Essential Tremors
Overview
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
- Holding a glass without spilling
- Performing self-care (e.g., getting dressed, shaving, putting on makeup)
- Using eating utensils
- Writing and drawing
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
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.
Differential Diagnosis
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.
Treatment
Essential tremor often does not require treatment.
Lifestyle changes, such as reducing stress and avoiding caffeine and alcohol, may improve symptoms. Physical therapy may help reduce essential tremor of the hands, arms, legs, and trunk, and speech therapy may be beneficial for people whose voice is affected.
Severe tremor that affects the patient's ability to perform daily tasks and interferes with their quality of life can be treated with medication or surgery.
Medication
Severe essential tremor can be reduced using medication in most (approx. 50-75%) cases. Beta-blockers, such as propranolol (Inderal®), and antiseizure medications (e.g., primidone [Mysoline®], gabapentin [Neurontin®]) often are prescribed.
Beta-blockers usually are prescribed for younger patients because they may cause memory loss and confusion in older patients. Other side effects of beta-blockers include dizziness, fatigue, shortness of breath, and nausea.
Side effects of antiseizure medications include drowsiness, nausea, difficulty concentrating, and lack of balance and coordination (ataxia).
Other medications used to treat essential tremor include benzodiazepines (e.g., diazepam [Valium®], clonazepam [Klonopin®], alprazolam [Xanax®]) and carbonic anhydrase inhibitors (e.g., methazolamide [Glauctabs®, Neptazane®], acetazolamide [Diamox®]).
Side effects of benzodiazepines include drowsiness, fatigue, ataxia, and blood clots (thrombosis). Carbonic anhydrase inhibitors may cause tingling in the hands and feet, ringing in the ears (tinnitus), fatigue, and malaise.
Botulinum toxin injections (BOTOX® Cosmetic) treat essential tremor by producing local muscle weakness. When used to treat tremor in the hands, it may cause weakness in the fingers.
Surgery
Surgery may be recommended when essential tremor is so severe that it causes disability. Thalamotomy is destruction of a portion of the area deep within the brain that receives sensory messages (thalamus). This procedure relieves essential tremor on one side of the body in approximately 75% of cases. Surgery on both sides of the thalamus rarely is performed because of the high risk for speech loss.
Deep brain stimulation (DBS) is another surgical option when severe essential tremor does not respond to medication. In this procedure, a hair-thin wire is implanted in the thalamus and connected to a device (called a neurostimulator) that is implanted under the collarbone. The neurostimulator sends electrical impulses along the wire to the thalamus to interrupt signals that cause tremor.
Patients can turn DBS on when needed and turn it off when tremors are infrequent (e.g., during sleep). Studies have shown that DBS reduces essential tremor and improves patients' ability to perform daily activities.
Prognosis
Essential tremor is rarely debilitating. Severe cases can usually be treated with medication.
Prevention
Essential tremor cannot be prevented.