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PubMed2005

The impact of ventrolateral thalamotomy on tremor and voluntary motor behavior in patients with Parkinson's disease.

A preferred target for parkinsonian tremor alleviation is the ventrolateral (VL) thalamus. The goal of the present study is to determine how lesions involving the presumed cerebellar and pallidal recipient areas of the "motor" thalamus would alter the tremor and motor behavior of ten patients with Parkinson's disease (PD). Tremor amplitude, power dispersion (a measure of sharpness of the power spectrum of tremor), and power distribution were quantified using a laser displacement sensor prior to, and a week after, VL thalamotomy. As well, the impact of surgery on tremor seen during movement was quantified in a manual-tracking (MT) task. Tremor-induced noise (a measure of the amount of tremor present during movement) and ERROR (difference between subject's performance and target) were quantified. Finally, bradykinesia was assessed with a rapid alternating movement (RAM) task. Duration, range, and amplitude irregularity of wrist pronation-supination cycles were computed. Both motor tasks were quantified using a highly sensitive forearm rotational sensor. Healthy age-matched control subjects were also tested. Magnetic resonance images with an integrated atlas of thalamic nuclei were used to confirm lesion location. Results show that the lesions were centered upon the posterior portion of the ventral lateral (VLp) nucleus of the thalamus, included the posterior part of the ventral lateral anterior nucleus (VLa), and extended posteriorly to encroach upon the most rostral sector of the sensory ventral posterior nucleus (VPLa). VL thalamotomy significantly decreased tremor amplitude in all cases. Power dispersion was increased significantly so that it became similar to that of control subjects. Changes in power distribution indicate that thalamotomy selectively targeted PD tremor oscillations. Tremor detected during the MT task was also markedly decreased, becoming similar to that of controls. Patients also showed significant decrease in ERROR during MT. RAM duration and range were not significantly modified by the surgery, and patients' performance remained impaired compared to healthy control subjects. Collectively, these results suggest that lesions involving the presumed "cerebellar" and "pallidal" recipient sectors of the motor thalamus do not worsen bradykinesia, suggesting that neural circuits other than the pallido-thalamo-cortical loop may be involved in slowness of movement in PD. A review of alternate pathways is presented.

Aged↗
PubMed2005

Characterization of tremor in phenylketonuric patients.

Tremor of unknown origin is detected in 10-30% of early-treated and in more than 30% late-treated phenylketonuric patients. With the aim of characterizing tremor in phenylketonuria, we carried out a systematic study in 54 patients aged 6 to 37 years. Tremor examination was done by applying the WHIGET Tremor Rating Scale and by accelerometer recording (BYOPAC System MP100WSW). Age at diet onset, IQ test results, concomitant plasma phenylalanine levels and index of dietary control were also studied. Tremor was not observed at rest in any case, but was apparent in 22 patients (40.7%) when carrying out a kinetic task. In 15 patients tremor was also evident during maintenance of a postural task at a frequency ranging between 7.5 and 12.7 Hz. Frequency of tremor was not significantly modified by loading the arms or by increasing muscle contraction. Patients with tremor had a later age at onset of phenylalanine restricted diet (p < 0.001). Other treatment-related variables did not differ between patients with and without tremor. Our results of the neurophysiological examination suggest that tremor in phenylketonuric patients is dependent on a dysfunction of central nervous system networks and may be an index of cerebral damage.

Adolescent↗
PubMed2006

Empirical mode decomposition: a novel technique for the study of tremor time series.

