Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0040822 (tremor)
 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

H2(15)O PET activation studies enable the brain systems involved in controlling different aspects of motor function to be defined. In Parkinson's disease (PD) freely chosen limb movements are performed slowly. This bradykinesia is associated with selective underactivity of the supplementary motor area and dorsal prefrontal cortex, frontal association areas that receive subcortical input principally from the basal ganglia. At the same time there is compensatory overactivity of the lateral premotor and parietal cortex, areas that have a primary role in facilitating motor responses to visual and auditory cues. This finding explains why PD patients find it easier to perform cued as opposed to freely chosen actions. Levels of activation of the supplementary motor area and dorsal prefrontal cortex in PD can be restored with dopaminergic medication, implants of fetal mesencephalic tissue, internal pallidotomy or high frequency electrical subthalamic stimulation. Activation studies suggest that Parkinsonian rest tremor arises from a combination of inappropriate overactivity of cerebellar connections and loss of dopaminergic function. When tremor is relieved by ventral thalamotomy or thalamic stimulation this cerebellar overactivity is corrected but at the expense of reducing levels of primary motor cortex activation. It has been hypothesised that dyskinesias in PD arise due to altered dopamine receptor binding following chronic exposure to levodopa stimulation. Functional imaging findings, however, are against this hypothesis and rather suggest that downstream increases in basal ganglia opioid neurotransmission are more likely to be relevant.
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PMID:Functional imaging of Parkinson's disease: is it possible to detect brain areas for specific symptoms? 1037 Sep 8

While voluntary movement blocks Parkinsonian rest tremor (PT), essential tremor (ET) is enforced by postural and/or kinetic action. We studied the effect of contralateral externally- and internally triggered hand movement on PT and ET to investigate the transhemispheric influences on tremor genesis. We measured the changes of tremor peak frequency power after flash signal (F), flash triggered (FM) and self-paced (SPM) movement of the contralateral hand in nine PT and seven ET patients using accelerometer. PT significantly decreased both during FM and SPM tasks, suggesting that it is generated by a constant subcortico-cortical network, which includes higher order motor areas. Intensity of ET showed a remarkable intra- and interindividual variability both during FM and SPM reflecting a different generator circuitry with variable functional connections.
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PMID:Contralateral voluntary hand movement inhibits human parkinsonian tremor and variably influences essential tremor. 1500 81

Classical Parkinsonian rest tremor typically fluctuates over time and can be provoked by stressful situations. We quantified and compared the influence of different provocation methods on classical rest tremor severity. The effect of counting backwards from 100, tapping of the contralateral foot and a Stroop test on the Unified Parkinson's Disease Rating Scale (UPDRS) III rest tremor scores and the accelerometrically measured tremor amplitudes (total power) were analyzed in 18 patients with Parkinson's disease and a Type I tremor. Each of the three provocation methods increased the UPDRS III rest tremor score by 1-2 and the total power by 1-2 orders of magnitude compared with baseline (P < 0.001). The maximal effect was reached on average after 2-3 minutes of provocation. The effects were not significantly different. Provocations clearly influence the result of clinical rest tremor ratings, with the kind of provocation being of minor importance. We therefore suggest that each assessment of Parkinsonian rest tremor should include a systematic provocation and this should be formally included in future versions of the UPDRS.
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PMID:Provocation of Parkinsonian tremor. 1838 37

Tremor in Parkinson's disease (PD) is generated by an oscillatory neuronal network consisting of cortex, basal ganglia and thalamus. The subthalamic nucleus (STN) which is part of the basal ganglia is of particular interest, since deep brain stimulation of the STN is an effective treatment for PD including Parkinsonian tremor. It is controversial if and how the STN contributes to tremor generation. In this study, we analyze neuronal STN activity in seven patients with Parkinsonian rest tremor who underwent stereotactic surgery for deep brain stimulation. Surface EMG was recorded from the wrist flexors and extensors. Simultaneously, neuronal spike activity was registered in different depths of the STN using an array of five microelectrodes. After spike-sorting, spectral coherence was analyzed between spike activity of STN neurons and tremor activity. Significant coherence at the tremor frequency was detected between EMG and neuronal STN activity in 76 out of 145 neurons (52.4%). In contrast, coherence in the beta band occurred only in 10 out of 145 neurons (6.9%). Tremor-coherent STN activity was widely distributed over the STN being more frequent in its dorsal parts (70.8-88.9%) than in its ventral parts (25.0-48.0%). Our results suggest that synchronous neuronal STN activity at the tremor frequency contributes to the pathogenesis of Parkinsonian tremor. The wide-spread spatial distribution of tremor-coherent spike activity argues for the recruitment of an extended network of subthalamic neurons for tremor generation.
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PMID:Tremor-correlated neuronal activity in the subthalamic nucleus of Parkinsonian patients. 1863 49

Functional magnetic resonance imaging studies suggest that different subcortico-cortical circuits control different aspects of Parkinsonian rest tremor. The basal ganglia were proposed to drive tremor onset, and the cerebellum was suggested to be responsible for tremor maintenance ("dimmer-switch" hypothesis). Although several electrophysiological correlates of tremor have been described, it is currently unclear whether any of these is specific to tremor onset or maintenance. In this study, we present data from a single patient measured repeatedly within 2 years after implantation of a deep brain stimulation (DBS) system capable of recording brain activity from the target. Local field potentials (LFPs) from the subthalamic nucleus and the scalp electroencephalogram were recorded 1 week, 3 months, 6 months, 1 year, and 2 years after surgery. Importantly, the patient suffered from severe rest tremor of the lower limbs, which could be interrupted voluntarily by repositioning the feet. This provided the unique opportunity to record many tremor onsets in succession. We found that tremor onset and tremor maintenance were characterized by distinct modulations of subthalamic oscillations. Alpha/low-beta power increased transiently immediately after tremor onset. In contrast, beta power was continuously suppressed during tremor maintenance. Tremor maintenance was additionally associated with subthalamic and cortical power increases around individual tremor frequency. To our knowledge, this is the first evidence of distinct subthalamic LFP modulations in tremor onset and tremor maintenance. Our observations suggest the existence of an acceleration signal for Parkinsonian rest tremor in the basal ganglia, in line with the "dimmer-switch" hypothesis.
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PMID:Longitudinal Recordings Reveal Transient Increase of Alpha/Low-Beta Power in the Subthalamic Nucleus Associated With the Onset of Parkinsonian Rest Tremor. 3089 40