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Buijink AWG, van der Stouwe AMM, Broersma M, Sharifi S, Groot PFC, Speelman JD, Maurits NM, van Rootselaar AF. Motor network disruption in essential tremor: a functional and effective connectivity study. Brain 2015; 138:2934-47. [PMID: 26248468 DOI: 10.1093/brain/awv225] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 06/19/2015] [Indexed: 11/14/2022] Open
Abstract
Although involvement of the cerebello-thalamo-cortical network has often been suggested in essential tremor, the source of oscillatory activity remains largely unknown. To elucidate mechanisms of tremor generation, it is of crucial importance to study the dynamics within the cerebello-thalamo-cortical network. Using a combination of electromyography and functional magnetic resonance imaging, it is possible to record the peripheral manifestation of tremor simultaneously with brain activity related to tremor generation. Our first aim was to study the intrinsic activity of regions within the cerebello-thalamo-cortical network using dynamic causal modelling to estimate effective connectivity driven by the concurrently recorded tremor signal. Our second aim was to objectify how the functional integrity of the cerebello-thalamo-cortical network is affected in essential tremor. We investigated the functional connectivity between cerebellar and cortical motor regions showing activations during a motor task. Twenty-two essential tremor patients and 22 healthy controls were analysed. For the effective connectivity analysis, a network of tremor-signal related regions was constructed, consisting of the left primary motor cortex, premotor cortex, supplementary motor area, left thalamus, and right cerebellar motor regions lobule V and lobule VIII. A measure of variation in tremor severity over time, derived from the electromyogram, was included as modulatory input on intrinsic connections and on the extrinsic cerebello-thalamic connections, giving a total of 128 models. Bayesian model selection and random effects Bayesian model averaging were used. Separate seed-based functional connectivity analyses for the left primary motor cortex, left supplementary motor area and right cerebellar lobules IV, V, VI and VIII were performed. We report two novel findings that support an important role for the cerebellar system in the pathophysiology of essential tremor. First, in the effective connectivity analysis, tremor variation during the motor task has an excitatory effect on both the extrinsic connection from cerebellar lobule V to the thalamus, and the intrinsic activity of cerebellar lobule V and thalamus. Second, the functional integrity of the motor network is affected in essential tremor, with a decrease in functional connectivity between cortical and cerebellar motor regions. This decrease in functional connectivity, related to the motor task, correlates with an increase in clinical tremor severity. Interestingly, increased functional connectivity between right cerebellar lobules I-IV and the left thalamus correlates with an increase in clinical tremor severity. In conclusion, our findings suggest that cerebello-dentato-thalamic activity and cerebello-cortical connectivity is disturbed in essential tremor, supporting previous evidence of functional cerebellar changes in essential tremor.
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Affiliation(s)
- Arthur W G Buijink
- 1 Department of Neurology and Clinical Neurophysiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands 2 Brain Imaging Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - A M Madelein van der Stouwe
- 3 Department of Neurology, University Medical Center Groningen, University of Groningen, The Netherlands 4 Neuroimaging Center, University Medical Center Groningen, University of Groningen, The Netherlands
| | - Marja Broersma
- 3 Department of Neurology, University Medical Center Groningen, University of Groningen, The Netherlands 4 Neuroimaging Center, University Medical Center Groningen, University of Groningen, The Netherlands
| | - Sarvi Sharifi
- 1 Department of Neurology and Clinical Neurophysiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands 2 Brain Imaging Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Paul F C Groot
- 2 Brain Imaging Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands 5 Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Johannes D Speelman
- 1 Department of Neurology and Clinical Neurophysiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Natasha M Maurits
- 3 Department of Neurology, University Medical Center Groningen, University of Groningen, The Netherlands 4 Neuroimaging Center, University Medical Center Groningen, University of Groningen, The Netherlands
| | - Anne-Fleur van Rootselaar
- 1 Department of Neurology and Clinical Neurophysiology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands 2 Brain Imaging Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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Kuiper M, Hendrikx S, Koehler PJ. Headache and Tremor: Co-occurrences and Possible Associations. Tremor Other Hyperkinet Mov (N Y) 2015; 5:285. [PMID: 26175954 PMCID: PMC4472994 DOI: 10.7916/d8p55mkx] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 05/12/2015] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Tremor and headache are two of the most prevalent neurological conditions. This review addresses possible associations between various types of tremor and headache, and provides a differential diagnosis for patients presenting with both tremor and headache. METHODS Data were identified by searching MEDLINE in February 2015, with the terms "tremor" and terms representing the primary headache syndromes. RESULTS Evidence for an association between migraine and essential tremor is conflicting. Other primary headaches are not associated with tremor. Conditions that may present with both tremor and headache include cervical dystonia, infectious diseases, hydrocephalus, spontaneous cerebrospinal fluid leaks, space-occupying lesions, and metabolic disease. Furthermore, both can be seen as a side effect of medication and in the use of recreational drugs. DISCUSSION No clear association between primary headaches and tremor has been found. Many conditions may feature both headache and tremor, but rarely as core clinical symptoms at presentation.
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Abstract
Neuroimaging studies are of crucial relevance in defining the pathophysiology of restless legs syndrome (RLS). MRI studies showed no structural brain lesions and confirmed a central iron deficiency. Structural and functional studies showed an involvement of the thalamus, sensorimotor cortical areas, and cerebellum in RLS and assessed neurotransmission abnormalities in the dopaminergic and opiate systems. Finally, glutamatergic hyperactivity has been proposed as a cause of disrupted and shortened sleep in RLS. Differences among the results of the studies make it difficult to draw any definitive conclusions, thus, suggesting the need for future research.
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Affiliation(s)
- Federica Provini
- Department of Biomedical and Neuromotor Sciences, Bellaria Hospital, University of Bologna, Via Altura 3, Bologna 40139, Italy; IRCCS Institute of Neurological Sciences of Bologna, Bologna, Italy.
| | - Giacomo Chiaro
- Department of Biomedical and Neuromotor Sciences, Bellaria Hospital, University of Bologna, Via Altura 3, Bologna 40139, Italy
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Lei X, Li H, Huang B, Rizak J, Li L, Xu L, Liu L, Wu J, Lü L, Wang Z, Hu Y, Le W, Deng X, Li J, Yao Y, Xu L, Hu X, Zhang B. 1-Methyl-4-phenylpyridinium stereotactic infusion completely and specifically ablated the nigrostriatal dopaminergic pathway in rhesus macaque. PLoS One 2015; 10:e0127953. [PMID: 26010745 PMCID: PMC4444358 DOI: 10.1371/journal.pone.0127953] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2015] [Accepted: 04/22/2015] [Indexed: 01/09/2023] Open
Abstract
Introduction Complete and specific ablation of a single dopaminergic (DA) pathway is a critical step to distinguish the roles of DA pathways in vivo. However, this kind of technique has not been reported in non-human primates. This study aimed to establish a lesioning method with a complete and specific ablation. Method A carefully designed infusion route based on a MRI stereotactic technique was developed to deliver the highly selective dopaminergic toxin 1-methyl-4-phenylpyridinium (MPP+) unilaterally into multiple sites of compact part of substantia nigra (SNc) and striatum in monkeys. The nigrostriatal DA pathway was selected because lesioning of this pathway may induce symptoms that are suitable for evaluation. The pathological, behavioral, neuropharmacological, and clinical laboratorial data were collected to evaluate the lesioning effects. Result Pathological examination revealed a complete ablation of tyrosine hydroxylase positive (TH+) neurons in the SNc, while preserving intact TH+ neurons in the ventral tegmental area (VTA) nearby. TH+ projections in the striatum were also unilaterally lost. The monkeys displayed stable (>28 weeks) rotations and symptoms which were expected with loss of DA neurons in the SNc, with rest tremor being an exception. No item implied the presence of a severe side effect caused by the operation or the intracerebral MPP+ infusion. The results suggested that rest tremor may not directly rely on the nigrostriatal pathway. Conclusion Taken together, in addition to providing a specific nigrostriatal DA lesioned model, this method, combined with brain stimulation or other techniques, can be applied as a powerful tool for the complete lesion of any desired DA pathway in order to study its specific functions in the brain.
