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PubMed2000

Essential tremor frequency decreases with time.

OBJECTIVE: To quantify the extent to which tremor frequency changes with time in patients with essential tremor. BACKGROUND: Tremor frequency tends to be lower in older patients. The author's previous study of 18 patients with essential tremor produced evidence that tremor frequency decreases slowly over a period of 4 to 8 years. A decrement in frequency will increase tremor amplitude because there is less attenuation of lower-frequency tremor by the low-pass filtering properties of muscle and limb mechanics. METHODS: Nineteen women and 25 men with essential tremor and no other neurologic conditions were followed for 4 years. Accelerometry and surface electromyography (EMG) were used to measure hand tremor and motor unit entrainment in the extensor carpi radialis brevis every 2 years. Tremor frequency was computed from the spectral peak in the rectified filtered EMG spectrum under the condition of 300-gram loading. RESULTS: The patients' mean +/- SD age was 68.0+/-9.95 years. The mean tremor frequency at baseline was 5.79+/-1.32 Hz. The mean decrement in tremor frequency over 4 years was 0.332 Hz (95% CI = 0.141 to 0.523) and was 0.270 Hz (95% CI = 0.122 to 0.418) when a 61-year-old outlier patient was excluded. Tremor frequency and patient age were linearly related: frequency = -0.061(age) + 9. 94 (r = 0.459; p<0.002). CONCLUSIONS: The frequency of essential tremor decreases by approximately 0.06 to 0.08 Hz/year. This decrement in frequency is consistent with the linear relationship between age and tremor frequency.

Adult↗
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↗
PubMed2000

Long-term deep brain stimulation in a patient with essential tremor: clinical response and postmortem correlation with stimulator termination sites in ventral thalamus. Case report.

Essential tremor can be suppressed with chronic, bilateral deep brain stimulation (DBS) of the ventralis intermedius nucleus (Vim), the cerebellar receiving area of the motor thalamus. The goal in this study was to correlate the location of the electrodes with the clinical efficacy of DBS in a patient with essential tremor. The authors report on a woman with essential tremor in whom chronic bilateral DBS directed to the ventral thalamus produced adequate tremor suppression until her death from unrelated causes 16 months after placement of the electrodes. Neuropathological postmortem studies of the brain in this patient demonstrated that both stimulators terminated in the Vim region of the thalamus, and that chronic DBS elicited minor reactive changes confined to the immediate vicinity of the electrode tracks. Although the authors could not identify neuropathological abnormalities specific to essential tremor, they believe that suppression of essential tremor by chronic DBS correlates with bilateral termination of the stimulators in the Vim region of the thalamus.

Brain Mapping↗
PubMed1984

The relation of essential tremor to Parkinson's disease.

To test the alleged genetic linkage between essential tremor and Parkinson's disease, the relatives of patients with essential tremor were examined to see whether Parkinson's disease occurred more frequently than expected. There was no increase of Parkinson's disease in the essential tremor families. It is concluded that essential tremor and Parkinson's disease are genetically independent diseases.

Adult↗
PubMed1999

Tolerance and tremor rebound following long-term chronic thalamic stimulation for Parkinsonian and essential tremor.

Fifty-eight patients, 36 with essential tremor (ET) and 22 with Parkinson's disease (PD), received deep brain stimulation (DBS) in the thalamic ventral intermediate (Vim) nucleus. The mean follow-up was 17 months for ET and 21 months for PD patients. Stimulation parameters were adjusted as needed, at various intervals after surgery. Results were assessed using routine clinical evaluation and established outcome scales. All patients needed incremental increase in stimulation parameters at various intervals during the first 6-12 months after surgery. The mean voltage 1 week postoperatively was 1. 45 V in PD patients, and 1.37 V in ET patients. Twelve months later, the figures were 2.14 V in PD and 2.25 V in ET patients. At 1 year, the Essential Tremor Rating Scale (ETRS) improved from 54 to 28 (p < 0.0001). The motor part of the Unified Parkinson's Disease Rating Scale (UPDRS) improved from 37 to 26 (p < 0.01). Tremor items of the UPDRS improved more markedly (p < 0.0001). One week postoperatively 90% of PD, and 89% of ET patients were tremor free. One year later, 70% of PD and 60% of ET patients remained mostly tremor free. Upon switching off stimulation, there was a clear tendency for tremor rebound (p = 0.07) in the PD group, requiring continuous 24-hour stimulation in some patients. Permanent non-adjustable ataxia was induced by stimulation in 2 PD patients.

