Essential tremor

Essential tremor
Classification and external resources
Specialty Neurology
ICD-10 G25.0
ICD-9-CM 333.1
OMIM 190300 602134
MedlinePlus 000762
eMedicine neuro/129
MeSH D020329

Essential tremor (ET, also referred to as benign tremor, familial tremor, or idiopathic tremor) is the most common movement disorder; its cause is unknown. It typically involves a tremor of the arms, hands or fingers but sometimes involving the head, vocal cords or other body parts during voluntary movements such as eating and writing.[1] It is distinct from Parkinson's disease—and often misdiagnosed as such—although some individuals have both conditions.[1] Essential tremor is commonly described as an action tremor (i.e., it intensifies when one tries to use the affected muscles) or postural tremor (i.e., present with sustained muscle tone) rather than a resting tremor, such as is seen in Parkinson’s, which is usually not included among its symptoms.[2]

Classification

This type of tremor is often referred to as "kinetic tremor".

Essential tremor has been known as "benign essential tremor", but the adjective "benign" has been removed in recognition of the sometimes disabling nature of the disorder.[3][4]

Signs and symptoms

In mild cases, ET can manifest as the inability to stop the tongue or hands from shaking, the ability to sing only in vibrato, and difficulty doing small precise tasks such as threading a needle. Even simple tasks like cutting in a straight line or using a ruler can range from difficult to impossible, depending on the severity of the condition. In disabling cases, ET can interfere with a person's activities of daily living, including feeding, dressing, and taking care of personal hygiene. Essential tremor generally presents as a rhythmic tremor (4–12 Hz) that occurs only when the affected muscle is exerting effort. Any sort of physical or mental stress will tend to make the tremor worse.[5]

The tremor may also occur in the head (neck), jaw and voice as well as other body regions, with the general pattern being that the tremor begins in the arms and then spreads to these other regions in selected patients. Women are more likely to develop the head tremor than are men. Other types of tremor may also occur, including postural tremor of the outstretched arms, intention tremor of the arms and rest tremor in the arms.[6] Some patients may have unsteadiness and problems with gait and balance.

ET-related tremors do not occur during sleep, but patients sometimes complain of an especially coarse tremor upon awakening that becomes noticeably less coarse within the first few minutes of wakefulness. Tremor and disease activity/intensity can worsen in response to fatigue, strong emotions, low blood sugar, cold and heat, caffeine, lithium salts, some antidepressants, and other factors. It is typical for the tremor to worsen in "performance" situations, such as when writing a check for payment at a store or giving a presentation.

Parkinson's disease and Parkinsonism can also occur simultaneously with ET.[1] In those cases the degree of tremor, rigidity, and functional disability does not differ from those people with idiopathic Parkinson's disease. Hand tremor predominates (as it does in Parkinson’s disease), and occurs in nearly all cases, followed by head tremor, voice tremor, neck, face, leg, tongue and trunk tremor. Most other tremors occur in association with hand tremor. Walking difficulties in essential tremor are common. About half of patients have associated dystonia, including cervical dystonia, writer's cramp, spasmodic dysphonia, and cranial dystonia, and 20% of the patients had associated parkinsonism. Olfactory dysfunction (loss of sense of smell) is common in Parkinson’s disease, and has also been reported to occur in patients with essential tremor. A number of patients with essential tremor also exhibit many of the same neuropsychiatric disturbances seen in idiopathic Parkinson's disease.[7]

Essential tremor with tremor onset after the age of 65 is associated with Mild cognitive impairement[8] and dementia.[9]

Cause

The underlying etiology of essential tremor is not clear but many cases seem to be familial.[10] Approximately one-half of the cases are due to a genetic mutation and the pattern of inheritance is most consistent with autosomal dominant transmission. No genes have been identified yet but genetic linkage has been established with several chromosomal regions.[11][12]