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Affiliation(s)
- Xiaoguang Lei
- Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Hao Li
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
- University of the Chinese Academy of Sciences, Beijing, China
| | - Baihui Huang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
- University of the Chinese Academy of Sciences, Beijing, China
| | - Joshua Rizak
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Ling Li
- Medical Imaging Department, Kunming General Hospital of PLA, Kunming, Yunnan, China
| | - Liqi Xu
- Medical Imaging Department, Kunming General Hospital of PLA, Kunming, Yunnan, China
| | - Li Liu
- Medical Imaging Department, Kunming General Hospital of PLA, Kunming, Yunnan, China
| | - Jing Wu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Longbao Lü
- Kunming Primate Research Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Zhengbo Wang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Yingzhou Hu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Weidong Le
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Xingli Deng
- Neurosurgery Department, 1st Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, China
| | - Jiali Li
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
| | - Yonggang Yao
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
- CAS Center for Excellence in Brain Science, Chinese Academy of Sciences, Shanghai, China
| | - Lin Xu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
- CAS Center for Excellence in Brain Science, Chinese Academy of Sciences, Shanghai, China
| | - Xintian Hu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China
- CAS Center for Excellence in Brain Science, Chinese Academy of Sciences, Shanghai, China
- * E-mail: (XH); (BZ)
| | - Baorong Zhang
- Department of Neurology, Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
- * E-mail: (XH); (BZ)
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Abstract
Parkinson's disease (PD) and essential tremor (ET) are the two most common movement disorders. Both have been associated with similar patterns of network activation leading to the suggestion that they may result from similar network dysfunction, specifically involving the cerebellum. Here, we demonstrate that parkinsonian tremors and ETs result from distinct patterns of interactions between neural oscillators. These patterns are reflected in the tremors' derived frequency tolerance, a novel measure readily attainable from bedside accelerometry. Frequency tolerance characterizes the temporal evolution of tremor by quantifying the range of frequencies over which the tremor may be considered stable. We found that patients with PD (N = 24) and ET (N = 21) were separable based on their frequency tolerance, with PD associated with a broad range of stable frequencies whereas ET displayed characteristics consistent with a more finely tuned oscillatory drive. Furthermore, tremor was selectively entrained by transcranial alternating current stimulation applied over cerebellum. Narrow frequency tolerances predicted stronger entrainment of tremor by stimulation, providing good evidence that the cerebellum plays an important role in pacing those tremors. The different patterns of frequency tolerance could be captured with a simple model based on a broadly coupled set of neural oscillators for PD, but a more finely tuned set of oscillators in ET. Together, these results reveal a potential organizational principle of the human motor system, whose disruption in PD and ET dictates how patients respond to empirical, and potentially therapeutic, interventions that interact with their underlying pathophysiology.
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Abstract
PURPOSE OF REVIEW The last several years have witnessed a remarkable increase in research on essential tremor, with consequent advances in our understanding of this entity. An attempt to both summarize and frame this work has not been undertaken. RECENT FINDINGS Here, I show that observations on essential tremor arising from clinical practice/clinical studies have guided scientific studies of this disorder. In turn, the results of scientific studies are beginning to be translated back to the bedside to improve treatment. Recent essential tremor research has given rise to several novel and intriguing ideas about the disease. These include the following: essential tremor may represent a family of diseases rather than a single disease; essential tremor seems to be a disease of the cerebellum or cerebellar system; essential tremor may be neurodegenerative; low gamma aminobutyric acid tone seems to be a central feature of essential tremor. As with many emerging ideas, there is significant discussion and debate over these emerging ideas, and this fuels additional scientific studies. SUMMARY The flow of ideas from clinical observations about essential tremor, to their translation into scientific studies, and their translation back to the bedside, is expected to eventually lead to improvements at the patient interface.
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Morphometric and functional MRI changes in essential tremor with and without resting tremor. J Neurol 2015; 262:719-28. [PMID: 25572161 DOI: 10.1007/s00415-014-7626-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 12/02/2014] [Accepted: 12/22/2014] [Indexed: 12/17/2022]
Abstract
The etiopathogenesis of essential tremor (ET) is still debated, since the predominant role of circuit dysfunction or brain degenerative changes has not been clearly established. The relationship with Parkinson's Disease (PD) is also controversial and resting tremor occurs in up to 20 % of ET. We investigated the morphological and functional changes associated with ET and we assessed potential differences related to the presence (ET+R) or absence (ET-R) of resting tremor. 32 ET patients (18 ET+R; 14 ET-R) and 12 healthy controls (HC) underwent 3T-MRI protocol including Spoiled Gradient T1-weighted sequence for Voxel-Based Morphometry (VBM) analysis and functional MRI during continuous writing of "8" with right dominant hand. VBM analysis revealed no gray and white matter atrophy comparing ET patients to HC and ET+R to ET-R patients. HC showed a higher BOLD response with respect to ET patients in cerebellum and other brain areas pertaining to cerebello-thalamo-cortical circuit. Between-group activation maps showed higher activation in precentral gyrus bilaterally, right superior and inferior frontal gyri, left postcentral gyrus, superior and inferior parietal gyri, mid temporal and supramarginal gyri, cerebellum and internal globus pallidus in ET-R compared to ET+R patients. Our findings support that the dysfunction of cerebello-thalamo-cortical network is associated with ET in absence of any morphometric changes. The dysfunction of GPi in ET+R patients, consistently with data reported in PD resting tremor, might suggest a potential role of this structure in this type of tremor.
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58
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Lucchini RG, Hashim D. Tremor secondary to neurotoxic exposure: mercury, lead, solvents, pesticides. HANDBOOK OF CLINICAL NEUROLOGY 2015; 131:241-249. [PMID: 26563793 DOI: 10.1016/b978-0-444-62627-1.00014-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Lead, mercury, solvents, and pesticide exposures are common in certain occupations and may cause nervous system dysfunction. Tremors may be the herald manifestation among a constellation of acute toxicity signs and symptoms. However, since tremors may also be the only sign on clinical presentation and since tremors also occur in other diseases, relating tremors to a specific occupational exposure can be challenging. Diagnosis of tremor etiology must be based on other findings on physical exam, laboratory results, and/or imaging. Discerning whether the tremor resulted from the occupational environment versus other etiologies requires knowledge of potential exposure sources, additional detail in history taking, and support of other health and industrial professionals. Reduction or removal from the exposure source remains the key first step in treating patients suffering from tremor that had resulted from occupational exposure toxicity.
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Affiliation(s)
- Roberto G Lucchini
- Department of Preventive Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Unit of Occupational Medicine, Department of Medical Surgical Specialties, Radiological Sciences and Public Health, University of Brescia, Brescia, Italy.
| | - Dana Hashim
- Department of Preventive Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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Jhunjhunwala K, Pal PK. The Non-motor Features of Essential Tremor: A Primary Disease Feature or Just a Secondary Phenomenon? TREMOR AND OTHER HYPERKINETIC MOVEMENTS (NEW YORK, N.Y.) 2014; 4:255. [PMID: 25120945 PMCID: PMC4122824 DOI: 10.7916/d8d798mz] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 07/06/2014] [Indexed: 12/01/2022]
Abstract
Essential tremor (ET) is a pathologically heterogeneous neurodegenerative disorder with both motor and increasingly recognized non-motor features. It is debated whether the non-motor manifestations in ET result from widespread neurodegeneration or are merely secondary to impaired motor functions and decreased quality of life due to tremor. It is important to review these features to determine how to best treat the non-motor symptoms of patients and to understand the basic pathophysiology of the disease and develop appropriate pharmacotherapies. In this review, retrospective and prospective clinical studies were critically analyzed to identify possible correlations between the severities of non-motor features and tremor. We speculated that if such a correlation existed, the non-motor features were likely to be secondary to tremor. According to the current literature, the deficits in executive function, attention, concentration, and memory often observed in ET are likely to be a primary manifestation of the disease. It has also been documented that patients with ET often exhibit characteristic personality traits. However, it remains to be determined whether the other non-motor features often seen in ET, such as anxiety, depression, and sleep disturbances are primary or secondary to motor manifestations of ET and subsequent poor quality of life. Finally, there is evidence that patients with ET can also have impaired color vision, disturbances of olfaction, and hearing impairments, though there are few studies in these areas. Further investigations of large cohorts of patients with ET are required to understand the prevalence, nature, and true significance of the non-motor features in ET.
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Affiliation(s)
- Ketan Jhunjhunwala
- Department of Neurology, National Institute of Mental Health & Neurosciences, Bangalore-560029, Karnataka, India
| | - Pramod K Pal
- Department of Neurology, National Institute of Mental Health & Neurosciences, Bangalore-560029, Karnataka, India
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Klaming R, Annese J. Functional anatomy of essential tremor: lessons from neuroimaging. AJNR Am J Neuroradiol 2014; 35:1450-7. [PMID: 23620075 DOI: 10.3174/ajnr.a3586] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The neuropathogenetic processes underlying essential tremor appear to cause subtle morphologic changes in neural networks that include multiple brain structures, primarily the cerebellum, brain stem, frontal lobes, and thalamus. One of the main challenges of neuroimaging in essential tremor is differentiating disease-specific markers from the spectrum of structural changes that occur due to aging. This review discusses recent neuroimaging studies in the light of current knowledge of the neuropsychology and pathology of the disease. We suggest that the application of multiple macroscopic and microscopic neuroimaging modalities, combined with personalized information relative to cognitive and behavioral symptoms, is the prerequisite for a comprehensive classification and correct diagnosis of essential tremor.
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Affiliation(s)
- R Klaming
- From The Brain Observatory, San Diego, California; and Department of Radiology, University of California, San Diego, San Diego, California
| | - J Annese
- From The Brain Observatory, San Diego, California; and Department of Radiology, University of California, San Diego, San Diego, California.
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Louis ED. From neurons to neuron neighborhoods: the rewiring of the cerebellar cortex in essential tremor. CEREBELLUM (LONDON, ENGLAND) 2014; 13:501-12. [PMID: 24435423 PMCID: PMC4077904 DOI: 10.1007/s12311-013-0545-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Remarkably little has been written on the biology of essential tremor (ET), despite its high prevalence. The olivary model, first proposed in the 1970s, is the traditional disease model for ET; however, the model is problematic for a number of reasons. Recently, intensive tissue-based studies have identified a series of structural changes in the brains of most ET cases, and nearly all of the observed changes are located in the cerebellar cortex. These studies suggest that Purkinje cells are central to the pathogenesis of ET and may thus provide a focus for the development of novel therapeutic strategies. Arising from these studies, a new model of ET proposes that the population of Purkinje cells represents the site of the initial molecular/cellular events leading to ET. Furthermore, a number of secondary changes/remodeling observed in the molecular and granular layers (i.e., in the Purkinje cell "neighborhood") are likely to be of additional mechanistic importance. On a physiological level, the presence of remodeling indicates the likely formation of aberrant synapses and the creation of new/abnormal cortical circuits in ET. Specific efforts need to be devoted to understanding the cascade of biochemical and cellular events occurring in the Purkinje cell layer in ET and its neuron neighborhood, as well as the physiological effects of secondary remodeling/rewiring that are likely to be occurring in this brain region in ET.
