Intention tremor of the head in patients with essential tremor (original) (raw)
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Eye movement abnormalities in essential tremor may indicate cerebellar dysfunction
Brain, 2003
Experimental and clinical data indicate that the cerebellum is involved in the pathophysiology of advanced stages of essential tremor (ET). The aim of this study was to determine whether a dysfunction also affects cerebellar structures involved in eye movement control. Eye movements of 14 patients with ET and 11 agematched control subjects were recorded using the scleral search-coil technique. Vestibular function was assessed by electro-oculography. Eight ET patients had clinical evidence of intention tremor (ET IT ); six had a predominantly postural tremor (ET PT ) without intention tremor. ET patients showed two major de®cits that may indicate cerebellar dysfunction: (i) an impaired smooth pursuit initiation; and (ii) pathological suppression of the vestibulo-ocular re¯ex (VOR) time constant by head tilts (`otolith dumping'). In the step ramp smooth pursuit paradigm, the initial eye acceleration in the ®rst 60 ms of pursuit generation was signi®cantly reduced in ET patients, particularly in ET IT patients, by~44% (mean 23.4°/s 2 ) compared with that of control subjects (mean 41.3°/s 2 ). Subsequent steady-state pursuit velocity and sinusoidal pursuit gain (e.g. 0.4 Hz: 0.90 versus 0.78) were also signi®cantly decreased in ET patients, whereas pursuit latency was unaffected. The intention tremor score correlated with the pursuit deficit, e.g. ET IT patients were signi®cantly more affected than ET PT patients. Gain and time constant (t) of horizontal VOR were normal, but suppression of the VOR time constant by head tilt (`otolith dumping') was pathological in 41% of ET patients, particularly in ET IT patients. Saccades and gaze-holding function were not impaired. The de®cit of pursuit initiation, its correlation with the intensity of intention tremor, and the pathological VOR dumping provide additional evidence of a cerebellar dysfunction in the advanced stage of ET, when intention tremor becomes part of the clinical symptoms, and point to a common pathomechanism. The oculomotor de®cits may indicate an impairment of the caudal vermis in ET.
Annals of Neurology, 1993
The origin of essential tremor is unknown. Animal models have suggested that the inferior olivary nucleus may act as a tremor generator. We used positron emission tomography to study changes in regional cerebral blood flow associated with involuntary postural tremor and passive wrist oscillation in patients with essential tremor. Activation due to voluntary wrist oscillation and arm extension without tremor was studied in normal control subjects. The essential tremor group had bilaterally increased cerebellar blood flow at rest (without tremor) compared with the control group. Involuntary postural tremor was associated with further bilateral cerebellar activation, and also contralateral striatal, thalamic, and sensorimotor cortex activation. Voluntary wrist oscillation, maintained arm extension without tremor, and passive wrist oscillation were all associated with significant ipsilateral rather than bilateral cerebellar activation. We conclude that essential tremor is asociated with increased bilateral cerebellar activity both at rest and during tremor. Jenkins IH, Bain I'G, Colebatch JG, Thompson PI), Findley IJ, Frackowiak RSJ, Marsden CD, Brooks DJ. A positron emission tomography smdy of essential tremor: evidence for overactivity of cerelxllar connections. Ann Neurol 1933;34:82-30 Essential tremor (ET) is considered to be the most common movement disorder. Various studies have reported an overall population prevalence of between 0.3 and 1.794, and up to 5.5% in the over-40 age group [I}. The variation in these figures may in part reflect differences both in the diagnostic criteria used and in the genetic makeup of the communities studied. The pathological bais of ET is not understood; no consistent lesions have been found at postmortem examinations [2-6]. The existence of a possible central generator for the tremor has been hotly debated. Ipsilateral hemiparesis { 7 ] , cerebellar stroke LS}, and stereotactic lesions of the contralateral nucleus ventralis intermedius (Vim) of the thalamus 197 can all abolish ET in humans, lending support to a central origin for El-. The pharmacology of ET fails to clarify the issue of central or peripheral tremor origin; patients with ET gain variable relief from centrally acting agents (alcohol, benzodiazepines, and the anticonvulsant primidone) {10-12}, while useful P-blockers, such as propranolol and sotalol, have peripheral Pz-antagonist action {I 31. Consequently, the mechanisms by which alcohol, P-blockers, and primidone reduce the amplitude of tremor are likely to be variable, involving the suppression of either central o r peripheral neural activity. Centrally acting agents that induce postural tremor in humans include cholinergic and monoaminergic agonists, the anticonvulsant (and y-;uninobutyric acid [GAUA} agonist) sodium valproate, heavy metals, metal chelators, and carbon tetrachloride 1141.
