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Background Objectives Methods Results Conclusions While deep brain stimulation (DBS) targeting the ventral intermediate nucleus (VIM) of thalamus or posterior subthalamic area (PSA) can suppress forms of action tremor in people with Essential Tremor, previous studies have suggested postural tremor may respond more robustly than kinetic tremor to DBS.In this study, we aimed to more precisely quantify the (1) onset/offset dynamics and (2) steady‐state effects of VIM/PSA‐DBS on postural and kinetic tremor.Tremor data from wireless inertial measurement units were collected from 11 participants with ET (20 unilaterally assessed DBS leads). Three postural hold tasks and one kinetic task were performed with stimulation turned off, in 2‐min intervals after enabling unilateral DBS at the clinician‐optimized DBS setting (15 min), and in 2‐min intervals following cessation of DBS (5 min).At baseline, kinetic tremor had significantly higher amplitudes, standard deviation, and frequency than postural tremor (P < 0.001). DBS had a more robust acute effect on postural tremors (54% decrease, P < 0.001), with near immediate tremor suppression in amplitude and standard deviation, but had non‐significant improvement of kinetic tremor on the population‐level across the wash‐in period (34% decrease). Tremor response was not equivalent between wash‐in and wash‐out timepoints and involved substantial individual variability including task‐specific rebound or long wash‐out effects.Programming strategies for VIM/PSA‐DBS should consider the individual temporal and effect size variability in postural versus kinetic tremor improvement. Improved targeting and programming strategies around VIM and PSA may be necessary to equivalently suppress both postural and kinetic tremors. [ABSTRACT FROM AUTHOR]

Background: Essential tremor (ET) is characterized by action tremor, although rest tremor may also occur. Despite this, rest tremor has not been studied extensively. A dearth of studies compare the relationship of rest tremor to other types of tremors in ET.Methods: Two-hundred-and-thirteen ET cases underwent detailed neurological examination, including evaluations of rest, simple kinetic, postural, and intention tremors. A movement disorders neurologist assessed the prevalence of each type of tremor. Each instance of tremor was classified as either symmetrical (present and equally severe on both sides of the body) or asymmetrical (only present on or more severe on one side of the body). Asymmetrical rest tremor that co-occurred with other types of asymmetrical tremors in a given case was further classified as either concordant (i.e., asymmetry on the same side of the body) or discordant (i.e., asymmetry on opposite sides of the body). Chi-square analyses examined the prevalence of concordant versus discordant pairings.Results: Sixty-two cases (29.2%) had rest tremor while seated. Fifteen (7.4%) had rest tremor while standing. Among asymmetric tremor pairings, concordant pairings occurred 2-2.7 times more frequently than discordant pairings - for pairings involving rest tremor while seated, 73.2% were concordant and 26.8% discordant (p < 0.001); for pairings involving rest tremor while standing, 66.7% were concordant and 33.3% were discordant (p = 0.25).Conclusions: Rest tremor often lateralized with other tremor types. These data add to our knowledge of the phenotypic manifestations of ET. [ABSTRACT FROM AUTHOR]

The spiral drawing task is a representative clinical test used to assess essential tremor. Many clinicians have used spirography to assess through visual rating of the drawings. We quantitatively investigated the clinical characteristics of action tremors during spiral drawing tasks using 3-axis gyro sensors. Eighteen essential tremor patients with sensors attached to their forefinger, dorsum of the hand, and forearm participated in a spiral drawing test. As quantitative variables, the average speed, maximum frequency and maximum power were derived from the gyro sensor signals. The average speed and maximum power were also logarithmically transformed. Two-way repeated measures analysis of variance (ANOVA) with tremor direction and joint (attachment location) as independent factors was performed to evaluate the main and interactive effects of direction and joint. Also, Spearman's correlation analysis was performed to evaluate the relationship between the quantitative variables and visual rating scores. The average speed showed a significant main effect of direction (P < 0. 0 1). Logarithmic variables showed interactive effects (P < 0. 0 1) as well as main effects (P < 0. 0 1). The interactive effects were attributed to no significant difference among the joints particularly in the roll direction (P > 0. 0 5). The logarithmic variables of roll direction were significantly greater than that of the other directions (P < 0. 0 0 1). Also, the quantitative variables were moderately correlated with visual rating scores (r = 0. 4 8 − 0. 7 3 , P < 0. 0 5). These results indicate that kinetic tremor during spiral drawing mainly appears in the roll direction and may contribute to the determination of sensor location and direction for continuous monitoring of patients with essential tremor. [ABSTRACT FROM AUTHOR]

