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Wagle Shukla A. Reduction of neuronal hyperexcitability with modulation of T-type calcium channel or SK channel in essential tremor. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2022; 163:335-355. [PMID: 35750369 DOI: 10.1016/bs.irn.2022.02.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Essential tremor is one of the most prevalent movement disorders. Propranolol and primidone are the first-line pharmacological therapies. They provide symptomatic control in less than 50% of patients. Topiramate, alprazolam, clonazepam, gabapentin, and botulinum toxin injections are the next line of treatments. These medications lead to modest improvements and are therefore commonly used as add-on agents. Surgical therapies, including deep brain stimulation (DBS) surgery and focused ultrasound beam targeted to the thalamus, are considered for treating tremor refractory to medications and lead to greater than 75% improvements in tremor symptoms. However, DBS is a costly and an invasive procedure; some patients report tolerance to benefits. Focused ultrasound therapy leading to brain lesions is associated with a possibility for permanent clinical deficits. Therefore, research efforts to develop the next generation of oral medications with greater benefits and lesser adverse effects are warranted. There is considerable evidence that the increased functions of calcium channels (P/Q-type and T-type channels) and reduced functions of calcium-activated potassium channels (SK channels) located in the neuronal membranes lead to tremor oscillations. Consequently, many new pharmacological studies have targeted these channels to leverage better clinical outcomes. The current review will discuss the pathophysiology, the specific importance of these channels, and the early clinical experience of using compounds targeting these channels to treat essential tremor.
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Affiliation(s)
- Aparna Wagle Shukla
- Department of Neurology, Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, United States.
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2
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Is essential tremor a degenerative disorder or an electric disorder? Degenerative disorder. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2022; 163:65-101. [PMID: 35750370 PMCID: PMC9846862 DOI: 10.1016/bs.irn.2022.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Essential tremor (ET) is a highly prevalent neurologic disease and is the most common of the many tremor disorders. ET is a progressive condition with marked clinical heterogeneity, associated with a spectrum of both motor and non-motor features. However, its disease mechanisms remain poorly understood. Much debate has centered on whether ET should be considered a degenerative disorder, with underlying pathological changes in brain causing progressive disease manifestations, or an electric disorder, with overactivity of intrinsically oscillatory motor networks that occur without underlying structural brain abnormalities. Converging data from clinical, neuroimaging and pathological studies in ET now provide considerable evidence for the neurodegenerative hypothesis. A major turning point in this debate is that rigorous tissue-based studies have recently identified a series of structural changes in the ET cerebellum. Most of these pathological changes are centered on the Purkinje cell and connected neuronal populations, which can result in partial loss of Purkinje cells and circuitry reorganizations that would disturb cerebellar function. There is significant overlap in clinical and pathological features of ET with other disorders of cerebellar degeneration, and an increased risk of developing other degenerative diseases in ET. The combined implication of these studies is that ET could be degenerative. The evidence in support of the degenerative hypothesis is presented.
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Ibrahim MF, Beevis JC, Empson RM. Essential Tremor - A Cerebellar Driven Disorder? Neuroscience 2020; 462:262-273. [PMID: 33212218 DOI: 10.1016/j.neuroscience.2020.11.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Revised: 10/23/2020] [Accepted: 11/01/2020] [Indexed: 02/07/2023]
Abstract
Abnormal tremors are the most common of all movement disorders. In this review we focus on the role of the cerebellum in Essential Tremor, a highly debilitating but poorly treated movement disorder. We propose a variety of mechanisms driving abnormal burst firing of deep cerebellar nuclei neurons as a key initiator of tremorgenesis in Essential Tremor. Targetting these mechanisms may generate more effective treatments for Essential Tremor.
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Affiliation(s)
- Mohamed Fasil Ibrahim
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin 9016, New Zealand.
