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Table 1.  

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 and toxin induced 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 non-visually 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 or toxin-induced tremors, and midbrain lesions. Includes dynamic or intention tremor, which occurs with target-directed movements, and simple kinetic tremor, which is present with non-targeted 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.

Classification of Tremor by Clinical Phenomenology

Table 2.  

Tremor Severity Scale: 0= None
1= Minimal (barely noticeable)
2= Obvious, noticeable but probably not disabling (<2 cm excursions)
3= Moderate, probably partially disabling (2 cm to 4 cm excursions)
4= Severe, coarse, and disabling (>4 cm excursions)
Definite ET: 2+ amplitude rating for bilateral arm tremor
2+ amplitude rating in one arm and 1+ amplitude rating in other arm
1+ amplitude rating in at least one arm and predominant cranial/cervical tremor with 2+ amplitude rating

Head tremor is rhythmic with no directional preponderance and without asymmetry of cervical muscles.

Exclude: obvious secondary causes (coexistent dystonia allowed; coexistent PD disallowed)
Probable ET: 1+ bilateral arm tremor
Isolated 2+ cranial/cervical tremor
Convincing history of ET
Exclude: obvious secondary causes (e.g., enhanced physiologic tremor, drug-induced or toxic tremor, coexistent peripheral neuropathies [such as CMT], etc.)

Coexistent dystonia allowed
Coexistent PD allowed if there is a convincing history of pre-existing ET
Possible ET: Isolated 1+ cranial/cervical tremor
Task- or position-specific arm tremor
Unilateral arm tremor
Orthostatic tremor
Unrateable ET: Tremor is coexistent with other neurologic disease, therapy with anti-tremor or tremor-promoting drugs, untreated thyroid disease, caffeine withdrawal/abstention, etc.

NIH Collaborative Genetic Criteria*

*Note: The NIH's Collaborative Genetic Criteria for ET were developed in 1996. At that time, interested investigators convened at the National Institutes of Health in Bethesda, Maryland with the purpose of reviewing research progress and reaching consensus concerning diagnostic criteria for genetic studies. The goal was to determine conservative criteria that would be of assistance during direct clinical examination as well as videotape assessment for diagnostic confirmation.

Table 3.  

Classic ET: Inclusion Criteria Bilateral, largely symmetric postural or kinetic tremor involving the hands and forearms that is persistent and visible
Classic ET: Exclusion Criteria 1. Other abnormal neurologic signs (particularly dystonia)
2. Presence of known causes of enhanced physiologic tremor
3. Historical or clinical evidence of psychogenic tremor
4. Convincing evidence of sudden onset or stepwise deterioration
5. Primary orthostatic tremor
6. Isolated voice tremor
7. Isolated position- or task-specific tremor
8. Isolated tongue or chin tremor
9. Isolated leg tremor

Consensus Statement of the Movement Disorder Society**

**Note: The Consensus Statement of the Movement Disorder Society on Tremor was discussed during the Society's tremor symposium in Kiel, Germany in 1997. Subsequently approved by MDS committees (Scientific Issues Committee, EXCO), the Consensus Statement represents the Society's proposal for a clinical classification of tremors. The main purpose of the statement is to communicate consistent nomenclature concerning tremor classification, thereby promoting clinical research with clearly defined patient populations.

Table 4.  

• Parkinson's disease (PD)
• Multiple system atrophy (MSA) (e.g., olivopontocerebellar atrophy [OPCA], striatonigral degeneration [SND])
• Huntington's disease (HD)
• Benign hereditary chorea
• Wilson's disease
• Fahr's disease
• Paroxysmal dystonic choreoathetosis (PDC)
• Ataxia-telangiectasia (AT)
• Familial intention tremor and lipofuscinosis
• Ramsay-Hunt syndrome (progressive myoclonic ataxia)
• Dystonia musculorum deformans
• DOPA-responsive dystonia (Segawa's syndrome)
• Spasmodic torticollis (cervical dystonia)
• Meige syndrome
• Task- or position-specific tremors (e.g., primary writing tremor, isolated voice tremor)
• Space-occupying lesions of the brain (e.g., cerebrovascular insults, trauma, cysts, tumors, hematomas)
• Various metabolic disturbances (e.g., hepatic encephalopathy, hypoglycemia, hyperthyroidism, hyperparathyroidism, hypocalcemia, etc.)
• Peripheral neuropathies (e.g., Charcot-Marie-Tooth disease, Guillain-Barré syndrome, Roussy-Levy syndrome, dysgammaglobulinemic neuropathies, etc.)

Differential Diagnosis of ET

Table 5.  

