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PubMed1999

Effect of Hand Posture on the Temporal and Kinematic Properties of Pointing and Drawing Movements Executed by Healthy Subjects and by a Patient With Primary Writing Tremor.

Healthy individuals (n = 6) and a patient with "pure" primary writing tremor executed pointing and drawing movements while adopting different hand postures. The control subjects and the patient exhibited similar kinematics for most conditions. The patient displayed a severe right hand 4- to 6-Hz tremor and prolonged movements only when drawing with his normal hand posture. His tremor was manifested after a ready cue, in anticipation of a go command. The premovement tremor was abolished when the authors simply eliminated the ready cue and instructed the patient to relax and not think about drawing until he heard the go cue. Thus, the patient's writing tremor depended not only upon the writing or drawing act but also upon the hand position adopted and the intent to write, even in the absence of movement. The present results suggest that (a) similar high-level control mechanisms exist for pointing and drawing in healthy subjects and (b) the patient's deficits are compatible with a higher motor defect in central nervous system structures involved in the control of pointing and drawing movements.

Journal Article↗

PubMed1996

Adrenalectomy protects ethanol-withdrawn rats from harmine-induced tremor.

A growing number of studies have implicated the hypothalamic-pituitary-adrenal (HPA) axis in acute and chronic alcoholization and in ethanol withdrawal. In order to study the ethanol/HPA axis interaction during alcohol withdrawal, we performed experiments using adrenalectomized (ADX) male rats alcoholized by a chronic pulmonary alcoholization procedure. Eight hours after the 3 weeks of the alcoholization procedure, the rats were evaluated for a tremor activity. In order to reduce the great variability of the withdrawal tremors, we estimated the supersensitivity of the withdrawn rats to the tremorogenic compound harmine. We also studied the effect of a hydrocortisone treatment given in the drinking bottle during the alcoholization procedure on the harmine-induced tremors of ADX and sham rats. Alcohol withdrawal resulted in increased tremor response to 10 mg/kg harmine, and a protective effect of adrenalectomy on this effect was observed. Hydrocortisone administration to ADX or sham rats did not affect the tremor profile of the alcohol withdrawn rats.

Adrenal Glands↗

PubMed1978

Neuronal mechanisms underlying physiological tremor.

1. Tremor force was recorded during stationary isometric contractions of intrinsic hand muscles of normal subjects. Subjects maintained a steady force level between their thumb and forefinger for 30 s. The force level varied from weak (0.2 kg) to strong contractions (7 kg). These experimental conditions were the same as those in two preceding studies, where single motor-unit activity (14) and the correlation between the discharges of two simultaneously recorded motor units and physiological tremor (11) have been investigated. 2. Two alterations of the power spectra were observed at successively stronger contractions: increase of tremor amplitude and changes in the shape of the power spectrum. At all force levels, the power spectra of tremor force show the well-known decay of tremor amplitude from the lower to the higher frequencies with a local peak at 6--10 Hz. This peak does not show a significant change with respect to frequency when the force level is varied. It is shifted toward lower frequencies in a pathological condition (Parkinsonism) where the recruitment firing rates of the motor units are significantly lower than in the normal. 3. Higher frequencies (greater than 20 Hz) are barely present in the power spectrum during the very weak contractions. They become significant as the contractions become stronger. 4. The steep decay of the power spectrum toward higher frequencies has a similar slope (--43 dB/decade) as the reduction in amplitude of the unfused part of the muscle contractions with increasing stimulus rates (--38 dB/decade). The cutoff of the power spectrum above 25 Hz parallels the achievement of total fusion of muscle twitches above this rate. 5. The results are consistent with the hypothesis that the power spectrum over the range of 6--25 Hz is mainly caused by the unfused parts of the twitch contractions of motor units firing between recruitment (6--8/s) and total fusion of the twitches (25--30/s). The decline of the power spectrum toward higher frequencies can be explained by mechanical damping, which results from increasing fusion of the twitch contractions. The low-frequency part of the power spectrum is assumed to be the result of the slow force deviations produced by changes in the net output of the motoneuron pool. 6. These assumptions were supported by additional animal experiments where the number and rate of force-producing elements could be controlled. Bundles of ventral root filaments innervating cat soleus and gastrocnemius muscles were stimulated synchronously and asynchronously at a number of different rates. The force output of the strain gauge was recorded, filtered, and analyzed in the same way as the human force records. 7. Stimualtion of one nerve bundle at one fixed frequency led to a sharp peak in the power spectrum at that frequency plus peaks of decreasing height representing the harmonics of the stimulation frequency. The height of the peaks decreased at --37 dB/decade. 8...