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Affiliation(s)
- Elan D Louis
- GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA,
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Schmouth JF, Dion PA, Rouleau GA. Genetics of essential tremor: From phenotype to genes, insights from both human and mouse studies. Prog Neurobiol 2014; 119-120:1-19. [DOI: 10.1016/j.pneurobio.2014.05.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 04/16/2014] [Accepted: 05/02/2014] [Indexed: 11/30/2022]
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Benito-León J. Essential tremor: a neurodegenerative disease? TREMOR AND OTHER HYPERKINETIC MOVEMENTS (NEW YORK, N.Y.) 2014; 4:252. [PMID: 25120943 PMCID: PMC4107287 DOI: 10.7916/d8765cg0] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 06/29/2014] [Indexed: 12/01/2022]
Abstract
Background Essential tremor (ET) is one of the most common neurological disorders among adults, and is the most common of the many tremor disorders. It has classically been viewed as a benign monosymptomatic condition, yet over the past decade, a growing body of evidence indicates that ET is a progressive condition that is clinically heterogeneous, as it may be associated with a spectrum of clinical features, with both motor and non-motor elements. In this review, I will describe the most significant emerging milestones in research which, when taken together, suggest that ET is a neurodegenerative condition. Methods A PubMed search conducted in June 2014 crossing the terms “essential tremor” (ET) and “neurodegenerative” yielded 122 entries, 20 of which included the term “neurodegenerative” in the article title. This was supplemented by articles in the author's files that pertained to this topic. Results/Discussion There is an open and active dialogue in the medical community as to whether ET is a neurodegenerative disease, with considerable evidence in favor of this. Specifically, ET is a progressive disorder of aging associated with neuronal loss (reduction in Purkinje cells) as well as other post-mortem changes that occur in traditional neurodegenerative disorders. Along with this, advanced neuroimaging techniques are now demonstrating distinct structural changes, several of which are consistent with neuronal loss, in patients with ET. However, further longitudinal clinical and neuroimaging longitudinal studies to assess progression are required.
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Affiliation(s)
- Julián Benito-León
- Department of Neurology, University Hospital "12 de Octubre", Madrid, Spain ; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain ; Department of Medicine, Complutense University, Madrid, Spain
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64
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Winkelman JW, Schoerning L, Platt S, Jensen JE. Restless legs syndrome and central nervous system gamma-aminobutyric acid: preliminary associations with periodic limb movements in sleep and restless leg syndrome symptom severity. Sleep Med 2014; 15:1225-30. [PMID: 25129262 DOI: 10.1016/j.sleep.2014.05.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 05/06/2014] [Accepted: 05/14/2014] [Indexed: 11/18/2022]
Abstract
BACKGROUND Previous research has demonstrated abnormalities in glutamate and N-acetyl aspartate (NAA) in the thalamus in individuals with restless legs syndrome (RLS) compared with healthy matched controls. However, levels of these transmitters in other RLS-related brain areas and levels of the most common inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), have not been assessed. METHODS This study examined GABA, glutamate, and NAA levels in the dorsal anterior cingulate cortex (ACC), thalamus and cerebellum with the use of proton magnetic resonance spectroscopy ((1)H-MRS) at 4 tesla (4 T) and Megapress difference-editing in 18 subjects with RLS and a matched control group without RLS. Actigraphy was performed on the nights before scans to assess periodic limb movements of sleep (PLMS). RESULTS Levels of GABA, glutamate, and NAA were no different between RLS and control subjects in any of the three voxels of interest. However, GABA levels were positively correlated with both PLM indices and RLS severity in the thalamus and negatively with both of these measures in the cerebellum in RLS subjects. In addition, NAA levels were higher in the ACC in RLS than in controls. CONCLUSION Our preliminary data suggest that known cerebellar-thalamic interactions may modulate the intensity of RLS sensory and motor symptoms. In addition, anterior cingulate cortex may be associated with the affective components of the painful symptoms in this disorder.
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Affiliation(s)
- John W Winkelman
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA; Departments of Psychiatry and Neurology, Sleep Disorders Clinical Research Program, Massachusetts General Hospital, Boston, MA, USA.
| | - Laura Schoerning
- Departments of Psychiatry and Neurology, Sleep Disorders Clinical Research Program, Massachusetts General Hospital, Boston, MA, USA
| | - Sam Platt
- Departments of Psychiatry and Neurology, Sleep Disorders Clinical Research Program, Massachusetts General Hospital, Boston, MA, USA
| | - J Eric Jensen
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA; Brain Imaging Center, McLean Hospital, Boston, MA, USA
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Abstract
For many years, little was written about the underlying biology of ET, despite its high prevalence. Discussions of disease mechanisms were dominated by a focus on tremor physiology. The traditional model of ET, the olivary model, was proposed in the 1970s. The model suffers from several critical problems, and its relevance to ET has been questioned. Recent mechanistic research has focused on the cerebellum. Clinical and neuroimaging studies strongly implicate the importance of this brain region in ET. Recent mechanistic research has been grounded more in tissue-based changes (i.e., postmortem studies of the brain). These studies have collectively and systematically identified a sizable number of changes in the ET cerebellum, and have led to a new model of ET, referred to as the cerebellar degenerative model. Hence, there is a renewed interest in the science behind the biology of ET. How the new understanding of ET will translate into treatment changes is an open question.
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Affiliation(s)
- Elan D Louis
- GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA,
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66
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Louis ED, Huang CC, Dyke JP, Long Z, Dydak U. Neuroimaging studies of essential tremor: how well do these studies support/refute the neurodegenerative hypothesis? TREMOR AND OTHER HYPERKINETIC MOVEMENTS (NEW YORK, N.Y.) 2014; 4:235. [PMID: 24918024 PMCID: PMC4038743 DOI: 10.7916/d8df6pb8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 05/05/2014] [Indexed: 02/08/2023]
Abstract
Background Tissue-based research has recently led to a new patho-mechanistic model of essential tremor (ET)—the cerebellar degenerative model. We are not aware of a study that has reviewed the current neuroimaging evidence, focusing on whether the studies support or refute the neurodegenerative hypothesis of ET. This was our aim. Methods References for this review were identified by searches of PubMed (1966 to February 2014). Results Several neuroimaging methods have been used to study ET, most of them based on magnetic resonance imaging (MRI). The methods most specific to address the question of neurodegeneration are MRI-based volumetry, magnetic resonance spectroscopy, and diffusion-weighted imaging. Studies using each of these methods provide support for the presence of cerebellar degeneration in ET, finding reduced cerebellar brain volumes, consistent decreases in cerebellar N-acetylaspartate, and increased mean diffusivity. Other neuroimaging techniques, such as functional MRI and positron emission tomography (PET) are less specific, but still sensitive to potential neurodegeneration. These techniques are used for measuring a variety of brain functions and their impairment. Studies using these modalities also largely support cerebellar neuronal impairment. In particular, changes in 11C-flumazenil binding in PET studies and changes in iron deposition in an MRI study provide evidence along these lines. The composite data point to neuronal impairment and likely neuronal degeneration in ET. Discussion Recent years have seen a marked increase in the number of imaging studies of ET. As a whole, the combined data provide support for the presence of cerebellar neuronal degeneration in this disease.
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Affiliation(s)
- Elan D Louis
- GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, New York, USA ; Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, USA ; Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA ; Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - Chaorui C Huang
- Brain and Mind Research Institute, Weill Medical College of Cornell University, New York, New York, USA
| | - Jonathan P Dyke
- Department of Radiology, Weill Cornell Medical College, New York, New York, USA
| | - Zaiyang Long
- School of Health Sciences, Purdue University, West Lafayette, Indiana, USA ; Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Ulrike Dydak
- School of Health Sciences, Purdue University, West Lafayette, Indiana, USA ; Department of Radiology and Imaging Sciences, Indiana University School of Medicine, Indianapolis, Indiana, USA
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Sharifi S, Nederveen AJ, Booij J, van Rootselaar AF. Neuroimaging essentials in essential tremor: a systematic review. NEUROIMAGE-CLINICAL 2014; 5:217-31. [PMID: 25068111 PMCID: PMC4110352 DOI: 10.1016/j.nicl.2014.05.003] [Citation(s) in RCA: 103] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 05/03/2014] [Accepted: 05/05/2014] [Indexed: 01/04/2023]
Abstract
Background Essential tremor is regarded to be a disease of the central nervous system. Neuroimaging is a rapidly growing field with potential benefits to both diagnostics and research. The exact role of imaging techniques with respect to essential tremor in research and clinical practice is not clear. A systematic review of the different imaging techniques in essential tremor is lacking in the literature. Methods We performed a systematic literature search combining the terms essential tremor and familial tremor with the following keywords: imaging, MRI, VBM, DWI, fMRI, PET and SPECT, both in abbreviated form as well as in full form. We summarize and discuss the quality and the external validity of each study and place the results in the context of existing knowledge regarding the pathophysiology of essential tremor. Results A total of 48 neuroimaging studies met our search criteria, roughly divided into 19 structural and 29 functional and metabolic studies. The quality of the studies varied, especially concerning inclusion criteria. Functional imaging studies indicated cerebellar hyperactivity during rest and during tremor. The studies also pointed to the involvement of the thalamus, the inferior olive and the red nucleus. Structural studies showed less consistent results. Discussion and conclusion Neuroimaging techniques in essential tremor give insight into the pathophysiology of essential tremor indicating the involvement of the cerebellum as the most consistent finding. GABAergic dysfunction might be a major premise in the pathophysiological hypotheses. Inconsistencies between studies can be partly explained by the inclusion of heterogeneous patient groups. Improvement of scientific research requires more stringent inclusion criteria and application of advanced analysis techniques. Also, the use of multimodal neuroimaging techniques is a promising development in movement disorders research. Currently, the role of imaging techniques in essential tremor in daily clinical practice is limited. We conducted a systematic review of neuroimaging studies in essential tremor. Cerebellar involvement is the most consistent finding. GABAergic dysfunction is worthwhile investigating more intensively. We encourage multimodal neuroimaging focussing on brain networks.