A number of environmental factors, including toxins, are also under active investigation as they may play a role in the disease's etiology.[13] Harmane or harmaline has been implicated not only in essential tremors, but is also found in greater quantities in the brain fluid of Parkinson's disease sufferers as well as cancer.[14][15][16] Higher levels of the neurotoxin are associated with greater severity of the tremors.[17][18] Exposure is primarily found from meat consumption of beef, pork, and especially chicken, even when cooked.[19][20][21] Indeed, the greatest meat consumers were significantly more likely to have essential tremor.[21] Harmaline's high lipid solubility enables accumulation in the brain tissue upon consumption from these environmental sources.[17]

In terms of pathophysiology, clinical, physiological and imaging studies point to an involvement of the cerebellum and/or cerebellothalamocortical circuits.[22] Changes in the cerebellum could also be mediated by alcoholic beverage consumption. Purkinje cells are especially susceptible to ethanol excitotoxicity.[23] Impairment of Purkinje synapses is a component of cerebellar degradation that could underlie essential tremor.[23] Some cases have Lewy bodies in the locus ceruleus.[24][25][26] ET cases that progress to Parkinson's disease are less likely to have had cerebellar problems.[27]

Recent post mortem studies have evidenced alterations in LINGO1 (Leucine rich repeat and Ig domain containing 1) gene[28][29] and GABA receptors[30] in the cerebellum of people with essential tremor. HAPT1 mutations have also been linked to ET, as well as to Parkinson's disease, multiple system atrophy, and progressive supranuclear palsy.[31]

In 2012, the National Toxicology Program concluded that there is sufficient evidence of an association between blood lead exposure at levels <10 μg/dL and essential tremor in adults, and limited evidence at blood lead levels <5 μg/dL.[32]

Diagnosis

Usually the diagnosis is established on clinical grounds. Tremors can start at any age, from birth through advanced ages (senile tremor).[33][34] Any voluntary muscle in the body may be affected, although the tremor is most commonly seen in the hands and arms and slightly less commonly in the neck (causing the patient's head to shake), tongue, and legs. A resting tremor of the hands is sometimes present.[7][35] Tremor occurring in the legs might be diagnosable as orthostatic tremor.

ET occurs within multiple neurological disorders besides Parkinson's Disease. This includes migraine disorders, where co-occurrences between ET and migraines have been examined.[36]

Treatment

Not all individuals with ET require treatment, but there are many treatment options depending on symptom severity.[1] Caffeine and stress should be avoided, and good sleep is recommended.[1]

When symptoms are sufficiently troublesome to warrant treatment, the first medication choices are beta blockers such as propranolol or alternately, nadolol and timolol. Atenolol and pindolol are not effective for tremor.[1] The anti-epileptic primidone is also effective for ET.[1]

Second-line or third-line medications can be added if the first-line medications do not control the tremor. Second-line medications are the anti-epileptics topiramate, gabapentin (as monotherapy) and levetiracetam, or benzodiazepines like alprazolam. Third-line medications are clozapine and mirtazapine.[1]

It should be noted that theophylline has been used by some practitioners to treat ET, even though it may also induce tremor. However, its use is debated due to conflicting data on its efficacy.[37] There is some evidence that low doses may lead to improvement.[38][39]

When medications do not control the tremor or the patient does not tolerate medication, botulinum toxin, deep brain stimulation or occupational therapy can be helpful.[1] The electrodes for deep brain stimulation are usually placed in the "tremor center" of the brain, the ventral intermediate nucleus of the thalamus.

Additionally, MR-guided high intensity focused ultrasound is a treatment option that shows promise in treating the tremors with about half of people improving at three months but a third having significant adverse events.[40] The US Food and Drug Administration (FDA) approved Insightec’s Exablate Neuro system to treat essential tremor in 2016.[41]

Prognosis

Although essential tremor is often mild, patients with severe tremor have difficulty performing many of their routine activities of daily living.[3][4] ET is generally progressive in most cases (sometimes rapidly, sometimes very slowly), and can be disabling in severe cases.[42][43][44]

Epidemiology

ET is one of the most common neurological diseases, with a prevalence of approximately 4% in persons age 40 and older and considerably higher among persons in their 60s, 70s, 80s, with an estimated 20% of individuals in their 90s and over.[45] Aside from enhanced physiological tremor, it is the most common type of tremor and one of the most commonly observed movement disorders.[46]

