Essential Tremor

Description

Essential tremor (ET) is a common neurologic movement disorder. Estimates suggest that ET may be as much as 10 to 20 times as prevalent as Parkinson's disease (PD), affecting from 5 million up to as many as 10 million people in the United States. In the past, the condition was often referred to as "benign essential tremor." However, many experts consider use of the term "benign" unfortunate, since it may inappropriately minimize the impact of ET on disability, handicap, and quality of life (QOL).

Tremor is defined as an involuntary, rhythmic oscillatory movement of a part or parts of the body, resulting from alternating or irregularly synchronous contractions of antagonist muscles.

Tremor is the most common form of involuntary movement. Almost all individuals have experienced tremor at some point in their lives; however, only a small fraction of those with tremor seek medical attention. Tremors may result from normal (physiologic) or pathologic processes and may be characterized by their etiology or phenomenology (i.e., activation state, frequency, amplitude, waveform). With the exception of those affecting the facial region, tremors are frequently defined or characterized by the joint around which the body part moves.

Rest tremor occurs when muscle is not voluntarily activated, whereas action tremor is present with voluntary contraction of muscle. Subtypes include postural, kinetic, and isometric tremor. Postural tremor is present while voluntarily maintaining a position against gravity. Kinetic tremor may occur during any form of voluntary movement. Intention or terminal tremor refers to exacerbation of kinetic tremor toward the end of a goal-directed movement. (Please refer to table 1.)

Table 1. Classification of Tremor by Clinical Phenomenology
Rest tremor	Present when skeletal muscles are not voluntarily activated and the relevant body part is fully supported against gravity. Associated with PD, secondary parkinsonism, hereditary chin quivering, and severe ET. Often suppressed with voluntary muscle contraction.
Action tremor	Occurs upon any voluntary muscle contraction and may include any combination of postural, kinetic, task- or position-specific, or isometric tremor.
Postural tremor	An action tremor that is present while voluntarily maintaining a position against gravity. Associated with ET, primary orthostatic tremor, physiologic and enhanced physiological tremors, drug-induced and toxic tremors, neuropathic tremor, cerebellar head tremor (titubation), and dystonic tremor.
Kinetic tremor	An action tremor that occurs with any form of voluntary movement including visually- or nonvisually-guided actions, such as speaking, pouring water into a cup, or finger-to-nose testing. Associated with ET, classic cerebellar tremor (e.g., seen in multiple sclerosis, infarction), dystonic tremor, drug-induced or toxic tremors, and midbrain lesions. Includes dynamic or terminal tremor, which occurs with target-directed movements, and simple kinetic tremor, which is present with nontarget-directed actions.
Task- or position-specific tremor	A kinetic tremor that occurs during performance of highly specialized, complex movements, such as writing, speaking, or smiling. Primary writing tremor and isolated voice tremor are included.
Isometric tremor	A kinetic tremor present during voluntary muscle contraction against a rigid stationary object, such as making a fist or flexing the wrist against a horizontal, flat surface.

Tremor may be further delineated by anatomic distribution (e.g., the head, including the chin, face, tongue, or palate, or the upper or lower extremities); frequency; and coexistent neurologic conditions, use of tremorogenic medications, or other causative states.

Please see the following topics related to essential tremor below, and available on the left side of this page.

• Clinical Classification of Tremors
• Syndromic Classification of Tremors
• Tremor Classification Based on Relative Frequency
• Epidemiology
• Genetics
• Pathophysiology
• Differential Diagnosis
• Clinical Diagnosis
• Approaches to Treatment
• No Treatment
• Physical/Psychological Measures/Lifestyle Changes
• Pharmacological Approaches
• Surgical Management
• Sequential Approach to the Management of Essential Tremor
• Emotional Support
• Summary
• Essential Tremor Resources

For pediatric forms of tremor, see: Pediatric Movement Disorders - Tremor.

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Essential Tremor Slide Set	Essential Tremor Rating Scales	Tremor Patient Fact Sheets	Anatomical Illustrations