Electrophysiologic transition from physiologic tremor to essential tremor.

We electrophysiologically examined the transition from physiologic tremor to essential tremor in people at risk for familial essential tremor. Two healthy people from different families with hereditary essential tremor were studied on multiple occasions. A 23-year-old man was studied in 1995, 1997, and 2004, and a 44-year-old woman was studied in 1993, 1995, 1997, and 2003. Hand acceleration and forearm electromyographic readings were measured with and without 300-g loading to determine the characteristic frequency-invariant motor unit entrainment of essential tremor. Clinically and electrophysiologically, the man and woman had normal tremor until the last examination, when both exhibited a fine tremulousness in the outstretched hands and frequency-invariant motor unit entrainment at 7.5 and 6.5 Hz, respectively. At no time did either patient exhibit a prominent 8-12 Hz component of physiologic tremor. Essential tremor in young adults may begin at frequencies less than 8-12 Hz, and this electrophysiologic abnormality is detectable when clinical examinations reveal only questionably abnormal tremor. More young adults at risk for essential tremor must be studied to determine whether initial frequencies less than 8 Hz are the rule or the exception. Nevertheless, the data from our 2 patients demonstrate that a prominent 8-12 Hz component of physiologic tremor does not always precede the development of essential tremor; therefore, the origins of essential tremor and the 8-12 Hz component of physiologic tremor may be different.     

Intention tremor of the head in patients with essential tremor.

Patients with essential tremor (ET) have kinetic arm tremor; this tremor can also have an intentional component. We are unaware of reports of intention tremor of the head in ET. Our aims were to describe, provide electrophysiological data and video documentation of, and estimate the prevalence of intention tremor of the head in our sample. Ten (9.0%; 95% confidence interval = 4.7%-14.3%) of 111 patients had intention tremor of the head; in 7 it involved the neck and in 3 the chin. These patients trended toward having more severe kinetic arm tremor and they had more severe intention tremor of the arms. These observations provide further support for the evolving view that the cerebellum may be involved in ET.     

Imaging essential tremor

To investigate over time changes in striatal dopamine transporter (DAT), we performed two sequential N‐ω‐fluoropropyl‐2β‐carbomethoxy‐3β‐(4‐iodophenyl) tropane single photon computed tomography (SPECT) scans in 20 subjects with essential tremor (ET), in 13 with Parkinson disease (PD) and in 23 healthy controls (HC, one scan only). We also performed an [^99mTc]ethyl cysteinate dimer bicisate SPECT exam for regional brain network analysis in 9 ET, in a second group of 18 PD (9 with tremor, tPD and 9 akinetic‐rigid dominant, arPD) and in 8 HC. PD subjects had a reduced DAT binding in comparison to ET and HC with an annual decline rate of 7.3% in the contralateral putamen. There were no mean uptake differences between ET and HC at baseline and no uptake loss over time in ET. A discriminant analysis grouped 30% (first scan) and 5% (second scan) of ET as PD and a partition analysis showed overlap between ET and PD for caudate nucleus uptake. Spatial covariance analysis revealed that the expression of the PD‐related regional pattern separated both tPD and arPD from ET and HC. In conclusion, PD and ET do not share a common pattern of dopaminergic loss over time. However, mild impairment of dopamine transporter in the caudate nucleus may contribute to tremor onset in ET. © 2010 Movement Disorder Society     

Alcohol consumption of patients with essential tremor

Most patients with essential tremor experience a transient improvement after ingesting a small amount of alcohol. It has been accordingly suggested that essential tremor patients may have an increased risk of developing alcoholism. In this study, the frequency and amount of alcohol intake of essential tremor patients were found to be largely similar to the drinking habits of a control sample from the general population. This indicates that essential tremor does not generally augment alcohol consumption, nor is it a common cause of alcoholism.     

Bilateral primary writing tremor

Primary writing tremor is a task-specific tremor that is considered to be unilateral. We report a 59-year-old man with a 5-year history of a typical primary writing tremor in the right hand who developed similar symptoms in teh left hand.     

Essential tremor in a Finnish population

A two-phase epidemiological study of essential tremor was carried out by investigating a rural population aged over 40 years in 2 municipalities in southwestern Finland. In the first phase, the subjects answered a questionnaire as to whether they had experienced tremor during the month preceding the inquiry. In the second phase, the persons who had tremor often or fairly often, were examined clinically. The total prevalence of essential tremor, calculated on the basis of clinically established cases, was 55.5‰ of the population aged over 40 years. The disease became more prevalent with advancing age and was, with the exception of the oldest age-group, more common in men than in women.     

Arm tremor in cervical dystonia—Is it a manifestation of dystonia or essential tremor?