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Affiliation(s)
- Sarvi Sharifi
- Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands ; Brain Imaging Center, Academic Medical Center, Amsterdam, The Netherlands
| | - Aart J Nederveen
- Brain Imaging Center, Academic Medical Center, Amsterdam, The Netherlands ; Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Jan Booij
- Brain Imaging Center, Academic Medical Center, Amsterdam, The Netherlands ; Department of Nuclear Medicine, Academic Medical Center, Amsterdam, The Netherlands
| | - Anne-Fleur van Rootselaar
- Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands ; Brain Imaging Center, Academic Medical Center, Amsterdam, The Netherlands
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Bhalsing KS, Saini J, Pal PK. Understanding the pathophysiology of essential tremor through advanced neuroimaging: A review. J Neurol Sci 2013; 335:9-13. [DOI: 10.1016/j.jns.2013.09.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Revised: 08/02/2013] [Accepted: 09/03/2013] [Indexed: 11/24/2022]
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Janicki SC, Cosentino S, Louis ED. The cognitive side of essential tremor: what are the therapeutic implications? Ther Adv Neurol Disord 2013; 6:353-68. [PMID: 24228071 DOI: 10.1177/1756285613489591] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
While essential tremor (ET) has traditionally been categorized as a pure motor disease, cross-sectional and longitudinal studies of cognition in ET have demonstrated that these patients may have cognitive dysfunction. Recent epidemiological studies demonstrate an association between ET (particularly with onset after age 65) and increased risk for cognitive impairment and dementia. Although existing studies have generally conceptualized cognitive changes in ET as consistent with a 'frontosubcortical' or 'corticocerebellar' profile, results from these same studies suggest that cognitive impairment in ET may in fact be heterogeneous. Furthermore, the underlying mechanisms remain uncertain. Cognitive changes could be a byproduct of the cerebellar dysfunction of ET itself; alternately, they may be a feature of concomitant neurodegenerative diseases that have been associated in several studies with ET, including Alzheimer's disease, Parkinson's disease or progressive supranuclear palsy. While the study of cognitive dysfunction in ET has received research attention in recent years, the results of these studies have not been translated into the clinical domain and clinical practice. This review first summarizes the current literature on the potential relationships between ET and cognitive change. We then suggest areas of further clinical evaluation and treatment; these suggestions are directed at physicians caring for ET patients who may demonstrate or complain of cognitive impairment. As we discuss, clinicians should ideally screen ET patients for possible signs or symptoms of cognitive impairment in addition to assessing for psychiatric comorbidity and quality of life. These recommendations are in contrast to most current clinical practice, which does not routinely include such assessment among ET patients. To our knowledge, there have been no pharmacotherapeutic trials to date of any agent for cognitive change associated with ET. We believe that studies for this indication are now called for. Future efforts in this direction will also need to take into account the pathobiology of cognitive changes in ET, which itself is an area that is ripe for future investigations.
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Affiliation(s)
- Sarah C Janicki
- Department of Neurology, G.H. Sergievsky Center, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY, USA
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Karas PJ, Mikell CB, Christian E, Liker MA, Sheth SA. Deep brain stimulation: a mechanistic and clinical update. Neurosurg Focus 2013; 35:E1. [DOI: 10.3171/2013.9.focus13383] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Deep brain stimulation (DBS), the practice of placing electrodes deep into the brain to stimulate subcortical structures with electrical current, has been increasing as a neurosurgical procedure over the past 15 years. Originally a treatment for essential tremor, DBS is now used and under investigation across a wide spectrum of neurological and psychiatric disorders. In addition to applying electrical stimulation for clinical symptomatic relief, the electrodes implanted can also be used to record local electrical activity in the brain, making DBS a useful research tool. Human single-neuron recordings and local field potentials are now often recorded intraoperatively as electrodes are implanted. Thus, the increasing scope of DBS clinical applications is being matched by an increase in investigational use, leading to a rapidly evolving understanding of cortical and subcortical neurocircuitry. In this review, the authors discuss recent innovations in the clinical use of DBS, both in approved indications as well as in indications under investigation. Deep brain stimulation as an investigational tool is also reviewed, paying special attention to evolving models of basal ganglia and cortical function in health and disease. Finally, the authors look to the future across several indications, highlighting gaps in knowledge and possible future directions of DBS treatment.
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Affiliation(s)
- Patrick J. Karas
- 1Department of Neurosurgery, The Neurological Institute, Columbia University Medical Center, New York, New York; and
| | - Charles B. Mikell
- 1Department of Neurosurgery, The Neurological Institute, Columbia University Medical Center, New York, New York; and
| | - Eisha Christian
- 2Department of Neurosurgery, Keck Hospital of the University of Southern California, Los Angeles, California
| | - Mark A. Liker
- 2Department of Neurosurgery, Keck Hospital of the University of Southern California, Los Angeles, California
| | - Sameer A. Sheth
- 1Department of Neurosurgery, The Neurological Institute, Columbia University Medical Center, New York, New York; and
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71
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Fang W, Lv F, Luo T, Cheng O, Liao W, Sheng K, Wang X, Wu F, Hu Y, Luo J, Yang QX, Zhang H. Abnormal regional homogeneity in patients with essential tremor revealed by resting-state functional MRI. PLoS One 2013; 8:e69199. [PMID: 23869236 PMCID: PMC3711903 DOI: 10.1371/journal.pone.0069199] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 06/06/2013] [Indexed: 01/23/2023] Open
Abstract
Essential tremor (ET) is one of the most common movement disorders in human adults. It can be characterized as a progressive neurological disorder of which the most recognizable feature is a tremor of the arms or hands that is apparent during voluntary movements such as eating and writing. The pathology of ET remains unclear. Resting-state fMRI (RS-fMRI), as a non-invasive imaging technique, was employed to investigate abnormalities of functional connectivity in ET in the brain. Regional homogeneity (ReHo) was used as a metric of RS-fMRI to assess the local functional connectivity abnormality in ET with 20 ET patients and 20 age- and gender-matched healthy controls (HC). The ET group showed decreased ReHo in the anterior and posterior bilateral cerebellar lobes, the bilateral thalamus and the insular lobe, and increased ReHo in the bilateral prefrontal and parietal cortices, the left primary motor cortex and left supplementary motor area. The abnormal ReHo value of ET patients in the bilateral anterior cerebellar lobes and the right posterior cerebellar lobe were negatively correlated with the tremor severity score, while positively correlated with that in the left primary motor cortex. These findings suggest that the abnormality in cerebello-thalamo-cortical motor pathway is involved in tremor generation and propagation, which may be related to motor-related symptoms in ET patients. Meanwhile, the abnormality in the prefrontal and parietal regions may be associated with non-motor symptoms in ET. These findings suggest that the ReHo could be utilized for investigations of functional-pathological mechanism of ET.