Primidone (Mysoline, Elan Pharma)
Beta-blockers such as propranolol (Inderal, Wyeth Pharmaceuticals)
Combination therapy (primidone and propranolol)
Gabapentin (Neurontin, Pfizer) or topiramate (Topamax, Ortho-McNeil)
Calcium channel blockers
Carbonic anhydrase inhibitors
Other tremorolytic medications

Drugs Used to Treat ET

Table 6.  

Method: Tablets 50 mg
Week Dose Given at Night
1 12.5 mg (1/4 tablet)
2 25.0 mg (1/2 tablet)
3 37.5 mg (3/4 tablet)
4 50.0 mg (1 tablet)

Sample Primidone Titration

Table 7.  

Advantages of DBS: Disadvantages of DBS:
Nondestructive Increased expense of the system
Reversible, no significant destruction to brain tissue or structures Need for implantation of foreign material, causing potential risk of inflammatory responses and infection
Adaptable (ability to change stimulation variables to minimize side effects and increase efficacy) Need to replace batteries and potential hardware malfunctions
Associated with stimulation-related complications that are typically reversible Time and effort required to optimize stimulation parameters
Ability to perform bilateral procedures with reduced risk of permanent morbidity  

Advantages and Disadvantages of DBS

Table 8.  

1. Initiate drug therapy by:
   a. Selecting an appropriate pharmacologic agent:
      • Primidone (12.5 to 25 mg/day PO at bedtime). Increase dose gradually in 25 mg increments to an upper limit of 125 to 250 mg/day, or
      • Propranolol (10 to 60 mg/day PO). Increase dose gradually in 20 mg increments to an upper limit of 120 mg/day up to 320 mg/day, or
      • A benzodiazepine (e.g., clonazepam at a starting dose of 0.25 mg/day PO that may be slowly increased to 1.0 to 2.0 mg/day in divided doses).
   b. Regulation of drug dose: identify the most efficacious dose with a minimum of adverse effects.
   c. If the medication is of no benefit at a dose that causes adverse effects, gradually taper down and discontinue.
   d. If a medication is documented to be helpful, continue at the regulated dose and add the next medication to attempt achieving further benefit.
2. If necessary, switch from propranolol to long-acting propranolol 80 mg/day. Increase in 60 or 80 mg increments as needed up to 160 to 320 mg/day.
3. If tremor control remains inadequate on monotherapy, initiate combination therapy with primidone and propranolol or add an additional medication such as gabapentin or topiramate.
4. If pharmacologic therapy is inadequate and the patient is an appropriate candidate, consider local injections of botulinum toxin.
5. If medical therapy fails, consider stereotactic surgery such as DBS.

Sequential Treatment Approach for Essential Tremor


Essential Tremor: A Clinical Review

  • Authors: Kelly E. Lyons, PhD ; Kapil D. Sethi, MD; Joy B. Leffler, BS, MLA ; Richard Robinson, BA
Start Activity

Target Audience and Goal Statement

This activity is intended for any clinician who treats adult patients.

The goal of this activity is to educate clinicians on diagnosing and treating essential tremor.

Upon completion of this activity, participants will be able to:

  1. Differentiate essential tremor (ET) from other movement disorders with tremor
  2. Perform a physical examination to help identify ET
  3. Prescribe medications for ET patients appropriately
  4. Determine when surgery or injections of botulinum toxin may be necessary for ET


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Medscape, LLC encourages Authors to identify investigational products or off-label uses of products regulated by the US Food and Drug Administration, at first mention and where appropriate in the content.


  • Kelly E. Lyons, PhD

    Director of Research and Education at the Parkinson's Disease and Movement Disorder Center, University of Kansas Medical Center, Kansas City, Kansas


    Disclosure: Kelly Lyons, PhD, has disclosed no relevant financial relationships.

  • Kapil D. Sethi, MD

    Professor of Neurology; Director, Movement Disorders Program, Medical College of Georgia, Augusta


    Disclosure: Kapil D. Sethi, MD, has disclosed that he has served as a consultant and speaker for Boehringer Ingelheim, GlaxoSmithKline, Novartis, and Allergan. Dr. Sethi has also disclosed that he owns stock with Elan, Merck, and Pfizer.

  • Joy B. Leffler, BS, MLA

    Senior Director of Education and Informatics, Movement Disorder Education Fund, dba WeMove, New York, NY


    Disclosure: Joy B. Leffler, BS, MLA, has disclosed no relevant financial relationships.

  • Richard Robinson, BA

    Richard Robinson, BA, is a Freelance medical writer, New York,Robinson, BA,  NY


    Disclosure: Richard Robinson, BA, has disclosed no relevant financial relationships.


