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 (voice box), tongue, and chin. Rarely, the lower body is affected.
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ET is not a life-threatening disorder, unless it prevents a person from caring for him or herself. Most people are able to live normal lives with this condition -- although they may find everyday activities like eating, dressing, or writing difficult. It is only when the tremors become severe that they actually cause disability.
What Causes Essential Tremor?
The true cause of essential tremor is still not understood, but it is thought that the abnormal brain activity that causes tremor is processed through the thalamus. The thalamus is a structure deep in the brain that coordinates and controls muscle activity.
Genetics is responsible for causing ET in half of all people with the condition. A child born to a parent with ET will have up to a 50% chance of inheriting the responsible gene, but may never actually experience symptoms. Although ET is more common in the elderly -- and symptoms become more pronounced with age -- it is not a part of the natural aging process.
Who Gets Essential Tremor?
Essential tremor is the most common movement disorder, affecting an estimated five million people in the U.S. Some figures estimate that one in 20 people over age 40 and one in 5 people over age 65 have ET.
While ET can occur at any age, it most often strikes for the first time during adolescence or in middle age (between ages 40 and 50).
What Are the Symptoms of Essential Tremor?
The primary symptoms associated with essential tremor include:
Uncontrollable shaking that occurs for brief periods of time
Tremors that worsen during periods of emotional stress
Tremors that get worse with purposeful movement
Tremors that lessen with rest
Balance problems (in rare cases)
The uncontrollable shaking associated with ET is not unique to this condition. Many different factors or diseases can also cause tremors, including Parkinson's disease, multiple sclerosis, fatigue after exercise, extreme emotional distress, brain tumors, some prescription drugs, metabolic abnormalities, and alcohol or drug withdrawal.
Can Essential Tremor Increase the Risk for Other Illnesses?
Essential tremor is linked to other illnesses. Other movement disorders, such as Parkinson's disease, have been associated with ET. Some reports have also linked ET with migraine headaches.
Drugs used to treat essential tremor may also increase a person's risk of becoming depressed.
Most experts believe that there is no increased risk for Parkinson's disease for people with ET. On the other hand, some people diagnosed as having ET are initially incorrectly diagnosed and subsequently turn out to have Parkinson's disease.