| | - Jessica C Beevis
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin 9016, New Zealand
| | - Ruth M Empson
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin 9016, New Zealand
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Lin CY, Louis ED, Faust PL, Koeppen AH, Vonsattel JPG, Kuo SH. Abnormal climbing fibre-Purkinje cell synaptic connections in the essential tremor cerebellum. ACTA ACUST UNITED AC 2014; 137:3149-59. [PMID: 25273997 DOI: 10.1093/brain/awu281] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Structural changes in Purkinje cells have been identified in the essential tremor cerebellum, although the mechanisms that underlie these changes remain poorly understood. Climbing fibres provide one of the major excitatory inputs to Purkinje cells, and climbing fibre-Purkinje cell connections are essential for normal cerebellar-mediated motor control. The distribution of climbing fibre-Purkinje cell synapses on Purkinje cell dendrites is dynamically regulated and may be altered in disease states. The aim of the present study was to examine the density and distribution of climbing fibre-Purkinje cell synapses using post-mortem cerebellar tissue of essential tremor cases and controls. Using vesicular glutamate transporter type 2 immunohistochemistry, we labelled climbing fibre-Purkinje cell synapses of 12 essential tremor cases and 13 age-matched controls from the New York Brain Bank. Normally, climbing fibres form synapses mainly on the thick, proximal Purkinje cell dendrites in the inner portion of the molecular layer, whereas parallel fibres form synapses on the thin, distal Purkinje cell spiny branchlets. We observed that, compared with controls, essential tremor cases had decreased climbing fibre-Purkinje cell synaptic density, more climbing fibres extending to the outer portion of the molecular layer, and more climbing fibre-Purkinje cell synapses on the thin Purkinje cell spiny branchlets. Interestingly, in essential tremor, the increased distribution of climbing fibre-Purkinje cell synapses on the thin Purkinje cell branchlets was inversely associated with clinical tremor severity, indicating a close relationship between the altered distribution of climbing fibre-Purkinje cell connections and tremor. These findings suggest that abnormal climbing fibre-Purkinje cell connections could be of importance in the pathogenesis of essential tremor.
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Affiliation(s)
- Chi-Ying Lin
- 1 Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
| | - Elan D Louis
- 1 Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA 2 GH Sergievsky Centre, Columbia University, New York, NY, USA 3 Taub Institute for Research of Alzheimer's disease and the Aging Brain, Columbia University, New York, NY, USA 4 Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, USA
| | - Phyllis L Faust
- 5 Department of Pathology and Cell Biology, Columbia University Medical Centre and the New York Presbyterian Hospital, New York, NY, USA
| | - Arnulf H Koeppen
- 6 Neurology and Research Services, Veterans Affairs Medical Centre, Albany, NY, USA 7 Departments of Neurology and Pathology, Albany Medical College, Albany, NY, USA
| | - Jean-Paul G Vonsattel
- 3 Taub Institute for Research of Alzheimer's disease and the Aging Brain, Columbia University, New York, NY, USA 5 Department of Pathology and Cell Biology, Columbia University Medical Centre and the New York Presbyterian Hospital, New York, NY, USA
| | - Sheng-Han Kuo
- 1 Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
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Lingo-1 expression is increased in essential tremor cerebellum and is present in the basket cell pinceau. Acta Neuropathol 2013; 125:879-89. [PMID: 23543187 DOI: 10.1007/s00401-013-1108-7] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 02/19/2013] [Accepted: 03/17/2013] [Indexed: 01/08/2023]
Abstract
The Lingo-1 sequence variant has been associated with essential tremor (ET) in several genome-wide association studies. However, the role that Lingo-1 might play in pathogenesis of ET is not understood. Since Lingo-1 protein is a negative regulator of axonal regeneration and neurite outgrowth, it could contribute to Purkinje cell (PC) or basket cell axonal pathology observed in postmortem studies of ET brains. In this study, we used Western blotting and immunohistochemistry to examine Lingo-1 protein in ET vs. control brains. In Western blots, Lingo-1 protein expression level was significantly increased in cerebellar cortex (1.56 ± 0.46 in ET cases vs. 0.99 ± 0.20 in controls, p = 0.002), but was similar in the occipital cortex (p = 1.00) of ET cases vs. controls. Lingo-1 immunohistochemistry in cerebellum revealed that Lingo-1 was enriched in the distal axonal processes of basket cells, which formed a "pinceau" structure around the PC axon initial segment (AIS). We found that some Lingo-1-positive pinceau had abnormally elongated processes, targeting PC axon segments distal to the AIS. In ET cases, the percentage of Lingo-1-positive pinceau that were ≥30 or ≥40 μm in length was increased 2.4- to 4.1-fold, respectively, vs. pinceau seen in control brains (p < 0.0001). Elongated Lingo-1-positive pinceau strongly correlated with number of PC axonal torpedoes and a rating of basket cell axonal pathology. The increased cerebellar Lingo-1 expression and elongated Lingo-1-positive pinceau processes could contribute to the abnormal PC and basket cell axonal pathology and cerebellar dysfunction observed in ET.
