Accelerometry to distinguish psychogenic from essential or parkinsonian tremor (original) (raw)
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.
Diagnosis and Treatment of Common Forms of Tremor
Seminars in Neurology, 2011
Tremor is the most common movement disorder presenting to an outpatient neurology practice and is defined as a rhythmical, involuntary oscillatory movement of a body part. The authors review the clinical examination, classification, and diagnosis of tremor. The pathophysiology of the more common forms of tremor is outlined, and treatment options are discussed. Essential tremor is characterized primarily by postural and action tremors, may be a neurodegenerative disorder with pathologic changes in the cerebellum, and can be treated with a wide range of pharmacologic and nonpharmacologic methods. Tremor at rest is typical for Parkinson's disease, but may arise independently of a dopaminergic deficit. Enhanced physiologic tremor, intention tremor, and dystonic tremor are discussed. Further differential diagnoses described in this review include drug-or toxin-induced tremor, neuropathic tremor, psychogenic tremor, orthostatic tremor, palatal tremor, tremor in Wilson's disease, and tremor secondary to cerebral lesions, such as Holmes' tremor (midbrain tremor). An individualized approach to treatment of tremor patients is important, taking into account the degree of disability, including social embarrassment, which the tremor causes in the patient's life.
The differential diagnosis and treatment of tremor
Deutsches Ärzteblatt international, 2014
Essential tremor is the most common type of tremor, with a prevalence of 0.4% in the overall population and 4-7% in persons over age 65. In general, tremor is so common that patients with tremor are frequently treated not only by neurologists, but also by physicians from other specialties. This review is based on publications retrieved by a selective PubMed search and on guidelines from Germany and abroad. Particular tremor syndromes are usually diagnosed on the basis of their typical clinical presentation and whatever accompanying manifestations may be present. Ancillary tests are usually unnecessary. Unilateral rest tremor accompanied by rigidity and bradykinesia is typical of Parkinson's disease. Essential tremor is a bilateral postural tremor. The most common cause of intention tremor is multiple sclerosis. Mild tremor syndromes can often be treated satisfactorily with drugs. In case of severe tremor, which is rarer, a stereotactic operation can be considered. The usual outc...
A patient with tremor, part 2: from diagnosis to treatment
Canadian Medical Association Journal, 2011
• An etiologically focused diagnostic method is helpful in determining the diagnosis in a patient presenting with tremor. • Asymmetric resting tremor is the hallmark of Parkinson disease, but those affected may also have associated postural tremor. • Essential tremor is usually monosymptomatic and is characterized by symmetric postural tremor.
Electrophysiologic characteristics of tremor in Parkinson's disease and essential tremor
Arquivos de neuro-psiquiatria, 2014
Tremor in essential tremor (ET) and Parkinson's disease (PD) usually present specific electrophysiologic profiles, however amplitude and frequency may have wide variations. To present the electrophysiologic findings in PD and ET. Patients were assessed at rest, with posture and action. Seventeen patients with ET and 62 with PD were included. PD cases were clustered into three groups: predominant rest tremor; tremor with similar intensity at rest, posture and during kinetic task; and predominant kinetic tremor. Patients with PD presented tremors with average frequency of 5.29±1.18 Hz at rest, 5.79±1.39 Hz with posture and 6.48±1.34 Hz with the kinetic task. Tremor in ET presented with an average frequency of 5.97±1.1 Hz at rest, 6.18±1 Hz with posture and 6.53±1.2 Hz with kinetic task. Seven (41.2%) also showed rest tremor. The tremor analysis alone using the methodology described here, is not sufficient to differentiate tremor in ET and PD.
