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

We studied the influence of proprioceptive and visual feedback on cerebellar tremor which occurred after arm perturbations and after voluntary elbow flexions. Cerebellar tremor was produced in monkeys by reversibly cooling through two probes implanted lateral and medial to the dentate nucleus. Cerebellar tremor was synchronized in different trials to torque pulse onset and to the end, but not the start, of voluntary movements. Addition of loads to the handle held by the monkey (increases in spring stiffness, viscosity, constant torque, and inertial load) changed the amplitude and frequency of tremor that follows arm perturbations or voluntary movements in the same way. In both situations EMG activity in each cycle of tremor followed stretch of its own muscle and attained a peak near peak velocity irrespective of the mechanical load. Removal of visual feedback did not alter the characteristics of the tremor or the associated EMG activity. We concluded that cerebellar intention tremor, which occurs when attempting to hold the arm in an intended position, is driven by stretch-evoked peripheral feedback and not by voluntary corrections based on vision.
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PMID:Dependence of cerebellar tremor on proprioceptive but not visual feedback. 671 45

Abnormal movements or dyskinesias are associated with hyperpathia and hyperalgesia in a number of conditions such as post amputation jumping stumps pseudothalamic syndromes following cerebro vascular accidents and in some cases of demyelinating diseases. Intermittent electrical stimulation of the specific sensory nucleus of the thalamus (I.T.S.) controls at the same time pain and dyskinesias with the same long lasting effect. In some cases where dyskinesias are associated with sensory deafferentation, but not with chronic pain or hyperpathia, the same positive effect of thalamic stimulation on the control of abnormal movements is achieved while in other cases of tremor or dyskinesias without sensory deafferentation such as parkinsonism, intention tremor etc.. the efficacy of I.T.S. is nil. Hence, discriminative sensory deaffrentation is the common link between the cases of tremor or dyskinesias that use to respond to I.T.S. which is up to now the only therapy of proven efficacy in such conditions.
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PMID:[Treatment of various dyskinesias by intermittent thalamic stimulation]. 698 26

Application of the microelectrode technique in human stereotactic surgery, which is especially important for tremor control, is now routine for the procedure in our surgical theater. Neurons responsible for tremor generation can very delicately and exactly be identified within the ventralis intermedius nucleus (Vim) of the thalamus, which automatically determines the location of the minimum required thermocoagulation lesion to abolish tremor. Neurons with rhythmic burst discharges, which are synchronus in phase to the peripheral tremor, are organized in delicate somatotopic fashion within the Vim. Electrical stimulation of the neuron area through this microelectrode usually inhibits tremor of the corresponding area and a small thermocoagulation lesion, usually 3 mm in diameter, permanently abolishes tremor. These three findings, i.e., existence of rhythmic bursts, effect of the stimulation and surgical lesion, are the same in parkinsonian tremor, postural tremor and intention tremor. Physiological interpretation of different types of tremor will be proposed. In the cases of idiopathic neck tremor, a single Vim neuron corresponded to four neck muscles, i.e., bilateral sternocleidomastoid muscle (SCM) and bilateral posterior neck muscles, and most markedly to the controlateral posterior neck muscle and the ipsilateral SCM. Instrumentation of microstereoencephalotomy is also explained.
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PMID:Importance of microstereoencephalotomy for tremor alleviation. 702 43

Patients with parkinsonian tremor and rigidity and cerebellar intention tremor can be effectively treated with thalamic lesions provided that an accurate neurophysiologic method is employed to compensate for individual spatial variability of subcortical structures. The method described employs a technique of microelectrode recording in which the homuncular organization in ventralis posterior is explored and gives information as to the ideal laterality of lateral thalamic nuclear mass lesions for the treatment of tremor. This procedure has been used in 11 patients, 9 with Parkinson's disease and 2 with cerebellar intention tremor with good results and no complications to date.
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PMID:Microelectrode recording for the somatotopic placement of stereotactic thalamic lesions in the treatment of parkinsonian and cerebellar intention tremor. 702 45

Resting and postural tremor, intention and action tremor, clonus and the cogwheel phenomenon in Parkinson's disease have been characterised in terms of frequency content using spectral analysis. Typical resting tremor ranged in peak frequency from 4 to 5.3 HZ with tremor in each individual varying only by 0.2 to 0.3 HZ. The peak frequency of postural tremor ranged between 6 and 6.2 HZ. Intention tremor appeared to be an exaggeration of postural tremor. Clonus evoked by active or passive stretch at the wrist had a frequency of 6 HZ and appeared to be a continuation of postural tremor. The cogwheel phenomenon was found at frequencies between 6 and 6.5 HZ and between 7.5 to 9 HZ. Action tremor was indistinguishable from the cogwheel phenomenon. Some patients had either a symptomatic resting tremor with a concurrent 6 HZ component of smaller amplitude or a symptomatic postural tremor with a 4-5 HZ component of smaller amplitude. These combinations would produce two peaks in the power spectrum. When this occurred EMG studies showed that individual muscles had two types of rhythmical activation suggesting that the tremors have separate mechanisms. Likewise some patients had a symptomatic 6 HZ tremor on posture with a second peak at 8-10 HZ in the physiological band. Therefore, the 6 HZ postural tremor is not an exaggeration of physiological tremor. On the basis of wave form and frequency similarities postural tremor, the low frequency type of active or passive cogwheeling, intention tremor and clonus possibly involve a common spinal mechanism. Higher frequency cogwheel phenomenon and action tremor may be an exaggeration of physiological tremor. More than 80% of patients with Parkinson's disease manifest tremors at both 4-5 HZ and 6 HZ. This combination would appear to be the strongest objective criterion for the diagnosis of basal ganglia disease.
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PMID:Tremor, the cogwheel phenomenon and clonus in Parkinson's disease. 727 68