Tremor is an involuntary, rhythmic, oscillatory movement of a body part. It is a central feature of a range of diseases resulting from pathological changes in the cerebellum. Interestingly, in modern times, the terms "cerebellar tremor" and "intention tremor" are often used synonymously and interchangeably. However, "cerebellar tremor" (i.e., tremors of cerebellar origin) do not always present exclusively as intention tremor. In this article, we comprehensively revisit the clinical phenomenology of tremors observed in various diseases that are based in the cerebellum. By this, we mean diseases for which the cerebellum and its various connections are often seen as playing a central and defining role. These include spinocerebellar ataxias, essential tremor, orthostatic tremor, dystonia, acute cerebellitis, cerebellar tumors, paraneoplastic cerebellar degeneration, and cerebellar strokes. The theme of this article is to highlight, through published data available in the current literature, that the clinical phenomenology of tremor of cerebellar origin is heterogeneous, and it extends beyond that of intention tremor to include postural tremors, kinetic tremor, rest tremor, and orthostatic tremor. This heterogeneity is consistent with the seminal work of Gordon Holmes, in which he described a variety of tremors aside from intention tremor in the setting of cerebellar lesions. In the end, it would seem that the notion that intention tremor is the sole signature of cerebellar lesions is an over-simplification and is not correct. Future studies are warranted to identify and further characterize the heterogeneity of tremors arising from the various cerebellar etiologies. [ABSTRACT FROM AUTHOR]

Introduction: Chronic inflammatory demyelinating polyneuropathy (CIDP) typically presents with a combination of sensory and motor impairments. Tremor is recognized as a common and debilitating feature in CIDP, although the underlying mechanisms are unclear.Methods: Clinical tremor severity and disability scores were collected prospectively in 25 CIDP patients and compared with 22 neuromuscular controls.Results: Postural and kinetic tremor were significantly more frequent in CIDP patients (80%) than in neuromuscular controls (35%; P < 0.005). Tremor severity and tremor-related disability were also significantly greater in CIDP patients than in controls. Accelerometry data confirmed the presence of a 5.5 Hz postural tremor and a 5 Hz kinetic tremor.Conclusions: Tremor appears to be a common clinical feature of CIDP that results in significant disability. Sensory and motor impairment may be associated with development of tremor in CIDP. Muscle Nerve 55: 338-343, 2017. [ABSTRACT FROM AUTHOR]

Essential tremor (ET) is a common movement disorder affecting millions of people. Studies of ET patients and perturbations in animal models have provided a foundation for the neural networks involved in its pathophysiology. However, ET encompasses a wide variability of phenotypic expression, and this may be the consequence of dysfunction in distinct subcircuits in the brain. The cerebello-thalamo-cortical circuit is a common substrate for the multiple subtypes of action tremor. Within the cerebellum, three sets of cerebellar cortex-deep cerebellar nuclei connections are important for tremor. The lateral hemispheres and dentate nuclei may be involved in intention, postural and isometric tremor. The intermediate zone and interposed nuclei could be involved in intention tremor. The vermis and fastigial nuclei could be involved in head and proximal upper extremity tremor. Studying distinct cerebellar circuitry will provide important framework for understanding the clinical heterogeneity of ET. [ABSTRACT FROM AUTHOR]

Cerebral venous thrombosis (CVT) has a broad spectrum of clinical presentation compared to arterial etiology. Seizure is one of the common symptoms and is more frequent than in other stroke types. Hence, transient neurological symptoms in CVT patients are usually due to epileptic seizures, while transient repetitive movement disorder is extremely rare except as a complication of epilepsy. We report a case of CVT in the superior sagittal sinus with a 1-year history of paroxysmal kinetic tremor without evident epilepsy. [ABSTRACT FROM AUTHOR]