Tremor is a clinical feature characterized by oscillations of a part of the body. The detection and study of tremor is an important step in investigations seeking to explain underlying control strategies of the central nervous system under natural (or physiological) and pathological conditions. It is well established that tremorous activity is composed of deterministic and stochastic components. For this reason, the use of digital signal processing techniques (DSP) which take into account the nonlinearity and nonstationarity of such signals may bring new information into the signal analysis which is often obscured by traditional linear techniques (e.g. Fourier analysis). In this context, this paper introduces the application of the empirical mode decomposition (EMD) and Hilbert spectrum (HS), which are relatively new DSP techniques for the analysis of nonlinear and nonstationary time-series, for the study of tremor. Our results, obtained from the analysis of experimental signals collected from 31 patients with different neurological conditions, showed that the EMD could automatically decompose acquired signals into basic components, called intrinsic mode functions (IMFs), representing tremorous and voluntary activity. The identification of a physical meaning for IMFs in the context of tremor analysis suggests an alternative and new way of detecting tremorous activity. These results may be relevant for those applications requiring automatic detection of tremor. Furthermore, the energy of IMFs was visualized as a function of time and frequency by means of the HS. This analysis showed that the variation of energy of tremorous and voluntary activity could be distinguished and characterized on the HS. Such results may be relevant for those applications aiming to identify neurological disorders. In general, both the HS and EMD demonstrated to be very useful to perform objective analysis of any kind of tremor and can therefore be potentially used to perform functional assessment.

Adult↗
PubMed2004

Quantifying postural tremor in workers exposed to low levels of manganese.

The aim of this study was: (1) To determine the minimum number of characteristics necessary to discriminate between postural tremor recorded in control subjects (CO), in subjects exposed to manganese (MN), and in patients with Parkinson's disease (PD), and (2) to examine the continuum of changes between the three groups examined. Workers previously exposed to Mn (n = 10), patients with PD (n = 10), and control subjects (CO) (n = 11) underwent a clinical examination. Blood Mn was measured at the end of exposure time for the MN group and 12 months later at the beginning of the experiment for all groups. Postural tremor with visual feedback was recorded in the index finger with a laser system. Statistical criteria were used to reduce computed tremor characteristics to a minimal set of reliable discriminating variables. Two variables were retained namely corrected wobble (CW), describing the morphology of the tremor oscillations, and variability ratio (VR), describing proportional power of tremor. Both variables had an overall correct classification rate of 77.4%. Blood Mn levels at the time of the experiment were similar for all groups and had insignificant correlation with tremor variables. However, blood Mn levels in workers which were also measured at the end of exposure time (i.e., 12 months before) showed significant correlation (Spearman's rank coefficient) with both harmonic index (rho = 0.70, P = 0.03) and first maximum of the autocorrelation function (rho = 0.89, P = 0.001). We conclude that (1) the tremor of workers exposed to Mn could be adequately described with only two variables; (2) a continuum of changes between tremor recorded in control subjects, in subjects exposed to Mn and in patients with PD was observed, with the MN group always found in between the control (CO) and the PD groups; (3) while blood Mn levels in workers were back at control levels at the time of the experiment, the effect of Mn on postural tremor was still detected. Thus our method has the potential to detect the effect of Mn on tremor with only two variables even after Mn level in the blood is back to normal values.

Chemical Industry↗
PubMed2003

Thalamic deep brain stimulation for tremor-predominant Parkinson's disease.

OBJECTIVES: Determine the long-term efficacy of thalamic deep brain stimulation (DBS) for treatment of tremor among individuals with tremor-predominant Parkinson's disease (PD).Design. Longitudinal, unblinded assessment of tremor and activities of daily living (ADL) at baseline (pre-surgical), and post-operative intervals of 1, 3, and 12 months, and annually thereafter up to 3 years. METHODS: A clinical series of 19 individuals undergoing placement of a DBS system for treatment of PD-related tremor. A battery of subjective and objective measures of tremor was completed at planned pre- and post-operative intervals. RESULTS: Stimulation was associated with significant improvement on subjective and objective measures of ADL performance, midline tremor, and contralateral upper and lower extremity tremor, including parkinsonian resting and action tremors, over the follow-up period. Ipsilateral tremor showed little or no effect of stimulation after the first 3 months. Antiparkinsonian medication use and stimulation parameters showed little or no change over the course of follow-up. About half (53%) of all individuals reported at least one side effect, generally mild, during the follow-up period, with paresthesias and dysarthria being the most common. A total of two leads required replacement due to (1) infection, and (2) adverse side effects (i.e. burning and tingling with stimulation). CONCLUSION: DBS is associated with stable tremor control in PD. Side-effects are typically easily managed with stimulation adjustments, although in some cases lead replacement may be required.