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Affiliation(s)
- Weidong Fang
- Department of Radiology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Fajin Lv
- Department of Radiology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Tianyou Luo
- Department of Radiology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
- * E-mail: (TL); (HZ)
| | - Oumei Cheng
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Wei Liao
- Center for Cognition and Brain Disorders, Hangzhou Normal University, Hangzhou, China
- Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, China
| | - Ke Sheng
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Xuefeng Wang
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Fei Wu
- Department of Radiology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yida Hu
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jing Luo
- Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Qing X. Yang
- Center for NMR Research, Department of Radiology, Penn State College of Medicine, Hershey, Pennsylvania, United States of America
| | - Han Zhang
- Center for Cognition and Brain Disorders, Hangzhou Normal University, Hangzhou, China
- Zhejiang Key Laboratory for Research in Assessment of Cognitive Impairments, Hangzhou, China
- * E-mail: (TL); (HZ)
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72
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Saifee TA, Edwards MJ. A normal inferior olive in essential tremor--peacemaker or pacemaker? Mov Disord 2013; 28:694-6. [PMID: 23728621 DOI: 10.1002/mds.25485] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 03/12/2013] [Accepted: 04/01/2013] [Indexed: 11/05/2022] Open
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Choi KH. The design and discovery of T-type calcium channel inhibitors for the treatment of central nervous system disorders. Expert Opin Drug Discov 2013; 8:919-31. [DOI: 10.1517/17460441.2013.796926] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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74
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Louis ED, Babij R, Cortés E, Vonsattel JPG, Faust PL. The inferior olivary nucleus: a postmortem study of essential tremor cases versus controls. Mov Disord 2013; 28:779-86. [PMID: 23483605 DOI: 10.1002/mds.25400] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 01/04/2013] [Accepted: 01/10/2013] [Indexed: 01/02/2023] Open
Abstract
The pathogenesis of essential tremor is poorly understood. Historically, it has been hypothesized that the inferior olivary nucleus plays an important role in the generation of tremor in essential tremor, yet a detailed, controlled, anatomic-pathological study of that brain region has yet to be conducted. A detailed postmortem study was undertaken of the microscopic changes in the inferior olivary nucleus of 14 essential tremor cases versus 15 age-matched controls at the Essential Tremor Centralized Brain Repository. A series of metrics was used to quantify microscopic neuronal and glial changes in the inferior olivary nucleus and its input and output tracts. Olivary linear neuronal density also was assessed. Cases and controls did not differ from one another with respect to any of the assessed metrics (P values ranged from 0.23 to 1.0). Olivary linear neuronal density also was similar in cases and controls (P = 0.62). Paddle-shaped neurons, a morphologic shape change in olivary neurons, which, to our knowledge, have not been previously recognized, occurred to an equal degree in essential tremor cases and controls (P = 0.89) and were correlated with several markers of neuronal loss and gliosis. A systematic postmortem study of the microscopic changes in the inferior olivary nucleus did not detect any differences between cases and controls. These data, along with positron emission tomography data, which have failed to identify any metabolic abnormality of the olive, indicate that, if the olive is involved in essential tremor, then there is no clearly identifiable structural or metabolic correlate.
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Affiliation(s)
- Elan D Louis
- G H Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, New York, USA
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75
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Cerebellar rTMS stimulation may induce prolonged clinical benefits in essential tremor, and subjacent changes in functional connectivity: An open label trial. Brain Stimul 2013; 6:175-9. [PMID: 22609238 DOI: 10.1016/j.brs.2012.04.009] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 04/20/2012] [Accepted: 04/21/2012] [Indexed: 11/21/2022] Open
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The distributed somatotopy of tremor: a window into the motor system. Exp Neurol 2013; 241:156-8. [PMID: 23298522 DOI: 10.1016/j.expneurol.2012.12.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2012] [Accepted: 12/26/2012] [Indexed: 01/11/2023]
Abstract
The posterior ventrolateral thalamus (VLp) plays a crucial role in Parkinson's tremor and in essential tremor: deep brain stimulation (DBS) of the VLp effectively diminishes both tremor types. Previous research has shown tremor oscillations in the VLp, but the spatial extent and somatotopy of these oscillations remained unclear. In this issue of Experimental Neurology, Pedrosa and colleagues measured neuro-muscular coherence at multiple sites in the VLp of patients with essential tremor and Parkinson's disease using implanted DBS electrodes (Pedrosa et al., 2012). They found multiple tremor clusters within the VLp, with spatially distinct tremor clusters for antagonistic muscles, and in many patients also multiple distinct tremor clusters for a single muscle. Interestingly, this group previously showed similar effects for the STN in tremulous Parkinson's disease (Reck et al., 2009, 2010). Together, these studies suggest that the distribution of tremor clusters is a general organizational principle of tremor, being present in two different tremor pathologies, and in two different nodes of the motor system. The presence of multiple tremor clusters also fits with the distributed somatotopy of the healthy motor system. Therefore, a further conclusion of this study could be that tremor is caused by aberrant synchronization within an otherwise healthy network, brought about by different pathophysiological neural triggers.
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Contarino MF, Groot PFC, van der Meer JN, Bour LJ, Speelman JD, Nederveen AJ, van den Munckhof P, Tijssen MAJ, Schuurman PR, van Rootselaar AF. Is there a role for combined EMG-fMRI in exploring the pathophysiology of essential tremor and improving functional neurosurgery? PLoS One 2012; 7:e46234. [PMID: 23049695 PMCID: PMC3462183 DOI: 10.1371/journal.pone.0046234] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Accepted: 08/29/2012] [Indexed: 11/30/2022] Open
Abstract
Background Functional MRI combined with electromyography (EMG-fMRI) is a new technique to investigate the functional association of movement to brain activations. Thalamic stereotactic surgery is effective in reducing tremor. However, while some patients have satisfying benefit, others have only partial or temporary relief. This could be due to suboptimal targeting in some cases. By identifying tremor-related areas, EMG-fMRI could provide more insight into the pathophysiology of tremor and be potentially useful in refining surgical targeting. Objective Aim of the study was to evaluate whether EMG-fMRI could detect blood oxygen level dependent brain activations associated with tremor in patients with Essential Tremor. Second, we explored whether EMG-fMRI could improve the delineation of targets for stereotactic surgery. Methods Simultaneous EMG-fMRI was performed in six Essential Tremor patients with unilateral thalamotomy. EMG was recorded from the trembling arm (non-operated side) and from the contralateral arm (operated side). Protocols were designed to study brain activations related to voluntary muscle contractions and postural tremor. Results Analysis with the EMG regressor was able to show the association of voluntary movements with activity in the contralateral motor cortex and supplementary motor area, and ipsilateral cerebellum. The EMG tremor frequency regressor showed an association between tremor and activity in the ipsilateral cerebellum and contralateral thalamus. The activation spot in the thalamus varied across patients and did not correspond to the thalamic nucleus ventralis intermedius. Conclusion EMG-fMRI is potentially useful in detecting brain activations associated with tremor in patients with Essential Tremor. The technique must be further developed before being useful in supporting targeting for stereotactic surgery.
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Affiliation(s)
- Maria Fiorella Contarino
- Department of Neurology/Clinical Neurophysiology, Academic Medical Center, Amsterdam, The Netherlands
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Passamonti L, Cerasa A, Quattrone A. Neuroimaging of Essential Tremor: What is the Evidence for Cerebellar Involvement? TREMOR AND OTHER HYPERKINETIC MOVEMENTS (NEW YORK, N.Y.) 2012; 2. [PMID: 23439960 PMCID: PMC3572634 DOI: 10.7916/d8f76b8g] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 01/26/2012] [Indexed: 12/13/2022]
Abstract
Background Clinical observations and electrophysiological studies have provided initial evidence for the involvement of the cerebellum in essential tremor (ET), the most frequent hyperkinetic disorder. Recently, this hypothesis has been reinvigorated by post-mortem studies that demonstrated a number of pathological changes in the cerebellum of ET patients compared with age-matched healthy controls. Advanced neuroimaging techniques have also made it possible to detect in vivo which cerebellar abnormalities are present in ET patients and to reveal the core mechanisms implicated in the development of motor and cognitive symptoms in ET. Objective We discuss the neuroimaging research investigating the brain structure and function of ET patients relative to healthy controls. In particular, we review 1) structural neuroimaging experiments assessing the density/volume of cortical/subcortical regions and the integrity of the white-matter fibers connecting them; 2) functional studies exploring brain responses during motor/cognitive tasks and the function of specific neurotransmitters/metabolites within cortical–cerebellar circuits. Methods A search in PubMed was conducted to identify the relevant literature. Discussion Current neuroimaging research provides converging evidence for the role of the cerebellum in the pathophysiology of ET, although some inconsistencies exist, particularly in structural studies. These discrepancies may depend on the high clinical heterogeneity of ET and on differences among the experimental methods used across studies. Further investigations are needed to disentangle the relationships between specific ET phenotypes and the underlying patterns of neural abnormalities.
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Affiliation(s)
- Luca Passamonti
- Unità di Ricerca Neuroimmagini, Istituto di Scienze Neurologiche, Consiglio Nazionale delle Ricerche, Catanzaro, Italy
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Bermejo-Pareja F, Puertas-Martín V. Cognitive features of essential tremor: a review of the clinical aspects and possible mechanistic underpinnings. TREMOR AND OTHER HYPERKINETIC MOVEMENTS (NEW YORK, N.Y.) 2012; 2. [PMID: 23440004 PMCID: PMC3572680 DOI: 10.7916/d89w0d7w] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 05/08/2012] [Indexed: 01/10/2023]
Abstract
The classical concept of essential tremor (ET) as a monosymptomatic tremorogenic disorder has been questioned in the last decade as new evidence has been described. Clinical, neuroimaging, and pathological studies have described a probable structural basis (mainly in cerebellum) and evidence that ET is associated with subtle clinical cerebellar deficits and several non-motor clinical manifestations, such as cognitive and mood disorders. We performed literature searches in Medline, ISI Web of Knowledge, and PsycInfo databases. The aim of this review is to describe cognitive deficits associated with ET. First, we present a brief history of ET cognitive disorders presented. Second, we describe several clinical cross-sectional series demonstrating that ET is associated with mild cognitive deficits of attention, executive functions, several types of memory (working memory, immediate, short term, delayed, and possibly others) and, mood disorders (depression). Recent neuroimaging studies favor a cerebellar basis for these cognitive deficits. Population-based surveys confirm that mild cognitive dysfunction is not limited to severe ET cases, the entire ET group, including mild and undiagnosed cases, can be affected. Cohort studies indicated that ET cognitive deficits could be progressive and that ET patients had an increased risk of dementia. The mood and cognitive deficits in ET are in agreement with cognitive affective cerebellar syndrome described in patients with cerebellar disorders. New evidence, mainly from functional (neuroimaging) and prospective clinical studies would further bolster recent descriptions of ET clinical manifestations.