Electric Stimulation Therapy↗
PubMed1988

Parkinson's disease and essential tremor in families of patients with early-onset Parkinson's disease.

The occurrence of Parkinson's disease and of essential tremor was examined in the parents and siblings of 52 Parkinson's disease patients with onset before the age of 45 years. The expected numbers of cases with Parkinson's disease or essential tremor were calculated according to the age and sex specific incidence rates of Parkinson's disease and essential tremor in the general population. Among the parents, there was one case of Parkinson's disease (expected 1.2), and 10 cases of essential tremor (expected 5.4); among the siblings there were two cases of Parkinson's disease (expected 0.7), and three cases of essential tremor (expected 5.3). The observed and expected incidence of Parkinson's disease or essential tremor were not significantly different. This does not support the inheritance of early-onset Parkinson's disease, or the association of Parkinson's disease with essential tremor.

Adult↗
PubMed1997

[Acute pharmacological test of clonidine in essential tremor].

Thirty-seven patients with essential tremor were given intramuscular clonidine injections of 0.3 mg. Physical examination and statistical analysis showed that response was highly positive (t = 13.47; p < 0.0001) 60 min after administration. The absence of peripheral alpha-adrenergic receptors for tremor suggest that the drug acts centrally, consistent with the theory that essential tremor originates in a central oscillating pacemaker.

Adrenergic alpha-Agonists↗
PubMed2005

Olanzapine versus propranolol in essential tremor.

PURPOSE: In this study, we evaluated the anti-tremor effect of olanzapine in patients with essential tremor (ET). MATERIAL AND METHODS: Thirty-eight patients with ET affecting upper limbs underwent a randomized, crossover study with olanzapine (20 mg/day) and propranolol (120 mg/day). Evaluation (baseline and 1 month after each drug) was done by using the tremor clinical rating scale and a self-reported disability scale. RESULTS: We did not find statistical difference in all tremor parameters before treatment in two groups. Both drugs improved essential tremor parameters. However, olanzapine significantly improved all tremor parameters except hygiene as compared to propronalol. CONCLUSION: These results suggest that olanzapine might be efficacious for essential tremor. Further clinical trials are indicated to establish the efficacy of olanzapine in patients with ET.

Adrenergic beta-Antagonists↗
PubMed1990

[Catecholamine metabolism in essential tremor].

The pathogenesis of essential tremor (ET) is evidently very complicated and involves various biochemical and pathophysiological mechanisms. The pathology of cerebral adrenergic systems is attributed a high value in the development of the disease. The general catecholamine (CA) metabolic indices were investigated in 40 ET patients. CA excretion was considerably decreased, especially that of norepinephrine, while the urinary level of a CA precursor DOPA was essentially normal. The excretion of a major epinephrine and norepinephrine metabolite vanillylmandelic acid also tended to decrease. Contrarily to the CA excretion, their blood levels did not change considerably. The data are supposed to point to a reduction of the general CA body pool, especially of norepinephrine. This yields the shift of relationship between lepinephrine and norepinephrine toward the latter, that can provide another mechanism for ET. Possible deterioration of noradrenergic neurotransmission as a pathogenic factor of ET, and adrenergic receptors hypersensitivity in particular, are still pending. Major genetically predetermined biochemical defect in ET leading to impaired control of complicated mechanisms behind the regulation of synchroneous activity of spinal motor structures, is believed to be closely related to CA systems modifying ET in response to various impacts and involving the mechanisms of central action alcohol.

Adolescent↗
PubMed2000

Essential tremor: an overdiagnosed condition?

