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Tremor Amplitude (tremor + amplitude)

Distribution by Scientific Domains

Medical Sciences	85%

Selected Abstracts

Searching for a significant correlation between volcanic tremor amplitude and SO2 emissions at Mount Etna volcano, Sicily

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2000
Sabrina Leonardi
Summary A strong correlation between the amplitude of volcanic tremor and the flux of SO2 has been found at Mount Etna volcano, Sicily, corresponding to enhanced volcanic activity in the period 1987,1995. We therefore suggest that tremors and SO2 emissions have a common physical origin linked to the magma dynamics of the volcano. [source]

Deep brain stimulation and medication for parkinsonian tremor during secondary tasks

MOVEMENT DISORDERS, Issue 8 2007
Molly M. Sturman PhD
Abstract This study examined the efficacy of subthalamic nucleus (STN), deep brain stimulation (DBS), and medication for resting tremor during performance of secondary tasks. Hand tremor was recorded using accelerometry and electromyography (EMG) from 10 patients with Parkinson's disease (PD) and ten matched control subjects. The PD subjects were examined off treatment, on STN DBS, on medication, and on STN DBS plus medication. In the first experiment, tremor was recorded in a quiet condition and during a cognitive task designed to enhance tremor. In the second experiment, tremor was recorded in a quiet condition and during isometric finger flexion (motor task) with the contralateral limb at 5% of the maximal voluntary contraction (MVC) that was designed to suppress tremor. Results showed that: (1) STN DBS and medication reduced tremor during a cognitive task that exacerbated tremor, (2) STN DBS normalized tremor frequency in both the quiet and cognitive task conditions, whereas tremor amplitude was only normalized in the quiet condition, (3) a secondary motor task reduced tremor in a similar manner to STN DBS. These findings demonstrate that STN DBS still suppresses tremor in the presence of a cognitive task. Furthermore, a secondary motor task of the opposite limb suppresses tremor to levels comparable to STN DBS. © 2007 Movement Disorder Society [source]

Gabapentin can improve postural stability and quality of life in primary orthostatic tremor

MOVEMENT DISORDERS, Issue 7 2005
Julian P. Rodrigues MD
Abstract Primary orthostatic tremor (OT) is characterized by leg tremor and instability on standing. High frequency (13,18 Hz) tremor bursting is present in leg muscles during stance, and posturography has shown greater than normal sway. We report on an open-label add-on study of gabapentin in 6 patients with OT. Six patients were studied with surface electromyography, force platform posturography, and a modified Parkinson's disease questionnaire (PDQ-39) quality of life (QOL) scale before and during treatment with gabapentin 300 mg t.d.s. If on other medications for OT, these were continued unchanged. Of the 6 patients, 4 reported a subjective benefit of 50 to 75% with gabapentin, 3 of whom showed reduced tremor amplitude and postural sway of up to 70%. Dynamic balance improved in all 3 patients who completed the protocol. QOL data from 5 patients showed improvement in all cases. No adverse effects were noted. Gabapentin may improve tremor, stability, and QOL in patients with OT, and symptomatic response correlated with a reduction in tremor amplitude and postural sway. The findings confirm previous reports of symptomatic benefit with gabapentin and provide justification for larger controlled clinical trials. Further work is required to establish the optimal dosage and to validate the methods used to quantify the response to treatment. © 2005 Movement Disorder Society [source]

Validation for tremor quantification of an electromagnetic tracking device

MOVEMENT DISORDERS, Issue 2 2001
Padraig E. O'Suilleabhain MB
Abstract An electromagnetic tracking system was used to record arm motion in subjects with Parkinson's disease (n = 23), essential tremor (n = 28) or without neurological disease (n = 4). Tremor magnitude was calculated by averaging the three-dimensional displacement of individual tremor bursts. Tremor magnitude calculated in this manner was quite closely correlated with a clinician's estimate (r = 0.88 and 0.86 for Parkinsonian and essential tremors, respectively) and was reproducible (r = 0.93 for repeated recordings). The accuracy of the device and algorithm was confirmed by mechanically generating oscillations of known magnitudes and frequencies. This device is adaptable for quantifying different types of tremors and its accuracy is easy to verify. Because position rather than acceleration is tracked, tremor amplitude can be stated in readily comprehensible units. © 2001 Movement Disorder Society. [source]

Computerized Tremor Analysis of Valproate-induced Tremor: A Comparative Study of Controlled-release versus Conventional Valproate

EPILEPSIA, Issue 2 2005
Martina Rinnerthaler
Summary:,Purpose: Valproate (VPA) induces postural tremor in 6,45% of patients. The characteristics of VPA-induced tremor have not yet been quantitatively assessed, and it is not known whether tremor prevalence or severity is affected by VPA formulation (controlled-release CR-VPA vs. conventional VPA). The aim of this study was quantitatively to assess tremor in epilepsy patients receiving VPA and to compare the effects of two VPA formulations (CR-VPA vs. VPA) on tremor severity. Methods: In a prospective study, 18 consecutive patients with newly diagnosed focal or generalized epilepsy were assigned to receive alternately either VPA (n = 10) or CR-VPA (n = 8) monotherapy. Computerized tremor analysis was performed at baseline 1 day before initiating VPA treatment and repeated after a seizure-free period of ,8 weeks, during which VPA doses had remained stable. Rest and postural tremor were recorded by accelerometry, and surface electromyograms (EMGs) were recorded from the wrist flexors and extensors. Results: At baseline, the two groups had similar postural tremor amplitudes. At follow-up, the CR-VPA group had remained at the same level, whereas VPA subjects exhibited a significant increase in tremor amplitudes (p < 0.05) despite comparable VPA doses and comparable plasma VPA concentrations at the time of tremor testing. Conclusions: This is the first study to assess quantitatively VPA-induced tremor by standardized tremor analysis. These results suggest that CR-VPA may cause less tremorigenic activity as compared with standard VPA. The mechanisms underlying this difference are unclear but may include greater peak,trough variation with VPA than with CR-VPA. [source]