Tremor can be the symptom of a variety of neurological conditions, however the word "essential" indicates that the tremor is not tied to any other condition.
Causes of Essential Tremor (ET)
The cause of essential tremor is not known, but it likely has a genetic basis, and oftentimes several generations of a family are affected.
Incidence of Essential Tremor
- 50 percent of all patients have a family history of tremor
- About 1 in 20 people older than age 40 may have essential tremor
- Approximately 1 in 5 people over 65 may have essential tremor
- There may be as many as 10 million people with essential tremor in the United States alone and many more worldwide
- Essential tremor is the most common of all other neurologic disease except for stroke, and it is even more common than Parkinson's disease
- The chance of developing essential tremor increases with advancing age
Symptoms of Essential Tremor
Essential tremor is most often seen in the hands, however it can affect almost any part of the body. It is identified as a rhythmic shaking of a body part when:
- Holding the body part in a fixed position (postural tremor)
- Trying to use the affected body part (kinetic or action tremor)
- Tremor may present in the hands, legs, head or voice
- Tremor may prevent someone from writing, eating with a spoon or fork or drinking from a cup without a straw
This type of tremor is a normally occurring fine tremor in all contracting muscle groups with the frequency of 8 to 12 Hertz (repetitions per second).
Causes of Enhanced (Increased) Physiologic Tremor
This tremor may be increased by:
Incidence of Physiologic Tremor
- Most people exhibit physiologic tremor with fine movements
Symptoms of Physiologic Tremor
Intensity of the tremor increases with stress and fine motor activities, especially in the hands.
Primary Orthostatic Tremor
Primary Orthostatic Tremor is a unique syndrome, identified by a high frequency (13 to 18 Hertz) tremor of the trunk and legs that occurs only while standing still. There is no tremor or symptoms while sitting or lying down and rarely when walking. It is common to feel dizzy or unsteady when standing up from a seated position. The tremor can be relieved by constantly moving the feet or marching in place.
Task- & Position-Specific Tremor
This is a group of tremor syndromes that shares the common feature of tremor activation when engaged in a specific task. The most common type is primary writing tremor, in which symptoms appear only or predominantly with that particular activity. Use of the limb with other activities (eating, weight-lifting, etc.) does not produce tremor.