The diagnosis of essential tremor (ET) and its differentiation from other types of tremor is often difficult. In 1994 Bain et al. defined a classical phenotype by studying 20 patients with pure essential tremor and similarly affected family members in at least three generations. We assessed how many of the patients diagnosed by different neurologists at our institution as having ET conformed to this defined phenotype. We randomly selected 50 patients who were diagnosed with ET by any neurologist at the National Hospital for Neurology and Neurosurgery since the publication of the Bain et al. report, and determined the number of patients who had clinical features compatible with the phenotype that it had defined. Only 25 (50%) of these patients had ET so defined. Ten patients clearly had alternative diagnoses: four had clear additional dystonia, two neuropathic tremor, two had unilateral leg tremor, one drug-induced tremor, and one sudden onset after head trauma. The remaining 15 patients also had atypical features including myoclonus (one), onset in a body part other than the arms (six), sudden onset (two), rest tremor (seven), onset after the age of 65 years (four), a family member with an isolated head tremor (one), or reduced armswing (two). The diagnosis of ET is overused even among experienced neurologists, and other types of tremor should be considered in atypical patients before making this diagnosis.

Adolescent↗
PubMed1998

How common is the most common adult movement disorder? estimates of the prevalence of essential tremor throughout the world.

Essential tremor (ET) is the most common adult movement disorder, as much as 20 times more prevalent than Parkinson's disease. Estimates of the crude prevalence of ET range widely from 0.08 to 220 cases per 1000 persons, a 2750-fold difference. There has been no formal attempt to synthesize these disparate results. Our purpose is to provide an overview of existing studies, to examine methodologic issues that may account for this tremendous variability in results, and to provide a more precise estimate of the prevalence of ET. Nineteen studies of the prevalence of ET were reviewed. Factors that contribute to the broad range of prevalence estimates include (a) differences in study design that influence validity and (b) differences in characteristics of study populations that influence comparability of studies. If we limit our examination to studies that (a) provided diagnostic criteria for ET, (b) defined ET as an action tremor, and (c) used community-based rather than service-based designs, then five studies remain, and the prevalence of ET is 4.1 to 39.2 cases per 1000, a 9.6-fold difference. Four of these five provided age-stratified data. Among these four, the prevalence of ET in those over the age of 60 years was 13.0 to 50.5 cases per 1000, a 3.9-fold difference.

Adult↗
PubMed1982

Essential tremor and buccolinguofacial dyskinesias.

Essential tremor (ET) has been described in association with major dyskinesias, such as dystonia musculorum deformans, torticollis, and dystonic writer's cramp. In a series of 104 patients affected by ET, the incidence of buccolinguofacial dyskinesias (BLFD) has been investigated, including a comparison with another dyskinesia involving the facial muscles--mimic muscle tremor. The association of ET and BLFD may be casual; however, on the other hand, it might suggest the existence of a subgroup of patients suffering from a non-specific sign of motor control impairment, such as ET, in which other non-specific disorders of voluntary movement, such as BLFD, can gradually develop, particularly late in life.

Adolescent↗
PubMed1986

Selective adrenergic beta-2-receptor blocking drug, ICI-118.551, is effective in essential tremor.

Eighteen patients with essential tremor were treated for 2 days with a non-selective adrenergic beta-blocking drug (dl-propranolol, 80 mg X 3), a beta-2-selective blocker (ICI-118.551, 50 mg X 3) and placebo (X 3) in a randomized double blind cross-over study. Postural hand tremor was recorded with an accelerometer before administration of the drugs and at the end of each treatment period. Compared with placebo, both the beta-blocking drugs caused a statistically significant decrease in tremor intensity and they possessed approximately similar antitremor potency. Subjective benefit was reported by 12 of the 18 patients receiving ICI-118.551, 13 when on propranolol and 3 when on placebo.

Adrenergic beta-Antagonists↗
PubMed1994

A study of hereditary essential tremor.