Animals↗

PubMed1987

Voice tremor: dysregulation of voluntary expiratory muscles.

We studied three patients: two with voice and hand tremor, and one with voice tremor. Voice tremor was associated with synchronous rhythmic contraction of cricothyroid and rectus abdominis muscles, but not always vocalis muscle. Voice tremor was manifested only in voluntary phonation or expiration, not in involuntary phonation, voluntary inspiration, or involuntary expiration and inspiration (breathing at rest). Impaired regulation of the CNS programs innervating the voluntary expiratory muscles probably causes voice tremor. Clonazepam and propranolol were helpful in blinded studies.

Clonazepam↗

PubMed2002

Neurophysiological investigations in patients with primary writing tremor.

The pathophysiology of primary writing tremor (PWT) is still unknown: it has been classified as a focal form of essential tremor and as a tremulous form of writer's cramp. We studied cortical and spinal excitability in patients with PWT and compared the results with published data of patients with essential tremor, and writer's cramp. We used electrical stimulation of median and radial nerve to study reciprocal inhibition of forearm antagonist muscles and paired transcranial magnetic stimulation at short and long interstimulus intervals (ISIs) to assess intracortical excitability. Both studies were conducted on patients with PWT and on control subjects. The early (presynaptic) and late (disynaptic) phases of reciprocal inhibition were normal as was intracortical excitability at short and long ISIs. Our study suggests that the pathophysiology of PWT is different from that of writer's cramp and partially also from that of essential tremor.

Aged↗

PubMedDate not supplied

Nonparkinsonian tremors.

Tremors other than those associated with Parkinson's disease are commonly encountered in clinical practice. The differentiation of tremor subtypes depends primarily on the presence of distinct clinical characteristics and is facilitated by the use of consistent nomenclature. Such differentiation can be helpful in determining the etiology of the tremor and assist in its management. In this review, the authors outline recently proposed changes to classification and review the clinical features, differential diagnosis, and current therapy for nonparkinsonian tremors.

Dystonia↗

PubMed2002

Movement disorders. Keys to identifying and treating tremor.

Tremor is one of the most common adult neurologic disorders. It is characterized by Involuntary, rhythmic and oscillatory movements of a body part. Tremor affects quality of life by impeding simple motor tasks and activities of daily living and heightening self consciousness. Severe tremor can undermine independence, relationships, and recreational and social activities. Initial clinical objectives include determining the tremor type and ruling out Parkinson's disease. Severe cases typically require pharmacologic therapy, and in some instances, surgical intervention; both strategies for severe cases, however, have drawbacks.

Aged↗

PubMed1986

Pharmacologic treatment of parkinsonian tremor.

The relative efficacy of trihexiphenidyl hydrochloride, amantadine hydrochloride, and low-dose carbidopa-levodopa in reducing parkinsonian tremor was investigated using objective techniques. Trihexiphenidyl and carbidopa-levodopa decreased tremor by greater than 50%. Some patients responded to one drug but not to the other. Amantadine decreased tremor less than 25%. Monotherapy with trihexiphenidyl or carbidopa-levodopa should be the initial treatment for the tremor of Parkinson's disease.

Amantadine↗

PubMed1986

The physiology of orthostatic tremor.

