Electrophysiological approach to the study of essential tremor in children and adolescents (original) (raw)
Related papers
Difference of disability between electrophysiologic subgroups of essential tremor
Canadian Journal of Neurological Sciences, 2000
The aim of the study was to test the validity of the controversial subdivision of essential tremor (ET) patients into electrophysiological subgroups. We evaluated a hundred patients with ET using surface electromyographic (EMG) recordings of antagonists forearm muscles and distinguished three groups: the first group showed synchronous activity of antagonistic muscles, the second showed alternating activity of antagonist muscles; and the third group consisted of patients whose EMG recordings were not compatible with the other two groups. We compared patients with synchronous and alternating activity in terms of sex, age at onset, duration of illness, family history of tremor, symmetry and frequency of tremor, and the scores of a disability scale. The only significant difference between the patients with synchronous and alternating activity was that the patients with synchronous activity were more disabled. This result adds to the evidence for distinct electrophysiological subgroups o...
Non-motor features of essential tremor, Updated review of evolving aspects
Sohag Medical Journal, 2021
Essential tremor (ET) is defined as an action tremor syndrome with a duration of more than three years in both upper limbs with or without tremor in other areas and with no other neurological signs. ET's non-motor characteristics add to the evidence of clinical variability in ET, a disease with a wide range of pathological and etiological characteristics. Problems in frontal-executive function, comparable to Parkinson's disease (PD), were one of the most common patterns of cognitive affection in ET. ET individuals who started tremor after the age of 65 were 64 to 70% more likely than control subjects to develop dementia, but ET cases who started tremor before the age of 65 have an equal chance to develop dementia as controls. Depression rates were considerably higher in ET than controls and more severe depression is found. A strong evidence linking anxiety and ET. Many studies have documented sleep disturbances in ET.
Evaluation of a screening instrument for essential tremor
Movement Disorders, 2008
To evaluate a screening instrument for essential tremor (ET) consisting of a seven-item questionnaire and a spiral drawing. A total of 2,448 Danish twins aged 70 years or more and a second sample aged 60 years or more (n 5 1,684) from a population-based northern German cross-sectional study (PopGen ET) were screened for ET. Inclusion criteria were a previous diagnosis of ET, a positive answer to two or more questions of the questionnaire or a spiral rating >4 (range of scale 0-9). Three hundred thirteen of 380 positively screened and 321 negatively screened subjects were clinically examined. Definite or probable ET was diagnosed in 104 patients, possible in 86 and other tremors in 98 patients. The sensitivity of the screening instrument was 70.5%, the positive predictive value was 64.9%, the specificity was 68.2%, and the negative predic-tive value was 73.5%. Tremor severity correlated significantly with higher spiral scores and more positive items. More patients were identified by spiral drawing in all tremor groups. The interrater and intrarater reliability for spirals ranged from 0.7 to 0.8 using intraclass coefficient. A cluster analysis revealed that the questionnaire can be reduced to three items, about uncontrollable tremor in any body part, tremor while drinking or pouring and other family members with tremor, without loosing efficacy. We present an easy to use and reliable screening instrument that is effective to identify patients with ET but not able to exclude patients with other tremor forms.
Journal of Clinical Neurophysiology, 2004
The objective of the current study was to investigate the diagnostic potential of the routine tremor neurophysiologic analysis for the diagnosis of essential tremor (ET) in patients with postural tremor syndrome. Three hundred consecutive outpatients attending for postural tremor were included. Accelerometry and surface electromyography was performed between 1 and 4 weeks after the first clinical visit. A final clinical diagnosis (mean follow-up period, 53 months) of the postural tremor syndrome was made by two neurologists blind to the neurophysiologic results. Six neurophysiologic criteria for the diagnosis of ET were applied to define the neurophysiologic examination as compatible or not compatible with ET (all criteria must be present): (1) rhythmic burst of postural tremor on EMG; (2) tremor frequency greater than or equal to 4 Hz; (3) absence of rest tremor or, if present, frequency 1.5 Hz lower than the postural tremor; (4) absence of tremor latency from rest to postural position; (5) changes of the dominant frequency peak less or equal to 1 Hz after the weight load test; and (6) no changes in tremor amplitude after mental concentration. The neurophysiologic criteria for ET showed a sensitivity of 97.7%, a specificity of 82.3%, a positive predictive value of 95.1%, a negative predictive value of 91.1%, and positive probability ratio of 5.5. The odds ratio was 198.43 (95% CI, 66.03 to 596.35). For the diagnosis of ET in patients with postural tremor, routine neurophysiologic tests have high diagnostic and predictive value that justifies its practice in movement disorders clinics.
Tremor analysis in two normal cohorts
Clinical Neurophysiology, 2004
Objective: Quantitative tremor analyses using almost identical methods were compared between two independent large normal cohorts, to separate robust measures that may readily be used diagnostically from more critical ones needing lab-specific normalization. Methods: Hand accelerometry and surface EMG from forearm flexors and extensors were recorded with (500 and 1000 g) and without weight loading under postural conditions in 117 and 67 normal volunteers in two different specialty centers for movement disorders in Germany. Results: Tremor amplitude (total power) and frequency fell within a similar range but differed significantly. A significant reduction of tremor frequency under 1000 g weight load (. 1 Hz), and a lack of rhythmic EMG activity at the tremor frequency in around 85-90% of the recordings were robust findings in both centers. Conclusions: The differences in frequency and total power indicate that these measures critically depend on the details of the recording conditions being slightly different between the two centers. Thus each lab needs to establish its own normative data. We estimate that at least 25 normal subjects have to be recorded to obtain normal values. The reduction of tremor frequency under load and lacking tremor-related EMG activity were well reproducible allowing a differentiation of physiological from low amplitude pathological tremor. Significance: This study provides a framework for more standardized tremor analyses in clinical neurophysiology.