Society and culture

The actress Katharine Hepburn (1907–2003) had an essential tremor, which she inherited from her grandfather,[47] that caused her head—and sometimes her hands—to shake.[48][49][50] According to Dickens (1990), the tremor was noticeable by the time of her performance in the 1979 film The Corn is Green, when critics mentioned the "palsy that kept her head trembling".[51] Hepburn's tremor worsened in the 1980s, when she was in her 70s to 80s.[49]

Research directions

Harmaline is a widely used model of essential tremor (ET) in rodents.[52] Harmaline is thought to act primarily on neurons in the inferior olive (IO). Olivocerebellar neurons exhibit rhythmic excitatory action when harmaline is applied locally.[52]

See also

References

  1. 1 2 3 4 5 6 7 8 9 Abboud H, Ahmed A, Fernandez HH (December 2011). "Essential tremor: choosing the right management plan for your patient". Cleve Clin J Med. 78 (12): 821–8. doi:10.3949/ccjm.78a.10178. PMID 22135272.
  2. ↑ "LINGO1 variant responsible for essential tremors and Parkinson's disease". news-medical.net. Retrieved October 27, 2014.
  3. 1 2 Bain PG, Mally J, Gresty M, Findley LJ (1993). "Assessing the impact of essential tremor on upper limb function". J Neurol. 241: 54–61. doi:10.1007/bf00870673.
  4. 1 2 Louis ED, Barnes LF, Albert SM, Cote L, Schneier F, Pullman SL, Yu Q (2001). "Correlates of functional disability in essential tremor". Mov Disord. 16: 914–920. doi:10.1002/mds.1184.
  5. ↑ "Essential Tremor Treatment at the Johns Hopkins Movement Disorders Center in Baltimore, MD". hopkinsmedicine.org. Retrieved October 27, 2014.
  6. ↑ Louis ED (2001). "Clinical Practice: Essential tremor". N Engl J Med. 345: 887–891. doi:10.1056/nejmcp010928.
  7. 1 2 Rajput, A. H.; Rozdilsky, B.; Ang, L.; Rajput, A. (May 1993). "Significance of parkinsonian manifestations in essential tremor". The Canadian Journal of Neurological Sciences. 20 (2): 114–7. doi:10.1017/s031716710004765x. PMID 8334571. INIST:4838591.
  8. ↑ Benito-León, Julián; Louis, Elan D.; Mitchell, Alex J.; Bermejo-Pareja, Félix (2011-01-01). "Elderly-onset essential tremor and mild cognitive impairment: a population-based study (NEDICES)". Journal of Alzheimer's disease: JAD. 23 (4): 727–735. doi:10.3233/JAD-2011-101572. ISSN 1875-8908. PMID 21304183.
  9. ↑ Benito-León, Julián; Louis, Elan D.; Bermejo-Pareja, Félix; Neurological Disorders in Central Spain Study Group (2006-05-23). "Elderly-onset essential tremor is associated with dementia". Neurology. 66 (10): 1500–1505. doi:10.1212/01.wnl.0000216134.88617.de. ISSN 1526-632X. PMID 16717208.
  10. ↑ Deng H, Le W, Jankovic J (2007). "Genetics of essential tremor". Brain. 130 (6): 1456–1464. doi:10.1093/brain/awm018.
  11. ↑ Higgins JJ, Pho LT, Nee LE (1997). "A gene (ETM) for essential tremor maps to chromosome 2p22-p25". Mov Disord. 12: 859–864. doi:10.1002/mds.870120605. PMID 9399207.
  12. ↑ Gulcher JR, Jonsson P, Kong A, et al. (1997). "Mapping of a familial essential tremor gene, FET1, to chromosome 3q13". Nature Genetics. 17: 84–87. doi:10.1038/ng0997-84. PMID 9288103.
