What's essential tremor?
Essential tremor (ET) is a nerve disorder characterized by uncontrollable shaking, or "tremors", in different parts and on different sides of the body. Areas affected often include the hands, arms, head, larynx, or voice box (making the voice sound shaky), tongue, chin and other areas. Rarely, the lower body is affected. Many people have what is called "essential
tremor," in which the tremor is the only symptom. This type of shaking affects between three and four million Americans.
All people have some degree of tremor that occurs during movement, This shaking is called physiologic (occurs normally), and it mainly involves the hands. Stressful circumstances, such as fatigue, anger, fear or using certain substances (such as coffee or cigarettes) may cause transient worsening of physiologic tremor, to the point that it may become visible to the naked eye.Essential tremor is the most common form of abnormal tremor, which resembles an exaggerated physiologic shaking. Essential tremor is worsened by the same factors that enhance physiologic tremor. Although the cause is unknown, new research shows that one part of the brain called cerebellum does not appear to function properly in patients who have essential tremor. The cerebellum is the part of the brain that coordinates muscle movements and therefore, provides accuracy and harmony to voluntary movement. Nevertheless, no evident brain lesions have been identified in patients with this form of tremor.
There is evidence that there are several different types of essential tremor (such as young-onset essential tremor or essential tremor with head tremor). These types differ in their response to treatment. If an essential tremor occurs in more than one member within a family group, it is termed a familial tremor. It therefore appears that essential tremor has some genetic basis, not only because of the hereditary pattern observed in some families, but also because the identical twin (who shares the same genetic makeup) of a person with essential tremor are twice as likely as a fraternal twin (who typically shares the same number of genes as other siblings) to have essential tremor. Since some identical twins do not share this condition, environmental factors must play a role as well. Essential tremors can occur at any age but are most common in people older than 65.
Essential tremor is a relatively benign condition, affecting movement or voice quality, but with no other effects. It involves a rhythmic, moderately rapid tremor of voluntary muscles. Purposeful movements may make the tremors worse, while avoiding hand movements may suppress the tremors completely. There may be difficulty holding or using small objects (such as silverware or writing utensils). Over time, the tremors may affect the hands, arms, head, voice box (larynx), eyelids, or other muscles. An essential tremor rarely involves the legs or feet. It may start in one body part but can progress to include other parts with time.
Medications result in symptom improvement in most patients, although one out of four patients may not benefit from treatment. Two medications are considered the first line of therapy: propranolol and primidone. Propranolol blocks the action of stimulant substances called neurotransmitters, particularly compounds related to adrenaline. Primidone is an anti-seizure medication, which also modulates the function of some neurotransmitters. Both medications are considered equally efficacious.
Recently, intramuscular injections of botulinum toxin in the hand have been used to reduce tremor by weakening local muscles. If tremor is severe and interfering with functioning, surgery may also be an option to alleviate the tremor. Such surgery usually involves implanting a device called deep brain stimulator in a specific area of the brain called the basal ganglia.
Caffeine, found in substances such as coffee and soda, and other stimulants should be avoided. Alcoholic beverages in small quantities may markedly decrease tremors but can lead to alcohol dependence if used in excess. The mechanism by which alcohol decreases an essential tremor is unknown.
Essential tremor most often appears when the hands are being used, whereas a person with Parkinson's disease will most often have a tremor while walking or while the hands are resting. People with essential tremor will usually have shaking head and hands, but the tremor may involve other parts of the body. The shaking often begins in the dominant hand and may spread to the other hand, interfering with eating and writing. Some people also develop a quavering voice.
Essential tremor is not a life-threatening disorder, unless it prevents a patient from caring for him/herself. Most people are able to live normal lives with this condition -- although they may find everyday activities like eating, dressing or writing difficult, which leads them to withdraw socially. But it is only when the tremors become severe that they actually cause disability.