Background: Observation of the signals recorded from the extremities of Parkinson's disease patients showing rest and/or action tremor reveal a distinct high power resonance peak in the frequency band corresponding to tremor. The aim of the study was to investigate, using quantitative measures, how clinically effective and less effective deep brain stimulation protocols redistribute movement power over the frequency bands associated with movement, pathological and physiological tremor, and whether normal physiological tremor may reappear during those periods that tremor is absent. Methods: The power spectral density patterns of rest and action tremor were studied in 7 Parkinson's disease patients treated with (bilateral) deep brain stimulation of the subthalamic nucleus. Two tests were carried out: 1) the patient was sitting at rest; 2) the patient performed a hand or foot tapping movement. Each test was repeated four times for each extremity with different stimulation settings applied during each repetition. Tremor intermittency was taken into account by classifying each 3-second window of the recorded angular velocity signals as a tremor or non-tremor window. Results: The distribution of power over the low frequency band (<3.5 Hz - voluntary movement), tremor band (3.5-7.5 Hz) and high frequency band (>7.5 Hz - normal physiological tremor) revealed that rest and action tremor show a similar power-frequency shift related to tremor absence and presence: when tremor is present most power is contained in the tremor frequency band; when tremor is absent lower frequencies dominate. Even under resting conditions a relatively large low frequency component became prominent, which seemed to compensate for tremor. Tremor absence did not result in the reappearance of normal physiological tremor. Conclusion: Parkinson's disease patients continuously balance between tremor and tremor suppression or compensation expressed by power shifts between the low frequency band and the tremor frequency band during rest and voluntary motor actions. This balance shows that the pathological tremor is either on or off, with the latter state not resembling that of a healthy subject. Deep brain stimulation can reverse the balance thereby either switching tremor on or off. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Determine the effect of concentric and eccentric movement and contraction intensity on the strength of rhythmic muscle activity in individuals with essential tremor (ET). Methods: 21 ET subjects and 22 healthy controls produced wrist flexion–extension movements while supporting sub-maximal loads (no-load, 5%, 15% and 25% 1-repetition maximum). Kinetic tremor and wrist extensor neuromuscular activity were recorded using an angular displacement sensor and electromyography (EMG). Results: Rhythmic muscle activity was twice as big during movement compared to previous results involving postural or isometric tasks. ET subjects with greater rhythmic muscle activity had (1) larger overall kinetic tremor amplitude, (2) greater tremor spectral power during eccentric compared to concentric movement and (3) a reduction in overall kinetic tremor amplitude and the percentage of EMG spectral power accounted for by the tremor spectral peak in the presence of inertial loading. Conclusions: Greater than normal kinetic tremor amplitude appears to be limited to ET subjects with higher levels of rhythmic muscle activity. Furthermore, rhythmic muscle activity is much greater during movement compared to during postural or closed-kinetic tasks. Significance: The strength of rhythmic muscle activity in ET is influenced by the type of contraction (i.e., static vs. dynamic) being performed. Clinicians and researchers should include measures of simple kinetic tremor as part of their assessments. [Copyright &y& Elsevier]

Abstract: Introductio n. It is a well-known fact that physiological tremor has a deleterious effect on small and precise movements. We recently showed that the amplitude of postural physiological tremor can be voluntarily reduced. Whether this is also applicable to tremor during small movements has not been explored. Objective. This study aims to characterize tremor during movement, assess whether it is possible to reduce tremor amplitude during voluntary movements, and quantify any changes in accuracy that may result from this modulation. Methods. Finger tremor was measured in 12 healthy volunteers using a laser displacement sensor and recorded during (A) a postural physiological tremor condition, (B) a slow target tracking task, and (C) the same tracking task while trying to reduce tremor amplitude. Results. The tremor characteristics such as distribution of power within the power spectrum remained similar during movement when compared to the static postural condition. Tremor amplitude was significantly reduced when participants attempted to do so. However, this reduction was accompanied with a systematic increase in error. Finally, mean error was significantly higher when the target line moved at higher velocity. Discussion. Our results demonstrate that tremor remains present during movement and that its amplitude can be voluntarily modulated. However, attempting to voluntarily reduce the amplitude of that tremor during movement is not an efficient way to improve tracking performance. [ABSTRACT FROM AUTHOR]

Human physiological tremor is a complex phenomenon that is modulated by numerous mechanical, neurophysiological, and environmental conditions. Researchers investigating tremor have suggested that acute hypoxia increases tremor amplitude. Based on the results of prior studies, we hypothesized that human participants exposed to a simulated altitude of 4,500 m would display an increased tremor amplitude within the 6-12 Hz frequency range. Postural and kinetic tremors were recorded with a laser system in 23 healthy male participants before, during, and after 1 h of altitude-induced hypoxia. A large panel of tremor characteristics was used to investigate the effect of hypoxia. Acute hypoxia increased tremor frequency content between 6 and 12 Hz during both postural and kinetic tremor tasks (P < 0.05, F = 6.142, Eta(2) = 0.24 and P < 0.05, F = 3.767 Eta(2) = 0.14, respectively). Although the physiological mechanisms underlying the observed changes in tremor are not completely elucidated yet, this study confirms that acute hypoxia increases tremor frequency in the 6-12 Hz range. Furthermore, this study indicates that changes in physiological tremor can be detected at lower hypoxemic levels than previously reported (blood saturation in oxygen = 80.9%). The effects of hypoxia mainly result from a cascade of events starting with the activation of the hypothalamic-pituitary-adrenal axis causing in turn an increase in catecholamine release, leading to an augmentation of tremor amplitude in the 6- to 12-Hz interval and heart rate increase. [ABSTRACT FROM AUTHOR]

