Orthostatic tremor: Clinical and electrophysiologic characteristics

Orthostatic tremor, sometimes known as ?shaky legs syndrome,”? is a disorder of middle-aged or elderly people characterized by feelings of unsteadiness in the legs and a fear of falling when standing. Patients stand on a wide base but walk normally. These symptoms are due to high-frequency (13–18 Hz) burst firing in weight-bearing muscles. They are attenuated by walking and are abolished immediately by sitting. Some authors believe that the disorder is a variant of essential tremor. This study reports the clinical and electrophysiologic features of orthostatic tremor in 30 patients. The findings indicate that orthostatic tremor is distinct from essential tremor, both clinically and electrophysiologically. The major differences are the frequency of electromyographic burst firing, the invariable involvement of lower limb and paraspinal muscles, and the task-specific nature of the tremor in orthostatic tremor. The study shows that the diagnosis can be established rapidly with surface electromyographic recordings. © 1993 John Wiley & Sons, Inc.     

Orthostatic tremor: report of two cases and an electrophysiological study

Two patients with legs tremor present on standing, but none on walking or sitting, are reported. Tremor was not exclusive or orthostatism and was also evoked by strong tonic contraction of leg muscles. Synchronous EMG bursts were recorded in antagonistic muscle groups at 8-10 Hz in the first patient and at 16 Hz in the second. EMG activity was synchronous in corresponding muscles of both legs. The occurrence of EMG activity was not influenced by stimulation of nerve afferent fibers. We suggest that this movement disorder may be an exaggeration of physiological tremor due to synchronization of motor units by spontaneous oscillations in central structures.     

Orthostatic tremor during modification of standing.

Primary orthostatic tremor (OT) occurs only during standing. We studied whether modification of the condition standing influences OT. In seven patients with OT, surface EMG was recorded from both tibialis anterior and gastrocnemius muscles during two maneuvers: relief, whereby the patient was gradually lifted by a crane, and tilting, whereby the patient was tilted by a tilting table to positions of 90 degrees (upright standing), 45 degrees (diagonal position), and 0 degrees (lying position). We determined the parameters tremor frequency, tremor intensity, coherence, and phase shift between the different muscles. Relief did not influence OT. In contrast, tilting modified significantly tremor intensity and phase shifts; tremor frequencies and coherences were not influenced. We chose both these maneuvers because of their different impact on the standing condition: relief modifies the factors afferent input and muscle forcing but not the factor postural set, whereas tilting modifies all three factors. The fact that tilting modifies OT, whereas relief does not, suggests an important role of postural set in OT generation. Afferent input and muscle forcing seem to play less important role.     

Arylsulphatase A (ASA) activity in parkinsonism and symptomatic essential tremor

Arylsulphatase A (ASA) activity was evaluated in 47 patients with a diagnosis of parkinsonism or essential tremor. Mean ASA activity was significantly reduced compared with both a healthy control group of 71 individuals (p < 0.01) and with a group of 44 neurological patients without movement disorders (p < 0.02). Using definite clinical criteria the patients were classified as typical or atypical with respect to Parkinson's disease (PD) or essential tremor (ET). A normal ASA level was found in all the cases showing typical clinical features (PD and ET), while ASA activity was significantly lowered (p < 0.01) in 55.6% of the atypical cases (Parkinsonian syndrome or symptomatic ET). Our data support the hypothesis of a non-casual association between low ASA level and the clinical features of parkinsonism or symptomatic ET.     

Familial orthostatic tremor and essential tremor in two young brothers: A rare entity

Orthostatic tremor (OT), is usually a disease of old age and is characterized by quivering movements of the legs during quiet standing or in the state of isometric contraction in the lower limbs. This is relieved on walking or on lying down. It is diagnosed by surface electromyography, particularly over the quadriceps femoris muscles which shows a distinctive frequency of 13 to 18 Hz on standing. Some investigators consider it as a variant of essential tremor (ET) and the two conditions often co-exist. The disease is usually non-familial. Two brothers presented with tremor in the lower limbs on standing and on the outstretched hands without any family history. Subsequently, they were proved to be suffering from OT and ET by clinical examination and surface EMG. Simultaneous occurrence of OT and ET in two young brothers without any family history in the previous generation has not been described before and they also appeared at a much earlier age than what is described in the literature.     

Orthostatic tremor: A review of 45 cases

ObjectiveTo evaluate the clinical characteristics, associated features, and treatment response of a large orthostatic tremor series seen over a 26-year period.MethodsWe reviewed the medical records of 45 patients seen between 1987 and 2013 who fulfilled the diagnostic criteria for orthostatic tremor.ResultsThe mean age at onset was 59.5 years and 23/45 (51%) were men. A family history of any tremor was noted in 23/45 (51%) patients. A family history of orthostatic tremor was reported in 3/45 (7%) patients. 40/45 (89%) had primary orthostatic tremor with (n = 30) or without (n = 10) an associated postural arm tremor. We found that 5/45 (11%) had orthostatic tremor plus additional neurological features. One patient was diagnosed with dementia with Lewy bodies preceded by orthostatic tremor for 20 years. Prospective follow-up data was available for 30/45 patients and averaged 54.4 months. Treatment response to medications was modest and inconsistent. In 11/30 cases, orthostatic tremor worsened over the follow-up period. One patient with primary orthostatic tremor underwent thalamic deep brain stimulation surgery.ConclusionsIn our population of orthostatic tremor patients, mild postural hand tremor was a frequent finding. Over half of our patients had a family history of tremor, but a family history of orthostatic tremor was uncommon. Additional neurological features were seen in the minority of patients and we report possibly the first case of dementia with Lewy bodies associated with orthostatic tremor. Our series is the largest series of orthostatic tremor reported in the literature and contributes to understanding the clinical characteristics of this rare disease.     