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Affiliation(s)
- Félix Bermejo-Pareja
- Head of the Neurology Department, University Hospital "12 de Octubre", Madrid, Spain ; Biomedical Research Network on Neurodegenerative Disorders (CIBERNED), Carlos III National Research Institute, Madrid, Spain ; Department of Biomedical Sciences (ANECA), Complutense University of Madrid, Spain
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Bareš M, Husárová I, Lungu OV. Essential tremor, the cerebellum, and motor timing: towards integrating them into one complex entity. Tremor Other Hyperkinet Mov (N Y) 2012; 2:tre-02-93-653-1. [PMID: 23439925 PMCID: PMC3572554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 05/26/2012] [Indexed: 10/27/2022] Open
Abstract
Essential tremor (ET) is the most common movement disorder in humans. It is characterized by a postural and kinetic tremor most commonly affecting the forearms and hands. Isolated head tremor has been found in 1-10% of patients, suggesting that ET may be a composite of several phenotypes. The exact pathophysiology of ET is still unknown. ET has been repeatedly shown as a disorder of mild cerebellar degeneration, particularly in postmortem studies. Clinical observations, electrophysiological, volumetric and functional imaging studies all reinforce the fact that the cerebellum is involved in the generation of ET. However, crucial debate exists as to whether ET is a neurodegenerative disease. Data suggesting that it is neurodegenerative include postmortem findings of pathological abnormalities in the brainstem and cerebellum, white matter changes on diffusion tensor imaging, and clinical studies demonstrating an association with cognitive and gait changes. There is also conflicting evidence against ET as a neurodegenerative disease: the improvement of gait abnormalities with ethanol administration, lack of gray matter volume loss on voxel-based morphometry, failure to confirm the prominent presence of Lewy bodies in the locus ceruleus, and other pathological findings. To clarify this issue, future research is needed to describe the mechanism of cellular changes in the ET brain and to understand the order in which they occur. The cerebellum has been shown to be involved in the timing of movement and sensation, acting as an internal timing system that provides the temporal representation of salient events spanning hundreds of milliseconds. It has been reported that cerebellar timing function is altered in patients with ET, showing an increased variability of rhythmic hand movements as well as diminished performance during predictive motor timing task. Based on current knowledge and observations, we argue that ET is essentially linked with cerebellar degeneration, or at least cerebellar dysfunction, together with disturbance of motor timing. We explain the context of our current understanding on this topic, highlighting possible clinical consequences for patients suffering from ET and future research directions.
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Affiliation(s)
- Martin Bareš
- Central European Institute of Technology, CEITEC MU, Behavioral and Social Neuroscience Research Group, Masaryk University, Brno, Czech Republic
- First Department of Neurology, Faculty of Medicine Masaryk University and St. Anne's Teaching Hospital, Brno, Czech Republic
| | - Ivica Husárová
- First Department of Neurology, Faculty of Medicine Masaryk University and St. Anne's Teaching Hospital, Brno, Czech Republic
| | - Ovidiu V. Lungu
- Psychiatry Department, Université de Montréal, Montréal, Québec, Canada
- Functional Neuroimaging Unit, Research Center of the Geriatric Institute affiliated with the Université de Montréal, Montréal, Québec, Canada
- Research Department, Donald Berman Maimonides Geriatric Centre, Montréal, Québec, Canada
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Ma K, Babij R, Cortés E, Vonsattel JPG, Louis ED. Cerebellar pathology of a dual clinical diagnosis: patients with essential tremor and dystonia. Tremor Other Hyperkinet Mov (N Y) 2012; 2:tre-02-107-6707. [PMID: 23439731 PMCID: PMC3535836 DOI: 10.7916/d8jd4vj5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 06/01/2012] [Indexed: 12/01/2022] Open
Abstract
BACKGROUND Clinical studies have implicated the cerebellum in the pathogenesis of essential tremor (ET), and recent postmortem studies have identified structural changes in the ET cerebellum. While the basal ganglia have traditionally been implicated in dystonia, cerebellar involvement has been suggested as well, and a recent study showed Purkinje cell (PC) loss. We conducted a detailed postmortem examination of the brain in four individuals with clinical diagnoses of ET and dystonia, and hypothesized that pathological changes in the cerebellum would be greater in these four ET cases than in published ET cases without dystonia. METHODS After a complete neuropathological assessment, a standard parasagittal neocerebellar tissue block was harvested in each brain. One 7-µm thick section was stained with luxol fast blue/hematoxylin and eosin, and one section with the Bielschowsky method. We quantified PCs, torpedoes, heterotopic PCs, PC dendritic swellings, and basket cell changes. RESULTS Two ET+dystonia cases had more microscopic changes in the cerebellum than published ET cases; the other two cases had similar changes to published ET cases. DISCUSSION This is the first report that uses human autopsy tissue to study patients with both ET and dystonia. The findings were heterogeneous. Additional studies, with larger samples, are needed.
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Affiliation(s)
- Karen Ma
- GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
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Gironell A, Figueiras FP, Pagonabarraga J, Herance JR, Pascual-Sedano B, Trampal C, Gispert JD. Gaba and serotonin molecular neuroimaging in essential tremor: a clinical correlation study. Parkinsonism Relat Disord 2012; 18:876-80. [PMID: 22595620 DOI: 10.1016/j.parkreldis.2012.04.024] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 04/13/2012] [Accepted: 04/20/2012] [Indexed: 11/18/2022]
Abstract
BACKGROUND Essential tremor is the most common movement disorder in adults, but its exact etiology and pathophysiology are still not fully understood. There is some consensus, however, about the involvement of the cerebellum and accumulating evidence points towards a dysfunction of the gabaergic system. We hypothesize that the serotonin neurotransmission system may also play a role as it does in tremor in Parkinson disease. This study aimed to investigate the association between the severity of tremor symptoms and the gabaergic and serotoninergic neurotransmission systems in essential tremor. MATERIAL AND METHODS We measured the tremor clinical rating scale score and acquired DASB and Flumazenil PET scans in 10 patients who presented with essential tremor at different stages of clinical severity. Statistically significant correlations were sought between the scale scores and parametric binding potential images. RESULTS The correlation analysis of cerebellar Flumazenil uptake and tremor clinical rating scale scores reached statistical significance (R2 = 0.423, p = 0.041), whereas no association was detected in the DASB scans. CONCLUSIONS The severity of tremor correlated with the abnormalities found in GABA receptor binding, suggesting a primary gabaergic deficiency or a functional abnormality at the level of GABA(A) receptor subtypes. These results may assist in the rational development of new pharmacological treatments for essential tremor.
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Affiliation(s)
- A Gironell
- Movement Disorders Unit, Department of Neurology, Sant Pau Hospital, Autonomous University of Barcelona, Catalonia, Spain.
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83
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Saini J, Bagepally BS, Bhatt MD, Chandran V, Bharath RD, Prasad C, Yadav R, Pal PK. Diffusion tensor imaging: tract based spatial statistics study in essential tremor. Parkinsonism Relat Disord 2012; 18:477-82. [PMID: 22297126 DOI: 10.1016/j.parkreldis.2012.01.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 01/02/2012] [Accepted: 01/08/2012] [Indexed: 11/15/2022]
Abstract
INTRODUCTION Essential tremor (ET) is a common movement disorder with motor and non-motor symptoms. We aimed to investigate the neurodegenerative changes in the brain white matter of patients with ET using Diffusion Tensor Imaging (DTI). METHODS Clinical and MRI data from 20 patients (5 women and 15 men; age-38.2 ± 16.5 yrs) with ET and 17 controls (3 women and 14 men; age-40.7 ± 16.5 yrs) were collected prospectively. The DTI data were analyzed using tract based spatial statistics (TBSS) software for tract wise analysis. Further region of interest (ROI) analysis was carried out in the genu of corpus callosum, anterior limb of internal capsule (ALIC), corticospinal tract (CS), and cerebellar peduncles. Effect of tremor severity, disease duration and age of onset on DTI metrics was also studied. RESULTS Patients with ET in comparison to controls showed significant (P(corrected) < 0.05) increase of mean diffusivity and radial diffusivity in right frontoparietal white matter. Axial diffusivity increase was seen in bilateral cerebral hemispheres, thalamus, brainstem and cerebellar hemisphere white matter. No significant change in fractional anisotropy of the white matter was seen. ROI analysis also revealed abnormalities in the ALIC and cerebellar peduncles. There was no correlation between the severity of white matter changes and clinical tremor severity score as well as disease duration. CONCLUSIONS This study provides in vivo evidence for axonal disintegration of the cerebral and cerebellar white matter fibres in patients with ET.