  13. ↑ Louis ED (2001). "Etiology of essential tremor: Should we be searching for environmental causes?". Mov Disord. 16: 822–829. doi:10.1002/mds.1183.
  14. ↑ Kuhn, W.; Müller, T.; Grosse, H.; Rommelspacher, H. (1996-01-01). "Elevated levels of harman and norharman in cerebrospinal fluid of parkinsonian patients". Journal of Neural Transmission (Vienna, Austria: 1996). 103 (12): 1435–1440. doi:10.1007/bf01271257. ISSN 0300-9564. PMID 9029410.
  15. ↑ Pfau, W.; Skog, K. (2004-03-25). "Exposure to beta-carbolines norharman and harman". Journal of Chromatography B. 802 (1): 115–126. doi:10.1016/j.jchromb.2003.10.044. ISSN 1570-0232. PMID 15036003.
  16. ↑ Louis, Elan D.; Pellegrino, Kathryn M.; Factor-Litvak, Pam; Rios, Eileen; Jiang, Wendy; Henchcliffe, Claire; Zheng, Wei (2008-09-15). "Cancer and blood concentrations of the comutagen harmane in essential tremor". Movement Disorders: Official Journal of the Movement Disorder Society. 23 (12): 1747–1751. doi:10.1002/mds.22084. ISSN 1531-8257. PMC 2597456Freely accessible. PMID 18709680.
  17. 1 2 Louis, Elan D.; Zheng, Wei; Mao, Xiangling; Shungu, Dikoma C. (2007-08-07). "Blood harmane is correlated with cerebellar metabolism in essential tremor: a pilot study". Neurology. 69 (6): 515–520. doi:10.1212/01.wnl.0000266663.27398.9f. ISSN 1526-632X. PMID 17679670.
  18. ↑ Louis, Elan D.; Factor-Litvak, Pam; Gerbin, Marina; Slavkovich, Vesna; Graziano, Joseph H.; Jiang, Wendy; Zheng, Wei (2011-03-01). "Blood harmane, blood lead, and severity of hand tremor: evidence of additive effects". Neurotoxicology. 32 (2): 227–232. doi:10.1016/j.neuro.2010.12.002. ISSN 1872-9711. PMC 3073713Freely accessible. PMID 21145352.
  19. ↑ Louis, Elan D.; Jiang, Wendy; Gerbin, Marina; Viner, Amanda S.; Factor-Litvak, Pam; Zheng, Wei (2012-06-15). "Blood Harmane (1-methyl-9h-pyrido[3,4-b]indole) Concentrations in Essential Tremor: Repeat Observation in Cases and Controls in New York". Journal of toxicology and environmental health. Part A. 75 (12): 673–683. doi:10.1080/15287394.2012.688485. ISSN 1528-7394. PMC 3412610Freely accessible. PMID 22757671.
  20. ↑ Louis, Elan D.; Zheng, Wei; Jiang, Wendy; Bogen, Kenneth T.; Keating, Garrett A. (2007-06-01). "Quantification of the neurotoxic beta-carboline harmane in barbecued/grilled meat samples and correlation with level of doneness". Journal of Toxicology and Environmental Health. Part A. 70 (12): 1014–1019. doi:10.1080/15287390601172015. ISSN 1528-7394. PMID 17497412.
  21. 1 2 Louis, Elan D.; Keating, Garrett A.; Bogen, Kenneth T.; Rios, Eileen; Pellegrino, Kathryn M.; Factor-Litvak, Pam (2008-05-01). "Dietary Epidemiology of Essential Tremor: Meat Consumption and Meat Cooking Practices". Neuroepidemiology. 30 (3): 161–166. doi:10.1159/000122333. ISSN 0251-5350. PMC 2821442Freely accessible. PMID 18382115.
  22. ↑ Louis ED, Vonsattel JP (2007). "The emerging neuropathology of essential tremor". Mov Disord. 23: 174–182. doi:10.1002/mds.21731.
  23. 1 2 Mostile, G.; Jankovic, J. (2010). "Alcohol in essential tremor and other movement disorders". Movement Disorders. 25 (14): 2274–2284. doi:10.1002/mds.23240. PMID 20721919.