This article describes the physiological findings in a patient with orthostatic tremor. The tremor primarily affected the legs, was alternating between antagonist muscle groups, and had a remarkably rapid frequency of 16 Hz. It was present only during certain postures and appeared to be of central origin. A tremor of the same frequency was also recorded in the arms during particular movements, but was cocontracting. We suggest that orthostatic tremor may be generated by spontaneous oscillation in those central structures responsible for organizing the motor programs for standing.

Electromyography↗

PubMed1991

Glutethimide treatment of disabling action tremor in patients with multiple sclerosis and traumatic brain injury.

Glutethimide has been used to control essential tremor. Its efficacy in the treatment of disabling cerebellar and rubral tremor was assessed in an open study of six patients with multiple sclerosis and two patients with traumatic brain injury. Functional and quantitative tremor severity was assessed before treatment and 7 to 14 days after a stable dose was achieved. Six of eight patients exhibited visible functional benefit from treatment with glutethimide; abstract testing results correlated well with functional status in most cases. Four patients chose to continue to receive medication. Controlled trials of glutethimide to compare its efficacy with that of other medications used in the treatment of action tremor are indicated.

Brain Injuries↗

PubMed1995

Differences in the prevalence of essential tremor among elderly African Americans, whites, and Hispanics in northern Manhattan, NY.

BACKGROUND: Until now there has been only one community-based study to examine interethnic differences in the prevalence of essential tremor (ET). The study suggested a higher prevalence among whites than African Americans. The present study is the first to examine differences in the prevalence of ET among Hispanics, African Americans, and whites. OBJECTIVE: To estimate the prevalence of essential tremor (ET) in a cohort of community-dwelling elderly of mixed ethnic background. METHODS: A random sample of 2117 Medicare recipients residing in Washington Heights-Inwood in northern Manhattan, NY, were interviewed. A standardized neurological assessment was performed on those who had neurological complaints and on a random sample of those who did not. Essential tremor was defined as a postural or kinetic tremor of the head or limbs. Diagnoses were independently confirmed by two neurologists based on videotaped examination. RESULTS: After age adjustment to the 1990 Washington Heights-Inwood census, the prevalence of ET was 40.2 per 1000 (95% confidence interval, 31.8 to 48.6). Among 46 cases with ET, ET was significantly more prevalent in men than in women (chi 2 = 5.0, P = .03). Prevalence increased significantly with age. The prevalence was higher in whites than African Americans. The prevalence in Hispanics was intermediate. CONCLUSION: The prevalence of ET increases with age and may be higher among men and whites. Prospective studies are needed to further examine these associations.

Black or African American↗

PubMed1998

Familial cortical tremor, epilepsy, and mental retardation: a distinct clinical entity?

OBJECTIVE: To describe a European family with cortical tremor, epilepsy, and mental retardation, the pedigree of which indicates an autosomal dominant inheritance of the disease. DESIGN: Clinical, laboratory, neurophysiological, and neuroimaging data were studied. SETTING: Institute for research on mental retardation. PATIENTS: Two siblings (aged 25 and 28 years) and their 49-year-old mother had postural and action tremor, seizures, and mental retardation. Only tremor was present in the maternal grandmother (aged 68 years). The electroencephalogram showed diffuse spike-and-wave complexes and/or posterior spikes, and a photoparoxysmal response in the 4 subjects. The typical electrophysiologic features of cortical reflex myoclonus, such as giant somatosensory evoked potentials, enhancement of the C-reflex, and jerk-locked premyoclonus spikes, were found in all patients. CONCLUSION: This syndrome may represent a specific form of familial cortical tremor with a benign form of epilepsy and a new genetic model of cortical hyperexcitability inherited with an autosomal dominant mechanism.

Adult↗

PubMed1999

Resetting of orthostatic tremor associated with cerebellar cortical atrophy by transcranial magnetic stimulation.

