor-unit activity responsible for 8- to 12-Hz component of human physiological finger tremor.

Tremor of the extended third digit and bipolar surface and needle electromyograms of the extensor digitorum were recorded from six healthy volunteers for the purpose of elucidating the motor-unit activity responsible for the 8- to 12-Hz component of physiological finger tremor. Tremor was measured with a force transducer during steady voluntary contractions of approximately 200-250 g. The surface EMGs were full-wave rectified and low-pass filtered (-3 dB at 21 Hz), producing the envelope of the surface EMG (the demodulated EMG). Spectral analyses of simultaneous tremor and demodulated EMG records were performed. In four of six subjects, a pronounced 8- to 12-Hz amplitude modulation in the surface EMG was present, and coherency analysis demonstrated that this modulation was strongly correlated with the well-known 8- to 12-Hz tremor. In two subjects this amplitude modulation and tremor were barely detectable, despite the sensitive recording and analysis techniques used in this study. Spectral analysis was performed on 43 motor-unit spike trains. Twenty-two spike trains, having mean firing frequencies in the range of 10-22 spikes/s, produced statistically significant spectral peaks at 8-12 Hz, in addition to the expected spectral peaks at the mean firing frequencies. Of the 22 8- to 12-Hz-producing motor units, 12 had mean firing frequencies in the range of 17-22 spikes/s and exhibited the greatest 8- to 12-Hz activities of all motor units recorded. These motor units displayed transient sequences of double discharges in which interspike intervals (ISIS) of approximately 8-30 ms alternated with ISIS of 60-90 ms, thus producing an 8- to 12-Hz spectral peak. Adjacent ISIS of these motor units were correlated in the range of -0.5 to -0.9. Coherency analyses demonstrated that the 8- to 12-Hz activities of these motor units were correlated with the 8- to 12-Hz finger tremor and surface EMG modulation. The remaining 10 8- to 12-Hz-producing motor units had mean firing frequencies in the range of 10-17 spike/s. Although these motor units did not display the intense double-discharge firing pattern of the more rapidly firing motor units, a tendency toward action potential grouping was present and resulted in 8- to 12-Hz spectral activities which were correlated with the tremor and surface EMG modulation. .. ..

Adult↗
PubMed2000

Childhood head tremor.

We report here four children (three girls, one boy) with head tremor followed longitudinally, ages 15 months to 11 years, with follow-up over 1 to 8 years. Each demonstrated onset of head tremor between the ages of 5 and 10 months. In each case head tremor was characterized by a predominant "yes-yes" or "no-no" movement of the head. In two of the children the movement was slightly skewed with chin movement toward the shoulder. Oscillations were at a frequency of about 1 to 2 Hz. They were accentuated when sitting upright without head support, increased at times of movement, and dissipated while lying flat or sleeping. The children were unable to voluntarily suppress the action and did not experience any sensation of movement. Three of the children had shuddering spells prior to onset of head tremor. Two children have developed mild dystonic posturing of the legs when intently concentrating. Their general and neurologic examinations were normal. Normal investigations included brain magnetic resonance imaging and computed tomography, urine amino acids and organic acids screening, serum lactate, erythrocyte sedimentation rate, antinuclear antibodies, and ceruloplasmin and copper levels. A family history of tremor was present in two children, maternal epilepsy in one child, and infantile shuddering occurred in the father of one child. Therapy included trials of selective and nonselective beta-adrenergic blockers, alpha-adrenergic agonists, anticholinergics, anticonvulsants, and amantadine. One child responded well to both timolol and trihexyphenidyl. A second child responded moderately to primidone. Two have not been treated. Two have had head tremor spontaneously remit. We conclude from this small series of children with head tremor that it can evolve from a prior history of shuddering spells, occurs in the context of a positive family history of tremor, and can be accompanied by the development of a mild dystonia. Therapeutic response is variable to multiple agents. Spontaneous remission occurs, suggesting a benign course.