Journal of Clinical Neuroscience, 2002
This study statistically evaluated a set of commonly measured tremor parameters to determine their individual and combined ability to discriminate between essential tremor (ET) and Parkinsonian tremor (PT). Accelerometer and surface electromyographic (EMG) records of moderate to severe upper limb tremor in 20 patients with ET and 22 patients with PT were used to quantitatively compare tremor amplitude, frequency and pattern of muscle bursting in two resting and three non resting postures. The group statistics showed significant differences between ET and PT with respect to tremor frequency in all five postures, tremor amplitude at rest and muscle bursting patterns. Discriminant function analysis showed that no single parameter or combination of parameters was able to correctly classify all patients. Frequency was much more discriminating than amplitude or muscle bursting patterns in all limb postures. The best amplitude discrimination was obtained when the hand and forearm were both fully supported. Muscle bursting patterns were poorly discriminating and did not assist in correct classification of single patients. Group statistics confirmed a highly significant biological difference between the two tremor types. Optimal classification of single PT (86% correct) and ET (95% correct) patients was obtained using frequency and two selected amplitude parameters from the resting limb. Limb posture was an important variable in optimising the discriminative ability of tremor studies. The implications for routine tremor studies are summarised. &
Diagnostic and pathophysiological aspects of psychogenic tremors
Movement Disorders, 1998
Twenty-five patients from our movement disorder clinic with the clinical diagnosis of psychogenic tremor were included. According to a modified version of Fahn's criteria for psychogenic dystonia,I3 the diagnosis of psychogenic tremor was accepted if
Sensitivity and specificity of a portable system measuring postural tremor
Neurotoxicology and Teratology, 1997
Sensitivity and specificity of a portable system measuring postural tremor. (2) 95-104, 1997.-A portable, accelerometric system measuring tremor was evaluated. That is, the validity and consistency of measurements as well as its ability to discriminate pathologic from physiological tremor were investigated. Control subjects and patients with Parkinson's disease were tested with this portable system and with an independent system that gave precise displacement data using lasers. It was found that amplitude of postural tremor as measured by the two systems differed significantly, but further investigation revealed that this difference was due 1) to the difference between amplitude of acceleration and amplitude of displacement, and 2) to changes in tremor over the time between tests, rather than to any inaccuracy or unreliability in the portable system. The other characteristics of tremor reported by the portable system were also valid and reasonably reliable in test-retest experiments, with the exception of the "harmonic index," which proved less stable. Most of the reported characteristics were distributed differently for the control group and for the patients with Parkinson's disease, but the large overlaps between distributions would make diagnosis difficult when tremor is not very pronounced. These results suggest that until better discriminating measures of tremor are available, tremor tests should be repeated and combined with other tests of motor function. 0 1997 Elsevier Science Inc.
Psychogenic tremor: long-term outcome
CNS spectrums, 2006
Psychogenic disorders, also referred to as somatoform, conversion, somatization, hysteria, and medically unexplained symptoms, are among the most challenging disorders to diagnose and treat. Psychogenic movement disorders are increasingly encountered in specialized clinics, and represent approximately 15% of all patients evaluated in the Baylor College of Medicine Movement Disorders Clinic. To characterize psychogenic tremor and provide data on prognosis and long-term outcome in a large group of patients with psychogenic tremor followed in a movement disorders clinic. Patients evaluated at the Baylor College of Medicine Movement Disorders Clinic in Houston, Texas, between 1990 and 2003 with the diagnosis of psychogenic movement disorder (PMD), who consented to be interviewed, were administered a structured questionnaire designed to assess current motor and psychological function. psychogenic tremor is the most common PMD, accounting for 4.1% of all patients evaluated in our clinic. ...
Using Frequency Domain Characteristics to Discriminate Physiologic and Parkinsonian Tremors
Journal of Clinical Neurophysiology, 1999
Address correspondence and reprint requests to Anne Beuter, Cognitive Neuroscience Laboratory (WB-5110), Université du Québec à M ontréal, CP 8888, succ. Centre-ville, M ontreal, Quebec, Canada H3C 3P8. Supported by Natural Sciences and Engineering Research Council of Canada (Canada), Fonds pour la Formation de chercheurs et l'aide á la recherche (Quebec), and the Cree Board of Health and Social Services of James Bay (M ontreal).