The classification of arm tremor in cervical dystonia is a controversial issue. There have been many, at times passionate disputes in the movement disorder community about whether it should be classified as a manifestation of dystonia or essential tremor associated with dystonia. There are arguments in favor of both views. Settling the issue might be relevant to the understanding of the etiological, presumably genetic, background because phenomenological grouping is the starting point for genetic analyses. From this point of view, we outline this tremor debate and add some new clinical data. © 2011 Movement Disorder Society     

特发性震颤的临床和电生理学特点

目的 探讨特发性震颤(EI)的临床和电生理学特点.方法 回顾性分析并比较33例ET患者(ET组)和30例生理性震颤患者(对照组)的震颤类型、程度、幅度和负重对其的影响,以总结ET的临床和电生理学特点.结果 ET组患者动作性震颤(KT)的震颤程度明显高于对照组,震颤幅度明显大于对照组(均P＜0.01);而姿势性震颤(PT...     

Clinical analysis in familial cortical myoclonic tremor allows differential diagnosis with essential tremor.

Familial cortical myoclonic tremor (FCMT) is a rare disorder often leading to a wrong clinical diagnosis of essential tremor. Electrophysiological data are usually considered to allow a correct diagnosis. We describe a FCMT French family with previously unreported clinical features such as sensitivity to glucose deprivation, vibration, repetitive visual patterns, and intense visual or auditory stimulation and contrasts. Electrophysiological studies of the propositus confirm the cortical reflex myoclonus elicited by photic stimulation and the absence of epileptic electroencephalographic discharges. We emphasize that a precise clinical analysis can lead to a correct diagnosis before electrophysiological confirmation. This is also the first-ever report of efficacy of levetiracetam in FCMT.     

Is essential tremor predominantly a kinetic or a postural tremor? A clinical and electrophysiological study

Both postural and kinetic tremors may occur in essential tremor (ET), however the relative contribution of each is not clear. ET has been variably defined with respect to kinetic and postural tremors. To examine the relative severity of postural and kinetic tremors in ET, 50 ET cases from a clinic and 55 from a community underwent a videotaped tremor examination. Kinetic and postural tremors were rated using a validated clinical rating scale (score range, 0-3). Thirty-one cases also underwent accelerometry to precisely quantify tremor amplitude. In clinic cases, the mean postural tremor rating was 1.25 (S.D., 0.89). The mean kinetic tremor rating was 52% higher (1.90; S.D., 0.57; P < 0.001). The community cases had similar characteristics. Sixty percent of the 105 cases had postural tremor ratings scoring 0 or 1 (no tremor or low amplitude, intermittent tremor). In clinic cases, the mean amplitude of postural tremor during tremor analysis was 0.51 mm (S.D., 0.66 mm), and the mean amplitude of kinetic tremor was 2.91 mm (S.D., 2.11 mm; P < 0.01). Similar values were obtained for community cases. These quantitative data suggest that kinetic tremor is more severe than postural tremor in ET. The majority of cases had mild or absent postural tremor. Despite this, ET is defined only as a postural tremor in many studies. Our data argue for a more consistent inclusion of kinetic tremor in diagnostic criteria for ET.     

Jaw tremor: prevalence and clinical correlates in three essential tremor case samples.

The spectrum of involuntary movements seen in essential tremor (ET) is limited. Jaw tremor is one such movement. The prevalence and clinical correlates of jaw tremor have not been studied in detail. The objective of this study was to estimate the prevalence and examine the clinical correlates of jaw tremor in ET using ET cases from three distinct settings (population, tertiary-referral center, brain repository). All ET cases underwent a videotaped tremor examination in which tremors (including limb, head, voice, and jaw) were assessed. The prevalence [95% confidence interval (CI)] of jaw tremor was lowest in the population sample (7.5%; 3.9%-14.2%), intermediate in the tertiary-referral center (10.1%; 6.8%-14.7%), and highest in the brain repository (18.0%; 12.3%-25.5%; P = 0.03). Jaw tremor was associated with older age (P < 0.001), more severe action tremor of the arms (P < 0.001), and presence of head and voice tremor (P < 0.001). Jaw tremor was present in 4/14 (28.6%) ET cases with consistent rest tremor vs. 15/193 (7.8%) cases without rest tremor (odds ratio = 4.8; 95% CI = 1.3-7.0; P = 0.009). The prevalence of jaw tremor was 7.5% to 18.0% and was dependent on the mode of ascertainment, being least prevalent in a population-based sample. ET cases with jaw tremor had a more clinically severe and more topographically widespread disorder. The association in our study between jaw tremor and rest tremor, along with the published observation that jaw tremor can occur in Parkinson's disease (PD), raises the question whether jaw tremor in ET is a marker for subsequent conversion to PD.