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Louis ED, Gillman A, Boschung S, Hess CW, Yu Q, Pullman SL. High width variability during spiral drawing: further evidence of cerebellar dysfunction in essential tremor. THE CEREBELLUM 2013; 11:872-9. [PMID: 22230985 DOI: 10.1007/s12311-011-0352-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Essential tremor (ET) is among the most prevalent neurological diseases, yet the location of the primary disease substrate continues to be a matter of debate. The presence of intention tremor and mild gait ataxia suggests an underlying abnormality of the cerebellum and/or cerebellar pathways. Uncovering additional signs of cerebellar dysfunction would further substantiate the proposition that ET is a disease of the cerebellar system. We evaluated 145 ET cases and 34 normal controls clinically and by computerized spiral analysis. Spiral analysis is a program that objectively characterizes kinematic and physiologic features of hand-drawn spirals using specific calculated spiral indices that correlate with spiral shape and motor execution. We used the spiral width variability index (SWVI), a measure of loop-to-loop spiral width variation with the influence of tremor removed, as a metric of drawing ataxia. The SWVI was higher in cases than controls (0.91 ± 1.94, median=0.46 vs. 0.40 ± 0.29, median=0.30, p<0.001). Cases with higher SWVI also had greater intention tremor during the finger-nose-finger maneuver, r=0.27, p=0.001), and cases with intention tremor of the head had the highest SWVI (1.57 ± 3.44, median=0.51, p<0.001). There was a modest association between SWVI and number of missteps during tandem gait (r=0.16, p=0.06). The primary anatomical substrate for ET continues to be a matter of speculation, yet these and other clinical data lend support to the notion that there is an underlying abnormality of the cerebellum and/or its pathways.
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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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Kuo SH, Tang G, Ma K, Babij R, Cortes E, Vonsattel JPG, Faust PL, Sulzer D, Louis ED. Macroautophagy abnormality in essential tremor. PLoS One 2012; 7:e53040. [PMID: 23300858 PMCID: PMC3531444 DOI: 10.1371/journal.pone.0053040] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 11/22/2012] [Indexed: 11/19/2022] Open
Abstract
Macroautophagy is a cellular mechanism for the clearance of protein aggregates and damaged organelles. Impaired macroautophagy has been observed in neurodegenerative disorders. We investigated the macroautophagy pathway in essential tremor (ET) cases compared to age-matched controls. We analyzed microtubule-associated protein light chain 3-II (LC3-II), S6K, phosphorylated S6K, beclin-1, and mitochondrial membrane proteins levels by Western blot in the post-mortem cerebellum of 10 ET cases and 11 controls. We also performed immunohistochemistry in 12 ET cases and 13 controls to quantify LC3 clustering in Purkinje cells (PCs). LC3-II protein levels were significantly lower in ET cases vs. controls on Western blot (0.84±0.14 vs. 1.00±0.14, p = 0.02), and LC3-II clustering in PCs by immunohistochemistry was significantly lower in ET cases vs. controls (2.03±3.45 vs. 8.80±9.81, p = 0.03). In ET cases, disease duration was inversely correlated with LC3-II protein level (r = −0.64, p = 0.046). We found that mitochondrial membrane proteins were accumulated in ET (TIM23: 1.36±0.11 in ET cases vs. 1.00±0.08 in controls, p = 0.02; TOMM20: 1.63±0.87 in ET cases vs. 1.00±0.14 in controls, p = 0.03). Beclin-1, which is involved in macroautophagy, was strikingly deficient in ET (0.42±0.13 vs. 1.00±0.35, p<0.001). Decreased macroautophagy was observed in the ET cerebellum, and this could be due to a decrease in beclin-1 levels, which subsequently lead to mitochondrial accumulation as a result of autophagic failure. This provides a possible means by which perturbed macroautophagy could contribute to PC pathology in ET.
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Affiliation(s)
- Sheng-Han Kuo
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Guomei Tang
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Karen Ma
- GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Rachel Babij
- GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Etty Cortes
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- Department of Pathology and Cell Biology, Columbia University Medical Center and the New York Presbyterian Hospital, New York, New York, United States of America
| | - Jean-Paul G. Vonsattel
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- Department of Pathology and Cell Biology, Columbia University Medical Center and the New York Presbyterian Hospital, New York, New York, United States of America
| | - Phyllis L. Faust
- Department of Pathology and Cell Biology, Columbia University Medical Center and the New York Presbyterian Hospital, New York, New York, United States of America
| | - David Sulzer
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Elan D. Louis
- Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, United States of America
- * E-mail:
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Abstract
The pathology of essential tremor (ET) is increasingly being studied. The main findings include a reduction in cerebellar Purkinje cells, other pathological changes of cerebellar degeneration and restricted Lewy bodies in the locus ceruleus. This paper will review those findings and put them into context with clinical studies in ET and findings in neurodegenerative disorders such as Parkinson's disease.
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Affiliation(s)
- Holly A Shill
- Banner Sun Health Research Institute, Sun City, AZ, USA.
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