Essential tremor
Encyclopedia
Essential tremor is a slowly progressive neurological disorder
Neurological disorder
A neurological disorder is a disorder of the body's nervous system. Structural, biochemical or electrical abnormalities in the brain, spinal cord, or in the nerves leading to or from them, can result in symptoms such as paralysis, muscle weakness, poor coordination, loss of sensation, seizures,...

 whose most recognizable feature is a tremor of the arm
Arm
In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods...

s that is apparent during voluntary movements such as eating and writing. 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. Other types of tremor may also occur, including postural tremor of the outstretched arms, intentional tremor
Intention tremor
Intention tremor, also known as cerebellar tremor, is a dyskinetic disorder characterized by a broad, course, and low frequency tremor. The amplitude of an intention tremor increases as an extremity approaches the endpoint of deliberate and visually guided movement...

 of the arms and rest tremor in the arms. Some patients may have unsteadiness and problems with gait and balance that are above and beyond that due to normal aging. 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. Recent studies have demonstrated that late-onset ET (onset > age 65) may be associated with an increased risk of developing dementia. 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. Aside from enhanced physiological tremor, it is the most common type of tremor
Tremor
A tremor is an involuntary, somewhat rhythmic, muscle contraction and relaxation involving to-and-fro movements of one or more body parts. It is the most common of all involuntary movements and can affect the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Most tremors occur in the...

 and one of the most commonly observed movement disorders. 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
Activities of daily living
Activities of Daily Living is a term used in healthcare to refer to daily self-care activities within an individual's place of residence, in outdoor environments, or both...

.

Cause

The underlying etiology is not clear but many cases seem to be familial. It has been estimated that approximately one-half of the cases is 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. A number of environmental factors, including toxins, are also under active investigation and these may play a role in disease etiology. In terms of pathophysiology, clinical, physiological and imaging studies point to an involvement of the cerebellum and/or cerebellothalamocortical circuits. Recent postmortem studies have demonstrated the presence of degenerative changes in the ET brain, with these changes including Purkinje cell
Purkinje cell
For the cells of the electrical conduction system of the heart, see Purkinje fibersPurkinje cells, or Purkinje neurons , are a class of GABAergic neurons located in the cerebellar cortex...

 axonal swellings and Purkinje cell loss in the majority of cases and brainstem Lewy bodies
Lewy body
Lewy bodies are abnormal aggregates of protein that develop inside nerve cells in Parkinson's disease , Lewy Body Dementia and some other disorders. They are identified under the microscope when histology is performed on the brain....

 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.

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
Gamma-aminobutyric acid
γ-Aminobutyric acid is the chief inhibitory neurotransmitter in the mammalian central nervous system. It plays a role in regulating neuronal excitability throughout the nervous system...

, a major inhibitory neurotransmitter. Further analysis showed elevated levels of two neurotoxins, lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 and harmane, a heterocyclic amine. Heterocyclic amines (HCA) are chemicals found in some foods. Harmane has been detected in coffee and cigarettes (see: http://www.ncbi.nlm.nih.gov/pubmed/21776263), but is especially prevalent in meats that have been barbecued or exposed to high heat.

Another research indicates there is a strong link between essential tremor in males and the amount of meat consumed, but the exact mechanism is yet unknown.

Diagnosis

Usually the diagnosis is established on clinical grounds. Tremors can start at any age, from birth
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...

 through advanced ages (senile tremor). Any voluntary muscle in the body may be affected, although the tremor is most commonly seen in the hands and arm
Arm
In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods...

s and slightly less commonly in the neck
Neck
The neck is the part of the body, on many terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...

 (causing the patient's head to shake), tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

, and legs. A resting tremor of the hands is sometimes present.

ET does sometimes occur in combination with other neurological disorders such as dystonia
Dystonia
Dystonia is a neurological movement disorder, in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures. The disorder may be hereditary or caused by other factors such as birth-related or other physical trauma, infection, poisoning or reaction to...

. In addition, there may be a link between ET and Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...

, with one study showing ET patients having an approximately 4 times greater likelihood of developing Parkinson's disease.