OBJECTIVES: To investigate the resetting effects of transcranial magnetic stimulation over motor cortex on orthostatic tremor, characterized by high-frequency electromyographic discharges in weight-bearing muscles, particularly orthostatic tremor (OT) associated with cerebellar cortical atrophy; and to compare our results with those obtained in primary OT, for which transcranial magnetic stimulation does not reset tremor. DESIGN: Study of 3 patients who clinically exhibited a sporadic pancerebellar syndrome associated with isolated cerebellar atrophy and features of OT. SETTING: Research hospital. MAIN OUTCOME MEASURES: Electromyograms and transcranial magnetic stimulation studies with a resetting index calculated on the basis of the timing of measured bursts and predicted bursts for a magnetic stimulus given at increasing delays. RESULTS: Surface electromyographic recordings in weight-bearing muscles showed tremor with a frequency of 14, 15, and 14 Hz in the 3 patients. Transcranial magnetic stimulus was able to reset OT. Resetting index was 0.72. CONCLUSIONS: Transcranial magnetic stimulus resets OT associated with cerebellar cortical atrophy, emphasizing the role of motor cortex in the genesis of OT associated with a cerebellar dysfunction. Our results argue in favor of a distinct pathophysiological mechanism of primary OT and OT associated with cerebellar cortical atrophy.

Atrophy↗

PubMed2003

Bilateral high-frequency synchronous discharges: a new form of tremor in humans.

OBJECTIVES: To report bilateral high-frequency synchronous discharges in a patient with a sporadic form of olivopontocerebellar atrophy; to investigate the electromyographic pattern, the coherence and cospectral density across limbs, and the resetting effects of electrical stimulation over the posterior fossa; and to highlight the clinical, electrophysiologic, and radiologic features of this new form of tremor associated with posterior fossa disorders. DESIGN: Case study of a patient clinically exhibiting a sporadic form of olivopontocerebellar atrophy associated with cerebellar and brainstem atrophy. SETTING: Research unit, university hospital. MAIN OUTCOME MEASURES: Electromyographic studies, coherence and cospectral density analysis, and calculation of a resetting index based on the timing of measured bursts and predicted bursts for an electrical stimulus given over the posterior fossa at increasing delays. RESULTS: Surface electromyographic recordings in forearm muscles revealed a low-frequency postural tremor in the upper limbs, with episodes of highly coherent tremor at a frequency of 14 Hz. Squared coherence and cospectral density was strong between agonist and antagonist muscles in the left and right upper limbs and across limbs for the high-frequency discharges. Electrical stimulation over the posterior fossa reset the explosive high-frequency bursts. The resetting index was 0.82 Hz. CONCLUSIONS: Our results show that bilateral high-frequency synchronous discharges may be associated with the sporadic form of olivopontocerebellar atrophy. Bilateral coherent bursting and resetting of this explosive postural tremor following electrical stimulation over the posterior fossa strongly suggest that the brainstem plays a key role in the network involved in the genesis of rhythmic bursts. We suggest that the high-frequency discharges are due to repetitive discharges in the reverberating cerebello-precerebellar circuits.

Aged↗

PubMed1998

Botulinum toxin restores presynaptic inhibition of group Ia afferents in patients with essential tremor.

We studied the effect of botulinum toxin A injection on the abnormal presynaptic phase of reciprocal inhibition between forearm antagonist muscles in patients with essential tremor. Ten patients with essential tremor were investigated before and 1 month after botulinum injection. Reciprocal inhibition was studied by conditioning the H reflex in forearm flexors with a radial-nerve stimulus delivered at a range of time intervals. Botulinum toxin produced a significant functional improvement in tremor (about 20%). Before botulinum toxin injection, patients had a reduced presynaptic phase of reciprocal inhibition. After botulinum toxin this phase was significantly more pronounced. The normal early disynaptic phase of reciprocal inhibition was normal before and after botulinum treatment. Although botulinum treatment reduced the size of the H reflex and the M wave to a similar extent, it left the H/M ratio unchanged. These findings show that botulinum toxin treatment restores presynaptic inhibition between forearm antagonist muscles. The results are also consistent with botulinum toxin having a beneficial effect in patients with essential tremor. Both effects probably depend upon the toxin's concurrent action on the extrafusal and intrafusal motor end-plates, the latter resulting in decreased spindle afferent input to the spinal cord.