Orthostatic tremor in progressive supranuclear palsy.

Patients with orthostatic tremor (OT) can be classified as having "primary OT," with or without postural arm tremor but no other abnormal neurological features, or "OT plus." We describe a patient with OT, with postural tremor of the arms and restless legs syndrome (RLS), who developed features typical of progressive supranuclear palsy (PSP). PSP can be accompanied by OT.     

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.     

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...     

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.     

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.     

Beta-blockers in isoproterenolenhanced essential tremor

Non-selective adrenergic beta-blocking drugs prevented isoproterenol enhancement of essential tremor amplitude far more effectively than beta-1-selective blockers.     

Faster rate of cognitive decline in essential tremor cases than controls: a prospective study

Background: Mild cognitive deficits have been reported in essential tremor (ET). However, these cognitive deficits have been assessed in cross‐sectional rather than longitudinal analyses. Objective: To determine whether decline in cognitive test scores occurs at a faster rate in ET cases than controls. Methods: In a population‐based study of older people (≥ 65 years) in central Spain (Neurological Disorders in Central Spain, NEDICES), non‐demented ET cases and controls were followed prospectively. Participants with baseline or incident Parkinson’s disease or dementia were excluded as were participants who developed incident ET. At baseline (1994–1995) and at follow‐up (1997–1998), a 37‐item version of the mini‐mental state examination (37‐MMSE) was administered. Results: A total of 2319 participants (72.4 ± 5.8 years) included 135 prevalent ET cases and 2184 controls. At baseline, the mean 37‐MMSE in cases was 28.8 ± 5.8 vs. 30.2 ± 4.8 in controls (P = 0.02). During the 3‐year follow‐up period, the 37‐MMSE declined by 0.70 ± 3.2 points in cases vs. 0.11 ± 3.8 points in controls (P = 0.03). In analyses that adjusted for age, education, and other potential confounders, the case–control difference remained robust. Discussion: In this population‐based, prospective study of non‐demented elders, baseline cognitive test scores were lower in ET cases than controls; moreover, during the 3‐year follow‐up period, these scores declined at a rate that was seven‐times faster in ET cases. This study provides evidence that cognitive deficits in ET are not static, and they appear to be progressing at a faster rate than in elders without this disease.     

Coherence analysis differentiates between cortical myoclonic tremor and essential tremor.

Familial cortical myoclonic tremor with epilepsy (FCMTE) is characterized by a distal kinetic tremor, infrequent epileptic attacks, and autosomal dominant inheritance. The tremor is thought to originate from the motor cortex. In our patient group, a premovement cortical spike could not be established on electroencephalogram (EEG) back-averaging. Corticomuscular and intermuscular coherence analysis can demonstrate a cortical common drive to muscles. We carried out coherence analysis of electromyography (EMG) of forearm muscles and EEG of contralateral motor cortex in 7 FCMTE patients, 8 essential tremor (ET) patients, and 7 healthy controls. Results showed strong cortico- and intermuscular coherence in the 8- to 30-Hz range in the FCMTE patients, with EEG preceding EMG. Healthy controls and ET patients showed normal weak coherence around 20 Hz. The ET patients showed some additional coherence at tremor frequency (6 Hz), probably the result of sensory information flowing back to the sensorimotor cortex. These findings point to a pathological cortical drive in FCMTE patients leading to tremulous movements. Coherence analysis is an easy and useful method to differentiate FCMTE from ET. Coherence analysis is helpful when investigating a cortical common drive in cortical tremor and other movement disorders.     

Olfaction in essential tremor patients with and without isolated rest tremor.

An olfactory deficit is present in patients with essential tremor (ET), but it is often milder than that in patients with Parkinson's disease (PD). In both, the deficit occurs early in the disease. Isolated rest tremor without other signs of parkinsonism can occur in patients with ET. If the rest tremor in these patients represents a manifestation of ET rather than early PD, we hypothesized that their University of Pennsylvania Smell Identification Test (UPSIT) scores would be similar to those of ET patients without rest tremor. The mean UPSIT score in 13 ET patients with isolated rest tremor did not differ from that of 58 ET patients without rest tremor (29.3 +/- 4.3 vs. 29.4 +/- 6.4; P = 0.69). Several ET patients with rest tremor had UPSIT scores that fell outside of the range that is seen in 95% of patients with PD. These data raise the possibility that some ET patients with isolated rest tremor may not have early PD and that the pathological process that is responsible for their ET is also involving the basal ganglia.     

Essential tremor centralized brain repository: diagnostic validity and clinical characteristics of a highly selected group of essential tremor cases.

We studied essential tremor (ET) cases enrolled in the Essential Tremor Centralized Brain Repository to (1) assess the validity of their diagnoses and (2) characterize the clinical features in a group of highly selected cases who might reflect a far end of the disease spectrum. Our over-arching goal was to provide a perspective of ET that complements that derived from population-based and clinic-based studies. Based on a history and videotaped examination, 94 of 100 ET cases had their diagnoses confirmed; most of the remainder had Parkinson's disease. When compared with ET cases ascertained through populations and clinics, a large proportion had been prescribed medication for tremor (87.2%), had a family history of tremor (88.3%), had rest tremor (33.0%), or had neck tremor (60.6%). One patient had facial tremor, which has not been reported previously. As has been reported once before, a large proportion wore hearing aids (26.9% of the 67 participants age>or=70). In summary, diagnostic validity was high. In terms of their clinical characteristics, the high proportion of cases with severe tremor and varied disease manifestations (neck tremor, rest tremor) make these cases a valuable resource in pathological studies; the high proportion with familial tremor would provide an enriched sample for genetic studies.     

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.