Tremor is involuntary trembling in part of the body. The most common type is essential tremor. It 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.

The cause of essential tremor in people without the genetic mutation is unknown.

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 of essential tremor is based on the observation of symptoms, a thorough medical history, physical examination, and neurological examination. 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.

Essential tremor often does not require treatment. Lifestyle changes, Physical therapy may improve symptoms. Severe tremor that affects the patient’s ability to perform daily tasks and interferes with their quality of life can be treated with medication. Surgery may be recommended when essential tremor is so severe that it causes disability.