Since the first description of the disorder which we now call “Parkinson’s Disease” (PD) much has changed not only because of new therapeutic possibilities. Initially only the rest tremor was described. Today it is generally accepted that PD can be accompanied by different forms of tremor. Nevertheless the kinetic tremor is hardly examined and no attention is paid to it in clinical rating scales although it can already be found in old published drawings of PD-patients. To date instrumented investigations do not capture the most common kinetic tremor of PD that seems to be frequent under everyday life conditions. In order to assess the significance of kinetic tremor in PD, tremor during a spiral drawing task was investigated in an open study involving 870 patients. The results indicate that a combination of rest, postural and kinetic tremors constitute the most frequent tremor constellation in PD. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The present study demonstrates that tremor can be detected during slow alternating movements (SAM) performed by patients with early Parkinson’s disease (PD) and that its relative amplitude is strongly correlated with patients’ rest and postural hand tremor amplitudes (Rho = 0.80 and 0.61, respectively, P<0.05). However, the tremor detected during SAM did not influence the accuracy of patients because of its relatively low amplitude. These results imply that the presence of tremor during movement is not restricted to advanced PD, but can also be detected in patients with early PD having relatively low amplitude tremor. Evidence that the tremor detected at rest, during posture and during voluntary movement share similar or overlapping neural substrates is also presented. [ABSTRACT FROM AUTHOR]

Parkinson's disease results in motor impairment that deteriorates patients' quality of life. One of the symptoms negatively interfering with daily activities is kinetic tremor which should be measured to monitor the outcome of therapy. A new instrumented method of quantification of the kinetic tremor is proposed, based on the analysis of circles drawn on a digitizing tablet by a patient. The aim of this approach is to obtain a tremor scoring equivalent to that performed by trained clinicians. Models are trained with the least absolute shrinkage and selection operator (LASSO) method to predict the tremor scores on the basis of the parameters computed from the patients' drawings. Signal parametrization is derived from both expert knowledge and the response of an artificial neural network to the raw data, thus the approach was named multimodal. The fitted models are eventually combined into model ensembles that provide aggregated scores of the kinetic tremor captured in the drawings. The method was verified with a set of clinical data acquired from 64 Parkinson's disease patients. Automated and objective quantification of the kinetic tremor with the presented approach yielded promising results, as the Pearson's correlations between the visual ratings of tremor and the model predictions ranged from 0.839 to 0.890 in the best-performing models. [ABSTRACT FROM AUTHOR]

Background: The basal ganglia and cerebellum are brain structures involved in movement initiation, execution and termination. They are thought to be involved in the tremor generation and movement deficits in Parkinson's disease (PD) and essential tremor (ET). Especially in PD, maintaining cyclic movement, such as walking or tapping can be significantly disturbed. Providing external cues improves timing of these movements in PD but its effect on ET has not yet been studied in depth. The aim of this study is to evaluate the usefulness of a bimanual tapping task as a tool during clinical decision making.Method: Hand movements and tremor was recorded using accelerometers and EMG (m. extensor carpi ulnaris) from PD and ET patients and healthy controls during a bimanual tapping task as a way to distinguish PD from ET. All subjects performed the tapping task at two different frequencies, 2 Hz and 4 Hz, with and without the presence of auditory cues.Results: No significant intra-group differences were found in the patient groups. Acceleration data revealed significantly less accurate tapping and more variable tapping in PD than in ET and healthy controls. ET subjects tapped less accurate and with a greater variability than healthy controls during the 4 Hz tapping task. Most interestingly the tapping accuracy improved in PD patients when kinetic tremor was recorded with EMG during the task.Conclusion: Providing ET and PD patients with an external cue results in different tapping performances between patient groups and healthy controls. Furthermore, the findings suggest that kinetic tremor in PD enables patients to perform the task with a greater accuracy. So far this has not been shown in other studies. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the study was to investigate the interplay between involuntary tremulous activities and task performance under volitional control for patients with Parkinson’s disease (PD) during position tracking. A volunteer sample of nine untreated patients and nine age-matched healthy subjects participated in this study. They performed a sinusoidal tracking maneuver with a shoulder and a static pointing task; meanwhile, a position trace of the index and accelerometer data in the upper limb were recorded to characterize tracking performance and postural–kinetic tremors. In reference to postural tremor, the kinetic tremor of control subjects during tracking was considerably modulated, leading to a lower regularity and greater spectral deviation. In contrast, patients with PD demonstrated greater postural and kinetic tremors than control subjects, and tremulous movements of the patients were comparatively task-invariant. The prominent coherence peak, which occurred at 8–12Hz in control subjects, was atypically presented at 5–8Hz for PD patients with poorer tracking performance. Functionally, congruency of position tracking was related to amplitude of kinetic tremor after subtracting from amplitude of postural tremor. In conclusion, task-dependent organization of tremulous movements was impaired in patients with PD. The inferior tracking performance of the patients correlated implicitly with kinetic tremor, signifying some sharing of neural substrates for manual tracking and tremor generation. [Copyright &y& Elsevier]