  • Carol Peckham

    Director, Editorial Development, Medscape, LLC


    Disclosure: Carol Peckham has disclosed no relevant financial relationships.

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Essential Tremor: A Clinical Review

Authors: Kelly E. Lyons, PhD ; Kapil D. Sethi, MD; Joy B. Leffler, BS, MLA ; Richard Robinson, BAFaculty and Disclosures



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 of action tremor 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. Isometric tremor is present during voluntary muscle contraction without movement. (Please refer to Table 1.)

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

Clinical Classification of Tremors

Tremor research typically relies on clinical classifications. The clinical classification of tremor may be based upon...

  • Clinical phenomenology

  • Anatomic or topographic distribution

  • Activities that activate tremor

  • Tremor frequency

  • Medical, drug and family history and clinical evaluation (i.e., to detect concomitant neurologic conditions, drug or toxin-induced tremors, etc.)

The clinical classification of ET is an ongoing, evolutionary process. Several classification schemes have been proposed, including the Tremor Investigation Group (TRIG) Criteria in 1995; the National Institutes of Health (NIH) Collaborative Genetic Criteria in 1996 [refer to Table 2]; and the Consensus Statement of the Movement Disorder Society (MDS) on Tremor in 1998 [refer to Table 3]. The use of such classification schemes may stimulate discussion among physicians regarding the definition of ET, leading to a clinical diagnostic framework for tremor including nomenclature; definitions based upon phenomenology, evaluation, and rating scales; differential diagnosis; and support for technical investigations. Such a definition may play an essential role in facilitating appropriate, early identification of ET and assisting in the development of new approaches to tremor research.

Syndromic Classification of Tremors

In addition to classic ET, the MDS consensus criteria describe several additional syndromes based upon clinical observations of specific tremor elements. Important in the differential diagnosis of ET, these syndromic classifications include the following:

Physiologic tremor. A normal phenomenon, physiologic tremor occurs in all contracting muscle groups. Ranging in frequency from 8 to 12 Hz, it is subtly detectable on electromyography (EMG). Although seldom visible to the naked eye, physiologic tremor may often be detected when the fingers are firmly outstretched with a piece of paper placed over the hands.

Enhanced physiologic tremor or an intensification of physiologic tremor to detectable levels. Physiologic tremor may be enhanced under conditions of stress, anxiety, fatigue, exercise, cold, hunger, stimulant use, alcohol withdrawal, or metabolic disturbances, such as hypoglycemia or hyperthyroidism. Although the tremor is typically low in amplitude and high in frequency (8 to 12 Hz), it may be clinically indistinguishable from ET. In fact, some authors suggest that certain kinetic and postural tremors, including ET, may represent enhanced physiologic tremor. More specifically, some believe that physiologic tremor may be a forme fruste of ET, with both originating from the same neuronal oscillators. These investigators indicate that ET may begin as enhanced physiologic tremor that progresses in severity to a pathologic tremor. However, evidence has been presented suggesting that physiologic tremor and ET are different. Thus, the issue remains unresolved.

Indeterminate tremor syndrome. Patients with indeterminate tremor syndrome fulfill the criteria for classic ET yet have additional neurologic signs that are insufficient for diagnosis of another neurologic disorder. Previously categorized as "possible ET type Ib" by the TRIG criteria, the designation "indeterminate tremor syndrome" has been proposed by the MDS consensus authors in an effort to avoid difficulties stemming from incorrect or conflicting diagnoses.

Primary orthostatic tremor, a postural tremor of lower limb, trunk, and, possibly, upper limb muscles during stance yet absent when sitting or reclining. In most patients, orthostatic tremor is suppressed upon walking. As seen on EMG, orthostatic tremor is characterized by high frequency, 13 to 18 Hz entrainment of synchronous motor unit activity of contralateral and ipsilateral muscles, primarily of the lower limbs.

Dystonic tremor. Although consensus has not been reached concerning the definition of dystonic tremor syndrome, authors of the MDS consensus criteria have proposed a number of definitions within this general category. For example, "dystonic tremor" refers to primarily postural and kinetic tremor occurring in a body part affected by dystonia. Dystonia is a neurologic movement disorder characterized by sustained muscle contractions that frequently cause repetitive, twisting, or writhing movements accompanied by distorted, sometimes painful, postures or positions. Dystonic tremor may affect any voluntary muscle in the body. Postural hand tremor commonly affects dystonia patients and is frequently indistinguishable from ET. As with dystonia, gestes antagoniste, such as tapping or stroking of affected or adjacent muscles, may alleviate dystonic tremor by reducing tremor amplitude. In addition, the designation of "tremor associated with dystonia" applies to dystonia patients who have tremor in a body part that is not affected by dystonia.