Symptoms

Essential tremor generally presents as a rhythmic tremor (4–12 Hz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

) that is present only when the affected muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 is exerting effort (in other words, it is not present at rest). Any sort of physical or mental stress
Stress (medicine)
Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...

 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
Caffeine
Caffeine is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug. Caffeine is found in varying quantities in the seeds, leaves, and fruit of some plants, where it acts as a natural pesticide that paralyzes and kills certain insects feeding on the plants...

, lithium salts, some antidepressant
Antidepressant
An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. According to Gelder, Mayou &*Geddes people with a depressive illness will experience a therapeutic effect to their mood;...

s or other factors. It is typical for the tremor to worsen in "performance" situations, such as when writing a cheque for payment at a store or giving a presentation.

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 sing only in vibrato, and difficulty to do 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 ability to perform tasks of daily living, including feeding, dressing, and activities of personal hygiene.

People with ET can sometimes have problems with word finding and can't articulate themselves effectively even with preparation. A person with ET may become shy, withdrawn, pessimistic, anxious and also have difficulties concentrating. It is common for those with ET to be embarrassed by the condition even though it is out of their control.

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

Though it is not directly a result of the condition, a high number of people with ET develop a dependence on alcohol. This is due to the fact alcohol helps alleviate the tremor, making things like social gatherings much more enjoyable for the sufferer. However the next day it is common to suffer from a "rebound tremor" where the tremor is more noticeable than normal. This leads to many people "chasing the tail" and leading to a problem far worse than the symptoms listed.

Treatment

There is no cure for Essential Tremor. Many of the treatments available are to lower the severity of the condition. These may include:

Medication

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

  • antiepileptic/anticonvulsants: primidone
    Primidone
    Primidone is an anticonvulsant of the pyrimidinedione class, the active metabolites of which, phenobarbital and phenylethylmalonamide , are also anticonvulsants...

     (Mysoline)


Self medication with small amounts of alcohol
Alcoholic beverage
An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...

 has been shown to give short term relief from tremor, although this form of self-medication is not recommended due an increased risk of alcohol dependence or abuse. However other alcohol groups such as 1-octanol are being researched to provide relief from essential tremor without providing the intoxication or toxicity that ethanol does.

Gabapentin
Gabapentin
Gabapentin is a pharmaceutical drug, specifically a GABA analogue. It was originally developed for the treatment of epilepsy, and currently is also used to relieve neuropathic pain...

 may be helpful in the treatment of essential tremor.

A trial of the benzodiazepine-anticonvulsant Clonazepam
Clonazepam
Clonazepamis a benzodiazepine drug having anxiolytic, anticonvulsant, muscle relaxant, and hypnotic properties. It is marketed by Roche under the trade name Klonopin in the United States and Rivotril in Australia, Brazil, Canada and Europe...

 (Klonopin, Rivotril) was found not to be an effective treatment; however, it is still recommended in some cases.

Topiramate
Topiramate
Topiramate is an anticonvulsant drug. It was originally produced by Ortho-McNeil Neurologics and Noramco, Inc., both divisions of the Johnson & Johnson Corporation. This medication was discovered in 1979 by Bruce E. Maryanoff and Joseph F. Gardocki during their research work at McNeil...

 has also been cited as a possible pharmaceutical treatment.

Other

Surgical
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

 treatments (which are generally reserved for the most severe cases) include thalamotomy
Thalamotomy
First introduced in the 1950s, thalamotomy is an invasive procedure, primarily effective for tremors such as those associated with Parkinson's Disease , where a selected portion of the thalamus is surgically destroyed...

 and deep brain stimulation
Deep brain stimulation
Deep brain stimulation is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain...

.

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 which are not affecting activities of daily life may not require any treatment. Use of wrist weights and avoiding triggers such as caffieine may be helpful.

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
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...

, 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
Camcorder
A camcorder is an electronic device that combines a video camera and a video recorder into one unit. Equipment manufacturers do not seem to have strict guidelines for the term usage...

.

Another free software application, SteadyMouse, filters mouse movement to remove tremors. Additionally it provides a mechanism for ignoring accidental right clicks which are a common problem for patients suffering from essential tremor. The software supports Windows 2000, XP, Vista, Windows 7 32-bit and Windows 7 64-bit.

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

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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