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Essential tremor

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Essential tremor
SpecialtyNeurology Edit this on Wikidata

Essential tremor (ET) is a slowly progressive neurological disorder whose most recognizable feature is a tremor of the arms that is apparent during voluntary movements such as eating and writing.[1] This type of tremor is often referred to as "kinetic tremor." 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.[2][3] Other types of tremor may also occur, including postural tremor of the outstretched arms, intentional tremor of the arms and rest tremor in the arms.[4] Some patients may have unsteadiness and problems with gait and balance that are above and beyond that due to normal aging.[5][6] In addition to these motor problems, a variety of non-motor features have recently been linked with ET. These include anxiety and depressive symptoms as well as cognitive difficulty.[7] Recent studies have demonstrated that late-onset ET (onset > age 65) may be associated with an increased risk of developing dementia.[8] 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, and 90s.[9][10] Aside from enhanced physiological tremor, it is the most common type of tremor and one of the most commonly observed movement disorders.[11] Essential tremor was also previously known as "benign essential tremor", but the adjective "benign" has been removed in recognition of the sometimes disabling nature of the disorder. Although often mild, patients with severe tremor have difficulty performing many of their routine activities of daily living.[12][13]

Cause

The underlying etiology is not clear but many cases seem to be familial.[14] It has been estimated that approximately one-half of the cases are due to a genetic mutation and the pattern of inheritance is most consistent with autosomal dominant transmission. As of yet, no genes have been identified but genetic linkage has been established with several chromosomal regions.[15][16] A number of environmental factors, including toxins, are also under active investigation and these may play a role in disease etiology.[17] In terms of pathophysiology, clinical, physiological and imaging studies point to an involvement of the cerebellum and/or cerebellothalamocortical circuits.[18] Recent postmortem studies have demonstrated the presence of degenerative changes in the ET brain, with these changes including Purkinje cell axonal swellings and Purkinje cell loss in the majority of cases and brainstem Lewy bodies in the remainder. These studies suggest that the disease is both heterogeneous and degenerative. In other words, ET might be a family of degenerative diseases rather than a single disease.[19][20]

However, emerging research based on brain autopsies of fifty deceased ET patients (as of Dec. 2009), showed clear degenerative and pathological abnormalities, including "messy" neurofilaments which can impede nerve impulses. Research by Dr. Elan Louis and colleagues revealed that 80% of autopsied brains also exhibited changes within the cerebellum particularly to neurons that produce GABA, a major inhibitory neurotransmitter. Further analysis showed elevated levels of two neurotoxins, lead and heterocyclic amines. Heterocyclic amines are chemicals found in some foods, but are especially prevalent in meats that have been barbecued or exposed to high heat.

Diagnosis

Usually the diagnosis is established on clinical grounds. Tremors can start at any age, from birth through advanced ages (senile tremor).[21][22] 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.[23][24]

ET does sometimes occur in combination with other neurological disorders such as dystonia. In addition, there may be a link between ET and Parkinson's disease, with one study showing ET patients having an approximately 4 times greater likelihood of developing Parkinson's disease.[25][26][27]

Symptoms

Essential tremor generally presents as a rhythmic tremor (4–12 Hz) that is present only when the affected muscle is exerting effort (in other words, it is not present at rest). Any sort of physical or mental stress will tend to make the tremor worse, often creating the false impression that the tremor is of psychosomatic origin.

Tremor intensity can worsen in response to fatigue, strong emotions, low blood sugar, cold, caffeine, lithium salts, some antidepressants or other factors. It is typical for the tremor to worsen in "performance" situations, such as when making out a check at a checkout stand.

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.

In mild cases, ET can manifest as the inability to stop the tongue or hands from shaking, the ability to only sing in vibrato, and difficulty to do small precise tasks such as threading a needle. In disabling cases, ET can interfere with a person's ability to perform tasks of daily living, including feeding, dressing, and activities of personal hygiene.

ET is generally progressive in most cases (sometimes rapidly, sometimes very slowly), and can be disabling in severe cases.[28][29][30]

Treatment

Drug treatment may include:

Medication

The two medications that are prescribed most commonly for control of ET symptoms are:

Self medication with small amounts of alcohol has been shown to give short term relief from tremor[31]. Although this form of self-medication is not recommended due an increased risk of alcohol dependence or abuse[32].

Gabapentin may be helpful in the treatment of essential tremor.[33]

A trial of the benzodiazepine-anticonvulsant Clonazepam (Klonopin, Rivotril) was found not to be an effective treatment[34]; however, it is still recommended in some cases [35].