Phenotypic Variability of Essential Tremor Based on the Age at Onset
Canadian Journal of Neurological Sciences/Journal Canadien des Sciences Neurologiques
ABSTRACT: Background: Essential tremor (ET) is reported to have a bimodal distribution of age at onset (AAO) with phenotypic variability based on the AAO. This study aims to explore the distribution of AAO based on mathematical modeling and ascertain the differences, if any, in the clinical features of groups. Methods: A chart review was conducted for 252 patients with ET diagnosed based on the Consensus statement of the Movement Disorder Society on Tremor. Finite mixture modeling was performed to identify groups of the cohort based on the AAO. Results: Three groups were defined: early onset (EO): AAO ≤ 22 years, n = 63, intermediate onset (IO): 23 ≤ AAO ≤ 35 years, n = 43, and late onset (LO): AAO ≥ 36 years, n = 146. There were no significant differences related to family history or responsiveness to alcohol. The EO group had significantly higher prevalence of upper limb and lower limb tremor. Head tremor and voice tremor was more prevalent in the IO and LO groups. Cerebellar sign...
Assessing the impact of essential tremor on upper limb function
Journal of Neurology, 1993
We compared the impact of essential tremor on the performance of three manual tasks: drawing spirals, holding a cup full of water and a joystick-controlled tracking test. Tremor amplitude and frequency were measured by accelerometry during the tracking test, when holding the cup and whilst a standard posture was maintained. The inter-relationships between tremor amplitude, frequency and task impairment were then examined. The results showed that the amplitude and frequency of essential tremor (measured from the principal spectral peak) changed with different activities, with the mildest postural tremors changing most in frequency (by up to 4-5 Hz). The amplitude of tremor decreased in almost every case during the tasks, relative to posture, and this decrement was greatest for the most severe tremors. We also dem-onstrate that for practical purposes, such as routine clinical situations and therapeutic trials, the effect of essential tremor upon upper limb function can be usefully assessed by two simple complementary techniques: rating spirals and measuring the volume of water split from a cup. The impairments in carrying out these tasks and the tracking test were highly correlated with one another and also with the amplitude and frequency of postural tremor. The concept of tremor "suppressability" is introduced: the relative percentage decrease in the amplitude of a particular tremor during the performance of a specific task compared to that recorded whilst holding a standard posture.
Limb positioning and magnitude of essential tremor and other pathological tremors
Movement Disorders, 1990
We examined the influence of maintaining different postural configurations of the upper extremity on the magnitude of tremor in patients with essential tremor and with postural tremor from a variety of other neurological disorders. Patients maintained postures requiring different angles of forward flexion in the sagittal plane, of horizontal flexion, and of elbow extension. The tremor of patients diagnosed with essential tremor was either unaffected or affected only little by changes in limb position. In contrast, patients with pathological tremors, of the cerebellar postural, parkinsonian, and other types, exhibited positional dependence of their tremor. When there was positional dependence of tremor, it was always largest when the hands were near the nose or chin. These observations suggest a practical method for assistance with the clinical discrimination of essential tremor from other postural tremors.
Essential tremor quantification during activities of daily living
Parkinsonism & Related Disorders, 2011
Background-Essential tremor (ET), characterized primarily by postural and kinetic tremor, is typically measured in the clinic with subjective tremor rating scales. These ratings are often used to adjust medications and assess efficacy in clinical trials. However, tremor ratings require the presence of a clinician and do not necessarily capture tremor fluctuations throughout the day during activities of daily living (ADL).
Electromyographic differentiation of tremors
Clinical Neurophysiology, 2001
The aim of this study was to explore the opportunity for differentiation of tremors on the basis of the electromyographic examination. Methods: We report data from 525 patients with different types of tremor included in this study. Two hundred and twenty patients with essential tremor, 110 patients with Parkinson's disease, 24 patients with midbrain tremor, 22 patients with cerebellar tremor, 120 patients with enhanced physiological tremor due to anxiety, and 29 patients with psychogenic tremor participated in the study. A detailed neurological and electromyographic examination was performed. The tremor was studied in all limbs positions. Surface electromyographic recordings of the most involved body part were performed to all patients. Results: According to the electromyographic examination all patients were divided to two groups: Patients with synchronous tremor and patients with alternating tremor in the antagonist muscles. The comparisons were performed only between the patients with tremor caused by different etiology within the group of synchronous or alternating tremor. The group of tremors with synchronous pattern included the patients with essential tremor type A (with synchronous activity), cerebellar, and enhanced physiological tremor. The group of tremors with alternating pattern included patients with Parkinsonian tremor, essential tremor type B (with alternating activity), rubral, and psychogenic tremors. Our results revealed that electromyographic examination of tremor pattern, frequency, amplitude, and burst duration is useful for tremor differentiation. Conclusion: The electromyographic examination may serve as a tool for differentiation of tremors.