Twenty index patients with hereditary essential tremor and their kindreds were studied to define the phenotype of this condition. Ninety-three first degree and 38 more distant relatives were examined; 53 definite and 18 possible secondary cases were identified. The age of tremor onset was bimodally distributed with a median at approximately 15 years. Segregation analysis indicated autosomal dominant inheritance and penetrance was virtually complete by the age of 65 years. There were no examples of the disease skipping a generation. Men and women were affected in equal proportions. About 50% of cases were alcohol responsive. In the majority of families alcohol responsiveness was either consistently present or did not occur, but in 20% of kindreds definite heterogeneity of responsiveness was encountered within each family. The typical phenotype was a mild symmetrical postural tremor of the upper limbs. Tremor of the legs, head, facial muscles, voice, jaw and tongue occurred but never in isolation and rest, task specific (e.g. primary writing tremor) and primary orthostatic tremors were not found. Head tremor was invariably mild and 75% was of a 'no-no' type. Dystonia (e.g. torticollis and writer's cramp) were not encountered, a finding which strongly suggests that many previous studies of 'essential tremor' were contaminated by cases of idiopathic or hereditary torsion dystonia. No association with Parkinson's disease was found but classical migraine occurred in approximately 26% of cases and co-segregated with tremor. The severity of arm tremor (assessed using a clinical rating scale and by scoring tremor in Archimedes spirals) and disability increased with advancing age and increasing tremor duration, but there was no correlation between age at tremor onset and either tremor severity or disability. Men and women were affected with equal severity. The sex of the affected parent had no influence on the severity of tremor or the degree of disability experienced by an affected child. Disability commenced in the second decade and progressively increased. All the index patients and 59% of the definite secondary cases had tremor induced disabilities. Eighty-five percent of index patients and 38% of secondary cases also reported some degree of social handicap. Twenty-five percent of index patients and 12% of secondary cases had been compelled to change jobs or retire. Biological fitness was normal.

Adolescent↗
PubMed1992

"Resetting" of postural tremors at the wrist with mechanical stretches in Parkinson's disease, essential tremor, and normal subjects mimicking tremor.

The response of postural wrist tremors to brief mechanical displacements was compared in two groups of patients, one with classical hereditary essential tremor (n = 18) and another with typical Parkinson's disease (n = 13). These groups were compared with an additional group of normal subjects mimicking wrist tremor (n = 9). The degree to which brief mechanical displacements of the wrist produced by torque pulses of three different sizes could modulate the timing of rhythmic electromyographic bursts in the forearm flexor muscles was quantified by deriving a resetting index, which could range between 0 (no phase resetting) and 1 (complete phase resetting). In all three groups of subjects studied, the resetting index varied significantly with the size of the mechanical perturbation and, in an inverse fashion, with the ongoing tremor amplitude. When due allowance for these factors was made, the difference in mean resetting indexes between the three groups of patients and subjects was reduced to the extent that no definitive statement could be made as to whether brief mechanical perturbations had more effect on essential tremor than parkinsonian tremor. The method is therefore unlikely to be useful in differentiating the common causes of postural wrist tremors.

Adult↗
PubMed1994

Red nuclear and cerebellar but no olivary activation associated with essential tremor: a positron emission tomographic study.

There has been debate as to whether essential tremor has a central origin and over the possible role of the inferior olivary nucleus in its genesis. We used positron emission tomography with radioactive water (H2(15)O) to detect abnormal patterns of cerebral activity associated with this condition, at rest, without tremor, and on posture when the tremor was present. At rest, cerebellar blood flow was significantly increased bilaterally in the group with essential tremor (30-40%) but no increased olivary activity was evident. Essential tremor during arm extension was associated with further abnormal increases in bilateral cerebellar and abnormal red nuclear activation. Again, no olivary overactivity was evident. Voluntary wrist oscillation in control subjects caused only ipsilateral cerebellar activation. We conclude that essential tremor is associated with abnormal bilateral overactivity of cerebellar and red nuclear connections but found no evidence of intrinsic overactivity of the inferior olivary nucleus, as evidenced by raised blood flow.

Adult↗
PubMed2000

Diagnostic criteria for essential tremor and differential diagnosis.

Classic essential tremor (ET) is a condition in which the upper limbs (approximately 95% of patients) and, less commonly, the head (approximately 34%), face (approximately 5%), voice (approximately 12%), trunk (approximately 5%), and lower limbs (approximately 20%) exhibit a mixed postural and kinetic tremor without other neurologic abnormalities. Most patients with ET probably inherit the disease through an autosomal dominant gene, but the true ratio of hereditary versus sporadic ET is unknown. Isolated focal, position-specific, and task-specific tremors are probably not ET in most patients and are often due to subtle dystonia. Unilateral tremor, gait disturbance, rigidity, bradykinesia, rest tremor, and rapid onset of symptoms are indications of other tremorogenic disorders.

Biomechanical Phenomena↗