Topiramate has also been cited as a possible pharmaceutical treatment.

Other

Surgical treatments (which are generally reserved for the most severe cases) include thalamotomy and deep brain stimulation.[36][37]

Minor cases of ET can be treated with physical therapy and development of the muscles in the sections of the body that are severe in their shaking.

Mild cases of ET have also shown demonstrable tremor reduction by the ingestion of B12 vitamin (1000mcg) and B Complex vitamin supplements on a daily basis in otherwise healthy individuals.

Support groups

The International Essential Tremor Foundation (IETF) provides information, services and support to individuals and families affected by essential tremor (ET). The organization encourages and promotes research in an effort to determine the causes, treatment and ultimately the cure for ET. The IETF is a worldwide organization dedicated to meeting the needs of those whose daily lives are challenged by ET. IETF, an international non-profit 501(c)(3) organization that derives its support entirely from its membership and the general public, was founded in 1988 and is guided by a board of directors and a medical advisory council. The organization's membership consists of patients, physicians, educators, parents, relatives and volunteers who provide education, community services and funding to help support tremor research.

The National Tremor Foundation(NTF), founded in 1992, is a British friendly organisation based in Essex, England, an affiliate of the International Tremor Foundation, which was founded in 1988. The organisation's primary work is production of a quarterly informational newsletter. The NTF also maintains a list of ITF medical advisors, and facilitates the formation of self-help groups. NTF was granted charitable status in 1994.

Help with technology

Tunic Software has released software to help people with essential tremor, Parkinson's disease, and other causes of hand tremor control their computer mouse. The software, MouseCage, automatically smooths mouse cursor motion to reduce the effects of unsteady or shaky hands.

IBM created a peripheral device that filters out tremoring movements of the hand. The hardware adapter, termed AMA, is connected between the computer and the input device. It is switched on or off and adjusted on the device for tremor severity.

IBM also offers a free smoothing mouse driver for Windows 2000 and XP which uses the same technology that helps steady the image in a handheld camcorder. Another option is SteadyMouse.

Other tools have also been adapted for people with tremors; for example, eating utensils which are weighted to help damp out tremor.