Chronic or contingent electrical stimulation at various sites in the region of the ventrolateral nucleus of the thalamus can suppress contralateral intention tremor and the resting tremor seen in Parkinson's disease and idiopathic tremor. The procedure appears to carry less risk, in producing physical or cognitive impairment, than stereotactic ablation. However, the procedure has been tried in few centres to date and long term follow-up studies are needed to place this treatment in its true clinical perspective. It is important to assess patients' needs very carefully to ensure that their functional objectives will be best met by treatments of this kind, and that the requirement for regular monitoring and periodic reassessment can be fully met during long term follow-up.
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PMID:Implants for tremor. 763 78

It has been estimated that about 75% of patients diagnosed with multiple sclerosis (MS) have tremor which can be exceedingly disabling. The most common tremor observed in patients with MS is a cerebellar intention tremor ('kinetic tremor') although postural tremor ('static tremor') is also common and often extremely incapacitating. Currently there is no effective medical treatment for the tremor of MS which, in some severe cases, may be abolished by stereotactic thalamotomy. It was reported recently that extracranial application of brief AC pulsed electromagnetic fields (EMFs) in the picotesla (pT) range produced improvement in motor and cognitive functions in patients with MS. The present communication concerns three MS patients with a chronic progressive course of the disease (mean age: 39.3 +/- 8.3 years; mean duration of illness: 11.3 +/- 3.2 years) in whom brief external applications of pulsed EMFs of 7.5 pT intensity reduced intention and postural tremors resulting in significant functional improvement. The report suggests that these extremely low intensity EMFs are beneficial also in the treatment of tremors in MS and that this treatment may serve as an alternative method to stereotactic thalamotomy in the management of tremor in MS. The mechanisms by which EMFs attenuate the tremors of MS are complex and are thought to involve augmentation of GABA and serotonin (5-HT) neurotransmission in the cerebellum and its outflow tracts.
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PMID:Weak electromagnetic fields attenuate tremor in multiple sclerosis. 774 62

We described two types of involuntary movement accompanied with a well-located thalmaic lesion shown by MR imaging in five patients. All patients had the involuntary movements of an upper limb contralateral to the thalamic lesion. Two patients (1 and 2) had choreoathetosis that became most prominent when their index finger approached their nose, where irregular and dysynchronous oscillation occasionally superimposed. This choreoathetosis was differentiated from pseudoathetosis caused by disturbance of proprioceptive sensations. The MRI lesion was located at the middle level of thalamus including nucleus centromedianus. The other three patients (3, 4 and 5) had a regular and rhythmic oscillation in their forearm. The oscillation began to appear after their index finger reached their nose on finger-to-nose test. We considered the oscillation as a postural tremor based on its rhythmicity and regularity. Patient 4 had additional tremor in movement. Their postural tremor continued while the arm kept the position. Surface electromyogram showed the reciprocal discharges between the forearm extensor and flexor muscles with a frequency of 3 to 4 Hz. This tremor was not accentuated during limb movement toward the nose nor was coarse, and was distinguished from intention tremor described by Charcot and Dejerine. This tremor was also different from hyperkinesis volitionnelle and movement oppositionist. The "rubral tremor" differed from the tremor shown in our cases for a lack of resting tremor. The responsible lesion shown by MRI located at caudal posterior thalamus including pulvinar in patient 3, or located at the upper level of thalamus in patient 4 and case 5 that was more rostral than the lesion of the choreoathetosis cases. In cases of cerebrovascular accidents, both types of involuntary movement appeared after several months from the stroke. This delayed appearance suggests that these involuntary movements were the result not only of functional disturbance of thalamus, but of secondary repairing mechanism occurring at the lesion.
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PMID:[Involuntary movements caused by thalamic lesion]. 799 88

Seven Domestic shorthair cats with a lysosomal storage disorder analogous to human Niemann-Pick disease type C, from a breeding colony were studied to characterize the neurological manifestations of this disorder. Affected cats were identified by means of liver biopsies at 4 to 6 weeks of age. Neurological examinations were performed at 2 week intervals from the onset of clinical signs. All cats displayed signs referrable to the cerebellum, with a subtle intention tremor noticed initially at 8 to 12 weeks of age; the disease was rapidly progressive. The tremor became more pronounced, menace response was lost, and severe dysmetria and ataxia developed. Three cats also had signs referrable to other areas of the central nervous system. Cats died or were euthanized between 12 and 43 weeks of age. Pathological findings included accumulation of substrate within neurons throughout the central nervous system, and axonal spheroid formation. The clinical and pathological findings in these cats are comparable to those in the human form of the disease.
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PMID:Neurological manifestations of Niemann-Pick disease type C in cats. 804 74

Tremor has been rarely described as a manifestation of stroke. A 21-year-old left-handed man developed severe action tremor of his distal left upper extremity and hand following a right parieto-occipital intracerebral hemorrhage. Strength of the left upper extremity improved gradually during a 3-month period but a severe action tremor developed. The patient was treated with the cardioselective beta-blocking agent, metoprolol, initially for elevated blood pressure and tachycardia at 25 mg twice daily for approximately 2 months. Metoprolol was then increased at weekly intervals by 25mg twice daily to a total of 100mg twice daily. Tremor intensity decreased clinically and graphically as monitored by a trace test by having the patient attempt to trace a horizontal and vertical axis and scoring the errors. The scores declined weekly from the first week (4,347), second week (3,786), third week (1,088), to the fourth week (484). No adverse cognitive or cardiopulmonary effects were noted. Action tremor should be considered as one of the movement disorders caused by hemorrhagic cerebral infarction. This case responded well to treatment with metoprolol.
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PMID:Metoprolol for action tremor following intracerebral hemorrhage. 808 22


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