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Query: UMLS:C0040822 (tremor)
 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cerebellum is assumed to play a major role in the pathophysiology of essential tremor (ET). As intention tremor is considered one of the classical features of cerebellar disease, we have assessed a large group of patients with ET for the semiology of the tremor and have performed objective quantitative analysis of a grasping movement in patients with ET, cerebellar disease and a normal control group. We found 25% of the patients to have a moderate or severe kinetic tremor with clear-cut features of a classical intention tremor. Another 33% of the patients had a mild intentional component of their kinetic tremor. Patients with intention tremor (ET(IT)) did not differ from those with predominant postural tremor (ET(PT)) with respect to alcohol sensitivity of the tremor and the frequency of a family history. ET(IT) patients were older and more often showed head and trunk involvement. The onset of this intention tremor has been assessed retrospectively. It was found to begin at a randomly distributed time interval after the onset of the postural tremor, but older patients had a shorter time to development of intention tremor. Quantitative accelerometry of postural tremor showed similar tremor frequencies in both patient groups, but ET(IT) patients had a slightly larger tremor amplitude. Quantitative analysis of a grasping movement using an infrared-camera system was performed in two subgroups of the patients with ET(PT) and ET(IT) and control groups with cerebellar disease or normal subjects. The intention tremor could be quantified objectively as an increased amplitude of curvature during the deceleration and target phase of the movement. The amplitude measurements of intention tremor were clearly abnormal and of comparable magnitude for ET(PT) and cerebellar disease. Additionally, the patients with ET(IT) had a significantly slowed grasping movement during the deceleration and target period. Hypermetria was significantly increased for the patients with ET(IT) and cerebellar disease. We conclude that intention tremor is a feature of ET. ET(IT) patients have abnormalities of their upper limb function compatible with cerebellar disease. This suggests that patients with more advanced ET show abnormalities of cerebellar functions.
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PMID:Essential tremor and cerebellar dysfunction clinical and kinematic analysis of intention tremor. 1090 87

One hundred patients with definite multiple sclerosis, who were randomly selected from a multiple sclerosis unit in London, were examined in order to study the prevalence, subtypes, clinical features and associated disability of tremor in this population. There were 35 males and 65 females with an average age of 47 years and an average disease duration of 18.8 years. The mean tremor duration was 13 years, with a median latency of 11 years from disease onset to appearance of tremor. Tremor was reported in 37 patients but was detected in 58. Tremor affected the arms (56%), legs (10%), head (9%) and trunk (7%). There were no examples of face, tongue or jaw tremor. All the patients had action tremor, either postural or kinetic (including intention). Rest, Holmes' ('rubral') and primary orthostatic tremors were not encountered. Tremor severity ranged from minimal in 27%, to mild in 16% and moderate or severe in 15% of cases. Tremor severity correlated with the degree of dysarthria, dysmetria and dysdiadochokinesia but not with grip strength. In order to determine the clinical characteristics of these tremors, the action tremors of the upper limbs were subclassified according to the predominant site and state of tremulous activity. Of the 50 patients with tremor in the right arm, 32% had distal postural tremor, 36% had distal postural and kinetic tremor, 16% had proximal postural and kinetic tremor; 4% had proximal and distal postural and kinetic tremor and 12% isolated intention tremor. Twenty-seven percent of the overall study population had tremor-related disability and 10% had incapacitating tremor. Patients with abnormal tremor (severity grade >1/10) were more likely than those without tremor to be wheelchair dependent and have a worse Expanded Disability Systems Score, but Barthel activities of daily living indices and cognitive scores were comparable in the two groups.
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PMID:A study of tremor in multiple sclerosis. 1128 72

Tremor is defined as rhythmic oscillatory activity of body parts. Four physiological basic mechanisms for such oscillatory activity have been described: mechanical oscillations; oscillations based on reflexes; oscillations due to central neuronal pacemakers; and oscillations because of disturbed feedforward or feedback loops. New methodological approaches with animal models, positron emission tomography, and mathematical analysis of electromyographic and electroencephalographic signals have provided new insights into the mechanisms underlying specific forms of tremor. Physiological tremor is due to mechanical and central components. Psychogenic tremor is considered to depend on a clonus mechanism and is thus believed to be mediated by reflex mechanisms. Symptomatic palatal tremor is most likely due to rhythmic activity of the inferior olive, and there is much evidence that essential tremor is also generated within the olivocerebellar circuits. Orthostatic tremor is likely to originate in hitherto unidentified brainstem nuclei. Rest tremor of Parkinson's disease is probably generated in the basal ganglia loop, and dystonic tremor may also originate within the basal ganglia. Cerebellar tremor is at least in part caused by a disturbance of the cerebellar feedforward control of voluntary movements, and Holmes' tremor is due to the combination of the mechanisms producing parkinsonian and cerebellar tremor. Neuropathic tremor is believed to be caused by abnormally functioning reflex pathways and a wide variety of causes underlies toxic and drug-induced tremors. The understanding of the pathophysiology of tremor has made significant progress but many hypotheses are not yet based on sufficient data. Modern neurology needs to develop and test such hypotheses, because this is the only way to develop rational medical and surgical therapies.
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PMID:The pathophysiology of tremor. 1136 Feb 55