  24. ↑ Elan D. Louis, MD, MS (Oct 2009). "The Essential Tremors: A Family of Neurodegenerative Disorders?". Arch Neurol. 66: 1202–8. doi:10.1001/archneurol.2009.217. PMC 2762114Freely accessible. PMID 19822775.
  25. ↑ Elan D. Louis; MD MS (2014). ""Essential Tremor" or "the Essential Tremors": Is This One Disease or a Family of Diseases?". Neuroepidemiology. 42 (2): 81–9. doi:10.1159/000356351. PMC 3945103Freely accessible. PMID 24335621.
  26. ↑ Elan D. Louis, Phyllis L. Faust, Jean-Paul G. Vonsattel, Lawrence S. Honig, Alex Rajput, Christopher A. Robinson, Ali Rajput, Rajesh Pahwa, Kelly E. Lyons, G.Webster Ross, Sarah Borden, Carol B. Moskowitz, Arlene Lawton, Nora Hernandez (December 2007). "Neuropathological changes in essential tremor: 33 cases compared with 21 controls". Brain. 130 (Pt 12): 3297–307. doi:10.1093/brain/awm266. PMID 18025031.
  27. ↑ Apostolia Ghika, Andreas Kyrozis, Constantinos Potagas, Elan D. Louis, and Julian Benito-Leon (monitoring editor) (August 2015). "Motor and Non-motor Features: Differences between Patients with Isolated Essential Tremor and Patients with Both Essential Tremor and Parkinson's Disease". Tremor Other Hyperkinet Mov (N Y). 5 (335). doi:10.7916/D83777WK. PMC 4548968Freely accessible. PMID 26336614.
  28. ↑ Delay, Charlotte,; Tremblay, Cyntia; et al. (2014). "Increased LINGO1 in the cerebellum of essential tremor patients". Mov Disord. 29: 1637–1647. doi:10.1002/mds.25819. PMID 24531928.
  29. ↑ Kuo, SH,; Tang G.; et al. (2013). "Lingo-1 expression is increased in essential tremor cerebellum and is present in the basket cell pinceau". Acta Neuropathol. 125 (6): 879–89. doi:10.1007/s00401-013-1108-7. PMID 23543187.
  30. ↑ Paris-Robidas, Sarah; Brochu E.; et al. (2012). "Defective dentate nucleus GABA receptors in essential tremor". Brain. 135 (Pt 1): 105–16. doi:10.1093/brain/awr301. PMID 22120148.
  31. ↑ C. Vilariño-Güell, PhD, A.I. Soto-Ortolaza, BSc, A. Rajput, MD, D.C. Mash, PhD, S. Papapetropoulos, MD, PhD, R. Pahwa, MD, K.E. Lyons, PhD, R.J. Uitti, MD, Z.K. Wszolek, MD, D.W. Dickson, MD, M.J. Farrer, PhD, and O.A. Ross, PhDcorresponding author (February 2011). "MAPT H1 haplotype is a risk factor for essential tremor and multiple system atrophy". Neurology. 76 (7): 670–672. doi:10.1212/WNL.0b013e31820c30c1. PMC 3053340Freely accessible. PMID 21321341.
  32. ↑ National Toxicology Program (June 2012). "NTP monograph on health effects of low-level lead" (PDF). NTP Monogr. Research Triangle Park: US Department of Health and Human Services: xiii, xv–148. PMID 23964424. Retrieved 3 November 2015.
  33. ↑ Louis ED, Dure L, Pullman S (2001). "Essential tremor in childhood". Mov Disord. 16: 921–923. doi:10.1002/mds.1182.
  34. ↑ Bain, P. G.; Findley, L. J.; Thompson, P. D.; Gresty, M. A.; Rothwell, J. C.; Harding, A. E.; Marsden, C. D. (1994). "A study of hereditary essential tremor". Brain. 117 (4): 805–24. doi:10.1093/brain/117.4.805. PMID 7922467.
  35. ↑ Cohen O, Pullman S, Jurewicz E, Watner D, Louis ED (2003). "Rest tremor in essential tremor patients: Prevalence, clinical correlates, and electrophysiological characteristics". Arch Neurol. 60: 405–410. doi:10.1001/archneur.60.3.405.