Aged↗
PubMed2003

Modulation of tremor amplitude during deep brain stimulation at different frequencies.

Rest tremor was quantified in the index finger tip of 16 patients with Parkinson's disease (PD) receiving deep brain stimulation (DBS) of the ventro-intermediate nucleus (Vim) of the thalamus, the subthalamic nucleus (STN), or the internal part of the globus pallidus (GPi) while being off L-dopa for 12h. Clinically, without DBS, tremor amplitude varied from absent to high. Tremor was recorded continuously for about 5 min under three conditions of DBS repeated twice, namely, effective frequency (E), ineffective frequency (I), and no DBS (O). No changes in tremor were observed across conditions in subjects with little or no tremor. However, in subjects with moderate to large amplitude tremor, DBS decreased tremor amplitude to near normal values within a few seconds. Generally, transitions were progressive and occurred with a varying time delay. Occasionally, tremor escaped from control regardless of the stimulation condition considered. In some cases tremor amplitude in one condition appeared to depend on the preceding condition. Finally, the results were reproducible on two consecutive days. We conclude that tremor control with DBS follows specific dynamical rules, which must be compatible with the hypotheses proposed regarding the underlying mechanisms of DBS.

Aged↗
PubMed2000

[Neurophysiologic study of tremor].

Tremor is frequently encountered in neurologic practice. Clinical examination supplies information regarding its approximative frequency, regularity, amplitude, topography and activation conditions. The neurophysiological study helps in confirming the tremor, in differentiating it from other movement disorders like myoclonus, and may provide distinctive features which are important for the aetiological diagnosis. The neurophysiological investigation includes accelerometry, which analyses the mechanics of the movement. Spectral analysis with FFT allows the determination of frequency and amplitude. Accelerometry is always associated with surface EMG of at least two antagonistic muscles. It may show rhythmic bursts, their frequency, duration and activation pattern (alternating or synchronous). This neurophysiological approach to tremor has multiple interests. It may help in differentiating a true rest tremor from a postural tremor seemingly persisting at rest. Brief interruptions or rhythm breaks during distraction manoeuvers are seen in psychogenic tremors. Surface EMG may also demonstrate positive myoclonic bursts, or brief silent periods corresponding to negative myoclonus, sometimes pseudorhythmic, thus appearing clinically like a tremor, but investigations, aetiologies and treatment are different. Several features, especially slow frequency, may suggest a midbrain tremor, thus requiring brain imagery centered around the posterior fossa. Finally, the neurophysiological examination is the only way to demonstrate a primary writing tremor, or a primary orthostatic tremor, the frequency of which is pathognomonic while clinical symptoms are rather misleading.

Diagnosis, Differential↗
PubMedDate not supplied

Validation of a new computerized system for recording and analysing drug-induced tremor in rats.

INTRODUCTION: Certain drugs can induce tremor in small animals and can be used as Parkinson's disease or essential experimental tremor models. However, the use of arbitrary scales for evaluating tremor in experimental models is limited by observer subjectivity. Progress in electronics and computer science has allowed a more precise quantification of tremor. The objective of the present study was to validate a newly developed low-cost method of spectral registration and analysis of tremor in free-moving rats. METHODS: Male Wistar rats, 3-4 months of age, previously placed for 5 min inside a sensor cage, were administered with different doses of eserine (0.25-1.5 mg/kg), oxotremorine (0.25-1.5 mg/kg) or harmaline (7.5-60 mg/kg). Drug-induced tremor was recorded during 10 min using a computerized system composed of force transducers, a signal conditioning circuit, a digitizing interface and a microcomputer. The signal transmitted to the computer was quantified, stored and analyzed for its amplitude and frequency by means of specific programs. RESULTS: Tremor was induced with an amplitude that was dose-dependent for all drugs used. Tremor frequency was dose-dependent for oxotremorine and eserine, but not for harmaline. The performance of the system was compared with that of other systems described in behavioral instrumentation literature. DISCUSSION: The present data indicate that the new system is capable of detecting the tremor induced by drugs, and that the programs used for spectral analysis allow the quantification of the amplitude and the frequency of the tremor in free-moving rats.

