Tremor is involuntary trembling in part of the body. Essential tremor is associated with purposeful movement (e.g., holding a glass to drink, shaving, writing, buttoning a shirt). It occurs most often in the hands and head and also may affect the arms, voice box (larynx), trunk, and legs.
Essential tremor is caused by abnormalities in areas of the brain that control movement and does not occur as the result of disease (e.g., Parkinson’s disease). It usually does not result in serious complications.
Incidence and Prevalence
Essential tremor affects approximately 5 million people in the United States. Incidence is highest in people over the age of 60.
Risk Factors and Causes
Age is a risk factor for essential tremor. It is more common in people over the age of 60.
There is often a family history of the disorder and approximately 50% of cases have a genetic link. Essential tremor is an autosomal dominant trait that has been linked to gene ETM1 and gene ETM2. Having a parent with the disorder increases the risk.
The cause of essential tremor in people without the genetic mutation is unknown.
Signs and Symptoms
Essential tremor usually develops gradually during middle age or later in life. Symptoms may remain mild or increase in severity over time. Stress, fatigue, anxiety, and hot or cold weather can worsen the disorder. Severe tremor may cause difficulty performing activities of daily living, such as:
- Brushing hair and teeth
- Writing and drawing
- Holding a glass without spilling
- Performing self-care (e.g., getting dressed, shaving, putting on makeup)
- Using eating utensils
Tremor is usually more severe during fine motor activities such as writing or threading a needle and does not occur during rest or sleep. If it occurs in the voice box, speech will be affected.
Diagnosis of essential tremor is based on the observation of symptoms, a thorough medical history, physical examination, and neurological examination. Performance tests, such as asking the patient to write, draw, hold an object, or drink from a glass, help the physician evaluate the tremor.
Results from blood and urine tests can help the physician rule out other causes such as the following:
- Heavy metal poisoning (usually caused by exposure to lead or mercury)
- Parkinson’s disease
- Side effect of medication (e.g., asthma drugs, antidepressants)
- Thyroid disease
Essential tremor is not related to Parkinson’s disease. Tremor caused by Parkinson’s is more pronounced during rest and usually does not affect the head or voice.
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