Bilateral cerebellar activation in unilaterally challenged essential tremor
NeuroImage: Clinical, 2016
Background: Essential tremor (ET) is one of the most common hyperkinetic movement disorders. Previous research into the pathophysiology of ET suggested underlying cerebellar abnormalities. Objective: In this study, we added electromyography as an index of tremor intensity to functional Magnetic Resonance Imaging (EMG-fMRI) to study a group of ET patients selected according to strict criteria to achieve maximal homogeneity. With this approach we expected to improve upon the localization of the bilateral cerebellar abnormalities found in earlier fMRI studies. Methods: We included 21 propranolol sensitive patients, who were not using other tremor medication, with a definite diagnosis of ET defined by the Tremor Investigation Group. Simultaneous EMG-fMRI recordings were performed while patients were off tremor medication. Patients performed unilateral right hand and arm extension, inducing tremor, alternated with relaxation (rest). Twenty-one healthy, age-and sex-matched participants mimicked tremor during right arm extension. EMG power variability at the individual tremor frequency as a measure of tremor intensity variability was used as a regressor, mathematically independent of the block regressor, in the general linear model used for fMRI analysis, to find specific tremor-related activations. Results: Block-related activations were found in the classical upper-limb motor network, both for ET patients and healthy participants in motor, premotor and supplementary motor areas. In ET patients, we found tremor-related activations bilaterally in the cerebellum: in left lobules V, VI, VIIb and IX and in right lobules V, VI, VIIIa and b, and in the brainstem. In healthy controls we found simulated tremor-related activations in right cerebellar lobule V. Conclusions: Our results expand on previous findings of bilateral cerebellar involvement in ET. We have identified specific areas in the bilateral somatomotor regions of the cerebellum: lobules V, VI and VIII.
A Voxel-Wise Meta-Analysis on the Cerebellum in Essential Tremor
Medicina
Background and Objectives: Essential tremor is a chronic progressive neurological condition. The clinical presentation of essential tremor is heterogeneous and includes involuntary tremor on hands or arms and progressively on head, jaw, and voice. More extensive and complex symptoms may also be noticed in several patients. Many studies have been carried out to identify biomarkers to help the diagnosis, however, all the efforts have not shown any substantial results yet. Materials and Methods: Here, we aimed to perform a voxel-based meta-analysis using a dedicated cerebellar mask to clarify whether the results from the previous studies are robust and have any clinical significance. We included studies with a total of 377 essential tremor patients and 338 healthy control individuals. Results: A significant regional decrease in the volume of the gray matter was detected in the right cerebellar hemispheric lobule IV/V, and in the cerebellar vermic lobule IV/V. Conclusions: This is the f...
The role of the cerebellum in the pathogenesis of essential tremor
Sohag Medical Journal, 2021
Abnormal activity in a neuronal network in which the cerebellum is included is coherent with continuous tremor oscillation. Within the cortico-Olivo-cerebella-thalamic circuit, the inferior olive could be an oscillator by having pacemaker properties. Despite that, the olivary pacemaker hypothesis faces many contradicting findings against the concept of a single oscillator. The attention has changed from the interactions between the elements and structures of the neural network in which the oscillators are contained to concentrate on its features. These features include the intensity and direction of the connection. Deficiency in the glutamatergic system in ET may be a better explanation for abnormal cerebellar function in ET. A reduction in dentate GABA receptor levels could be a basic defect in this disease. This may be explained by the reduced production of GABA from Purkinje cells at the postsynaptic neurons. This results in the release of deep cerebellar nuclei from previous inhibition. The correlation between genetic abnormalities and cerebellar dysfunction may explain this in the future.
Role of altered cerebello-thalamo-cortical network in the neurobiology of essential tremor
Neuroradiology, 2017
Introduction Essential tremor (ET) is the most common movement disorder among adults. Although ET has been recognized as a mono-symptomatic benign illness, reports of non-motor symptoms and non-tremor motor symptoms have increased its clinical heterogeneity. The neural correlates of ET are not clearly understood. The aim of this study was to understand the neurobiology of ET using resting state fMRI. Methods Resting state functional MR images of 30 patients with ET and 30 age-and gender-matched healthy controls were obtained. The functional connectivity of the two groups was compared using whole-brain seed-to-voxel-based analysis. Results The ET group had decreased connectivity of several cortical regions especially of the primary motor cortex and the primary somatosensory cortex with several right cerebellar lobules compared to the controls. The thalamus on both hemispheres had increased connectivity with multiple posterior cerebellar lobules and vermis. Connectivity of several right cerebellar seeds with the cortical and thalamic seeds had significant correlation with an overall score of Fahn-Tolosa-Marin tremor rating scale (FTM-TRS) as well as the subscores for head tremor and limb tremor. Conclusion Seed-to-voxel resting state connectivity analysis revealed significant alterations in the cerebello-thalamocortical network in patients with ET. These alterations correlated with the overall FTM scores as well as the subscores for limb tremor and head tremor in patients with ET. These results further support the previous evidence of cerebellar pathology in ET.
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.
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.