Animals↗
PubMed1999

Side-to-side correlation of muscle activity in physiological and pathological human tremors.

OBJECTIVE: Many tremors occur always or often bilaterally. The question arises whether this could be explained by a common source or commonly transmitting pathways or by bilaterally represented, independent structures with the same oscillatory properties. A similar tremor frequency does not provide sufficient information to clarify this question. METHODS: We analyze coherencies between surface electromyographies (EMG) to investigate if bilateral physiologic (PT), essential (ET), Parkinsonian (PD) and orthostatic (OT) tremors originate from a common source for both sides of the body. We show that commonly used techniques to test whether coherencies are significant could lead to false positive results for tremor EMGs. A new estimation procedure is proposed to test EMG tremor time series on their linear independence. We apply this test to bilateral tremors. RESULTS: All measured EMG-pairs in OT (n = 7) were highly coherent between both sides with reproducible coherency values of up to 0.99. All other investigated tremors, i.e. PT and enhanced physiological tremors (EPT, n = 117), ET (n = 76) and PD resting and postural tremors (n = 70) do not show a significant side-to-side correlation. CONCLUSIONS: This finding shows that the pathophysiologies of OT and other pathological tremors are definitely different. Either they have different origins or different kinds of transmitting pathways. The proposed method might also be used to investigate other electrophysiological data and is a helpful, easy to use investigation for a daily clinical routine.

Computer Simulation↗
PubMed2004

Biobehavioral intervention for older adults coping with essential tremor.

Four questions were addressed: (a) does biobehavioral intervention result in within-session reduction of tremor severity; (b) do relaxation and electromyographic (EMG) biofeedback training produce differential effects; (c) do within-session treatment effects generalize to daily performance; and (d) are reductions in tremor severity maintained at follow-up assessment? Three adults, ages 51, 77, and 83, each with a diagnosis of essential tremor (ET), and a long standing history of tremor of the hands uncontrolled by medication, took part. A repeated pre-post-training single-case experimental design embedded within a sequential A--B--C--D design was used; in addition, 1 participant received a return to the B phase. Outcome measures included within-session clinical and self-ratings of tremor severity, surface electromyography (sEMG) of forearm muscles, and daily self-ratings of tremor at home. Tremor was measured while participants engaged in eating or drinking tasks. The Behavioral Relaxation Scale (BRS) served as a process measure to assess relaxation proficiency. Clinical ratings of tremor and the BRS had high interobserver agreement. Visual inspection and statistical tests of single-case data were used to evaluate outcomes. Each participant showed significant within-session improvements on various measures of tremor and improvement during intervention as compared to baseline phases. There were no clear-cut differences between relaxation and biofeedback phases. Improvements declined somewhat at a 12-week follow-up. Relationships among measures of tremor are discussed. Biobehavioral interventions hold promise for older adults coping with ET. Further research is needed using an array of biobehavioral measures to assess intervention outcome.

Aged↗
PubMed1975

Beta-adrenergic mechanisms in action tremor.

To study the mechanisms by which propranolol suppresses essential tremor, accelerometric recordings were made from four normal subjects and eight patients with that tremor, and small amounts of isoproterenol and propranolol were infused intravenously or into one brachial artery. Intra-arterial isoproterenol increased tremor amplitude selectively in that arm in normal subjects and in patients with essential tremor (range, 1.85 to 3.50 with mean 2.74 times the base-line level). Intra-arterial or intravenous propranolol quickly blocked the enhanced action tremor in both groups. It did not simultaneously affect the underlying essential tremor, whereas long-term oral propranolol therapy did diminish the amplitude of the essential tremor in each patient. Peripheral beta-adrenergic tremorogenic receptors function normally even in patients with essential tremor; their function is not necessary for the production of essential tremor, and the efficacy of chronic propranolol therapy in the suppression of essential tremor is not mediated via its peripheral beta-adrenergic blocking action.

