Essential tremor

Infobox_Disease
Name = PAGENAME


Caption =
DiseasesDB =
ICD10 = ICD10|G|25|0|g|20
ICD9 = ICD9|333.1
ICDO =
OMIM = 190300
OMIM_mult = OMIM2|602134 | MedlinePlus = 000762
eMedicineSubj = neuro
eMedicineTopic = 129
MeshID = D020329

Essential tremor (ET) is a progressive neurological disease whose most recognizable feature is a tremor of the arms that is apparent during voluntary movements such as eating and writing. [ Benito-Leon J, Louis ED. Clinical update: Diagnosis and treatment of essential tremor. The Lancet 2007;369:1152-1153.] 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. [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.] [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.] 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. [Louis ED. Clinical Practice: Essential tremor. N Engl J Med 2001;345:887-891.] Some patients may have unsteadiness and problems with gait and balance that are above and beyond that due to normal aging. [Stolze H, Petersen G, Raethjen J, Wenzelburger R, Deuschl G. The gait disorder of advanced essential tremor. Brain. Nov 2001;124(Pt 11):2278-2286.] [Singer C, Sanchez-Ramos J, Weiner WJ. Gait abnormality in essential tremor. Mov Disord. Mar 1994;9(2):193-196.] 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. [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. Sep 2005;11(6):375-380.] Recent studies have demonstrated that ET may be associated with an increased risk of developing dementia [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.] . ET is one of the most common neurological diseases, with a prevalence of approximately 4% in persons aged 40 and older and considerably higher among persons in their 60s, 70s, 80s, and 90s. [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.] [ 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. ] Aside from enhanced physiological tremor, it is the most common type of tremor and also one of the most commonly observed movement disorders. [Benito-Leon J, Louis ED. Essential tremor: emerging views of a common disorder. Nat Clin Pract Neurol 2006;2:666-678.] 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. [Bain PG, Mally J, Gresty M, Findley LJ. Assessing the impact of essential tremor on upper limb function J Neurol 1993;241:54-61.] [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.]

Cause

The underlying etiology is not clear but many cases seem to be familial [Deng H, Le W, Jankovic J. Genetics of essential tremor. Brain. Jun 2007;130(Pt 6):1456-1464.] . 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. [Higgins JJ, Pho LT, Nee LE. A gene (ETM) for essential tremor maps to chromosome 2p22-p25. Mov Disord. 1997;12:859-864] [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.] A number of environmental factors, including toxins, are also under active investigation and these may play a role in disease etiology [Louis ED. Etiology of essential tremor: Should we be searching for environmental causes? Mov Disord 2001;16:822-829.] . In terms of pathophysiology, clinical, physiological and imaging studies point to an involvement of the cerebellum and/or cerebellothalamocortical circuits [Louis ED, Vonsattel JP. The emerging neuropathology of essential tremor. Mov Disord 2007;23:174 - 182.] . 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. [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. ] [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.]

Diagnosis

Usually the diagnosis is established on clinical grounds. Tremors can start at any age, from birth through advanced ages (senile tremor). [Louis ED, Dure L, Pullman S. Essential tremor in childhood. Mov Disord 2001;16:921-923.] [Bain PG, Findley LJ, Thompson PD, et al. A study of hereditary essential tremor. Brain. Aug 1994;117 ( Pt 4):805-824.] 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. [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. ] [Rajput AH, Rozdilsky B, Ang L, Rajput A. Significance of Parkinsonian manifestations in essential tremor. Can J Neurol Sci 1993;20:114-117.]

ET does sometimes occur in combination with other neurological disorders such as dystonia. In addition, there is a link between ET and Parkinson's disease, with ET patients approximately 4 - 5 times more likely to develop Parkinson's disease. [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)] [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]

ymptoms

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. [Critchley M. Observations on essential (heredofamilial) tremor. Brain. 1949;72:113-139.] [Busenbark KL, Nash J, Nash S, Hubble JP, Koller WC. Is essential tremor benign? Neurology. Dec 1991;41(12):1982-1983.] [Louis ED, Ford B, Barnes LF. Clinical subtypes of essential tremor. Arch Neurol 2000;57:1194-1198.]

Treatment

Drug treatment may include tranquilizers, beta-blockers, or antiepileptic drugs. Surgical treatments (which are generally reserved for the most severe cases) include thalamotomy and deep brain stimulation. [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.] [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. Feb 17 2000;342(7):461-468.]

The two medications that are prescribed most commonly for control of ET symptoms are the anticonvulsant Primidone (Mysoline) and the beta-blocker propranolol (Inderal). Self medication with small amounts of alcohol has been shown to give short term relief from tremor [cite journal |author=Lou JS, Jankovic J |title=Essential tremor: clinical correlates in 350 patients |journal=Neurology |volume=41 |issue=2 ( Pt 1) |pages=234–8 |year=1991 |month=February |pmid=1992367 |doi= |url=] .

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.

There is evidence that ET can be resolved with acupuncture [http://www.medicalacupuncture.org/aama_marf/journal/vol1_1/tremor.html]

upport 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 [http://www.essentialtremor.org/ 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 offer a free [http://www.alphaworks.ibm.com/tech/mousesmoothing 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 [http://www.steadymouse.com/about/ SteadyMouse] .

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

References

External links

* [http://www.essentialtremor.org/ International Essential Tremor Foundation] (USA)
* [http://www.tremoraction.org/ Tremor Action Network] (USA)
* [http://www.tremor.org.uk/ National Tremor Foundation] (UK)
* [http://www.aptes.org/ Association APTES] (France)
* [http://www.essentialtremorinfo.com/ Info For Sufferers Of Essential Tremor]