Child↗
PubMed1979

Finger tremor and extrapyramidal side effects of neuroleptic drugs.

Finger tremor and extrapyramidal side-effects (EPSEs) were measured in seven patients before and during neuroleptic drug treatment to assess the relationship between the onset of EPSEs and changes in finger tremor spectra. Tremor and EPSEs were also measured in twelve patients stabilized on neuroleptic drugs to determine whether tremor could provide a reliable index of the presence and severity of extrapyramidal system disturbance. A downward shift in peak tremor frequently was noted within 48 hours of starting neuroleptic drug therapy, usually before the onset of EPSEs, and a significant negative relationship between the severity of EPSEs and tremor frequency (but not tremor amplitude). The peak frequency of finger tremor is thus a sensitive index of extrapyramidal disturbance and might be of value in predicting which patients taking neuroleptic drugs need anti-parkinsonian therapy.

Antipsychotic Agents↗
PubMed2003

Tremor response to polarity, voltage, pulsewidth and frequency of thalamic stimulation.

BACKGROUND: Thalamic deep brain stimulation ameliorates essential and parkinsonian tremors refractory to medications. Stimulus voltage, polarity configuration, frequency, and pulsewidth can each be adjusted in order to optimize tremor control and maximize battery life. The relative impacts of these programmable variables have not previously been quantified. METHODS: The thalamus of 11 patients (bilaterally in 2) was studied 4 to 59 months postoperatively. The stimulator was inactivated and medications withheld for 12 hours, and optimal electrode contacts were selected. Stimulation followed at a range of voltages (0, 1, 2, 3, or 4 V), pulsewidths (60, 90, or 120 micros), and frequencies (130, 160, or 185 Hz) for both monopolar and bipolar configurations. Seventy-eight combinations of variables were programmed in random sequence. Postural and action tremors were measured with an electromagnetic tracker, tremor was subjectively graded, and side effects were noted. RESULTS: Voltage was consistently predictive of tremor response. Mean postural tremor amplitude in PD fell from 6.4 cm at 0 V to 2.6, 1.0, 0.3, and 0 cm at 1 through 4 V (bipolar configuration). The voltage response curve for essential tremor was flatter. The monopolar configuration was 10 to 25% more effective than bipolar. The longest pulsewidth tested was up to 30% more effective than the shortest, but frequency changes had little effect on tremor amplitude. Side effects occurred only with monopolar stimulation, and the only setting that was intolerable for the majority was 4 V, 120 micros, and 185 Hz. CONCLUSION: Bipolar deep brain stimulation at 90 micros, 130 Hz, adjusting the voltage up to 3 V, tends to be effective and well tolerated. Monopolar provides similar benefits for lower voltage, but side effects become common at 3 or 4 V.

Aged↗
PubMed1982

Valproate tremors.

We made accelerometric recordings of the tremor induced by valproic acid. The tremor was similar to essential tremor and appeared within a month of starting therapy. It was present at rest and exacerbated by action or antigravity positioning. There was no close correlation of tremor severity and plasma valproate level, but the tremor usually appeared at dosages greater than 750 mg per day. This tremor has appeared in 20 of 25 patients recently studied. In some patients the tremor is markedly active; however, others note only minimal tremor activity.

Adolescent↗
PubMed1984

Propranolol therapy for essential tremor of the head.

The effect of propranolol on essential tremor affecting the head was studied in a placebo-controlled trial. Clinical tremor scores and tremor amplitude as measured by an accelerometer were significantly decreased for both head and hand tremor by 160-mg/d and 320-mg/d doses of propranolol. Placebo and 80 mg/d were without effect. In individual patients, the responsiveness of head tremor tended to parallel that of hand tremor. The head tremor of essential tremor can be treated successfully with propranolol therapy.

Clinical Trials as Topic↗
PubMed1985

Time course of a single oral dose of propranolol in essential tremor.