Administration, Oral↗
PubMedDate not supplied

A portable hand-held device for quantifying and standardizing tremor assessment.

We describe the results of a hand-held device for quantifying tremor in the upper extremity. The specific aims of the study were to evaluate: (1) the reliability of the device to record tremor frequency and amplitude; (2) the relationship between observer ratings of tremor severity and spectral power derived from the instrument; (3) the effects of limb posture on tremor properties recorded by the instrument; and (4) whether scores from the instrument can discriminate types of tremor with sufficient accuracy to be of diagnostic value. Results from 242 subjects with tremor showed significant effects of limb posture on tremor frequency detected by the device which could not be revealed using traditional observer severity ratings. Subjects with tremor associated with idiopathic Parkinson's disease were distinguished from patients with drug-induced parkinsonian tremor with 83% accuracy. These and other findings on instrument validity demonstrate that tremor assessment can be performed using standard quantitative procedures which overcome many of the limitations inherent in subjective observer ratings. The portability of this instrument, referred to as the Tremorometer, makes it a useful tool for multi-site collaborative studies in community settings.

Aged↗
PubMed1994

Symptomatic and essential palatal tremor. 1. Clinical, physiological and MRI analysis.

Palatal tremor (brief, rhythmic involuntary movements of the soft palate) apparently comprises two different nosological entities: essential palatal tremor (EPT) and symptomatic palatal tremor (SPT). The site of the abnormality in EPT is unknown, whereas SPT is believed to arise from a lesion of the brainstem or cerebellum (within the Guillain-Mollaret triangle). The clinical and physiological properties of these conditions were studied in four patients with EPT and six patients with SPT. Patients with EPT had normal cerebellar function, but those with SPT had clinical signs of cerebellar dysfunction. The palatal movements were consistent with activation of the tensor veli palatini muscle in EPT and of the levator veli palatini muscle in SPT. During sleep, EPT stopped, whereas SPT continued with only slight variations in the tremor rate. The cycle of palatal tremor could not be reset by stimulation of trigeminal afferents in either EPT or SPT patients, and Valsalva's manoeuvre did not consistently affect the rhythm of the tremor in either group. The palatal tremor cycle exerted remote effects on the tonic electromyographic activity of the upper and lower extremities only in patients with SPT. These effects were present only on the side of the cerebellar signs (opposite the side with the enlarged inferior olive) in patients with a unilateral syndrome. Essential palatal tremor patients had only polysynaptic brainstem reflex abnormalities, whereas SPT patients had abnormalities of monosynaptic, oligosynaptic and polysynaptic brainstem reflexes. Magnetic resonance imaging showed no evidence of structural abnormalities in EPT patients, but SPT patients had a hyperdense signal of the ventral upper medulla (the region of the inferior olive) on T2-weighted images. These observations support the hypothesis that EPT and SPT are two different diseases. In SPT, cerebellar dysfunction ipsilateral to the palatal tremor may be due, in part, to abnormal function of the contralateral hypertrophic inferior olive. The proposed basis of SPT is a disturbance of electrotonic coupling between the cells of the inferior olive induced by a lesion of the dentato-olivary pathway. Similar mechanisms could be responsible for postural tremors in general. The pathophysiological basis of EPT remains unknown.

Adult↗
PubMed2001

Stereotactic lesional surgery for the treatment of tremor in multiple sclerosis: a prospective case-controlled study.