Orthostatic tremor: An electrophysiological analysis
Movement Disorders, 1998
Orthostatic tremor (OT) is a clinically defined syndrome of leg tremor while standing. Controversy surrounds whether OT is a distinct syndrome or is an essential tremor (ET) variant. We report two patients with OT. Electrophysiological testing included polymyography, accelerometry, nerve conduction, and evoked potential studies. The effects of various maneuvers and body positions on the tremor were assessed. The findings included rapid (15-17 Hz) lower-extremity tremor burst frequency evoked by standing but not by walking or swaying; rapid upper-extremity burst pattern synchronous with lower-extremity bursts; and failure of electrical stimulation or mental concentration to "reset" the tremor. Additionally, there was the novel finding of accelerometric recordings in the legs
Journal of Clinical Movement Disorders
Background To quantify pharmacological effects on tremor in patients with essential tremor (ET) or Parkinson’s Disease (PD), laboratory-grade accelerometers have previously been used. Over the last years, consumer products such as smartphones and smartwatches have been increasingly applied to measure tremor in an easy way. However, it is unknown how the technical performance of these consumer product accelerometers (CPAs) compares to laboratory-grade accelerometers (LGA). This study was performed to compare the technical performance of CPAs with LGA to measure tremor in patients with Parkinson’s Disease (PD) and essential tremor (ET). Methods In ten patients with PD and ten with ET, tremor peak frequency and corresponding amplitude were measured with 7 different CPAs (Apple iPhone 7, Apple iPod Touch 5, Apple watch 2, Huawei Nexus 6P, Huawei watch, mbientlabMetaWear (MW) watch, mbientlab MW clip) and compared to a LGA (Biometrics ACL300) in resting and extended arm position. Results...
Re-emergent tremor in Parkinson's disease: A clinical and electromyographic study
Journal of the Neurological Sciences, 2016
Re-emergent tremor (RET) and the classical parkinsonian rest tremor were considered as two different phenomena of the same central tremor circuit. However, clinical and accelerometric characteristics of these tremors were not previously compared in a single study. We evaluated disease characteristics and accelerometric measurements of two tremor types in 42 patients with Parkinson's disease. Disease specific features and accelerometric measurements of peak frequency, amplitude at peak frequency and the root mean square (RMS) amplitude of two tremor types were compared. Eighteen patients had RET and the mean latency of the RET was 9.48 (±9.2) s. Groups of only rest tremor and RET did not differ significantly in age of disease onset, disease duration and severity and mean levodopa equivalent dose. Comparison of peak frequency and amplitude at peak frequency were not different between the groups, but RMS amplitude was significantly higher in the RET group (p = 0.03). RMS amplitude of RET was also correlated with disease severity (r = .48, p = 0.04). These results support the previous notion that rest tremor and RET are analogue, both are triggered by the same central ossilator with RET being only the suppression of the rest tremor due to arm repositioning.
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.
Effect of stimulation frequency on tremor suppression in essential tremor
Movement Disorders, 2004
We sought to determine the effect of deep brain stimulation (DBS) frequency on tremor suppression in essential tremor (ET) patients with deep brain stimulators implanted in the ventral intermediate nucleus (VIM) of the thalamus. A uniaxial accelerometer was used to measure tremor in the right upper extremity of subjects with a diagnosis of ET who had DBS electrodes implanted in the left VIM. The root-meansquare acceleration was used as the index of tremor magnitude and normalized to the OFF DBS condition. There was a highly significant inverse sigmoidal relationship between stimulation frequency and normalized tremor acceleration (X 2 /DoF ϭ 0.42, r 2 ϭ 0.997). Tremor acceleration had a nearly linear response to stimulation frequencies between 45 and 100 Hz with little additional benefit above 100 Hz. These findings have two important implications. Clinically, frequency of thalamic stimulation is an important variable for optimal tremor control with maximal benefit achieved with 100 to 130 Hz in most patients. Second, thalamic DBS provides tremor benefit in a graded manner and is not an all-or-nothing phenomenon.
Quantitative Assessment of Parkinsonian Tremor Based on an Inertial Measurement Unit
Sensors, 2015
Quantitative assessment of parkinsonian tremor based on inertial sensors can provide reliable feedback on the effect of medication. In this regard, the features of parkinsonian tremor and its unique properties such as motor fluctuations and dyskinesia are taken into account. Least-square-estimation models are used to assess the severities of rest, postural, and action tremors. In addition, a time-frequency signal analysis algorithm for tremor state detection was also included in the tremor assessment method. This inertial sensor-based method was verified through comparison with an electromagnetic motion tracking system. Seven Parkinson's disease (PD) patients were tested using this tremor assessment system. The measured tremor amplitudes correlated well with the judgments of a neurologist (r = 0.98). The systematic analysis of sensor-based tremor quantification and the corresponding experiments could be of great help in monitoring the severity of parkinsonian tremor.