References

  1. ^ Benito-Leon J, Louis ED. Clinical update: Diagnosis and treatment of essential tremor. The Lancet 2007;369:1152-1153.
  2. ^ Hubble JP, Busenbark KL, Pahwa R, Lyons K, Koller WC. Clinical expression of essential tremor: Effects of gender and age. Mov Disord 1997;12:969-972.
  3. ^ Louis ED, Ford B, Frucht S. Factors associated with increased risk of head tremor in essential tremor: A community-based study in northern manhattan. Mov Disord 2003;18:432-436.
  4. ^ Louis ED. Clinical Practice: Essential tremor. N Engl J Med 2001;345:887-891.
  5. ^ Stolze H, Petersen G, Raethjen J, Wenzelburger R, Deuschl G. The gait disorder of advanced essential tremor. Brain. November 2001;124(Pt 11):2278-2286.
  6. ^ Singer C, Sanchez-Ramos J, Weiner WJ. Gait abnormality in essential tremor. Mov Disord. March 1994;9(2):193-196.
  7. ^ Tan EK, Fook-Chong S, Lum SY, et al. Non-motor manifestations in essential tremor: use of a validated instrument to evaluate a wide spectrum of symptoms. Parkinsonism Relat Disord. September 2005;11(6):375-380.
  8. ^ Bermejo-Pareja F, Louis ED, Benito-Leon J. Risk of incident dementia in essential tremor: A population-based study. Mov Disord 2007;22:1573-1580.
  9. ^ Louis ED, Ottman R, Hauser WA. How common is the most common adult movement disorder?: Estimates of the prevalence of essential tremor throughout the world. Mov Disord 1998;13:5-10.
  10. ^ Dogu O, Sevim S, Camdeviren H, Sasmaz T, Bugdayci R, Aral M, Kaleagasi H, Un S, Louis ED. Prevalence of essential tremor: Door-to-door neurological exams in Mersin Province, Turkey. Neurology 2003;61:1804-1807.
  11. ^ Benito-Leon J, Louis ED. Essential tremor: emerging views of a common disorder. Nat Clin Pract Neurol 2006;2:666-678.
  12. ^ Bain PG, Mally J, Gresty M, Findley LJ. Assessing the impact of essential tremor on upper limb function J Neurol 1993;241:54-61.
  13. ^ Louis ED, Barnes LF, Albert SM, Cote L, Schneier F, Pullman SL, Yu Q. Correlates of functional disability in essential tremor. Mov Disord 2001;16:914-920.
  14. ^ Deng H, Le W, Jankovic J. Genetics of essential tremor. Brain. June 2007;130(Pt 6):1456-1464.
  15. ^ Higgins JJ, Pho LT, Nee LE. A gene (ETM) for essential tremor maps to chromosome 2p22-p25. Mov Disord. 1997;12:859-864
  16. ^ Gulcher JR, Jonsson P, Kong A et al. Mapping of a familial essential tremor gene, FET1, to chromosome 3q13. Nature Genetics 1997;17:84-87.
  17. ^ Louis ED. Etiology of essential tremor: Should we be searching for environmental causes? Mov Disord 2001;16:822-829.
  18. ^ Louis ED, Vonsattel JP. The emerging neuropathology of essential tremor. Mov Disord 2007;23:174 - 182.
  19. ^ Louis ED, Faust PL, Vonsattel JPG, Honig LS, Rajput A, Robinson CA, Rajput A, Pahwa R, Lyons KE, Ross W, Borden S, Moskowitz CB, Lawton A, Hernandez N. Neuropathological changes in essential tremor: 33 cases compared with 21 controls. Brain 2007;130:3297-3307.
  20. ^ Shill HA, Adler CH, Sabbagh MN, Connor DJ, Caviness JN, Hentz JG, Beach TG: Pathologic findings in prospectively ascertained essential tremor subjects. Neurology 2008;70:1452-1455.
  21. ^ Louis ED, Dure L, Pullman S. Essential tremor in childhood. Mov Disord 2001;16:921-923.
  22. ^ Bain PG, Findley LJ, Thompson PD, et al. A study of hereditary essential tremor. Brain. August 1994;117 ( Pt 4):805-824.
  23. ^ Cohen O, Pullman S, Jurewicz E, Watner D, Louis ED. Rest tremor in essential tremor patients: Prevalence, clinical correlates, and electrophysiological characteristics. Arch Neurol 2003;60:405-410.
  24. ^ Rajput AH, Rozdilsky B, Ang L, Rajput A. Significance of Parkinsonian manifestations in essential tremor. Can J Neurol Sci 1993;20:114-117.
  25. ^ Minen M, Louis ED. Emergence of Parkinson’s disease in essential tremor: A study of the clinical correlates in 53 patients. Mov Disord 2008 (In Press)
  26. ^ Yahr MD, Orosz D, Purohit DP. Co-occurrence of essential tremor and Parkinson’s disease: a clinical study of a large kindred with autopsy findings. Parkinsonism Relat Disord 2003; 9:225-231
  27. ^ Benito-Leon J, Louis ED, Permejo-Pareja F. Risk of incident Parkinson's disease and parkinsonism in essential tremor: a population-based study. J Neurology Neurosurgery Psychiatry 2008 (in press).
  28. ^ Critchley M. Observations on essential (heredofamilial) tremor. Brain. 1949;72:113-139.
  29. ^ Busenbark KL, Nash J, Nash S, Hubble JP, Koller WC. Is essential tremor benign? Neurology. December 1991;41(12):1982-1983.
  30. ^ Louis ED, Ford B, Barnes LF. Clinical subtypes of essential tremor. Arch Neurol 2000;57:1194-1198.
  31. ^ Lou JS, Jankovic J (1991). "Essential tremor: clinical correlates in 350 patients". Neurology. 41 (2 ( Pt 1)): 234–8. PMID 1992367. {{cite journal}}: Unknown parameter |month= ignored (help)
  32. ^ http://www.nlm.nih.gov/medlineplus/ency/article/000762.htm
  33. ^ http://www.uwo.ca/cns/ebn/PDFCATs/move-tremor-gabapentin-therapy.pdf
  34. ^ Thompson C, Lang A, Parkes JD, Marsden CD (1984). "A double-blind trial of clonazepam in benign essential tremor". Clin Neuropharmacol. 7 (1): 83–8. doi:10.1097/00002826-198403000-00004. PMID 6367975.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  35. ^ http://www.aafp.org/afp/20051101/practice.html
  36. ^ Zesiewcz TA, Elble R, Louis ED, Hauser RA, Sullivan KL, Dewey RB, Ondo WG, Gronseth GS, Weiner WJ. Practice parameter: Therapies for essential tremor. Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 2005;64:2008-2020.
  37. ^ Schuurman PR, Bosch DA, Bossuyt PM, et al. A comparison of continuous thalamic stimulation and thalamotomy for suppression of severe tremor. N Engl J Med. February 17 2000;342(7):461-468.


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