The effect of stereotactic lesional surgery for the treatment of tremor in multiple sclerosis was examined in a prospective case-controlled study. Surgery was not undertaken in 33 patients (72% of 46 cases referred for stereotactic surgery), two of whom died within 4 months of referral. Twenty-four multiple sclerosis patients were included in the study; 13 underwent surgery and were matched against 11 controls on the basis of age, sex, expanded disability system scores (EDSS) and disease duration. Assessments were carried out at baseline/preoperatively, and then 3 and 12 months later; these included accelerometric and clinical ratings of tremor, spirography, handwriting, a finger-tapping test, nine-hole peg test, tremor-related disability, general neurological examination, Barthel Activities of Daily Living (ADL) Index of general disability, EDSS, a 0-4 ataxia scale, Mini-Mental State (MMS) examination, speech and swallowing assessments and grip strength. Postoperative MRI scans demonstrated that tremor could be attenuated by lesions centred on the thalamus in seven cases, on the zona incerta in five cases and in the subthalamic nucleus in one case. Two patients developed hemiparesis and in two cases epilepsy recurred. Two surgical patients and one control patient died between the 3 and 6 months assessments. Both groups had a significant deterioration in EDSS but not Barthel ADL Index scores at 1 year, but the difference between the groups was not significant. Similarly, no differences between the groups' rates of deterioration of speech or swallowing or MMS were found. Significant improvements in contralateral upper limb postural (P2) and kinetic tremors, spiral scores and head tremor were detected at 3 and 12 months after surgery (but not handwriting or nine-hole peg test performance). Tremor-related disability and finger-tapping speed were also significantly better 12 months after surgery, the latter having significantly worsened for the control group. A 3 Hz 'filter' for postural (P2) upper limb tremor was detected by accelerometry/spectral analysis above which tremor was always abolished and at or below which some residual tremor invariably remained. Criteria for selecting multiple sclerosis patients for this form of surgery are discussed.

Activities of Daily Living↗
PubMed2004

Effects of subthalamic nucleus stimulation and medication on resting and postural tremor in Parkinson's disease.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) and antiparkinsonian medication have proved to be effective treatments for tremor in Parkinson's disease. To date it is not known how and to what extent STN DBS alone and in combination with antiparkinsonian medication alters the pathophysiology of resting and postural tremor in idiopathic Parkinson's disease. The purpose of this study was to examine the effects of STN DBS and antiparkinsonian medication on the neurophysiological characteristics of resting and postural hand tremor in Parkinson's disease. Resting and postural hand tremor were recorded using accelerometry and surface electromyography (EMG) from 10 Parkinson's disease patients and 10 matched control subjects. The Parkinson's disease subjects were examined under four treatment conditions: (i) off treatment; (ii) STN DBS; (iii) medication; and (iv) medication plus STN DBS. The amplitude, EMG frequency, regularity, and 1-8 Hz tremor-EMG coherence were analysed. Both STN DBS and medication reduced the amplitude, regularity and tremor-EMG coherence, and increased the EMG frequency of resting and postural tremor in Parkinson's disease. STN DBS was more effective than medication in reducing the amplitude and increasing the frequency of resting and postural tremor to healthy physiological levels. These findings provide strong evidence that effective STN DBS normalizes the amplitude and frequency of tremor. The findings suggest that neural activity in the STN is an important modulator of the neural network(s) responsible for both resting and postural tremor genesis in Parkinson's disease.

Adult↗
PubMed2001

Concepts and methods in chronic thalamic stimulation for treatment of tremor: technique and application.