Many patients with upper limb intention tremor encounter difficulties in mouse-driven interaction with the personal computer (PC). An assistive technology system ("the Tremor Control System"), consisting of a motion-filtering software program that supports multiple interfaces, was developed and validated with 36 persons with Multiple Sclerosis in a multi-center trial. PC-tests, requiring basic functions such as cursor placement and click and drag function, were able to differentiate between patients and control subjects (ANOVA: p<0.05). A significant time improvement on the PC-tests was found when using an optimal alternative interface instead of the standard PC-mouse (paired t-tests: p<0.01 for Point & Click test, p<0.05 for Drag & Drop test and p<0.1 for Double Click test). A significant time improvement was found for the Double Click test (paired t-tests: p<0.05) when the motion-filtering program was implemented. The number of patients able to perform fully the PC-tests increased with the Tremor Control System. Patients with marked intention tremor seemed to profit especially from this assistive technology. These users reported that working with the Tremor Control System was less fatiguing and more comfortable compared to the use of the standard PC-mouse.
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PMID:Assistive technology to improve PC interaction for people with intention tremor. 1139 56

Gait disturbances of patients with essential tremor (ET) have been described anecdotally, but have never been investigated quantitatively. Recent studies provided evidence for a cerebellar-like hand tremor in some patients with ET. Therefore, we designed a study to assess cerebellar-like abnormalities of leg function. Twenty-five patients with ET, eight patients with cerebellar diseases (CD) and 21 age-matched healthy subjects were studied for their normal and tandem gait using a three-dimensional gait analysis system. During normal walking, CD and ET patients showed only slight abnormalities. However, ET patients exhibited abnormalities in tandem gait with an increased number of mis-steps and a broad-based, ataxic and dysmetric gait which was indistinguishable from the findings in CD. When ET patients were separated into groups of those with or without intention tremor of the hands, the gait disorder was found to be much more pronounced in the intention tremor group. Patients with this gait disorder were more severely disturbed in their activities of daily living, and suffer from an advanced stage of ET. The present results quantitatively describe a gait disturbance in advanced ET which affects tandem gait, but leaves normal gait almost unaffected. This is strong evidence for a cerebellar-like disturbance in ET.
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PMID:The gait disorder of advanced essential tremor. 1167 28

Cerebellar tremor is a frequent and disabling symptom in multiple sclerosis (MS) patients. Supportive pharmacological treatment with different drugs showed only minor effects in a few studies and in clinical practice. Encouraged by previous studies with ondansetron, a 5HT3-antagonist, we conducted a small open-label, prospective and controlled study with 14 MS patients suffering predominantly from cerebellar tremor of the upper extremities. Principal outcome measure to evaluate a functional improvement of the single intravenous administered ondansetron injection was the subject performance in the 9-hole-peg-test (9HPT) and 3 blind assessed upper extremity writing and copying tasks. We neither found significant improvement in the upper extremity tests nor in the subjective response of the patients. In conclusion we could not confirm a beneficial effect of ondansetron on cerebellar tremor of MS patients.
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PMID:Failure of ondansetron in treating cerebellar tremor in MS patients--an open-label pilot study. 1169 26