Adult↗

PubMed1979

A curvilinear relationship between alcoholic withdrawal tremor and personality.

Many studies cite no more than 80% incidence of hand tremor during withdrawal in known alcoholics, although this symptom is one of the diagnostic signs of addiction. We found that of 48 patients tested, hand tremor increased in 29 Ss after the application of a passive relaxation technique while it decreased in 28. It was found that MMPI data obtained for both groups fitted the inverted U curve in that the most distressed Ss tremored as little as did the least distressed originally, while the tremor increased in the high stress group after relaxation therapy while it decreased in the least stressed group. Implications for alcoholism research and theory were discussed, and the possible superiority of the CES to drug therapy for withdrawal was noted.

Acute Disease↗

PubMed1999

Acute and chronic effects of clozapine in essential tremor.

Patients with essential tremor (ET) may not respond to commonly used drugs. Clozapine, an atypical neuroleptic drug, has been reported to improve postural Parkinson's disease tremor clinically resembling ET. The effects of a single dose of 12.5 mg clozapine and placebo were evaluated in a randomized, double-blind, crossover study in 15 drug-resistant patients with ET. Patient responders with more than 50% improvement after a single dose of clozapine subsequently received the drug (39+/-9 mg up to 50 mg) unblinded for a period of 15.8+/-7.7 months. Tremor was effectively reduced by a single dose of clozapine in 13 of 15 patients (p <0.01). Sedation was the only side effect reported during the clozapine test; however, the time course of sedation and of the antitremor effect were not coincident. A significant reduction of tremor was reported with chronic clozapine treatment (p <0.01) with no tolerance to drug antitremor effect, whereas sedation markedly decreased after 6-7 weeks of therapy. No clozapine-induced hematologic side effects were observed in our cohort of patients during long-term treatment. Our results suggest that in selected drug-resistant ET cases, clozapine should be considered before resorting to neurosurgical options.

Antipsychotic Agents↗

PubMed2000

Multiple oscillators are causing parkinsonian and essential tremor.

The tremors of Parkinson's disease (PD) and essential tremor (ET) are traditionally considered to depend on a central oscillator producing rhythmic activation of the motoneurones of all extremities. To test this hypothesis, we have compared electromyographic tremor activity in different muscles of the affected limbs using cross spectral analysis, including coherence and phase. Surface electromyographic recordings from both arms, legs, and the neck were analyzed in 22 patients with PD and 28 patients with ET. Volume conduction between neighboring muscles producing artificial "coherence" has been found to be an important methodologic problem. We have developed a mathematical test to exclude data that could distort the results. According to this test, 10% or 25% of muscle combinations from the same limb had to be excluded from further analysis in PD or ET, respectively. In both, patients with PD and ET, we found a considerable number of muscle combinations oscillating at virtually the same frequency (delta frequency <0.4 Hz) without showing a significant coherence. Thus, the frequency difference between different muscles is not sufficient to measure the correlation between two muscles. Significant coherencies between muscles within the same arm or leg were found in 70% or 90% of patients with PD or ET, respectively, whereas only one patient with PD and not a single patient with ET showed significant coherencies between muscles from different limbs. The phase between coherent muscles of the same arm of patients with PD showed a preference of either a reciprocal alternating pattern for antagonistic muscles in forearm flexor and upper arm extensor as opposed to a co-contraction pattern between the hand flexors and the triceps brachii. In patients with ET such clear differences were lacking. We conclude that multiple oscillators are responsible for the tremor in different extremities of patients with PD and ET. Differences between PD and ET concerning the phase relation within the arm may either be related to the topography within the basal ganglia or to differently involved-spinal pathways.

Arm↗