  36. ↑ Biary N.; Koller W.; Langenberg P. (1990). "Correlation between essential tremor and migraine headache". J. Neurol. Neurosurg. Psychiatry. 53: 1060–1062. doi:10.1136/jnnp.53.12.1060.
  37. ↑ Zesiewicz, T. A.; Elble, R.; Louis, E. D.; Hauser, R. A.; Sullivan, K. L.; Dewey, R. B.; Ondo, W. G.; Gronseth, G. S.; Weiner, W. J. (2005-06-28). "Practice Parameter: Therapies for essential tremor Report of the Quality Standards Subcommittee of the American Academy of Neurology". Neurology. 64 (12): 2008–2020. doi:10.1212/01.WNL.0000163769.28552.CD. ISSN 0028-3878. PMID 15972843.
  38. ↑ Mally, Judit; Stone, Trevor W. (1991-06-01). "The effect of theophylline on essential tremor: The possible role of GABA". Pharmacology Biochemistry and Behavior. 39 (2): 345–349. doi:10.1016/0091-3057(91)90190-D.
  39. ↑ Mally, Judit; Stone, T.W. (1995-10-01). "Efficacy of an adenosine antagonist, theophylline, in essential tremor: comparison with placebo and propranolol". Journal of the Neurological Sciences. 132 (2): 129–132. doi:10.1016/0022-510x(95)00128-o. ISSN 0022-510X.
  40. ↑ Gallay, Marc N.; Moser, David; Rossi, Franziska; Pourtehrani, Payam; Magara, Anouk E.; Kowalski, Milek; Arnold, Alexander; Jeanmonod, Daniel (13 February 2016). "Incisionless transcranial MR-guided focused ultrasound in essential tremor: cerebellothalamic tractotomy". Journal of Therapeutic Ultrasound. 4 (1). doi:10.1186/s40349-016-0049-8.
  41. ↑ FDA News Release. "FDA approves first MRI-guided focused ultrasound device to treat essential tremor", FDA, July 11, 2016
  42. ↑ Critchley M (1949). "Observations on essential (heredofamilial) tremor". Brain. 72: 113–139. doi:10.1093/brain/72.2.113.
  43. ↑ Busenbark KL, Nash J, Nash S, Hubble JP, Koller WC (1991). "Is essential tremor benign?". Neurology. 41 (12): 1982–1983. doi:10.1212/wnl.41.12.1982.
  44. ↑ Louis ED, Ford B, Barnes LF (2000). "Clinical subtypes of essential tremor". Arch Neurol. 57: 1194–1198. doi:10.1001/archneur.57.8.1194.
  45. ↑ Louis, Elan D.; Ferreira, Joaquim J. (2010-04-15). "How common is the most common adult movement disorder? Update on the worldwide prevalence of essential tremor". Movement Disorders: Official Journal of the Movement Disorder Society. 25 (5): 534–541. doi:10.1002/mds.22838. ISSN 1531-8257. PMID 20175185.
  46. ↑ Benito-Leon J, Louis ED (2006). "Essential tremor: emerging views of a common disorder". Nat Clin Pract Neurol. 2: 666–678. doi:10.1038/ncpneuro0347.
  47. ↑ Healy, David (director) (January 18, 1993). Katharine Hepburn: All About Me. Turner Home Entertainment.
  48. ↑ Claiborne Ray C (July 22, 2003). "Q & A; Head and Hand Tremors". The New York Times. Retrieved November 3, 2013.
  49. 1 2 Berg AS (2004) [2003]. Kate Remembered: Katharine Hepburn, a personal biography. London: Pocket. p. 260. ISBN 0-7434-1563-9.
  50. ↑ Conova S (January 29, 2003). "Stopping essential tremor". In vivo. Columbia University Health Sciences. 2 (2).
  51. ↑ Dickens H (1990) [1971]. The Films of Katharine Hepburn. New York City, NY: Carol Publishing Group. p. 31. ISBN 0-8065-1175-3.
  52. 1 2 Miwa, H. (2007). "Rodent models of tremor". The Cerebellum. 6 (1): 66–72. doi:10.1080/14734220601016080. PMID 17366267.
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