Task- and position-specific tremors. These tremors occur upon performance of specific, highly specialized motor activities. They include primary writing tremor, defined as tremor occurring solely or primarily while writing yet not with other hand activities; occupational tremors, such as specific tremors affecting athletes or musicians; or isolated voice tremors. Voice tremor may be characterized by tremulousness of the voice in the absence of other tremor manifestations -- or by focal dystonia of the vocal cords, such as tremor that subsides with changes in pitch or gestes antagoniste.

Parkinsonian tremor syndromes, i.e., the presence of pathologic tremor in patients with PD or parkinsonism. PD is a slowly progressive, degenerative disorder of the central nervous system (CNS) that may be characterized by tremor (primarily resting tremor), rigidity, and bradykinesia (slowness and poverty of movement). Additional findings may include postural instability, shuffling gait, start hesitancy and freezing, "mask-like" facies, hypophonia, micrographia, depression, or dementia. Whereas rest tremor is the most common, other forms of tremor may also be present. For example, some parkinsonian patients may have rest tremor and kinetic/postural tremor with similar or higher, non-harmonically related frequencies. Less commonly, isolated postural/kinetic tremors may be present.

Cerebellar tremor syndromes, described as pure or primary intention tremors with a frequency predominantly less than 5 Hz, possibly in association with postural (but not resting) tremor. The terms "cerebellar" and "intention" tremor are often used interchangeably. Other forms of tremor, such as postural tremor, are deemed of cerebellar origin only when coexistent with other cerebellar signs.

Holmes tremor. Traditionally known as rubral or midbrain tremor, so-called Holmes tremor is defined as a symptomatic rest, intention, and possibly postural tremor due to lesions affecting the cerebellothalamic and dopaminergic systems -- such as involving the brainstem, cerebellum, and thalamus and, possibly, their pathways.

Palatal tremors. These rhythmic movements of the soft palate may or may not occur subsequent to lesions of the brainstem and cerebellum and associated olivary pseudohypertrophy.

Neuropathic tremor syndrome. Certain peripheral neuropathies, particularly dysgammaglobulinemic neuropathies, are commonly associated with tremor, primarily kinetic and postural tremor of the affected extremities.

Drug-induced and toxic tremor syndromes. Pharmacologic agents used to treat other medical conditions may induce tremor. Such medications may include theophylline, valproate, lithium, tricyclic antidepressants, neuroleptics, sympathomimetics, amphetamines, steroids, certain agents used to treat endocrine and metabolic disorders, or other miscellaneous agents. Toxin-induced tremor, such as seen in manganese, arsenic, or mercury intoxication or poisoning, occurs in association with other neurologic symptoms, such as gait disturbances, rigidity, dystonia, ataxia, dysarthria, confusion, etc.

Psychogenic tremor. This form of tremor may be suggested by a history of somatization, the presence of unrelated neurologic signs, and sudden tremor onset or remissions. Additional signs may include a decrease of amplitude or variation of frequency upon distraction, unusual combinations of postural/intention and rest tremors, and co-activation resembling voluntary co-contraction during passive movements of a trembling limb about a joint.

Myorhythmia. A slow tremor of 2 to 4 Hz as seen in patients with lesions of the brainstem (similar to Holmes tremor).

Tremor Classification Based on Relative Frequency

Tremors may also be classified based on the number of repetitions of complete waveforms per second. Physiologic and enhanced physiologic tremor have a relatively high frequency, often ranging from approximately 7 to 12 cycles per second. In contrast, the rate of many pathologic tremors is about 2 to 7 Hz. Primary orthostatic tremor is a notable exception, with a 13 to 18 Hz entrainment of motor unit activity. In addition, cortical tremor, recognized as a form of rhythmic myoclonus, is characterized by irregular, postural and kinetic tremor-like jerks with a range between 7 to 18 Hz.

Cerebellar and rubral or Holmes tremors tend to be of relatively low frequency, primarily occurring below 4.5 or 5 Hz. The pure rest tremor seen in some with PD is characteristically greater than 4 Hz, although the upper frequency limit of these tremors has not been firmly established. For those parkinsonian patients with a combination of rest and postural/kinetic tremors, relative frequencies may be similar -- or postural/kinetic tremors may have a frequency that is more than 1.5 Hz higher as related to rest tremor rate.

In classic ET, the rate of tremor may vary between 4 to 12 Hz, with older patients typically demonstrating tremor frequencies toward the lower range. In contrast, younger patients with mild ET tend to have tremor frequencies that extend into the 7 to 12 Hz range of physiologic tremor.