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Affiliation(s)
- Jitender Saini
- Department of Neuroimaging and Interventional Radiology, National Institute of Mental Health & Neurosciences, Hosur Road, Bangalore-560029, Karnataka, India
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Miwa H, Kondo T. T-type calcium channel as a new therapeutic target for tremor. THE CEREBELLUM 2012; 10:563-9. [PMID: 21479969 DOI: 10.1007/s12311-011-0277-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Voltage-gated calcium channels play an important role in many physiological and pathological processes. Accumulating studies suggest that the T-type calcium channel is a potential target for the treatment of various neurological disorders, such as epilepsy, insomnia, and neuropathic pain. Here, we highlight recent advances in our understanding of T-type calcium channel regulation and their implications for tremor disorders. Several T-type calcium channel blockers effectively suppressed experimental tremors that have been suggested to originate from either the cerebellum or basal ganglia. Among T-type calcium channel blockers that have been used clinically, the anti-tremor efficacy of zonisamide garnered our attention. Based on both basic and clinical studies, the possibility is emerging that T-type calcium channel blockers that transit into the central nervous system may have therapeutic potentials for tremor disorders.
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Affiliation(s)
- Hideto Miwa
- Department of Neurology, Wakayama Medical University, 811-1 Kimiidera, Wakayama, 641-8510, Japan.
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85
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The oscillating central network of Essential tremor. Clin Neurophysiol 2011; 123:61-4. [PMID: 22055842 DOI: 10.1016/j.clinph.2011.09.024] [Citation(s) in RCA: 124] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2011] [Revised: 09/27/2011] [Accepted: 09/27/2011] [Indexed: 11/22/2022]
Abstract
Essential tremor (ET) is a centrally driven tremor. It is meanwhile well established that it does not emerge from one single oscillator but an oscillatory network comprising most parts of the physiological central motor network. Several lines of evidence hint at the olivocerebellar system and the thalamus as key structures within this network whereas the cortical motor regions are only intermittently entrained in the tremor rhythm in thalamocortical loops. Dynamic changes in network composition and the interaction in symmetric loops seem to be specific to the generation of tremor. The same network in voluntary motor control is more fixed and subcortico-cortical interactions are preferentially via thalamocortical relays. Thus it is not primarily the network topography but the dynamics and interaction within the network that determines whether involuntary tremor or voluntary movements emerge. And this may be the basis for the selective effect of deep brain stimulation on tremor.
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86
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LaRoia H, Louis ED. Association between essential tremor and other neurodegenerative diseases: what is the epidemiological evidence? Neuroepidemiology 2011; 37:1-10. [PMID: 21757958 DOI: 10.1159/000328866] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Accepted: 04/27/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The possible links between essential tremor (ET) and Parkinson's disease (PD) and, more recently, between ET and Alzheimer's disease (AD) have been of great interest, particularly with the emergence of postmortem data suggesting that ET itself may be a neurodegenerative disease. Given the very high population prevalence of ET, its possible role as a risk factor for PD and AD is of special significance. At the center of this debate is the burgeoning evidence from epidemiological studies, examining whether there is an increased co-occurrence of these conditions within the same individuals or within families. METHODS We conducted a PubMed search from 1966 to March 2011 and reviewed the epidemiological evidence, restricting our analyses to studies that generated quantifiable measures of association (odds ratios or relative risks), thereby being able to assess the role of chance. RESULTS The most robust evidence, from case-control, prospective and familial aggregation studies, indicates that ET is associated with increased odds and increased risks of both PD and AD. CONCLUSIONS There is reasonable epidemiological evidence to support a link between ET and these neurodegenerative diseases. Further studies are needed to corroborate the current results, provide additional estimates of effect and begin to explore the mechanistic underpinnings for these intriguing associations.
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Affiliation(s)
- Hiral LaRoia
- Department of Neurology, Columbia University, New York, NY, USA
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87
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Louis ED, Faust PL, Ma KJ, Yu M, Cortes E, Vonsattel JPG. Torpedoes in the Cerebellar Vermis in Essential Tremor Cases vs. Controls. THE CEREBELLUM 2011; 10:812-9. [PMID: 21656041 DOI: 10.1007/s12311-011-0291-0] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Bagepally BS, Bhatt MD, Chandran V, Saini J, Bharath RD, Vasudev MK, Prasad C, Yadav R, Pal PK. Decrease in Cerebral and Cerebellar Gray Matter in Essential Tremor: A Voxel-Based Morphometric Analysis under 3T MRI. J Neuroimaging 2011; 22:275-8. [DOI: 10.1111/j.1552-6569.2011.00598.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Muthuraman M, Heute U, Deuschl G, Raethjen J. The central oscillatory network of essential tremor. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2010:154-7. [PMID: 21096526 DOI: 10.1109/iembs.2010.5627211] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The responsible pathological mechanisms of essential tremor are not yet clear. In order to understand the mechanisms of the central network its sources need to be found. The cortical sources of both the basic and first "harmonic" frequency of essential tremor are addressed in this paper. The power and coherence were estimated using the multitaper method for EEG and EMG data from 6 essential tremor patients. The Dynamic Imaging of Coherent Sources (DICS) was used to find the coherent sources in the brain. Before hand this method was validated for the application of finding multiple sources for the same oscillation in the brain by using two model simulations which indicated the accuracy of the method. In all the essential tremor patients the corticomuscular coherence was also present in the basic and the first harmonic frequency of the tremor. The source for the basic frequency and the first harmonic frequency was in the region of primary sensory motor cortex, prefrontal and in the diencephalon on the contralateral side for all the patients. Thus the generation of these two oscillations involves the same cortical areas and indicates the oscillation at double the tremor frequency is a harmonic of the basic tremor frequency.
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Affiliation(s)
- M Muthuraman
- Department of Neurology, University of Kiel, 24105 Germany. m.muthuraman@neurologie..uni-kiel.de
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92
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Abstract
Essential tremor (ET) is among the most common neurological disorders. This chapter reviews the epidemiology, clinical features, and pathophysiology of ET. The defining feature is a kinetic tremor of the arms. Patients often have a postural tremor as well. Other body regions may also be involved (especially the head). The severity of tremor may range from mild cases in population settings to more severe cases in treatment settings. Motor features aside from tremor have been described in ET, including tandem gait difficulty. Mild cognitive changes (especially executive dysfunction) have been documented in many studies as well. Despite being regarded as one of the most common hyperkinetic movement disorders, establishing a precise prevalence has been difficult, yet the prevalence among persons aged 40 and older seems to be 4% or higher. There are numerous examples of families in which the disease appears to be inherited yet genetic studies have not progressed to the point where ET genes have been identified. There is also a growing understanding that environmental factors are likely to contribute to the etiology of ET. More recent postmortem studies have helped localize the possible source of ET to structural alterations in the cerebellum and its connecting pathways.
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Jia L, Jia-Lin S, Qin D, Qing L, Yan Z. A diffusion tensor imaging study in essential tremor. J Neuroimaging 2010; 21:370-4. [PMID: 21091815 DOI: 10.1111/j.1552-6569.2010.00535.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE Essential tremor (ET) is suggested to be a neural degenerative disease. The authors investigated the fractional anisotropy (FA) and apparent diffusion coefficient (ADC) value in basal ganglia, thalamus, red nucleus, and substantia nigra in ET patients using diffusion tensor image (DTI). METHODS DTI examination was carried out in patients with ET and controls. FA and ADC values were obtained from various brain structures, including caudate, putamen+pallidum, thalamus, red nucleus, and substantia nigra. RESULTS The ADC value of the red nuclei in patients with ET was higher compared with controls (.90 vs .77; P= .000). However, no significant differences were demonstrated for FA, or ADC values of other structures. CONCLUSIONS The increased ADC value in the red nucleus indicates that there is neuronal damage or loss present, suggesting that ET may be a neurodegenerative disease.
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Affiliation(s)
- Liu Jia
- Department of Radiology, Renji Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai 200127, China
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Sahni H, Jayakumar PN, Pal PK. Functional magnetic resonance imaging in primary writing tremor and writer's cramp: A pilot study. Ann Indian Acad Neurol 2010; 13:192-7. [PMID: 21085530 PMCID: PMC2981757 DOI: 10.4103/0972-2327.70884] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2010] [Revised: 01/14/2010] [Accepted: 03/06/2010] [Indexed: 11/04/2022] Open
Abstract
OBJECTIVES The precise pathophysiology of primary writing tremor (PWT) and writer's cramp (WC) is not known. The aim of this study is to compare the cerebral activation patterns in patients of PWT, WC and healthy controls, during a task of signing on paper, using functional magnetic resonance imaging (fMRI). MATERIALS AND METHODS Six subjects with PWT, three with WC and six healthy volunteers were examined using a 1.5-Tesla scanner. The paradigm consisted of three times repetition of a set of period of rest and activity. Each set consisted of 10 blood oxygen level dependent (BOLD) echo-planar imaging (EPI) acquisitions at rest followed by 10 BOLD EPI acquisitions while signing their names on paper using the dominant right hand. Entire brain was covered. SPM99 analysis was done. RESULTS IN COMPARISON TO THE HEALTHY CONTROLS, THE FOLLOWING DIFFERENCES IN CEREBRAL ACTIVATION WERE NOTED IN THE PATIENTS: (a) primary and supplementary motor areas showed overactivation in patients of PWT and underactivation in patients of WC, (b) the cingulate motor area showed underactivation in patients of PWT and overactivation in patients of WC and (c) the cerebellar activity was reduced in both WC and PWT. CONCLUSION Our preliminary findings suggest that the cerebral and cerebellar activation patterns in PWT and WC during signing on paper are distinct from each other and from healthy controls. There may be cerebellar dysfunction in addition to motor dysfunctions in the pathogenesis of these disorders.
