Primary Orthostatic Tremor

Primary Orthostatic Tremor

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Primary Orthostatic Tremor is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • idiopathic orthostatic tremor

Disorder Subdivisions

  • None

General Discussion

Summary

Primary orthostatic tremor is a rare movement disorder characterized by a rapid tremor in the legs that occurs when standing. The tremor disappears partially or completely when an affected person is walking or sitting. Individuals with primary orthostatic tremor experience feelings of unsteadiness or imbalance. The tremor is sometimes described as causing "shaky legs" and can cause affected individuals to immediately attempt to sit or walk because of a fear of falling. In many cases, the tremors become more severe over time. Primary orthostatic tremor is a constant problem that can affect the quality of life of affected individuals. The exact cause of primary orthostatic tremor is unknown.



Introduction

Primary orthostatic tremor was first described in 1984 by Heilman. There is controversy within the medical literature regarding whether primary orthostatic tremor is a variant of essential tremor, an exaggerated physiological response to standing still or a distinct clinical entity.

Symptoms

The main symptom of primary orthostatic tremor is the occurrence of a rapid tremor affecting both legs while standing. A tremor is involuntary, rhythmic contractions of various muscles. Orthostatic tremor causes feelings of unsteadiness or imbalance in the legs. The tremor associated with primary orthostatic tremor has such high frequency that it may not visible to the naked eye but can be palpated by touching the thighs or calves or can be detected by listening to these muscles with a stethoscope. The tremor is position-specific (standing) and disappears partially or completely when an affected individual walks, sits or lies down. In many cases, the tremor becomes progressively more severe and feelings of unsteadiness become more intense. Some affected individuals can stand for several minutes before the tremor begins; others can only stand momentarily. Eventually, affected individuals may experience stiffness, weakness and, in rare cases, pain in the legs. Orthostatic tremor, despite usually becoming progressively more pronounced, does not develop into other conditions or affect other systems of the body.



In some cases, affected individuals may also have a tremor affecting the arms. In one case reported in the medical literature, overgrowth of the affected muscles (muscular hypertrophy) occurred in association with primary orthostatic tremor.

Causes

The exact cause of primary orthostatic tremor is unknown (idiopathic). Some researchers believe that the disorder is a variant or subtype of essential tremor. Other researchers believe the disorder is a separate entity. Some individuals with primary orthostatic tremor have had a family history of tremor suggesting that in these cases genetic factors may play a role in the development of the disorder. However, more research is necessary to determine the exact, underlying cause(s) of primary orthostatic tremor.

Affected Populations

Primary orthostatic tremor affects males and females in equal numbers. More than 200 cases have been reported in the medical literature. However, because many cases of primary orthostatic tremor often go unrecognized or misdiagnosed, the disorder is believed by some to be under-diagnosed, making it difficult to determine the true frequency of this disorder in the general population.

Standard Therapies

Diagnosis

A diagnosis of primary orthostatic tremor is based upon a thorough clinical evaluation, a detailed patient history, and supported by specialized tests such as a surface electromyogram (EMG). Misdiagnosis is common. Many individuals may be initially suspected of having a psychogenic disorder (a disorder caused by a psychological cause rather than a physical one).



Clinical Testing and Work-Up

A surface EMG measures the electrical impulses of muscles at rest and during contraction. A surface electromyogram can often rapidly establish a diagnosis of primary orthostatic tremor by reproducing the characteristic tremor in the legs. With a surface electromyogram electrodes are placed on the skin overlying the muscles that are to be tested.



Treatment

Various medications may help relieve symptoms associated with primary orthostatic tremor. In most cases, affected individuals are treated with a drug called clonazepam (Klonopin). However, some affected individuals do not respond to this first-line drug treatment.



Some affected individuals responded favorably after being treated with an anti-seizure (anticonvulsant) drug called gabapentin (Neurontin). A very small double-blind, placebo controlled study demonstrated that affected individuals experienced a sustained improvement when treated with the drug. Authors of the study suggested that gabapentin be considered a first-line therapy for individuals with primary orthostatic tremor.



Additional drug therapies that have been used to treat individuals with primary orthostatic tremor include primidone (Mysoline), chlordiazepoxide (Librium), pregabalin (Lyrica), pramipexole (Mirapex), phenobarbital and valproic acid (Depakote). Drugs commonly used to treat people with Parkinson's disease (levodopa or pramipexole) may also be prescribed for individuals with primary orthostatic tremor. Additional treatment is symptomatic and supportive.