OBJECTIVE: To rationalize the technique and reduce the costs associated with chronic deep brain stimulation of the thalamus for treatment of refractory tremor. METHODS: The efficacy and safety of a modification in surgical techniques was prospectively assessed in 94 patients with tremor. Bilateral electrodes were implanted in 29 patients, and 65 patients received unilateral implants. Forty-five patients had Parkinson's disease tremor, 42 patients had essential tremor, and 7 patients had kinetic tremors of different causes. In all instances, intraoperative stimulations to analyze the thresholds of intrinsic and extrinsic responses were performed directly with the implanted leads. The electrodes were repositioned until satisfactory results were achieved. The pulse generators were implanted directly after the first step in the same operative session. Patients were not subjected to interoperative test stimulation trials. RESULTS: Postoperative improvement of tremor at a mean follow-up of 11.9 months was rated as excellent in 47 patients (50%), marked in 37 patients (39%), moderate in 8 patients (9%), and minor in 2 patients (2%). There was no persistent morbidity related to surgery. In patients with Parkinson's disease, the symptomatic improvement of tremor was rated as excellent in 51% of patients, marked in 36%, moderate in 11%, and minor in 2%. In patients with essential tremor, symptomatic outcome was classified as excellent in 57% of patients, marked in 36%, moderate in 5%, and minor in 2%. Six of the seven patients with kinetic tremor achieved marked symptomatic improvement, and one patient experienced moderate improvement. Forty patients experienced stimulation-related side effects. Side effects were mild in general, and they were reversible with a change in electrical parameters. They occurred more frequently in patients who had bilateral stimulation. CONCLUSION: Excellent to marked improvement of tremor is achieved in the majority of patients with physiological target determination via implanted leads in thalamic deep brain stimulation. Interoperative test stimulation trials are unnecessary. Modifications in technique may help to reduce the costs of the related hospital stay.

Adult↗
PubMed2001

Physiological tremor in human subjects with X-linked Kallmann's syndrome and mirror movements.

Human physiological tremor consists of mechanical-reflex and neurogenic components. The origin of the neurogenic component, classically detected in the frequency range 7-12 Hz, has been much debated. We have studied six subjects with X-linked Kallmann's syndrome (XKS) and mirror movements. In these subjects unilateral magnetic brain stimulation results in abnormal bilateral EMG responses. Furthermore, abnormal sharing of central nervous inputs between the left and right motoneurone pools results in both abnormal motor unit synchronisation between left and right EMGs and abnormal sharing of long but not short-latency cutaneomuscular reflexes. XKS subjects with mirror movements thus provide a model for studying the central origin of physiological tremor. During sustained co-extension of the left and right index fingers, simultaneous finger tremor and extensor indicis (EI) EMGs were recorded and cross-correlated. The tremor and EMG signals were also subjected to time and frequency domain analysis.Results of frequency domain analysis between ipsilateral finger tremor and EI EMG were similar for both control and XKS subjects. However, in contrast to the controls, short-term synchronisation of left and right EI motor unit activity and significant coherence between left and right EMG, left and right tremor, left EMG and right tremor and right EMG and left tremor were found in XKS subjects. The frequency range (6-40 Hz) and coherence values between left and right were similar to ipsilateral coherence values of rectified EMG and tremor. These data provide strong evidence to support the hypothesis that the neurogenic component of physiological tremor is supraspinal in origin and ranges from 6 to 40 Hz.

Adult↗
PubMed1992

Alterations of benzodiazepine receptor binding in tremor rats with absence-like seizures.

Tremor rats begin to exhibit clinical or electrical absence-like seizures after 6 weeks of age, and by 14 weeks of age, all have seizures. Central-type benzodiazepine receptor binding was investigated in tremor rats and control rats, aged 4 weeks and 16 weeks. Significantly lower benzodiazepine receptor density and no differences in affinity were found in the hippocampus of the tremor rats in comparison with that of control rats at both ages. This abnormality is considered to be due to a tremor gene and may be the cause of absence-like seizures in tremor rats. A significantly lower receptor density was found in the cerebellum at 4 weeks of age in the tremor rats than in the control rats. These changes may be related to tremorous movements in the tremor rats. Receptor density was significantly lower in the brainstems of tremor rats and control rats at 16 weeks of age than at 4 weeks of age, and the decrease was more marked in control rats. These facts may reflect a reduced decrease in the response to the dysfunction of gamma-aminobutyric acidergic neurons, or the function of the gamma-aminobutyric acid/benzodiazepine receptor system may be secondarily increased to suppress seizures in 16-week-old tremor rats.

Animals↗