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Affiliation(s)
- Hirdesh Sahni
- Departments of Neuro Imaging and Interventional Radiology Bangalore, Karnataka, India
| | | | - Pramod Kumar Pal
- Neurology, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India
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Boecker H, Weindl A, Brooks DJ, Ceballos-Baumann AO, Liedtke C, Miederer M, Sprenger T, Wagner KJ, Miederer I. GABAergic dysfunction in essential tremor: an 11C-flumazenil PET study. J Nucl Med 2010; 51:1030-5. [PMID: 20554735 DOI: 10.2967/jnumed.109.074120] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
UNLABELLED Essential tremor is the most common movement disorder, but the underlying pathophysiology is not well understood. A primary overactivity of cerebellothalamic output pathways is the most conspicuous finding, as indicated by animal and human studies. It has been argued that this overactivity may be due to impaired central inhibition, and converging evidence points toward a potential role of gamma-aminobutyric acid (GABA) dysfunction in tremor generation. METHODS Using (11)C-flumazenil and PET, we calculated the distribution volume, an index of availability of benzodiazepine receptor sites of the GABA(A) complex, in a group of 8 patients with bilateral essential tremor, as compared with 11 healthy controls. RESULTS Significant increases in binding of (11)C-flumazenil at the benzodiazepine receptor site of the GABA(A) receptor in the cerebellum, the ventrolateral thalamus, and the lateral premotor cortex were identified in the essential tremor group. CONCLUSION Essential tremor is associated with reduced GABAergic function and increased availability of benzodiazepine receptor sites in brain regions implicated specifically in tremor genesis. This finding is thought to reflect overactivity of cerebellothalamic circuits and, hence, lends support to the "GABA hypothesis" of essential tremor.
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Affiliation(s)
- Henning Boecker
- Nuklearmedizinische Klinik, Klinikum rechts der Isar, Technische Universität München, Munich, Germany.
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Handforth A, Homanics GE, Covey DF, Krishnan K, Lee JY, Sakimura K, Martin FC, Quesada A. T-type calcium channel antagonists suppress tremor in two mouse models of essential tremor. Neuropharmacology 2010; 59:380-7. [PMID: 20547167 DOI: 10.1016/j.neuropharm.2010.05.012] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 05/14/2010] [Accepted: 05/24/2010] [Indexed: 11/17/2022]
Abstract
Essential tremor is a common disorder that lacks molecular targets for therapeutic development. T-type calcium channel activation has been postulated to underlie rhythmicity in the olivo-cerebellar system that is implicated in essential tremor. We therefore tested whether compounds that antagonize T-type calcium channel currents suppress tremor in two mouse models that possess an essential tremor-like pharmacological response profile. Tremor was measured using digitized spectral motion power analysis with harmaline-induced tremor and in the GABA(A) receptor α1 subunit-null model. Mice were given ethosuximide, zonisamide, the neuroactive steroid (3β,5α,17β)-17-hydroxyestrane-3-carbonitrile (ECN), the 3,4-dihydroquinazoline derivative KYS05064, the mibefradil derivative NNC 55-0396, or vehicle. In non-sedating doses, each compound reduced harmaline-induced tremor by at least 50% (range of maximal suppression: 53-81%), and in the GABA(A) α1-null model by at least 70% (range 70-93%). Because the T-type calcium channel Cav3.1 is the dominant subtype expressed in the inferior olive, we assessed the tremor response of Cav3.1-deficient mice to harmaline, and found that null and heterozygote mice exhibit as much tremor as wild-type mice. In addition, ECN and NNC 55-0396 suppressed harmaline tremor as well in Cav3.1-null mice as in wild-type mice. The finding that five T-type calcium antagonists suppress tremor in two animal tremor models suggests that T-type calcium channels may be an appropriate target for essential tremor therapy development. It is uncertain whether medications developed to block only the Cav3.1 subtype would exhibit efficacy.
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Affiliation(s)
- Adrian Handforth
- Neurology Service (W127), Veterans Affairs Greater Los Angeles Healthcare System, 11301 Wilshire Blvd, Los Angeles, CA 90073, USA.
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97
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Essential tremor: evolving clinicopathological concepts in an era of intensive post-mortem enquiry. Lancet Neurol 2010; 9:613-22. [PMID: 20451458 DOI: 10.1016/s1474-4422(10)70090-9] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Essential tremor (ET) is one of the most common neurological disorders. In recent years, as a result of systematic post-mortem examinations, our knowledge of the pathophysiology of this disease has grown substantially. Clearly identifiable structural changes (ie, Purkinje cell loss, Lewy bodies) have been observed in the brains of individuals with ET. These changes are not uniform and seem to follow several patterns, localising to the cerebellum itself or to a collection of brainstem neurons that synapse directly with Purkinje cells. Furthermore, these changes are similar to those seen in degenerative diseases. A wealth of clinical, epidemiological, and now post-mortem data indicate that this disease, or perhaps this family of diseases, is likely to be neurodegenerative. The molecular mechanisms that underlie these structural changes in ET are unknown. However, with more controlled, tissue-based studies being done, it is hoped that these mechanisms will be elucidated, thereby laying the foundation for the development of more targeted, effective pharmacotherapeutic interventions.
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98
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"Hairy baskets" associated with degenerative Purkinje cell changes in essential tremor. J Neuropathol Exp Neurol 2010; 69:262-71. [PMID: 20142764 DOI: 10.1097/nen.0b013e3181d1ad04] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Essential tremor (ET) is one of the most common neurologic diseases. Increased numbers of torpedoes and Purkinje cell (PC) loss have been documented in the brains of patients with ET. We recently observed a dense and tangled appearance ("hairiness") of the basket cell axonal plexuses that surround PC soma in Bielschowsky preparations of cerebellar cortex in ET brains. Here, we assessed basket cell "hairiness" in 37 ET (32 cerebellar ET; 5 Lewy body variant ET), 21 nondisease control, and 48 disease control brains using a semiquantitative scale. In 8 cerebellar ET cases (25%), there were high basket scores (rating = 3), whereas no Lewy body variant ET, 1 nondisease control (4.8%), and 2 diseased controls (4.2%) had high basket scores (p = 0.001). The hairy basket scores correlated with numbers of torpedoes (p < 0.001) and inversely with numbers of PCs (p = 0.06). Axonal plexus density obtained by image analysis of basket cell processes traced from digitized images was higher in ET than in nondiseased control cases (p = 0.016). Closely spaced sites of synaptic contact between basket cell processes and PCs were identified by electron microscopy in ET cases. These data indicate that structural changes are not restricted to PCs in ET, and that other neurons within their functional network may be involved in its pathogenesis.
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99
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Nahab FB, Hallett M. Current role of functional MRI in the diagnosis of movement disorders. Neuroimaging Clin N Am 2010; 20:103-10. [PMID: 19959022 DOI: 10.1016/j.nic.2009.08.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The functional magnetic resonance (fMR) technique for brain mapping is a valuable tool for understanding both normal physiology and the dysfunction taking place in disorders of the brain. This article provides an overview of fMR imaging methods and their applications in the study of neurologic movement disorders. The article also reviews the current neuroimaging literature regarding parkinsonisms, dystonia, essential tremor, and Huntington disease, and includes a discussion of current methodological limitations and future directions for this exciting field.
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Affiliation(s)
- Fatta B Nahab
- University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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100
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Lu MK, Jung P, Bliem B, Shih HT, Hseu YT, Yang YW, Ziemann U, Tsai CH. The Bereitschaftspotential in essential tremor. Clin Neurophysiol 2010; 121:622-30. [PMID: 20097128 DOI: 10.1016/j.clinph.2009.12.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2009] [Revised: 12/01/2009] [Accepted: 12/14/2009] [Indexed: 02/08/2023]
Abstract
OBJECTIVE Essential tremor (ET) is an involuntary postural oscillation. It is unclear to which extent motor cortical activity in preparation of volitional movement is abnormal in ET. We measured the Bereitschaftspotential (BP) to address this question. METHODS Given the known influence of the cerebello-dentato-thalamo-cortical projection in the generation of the BP, patients were divided into two groups, defined by purely postural tremor (ET(PT)) or additional presence of intention tremor (ET(IT)) and compared to healthy controls. BP was recorded during self-paced rapid wrist extension movements. RESULTS The late BP (500-0 ms before movement onset) was increased over the mid-frontal area in ET(PT), whereas it was reduced over the mid-parietal area in ET(IT) when compared to healthy controls. In addition, the late BP was reduced over a widespread centro-parietal area in ET(IT) compared to ET(PT). CONCLUSIONS Findings suggest that presence vs. absence of cerebellar signs (intention tremor) in ET results in differential affection of volitional preparatory motor cortical activity. The BP increase in ET(PT) may indicate compensatory activity, whereas the widespread centro-parietal BP reduction in ET(IT) suggests dysfunction of the cerebello-dentato-thalamo-cortical projection. SIGNIFICANCE Reduction of the late BP amplitude may serve as a surrogate marker for dysfunction of the cerebello-dentato-thalamo-cortical projection in ET.
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Affiliation(s)
- Ming-Kuei Lu
- Neuroscience Laboratory, Department of Neurology, China Medical University Hospital, Taiwan
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