Investigational Therapies

The medical literature details several cases of individuals with primary orthostatic tremor who have been treated by thalamic deep brain stimulation. Thalamic refers to the thalamus, a portion of the brain that relays sensory information. It is believed that some types of tremors occur due to abnormal brain activity that is processed in the thalamus. During this procedure, an electrode is placed into the thalamus and a thin wire is passed under the skin is connected to a small battery pack (which is also placed underneath the skin. The electrode is used to send electrical impulses (stimulate) to the brain and interrupt aberrant nerve signals that contribute to tremors. In some cases reported in the medical literature, tremors of individuals with primary orthostatic tremor were successfully controlled with thalamic deep brain stimulation. However, more research is necessary to determine the long-term safety and effectiveness of this potential therapy for primary orthostatic tremor.



Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.



For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:



Toll-free: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com

References

JOURNAL ARTICLES

Fekete R, Jankovic J. Revisiting the relationship between essential tremor and Parkinson's disease. Mov Disord. 2011;26:391-398. http://www.ncbi.nlm.nih.gov/pubmed/21462256



Bain P, Jones L. Characterising orthostatic tremor: a study of 56 patients. J Neurol Neurosurg Psychiatry. 2010;81:e22. http://jnnp.bmj.com/content/81/11/e22.3



Ramtahal J, Larner AJ. Shaky legs? Think POT! Age Ageing. 2009;38:352-353. http://www.ncbi.nlm.nih.gov/pubmed/19252207



Guridi J, Rodriquez-Oroz MC, Arbizu J, et al. Successful thalamic deep brain stimulation for orthostatic tremor. Mov Disord. 2008;23:1808-1811. http://www.ncbi.nlm.nih.gov/pubmed/18671286



Glass GA, Ahlskog JE, Matsumoto JY. Orthostatic myoclonus: a contributor to gait decline in selected elderly. Neurology. 2007;68:1826-1830. http://www.neurology.org/content/68/21/1826.long#T1



Rodrigues JP, Edwards DJ, Walters SE, et al. Blinded placebo crossover study of gabapentin in primary orthostatic tremor. Mov Disord. 2006;21:900-905. http://www.ncbi.nlm.nih.gov/pubmed/16532455



Rodrigues JP, Edwards DJ, Walters SE, et al. Gabapentin can improve postural stability and quality of life in primary orthostatic tremor. Mov Disord. 2005;20:865-870. http://www.ncbi.nlm.nih.gov/pubmed/15719416



Gerschlager W, Munchau A, Katzens - chlager R, et al. Natural history and syndromic associations of orthostatic tremor: a review of 41 patients. Mov Disord. 2004;19:788-95. http://www.ncbi.nlm.nih.gov/pubmed/15254936



Lopez del Val LJ, Santos S. Gabapentin in the treatment of tremor. Rev Neurol. 2003;36:322-6. http://www.ncbi.nlm.nih.gov/pubmed/12599126



Sharott A, Mardsen J, Brown P. Primary orthostatic tremor is an exaggeration of a physiological response to instability. Mov Disord. 2003;18:195-9. http://www.ncbi.nlm.nih.gov/pubmed/12539215



Fung VS, Sauner D, Day BL. A dissociation between subjective and objective unsteadiness in primary orthostatic tremor. Brain. 2001;124:322-30. http://www.ncbi.nlm.nih.gov/pubmed/11157559



Finkel MF. Pramipexole is a possible effective treatment for primary orthostatic tremor (shaky leg syndrome). Arch Neurol. 2000;57:1519-20. http://www.ncbi.nlm.nih.gov/pubmed/11030807

Resources

WE MOVE (Worldwide Education and Awareness for Movement Disorders)

5731 Mosholu Avenue

Bronx, NY 10471

USA

Tel: (347)843-6132

Fax: (718)601-5112

Email: wemove@wemove.org

Internet: http://www.wemove.org



NIH/National Institute of Neurological Disorders and Stroke

P.O. Box 5801

Bethesda, MD 20824

Tel: (301)496-5751

Fax: (301)402-2186

Tel: (800)352-9424

TDD: (301)468-5981

Internet: http://www.ninds.nih.gov/



OT Resource

Email: 25nelson@comcast.net

Internet: http://www.orthostatictremor.org



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/



Movement Disorder Society

555 E. Wells Street

Suite 1100

Milwaukee, WI 53202-3823

Tel: (414)276-2145

Fax: (414)276-3349

Email: info@movementdisorders.org

Internet: http://www.movementdisorders.org



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into myCigna.com. For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html.

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