We studied the effects of a single oral dose (120 mg) of propranolol on essential tremor in 12 patients. Postural hand tremor was recorded by an accelerometer, and its amplitude and frequency determined by spectral analysis. Variable patterns of individual responses gave a mean reduction of tremor amplitude of 50% at 2 hours. Tremor was suppressed as long as 8 hours in some patients. Similar tremor reduction was found on chronic therapy. Even without treatment, tremor amplitude varied from 30 to 50%. A single oral dose of propranolol produces a rapid and sustained reduction of essential tremor, but there are diurnal fluctuations of tremor intensity regardless of treatment.

Aged↗
PubMed1999

Bilateral thalamic stimulation for the treatment of essential tremor.

OBJECTIVE: To determine the safety and efficacy of bilateral thalamic stimulation in the treatment of essential tremor (ET). METHODS: Nine ET patients with disabling tremor refractory to pharmacotherapy underwent bilateral staged implants. Tremor was assessed by the Fahn-Tolosa-Marin Tremor Rating Scale at baseline 1 (before first implant), baseline 2 (before second implant), and at 6-month and 1-year follow-up. Blinded evaluations were performed at 3 months. Associated changes in speech were evaluated in six patients. There were seven men and two women with a mean age of 73.8 years. RESULTS: There was a significant improvement in the mean total tremor score from a baseline of 66.1+/-11.6 to 28.4+/-12.8 12 months after the second surgery. Similarly, the mean motor tremor subscore was 20.1+/-5.0 before the first surgery and improved significantly to 14.1+/-3.6 before the second surgery. Motor tremor scores 6 months after the second surgery (6.0+/-3.7) and 12 months after the second surgery (7.5+/-3.9) also improved significantly relative to the preoperative scores. The mean activities of daily living (ADL) subscore at baseline was 18.2+/-2.9 and improved significantly before the second surgery to 9.0+/-3.2. These ADL scores further improved 6 months (6.2+/-5.2) and 12 months (7.9+/-5.7) following the second surgery, but these gains were not significant. Blinded evaluations also revealed a similar degree of improvement. Complications were noted in five patients: asymptomatic intracranial hematoma (1), postoperative seizures (1), a hematoma over the implanted pulse generator (IPG) (1), lead repositioning (1), and IPG malfunction (1). Adverse effects related to stimulation were mild and resolved with adjustment of the stimulation parameters. Three of the six patients demonstrated worsening of dysarthria with both stimulators on. CONCLUSIONS: Bilateral thalamic stimulation is effective in reducing tremor and functional disability in ET; however, dysarthria is a possible complication.

Activities of Daily Living↗
PubMed2001

Samuel Adams' tremor.

BACKGROUND: Samuel Adams (1722--1803), the American Revolutionist and brewer, is said to have had a tremor. There has not been a formal study of the clinical characteristics and progression of his tremor. OBJECTIVE: To use historical accounts and original materials to document the clinical characteristics and progression of Adams' tremor. MATERIALS: In addition to historical accounts of Adams, the following materials were reviewed: 1) Samuel Adams' known writings, including personal and political letters, published posthumously in a four-volume book; and 2) original letters and speeches (handwritten by Adams) that are held in collection in the Manuscripts and Archives Division of the New York Public Library. RESULTS: Adams had a tremor that affected his hands, head, and voice. Although mild, the tremor was already manifest when Adams was in his early 40s. Adams, who was very prolific, experienced progressive difficulty with his ability to write while in his 50s and early 60s. His letters contain frequent references to his illness and reveal a penmanship that became more compromised with time. By age 71, he was forced to dictate all his correspondence. His tremor was familial, affecting his daughter Hannah and her children. CONCLUSIONS: Samuel Adams' progressive tremor rendered him unable to write his own letters for the last 10 years of his life. Adams had one of the earliest documented cases of essential tremor.

History, 18th Century↗