Tremor that occurs as a result of a cerebellar lesion, cerebellar tremor, is characteristically an intention tremor. Thalamic activity may be related to cerebellar tremor because transmission of some cerebellar efferent signals occurs via the thalamus and cortex to the periphery. We have now studied thalamic neuronal activity in a cerebellar relay nucleus (ventral intermediate-Vim) and a pallidal relay nucleus (ventralis oral posterior-Vop) during thalamotomy in patients with intention tremor and other clinical signs of cerebellar disease (tremor patients). The activity of single neurons and the simultaneous electromyographic (EMG) activity of the contralateral upper extremity in tremor patients performing a pointing task were analyzed by spectral cross-correlation analysis. EMG spectra during intention tremor often showed peaks of activity in the tremor-frequency range (1.9-5.8 Hz). There were significant differences in thalamic neuronal activity between tremor patients and controls. Neurons in Vim and Vop had significantly lower firing rates in tremor patients than in patients undergoing thalamic surgery for pain (pain controls). Other studies have shown that inputs to Vim from the cerebellum are transmitted through excitatory connections. Therefore the present results suggest that tremor in these tremor patients is associated with deafferentation of the thalamus from cerebellar efferent pathways. The thalamic X EMG cross-correlation functions were studied for cells located in Vim and Vop. Neuronal and EMG activity were as likely to be significantly correlated for cells in Vim as for those in Vop. Cells in Vim were more likely to have a phase lag relative to EMG than were cells in Vop. In monkeys, cells in the cerebellar relay nucleus of the thalamus, corresponding to Vim, are reported to lead movement during active oscillations at the wrist. In view of these monkey studies, the present results suggest that cells in Vim are deafferented and have a phase lag relative to tremor that is not found in normal active oscillations. The difference in phase of thalamic spike X EMG activity between Vim and Vop may contribute to tremor because lesions of pallidum or Vop are reported to relieve cerebellar tremor.
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PMID:Single-neuron analysis of human thalamus in patients with intention tremor and other clinical signs of cerebellar disease. 1192 26

The aim of this study was to re-evaluate the controversial clinical and electromyographic findings of cerebellar and midbrain tremors. Neurological examination and surface electromyographic tremor recordings were performed on 46 patients (24 with midbrain and 22 with cerebellar tremor). Our results revealed that the midbrain tremor has involved the hand, sometimes the ipsilateral leg and regions outside the limbs. Usually it was combined rest, postural, kinetic and intention tremor, the amplitude of each next tremor progressively increased. The tremor had high amplitude, low frequency and typical long burst duration. The cerebellar tremor was quite different, as it was predominantly postural and kinetic and involved the upper limbs. The tremor had synchronous electromyographic pattern, high frequency, low amplitude and short burst duration. In conclusion although the cerebellar and midbrain tremors are caused by involvement of very close anatomical regions and sometimes one type of tremor may become into another, they have quite different clinical and electromyographic presentations.
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PMID:Clinical and electromyographic examinations of patients with midbrain and cerebellar tremor. 1193 92

Patients with nonparkinsonian tremors are the second largest group treated with functional neurosurgery. We summarize the present pathophysiological knowledge of these conditions. Essential tremor (ET) may be due to oscillations within the olivocerebellar circuit. There is experimental evidence from animal models for such a mechanism, and clinical data indicate an abnormal function of the cerebellum in ET. Cerebellar tremor may be closely related to the tremor seen in advanced ET. The malfunction of the cerebellum causes a pathological feed-forward control. Additionally an oscillator within the cerebellum or its input/output pathways may cause cerebellar tremor. Almost nothing is known about the pathophysiology of dystonic tremor. Holmes tremor is based on a nigral and a cerebellar malfunction and presents clinically as the combination of tremor in Parkinson's disease and cerebellar tremor. Neuropathic tremor can be extremely disabling and is thought to be due to an abnormal interaction of the disturbances within the periphery and abnormal cerebellar feedback. Unlike the case of Parkinson's disease, functional neurosurgery of nonparkinsonian tremors is not yet based on a solid pathophysiological background.
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PMID:Pathophysiology of nonparkinsonian tremors. 1194 54

The selection of patients with movement disorders for deep brain stimulation is becoming a common neurological and neurosurgical task. Deep brain stimulation is suitable for different forms of tremor, which can often not be treated with medication. This suitability applies for essential tremor, monosymptomatic tremor at rest, cerebellar or multiple sclerosis tremor, Holmes' tremor, primary writing tremor or tremor in neuropathies. The appropriate selection of patients is critical for the outcome of surgical relief of tremors. Considering the risks of any stereotactic intervention, the following must apply: (1) motor symptoms lead to a relevant disability in activities of daily living, despite optimal medical treatment; (2) biological age of the patient; (3) neurosurgical contraindications; (4) the patient is neither demented nor severely depressed. If these conditions are fulfilled, the individual chances of improvement of the target symptoms need to be checked, based on the following guidelines: (1) the kind of tremor, (2) the natural course of the tremor, (3) the chances for medical treatment in a particular patient, (4) the outcome of surgery in a specific condition, (5) the individual risks for a patient to suffer from complications. The outcome of surgery for tremor depends on the clinical type and distribution. Distal limb tremors are easier to treat than proximal limb tremors. Intention tremor is more difficult to treat than rest or postural tremor. The indication for surgical treatment depends on the analysis of the individual risk-benefit ratio, which also has to take into account the patients' social, professional, and familial background. The patient needs to be well informed about his individual risk-benefit ratio and of alternative treatments, before undergoing stereotactic surgery.
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PMID:Deep brain stimulation for tremor [correction of trauma]: patient selection and evaluation. 1194 63


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