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Orthostatic Tremor

Orthostatic Tremor

Information, News, Research, and Discussion

Orthostatic Tremor Glossary

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(the reference link after each description will bring you to the original source materials for additional information)

Ataxia: Persons who are diagnosed with ataxia experience a failure of muscle control in their arms and legs which may result in a lack of balance, coordination, and possibly a disturbance in gait. Ataxia may affect the fingers, hands, arms, legs, body, speech, and even eye movements. reference

Balance: Maintaining balance depends on information received by the brain from three peripheral sources: eyes, muscles and joints, and vestibular organs. All three of these sources send information to the brain in the form of nerve impulses from special nerve endings called sensory receptors. - reference

EMG: Electromyogram - An electromyogram (EMG) measures the electrical activity of muscles at rest and during contraction. Nerve conduction studies measure how well and how fast the nerves can send electrical signals. reference - see also Surface EMG

Force Platform, Force Plate instrument: Force platforms or force plates are measuring instruments that measure the ground reaction forces generated by a body standing on or moving across them, to quantify balance, gait and other parameters of biomechanics. reference 1 , reference 2 - OT can be efficiently diagnosed by visually inspecting frequency spectra derived from force platform signals, which show the high frequency postural tremor.reference

Gait Apraxia, Gait Initiation Difficulty, Gait Initiation Failure: As related to OT or OM it is characterized by an inability or difficulty to initiate the process of walking. Many terms overlap, and may be used incorrectly - reference

Helicopter sign: A unique feature of Orthostatic Tremor is the sound resembling a distant helicopter during auscultation (use of stethoscope) over the thigh or calf. This “helicopter sign” can also apply to the sound generated during surface EMG of affected muscles. reference

Hem sign: Fast trembling of the hem of skirt, revealing orthostatic tremor in legs and thighs reference

Hz - Hertz: the frequency of the tremor, tremors per second. The "common" and unique frequency for Orthostatic Tremor is a range of 13-18Hz, the common range of Essential Tremor is 4-12Hz and Parkinson's range of 4 to 6Hz. In the example of 18Hz (Hertz) this would be considered an extremely fast or fine tremor. 18 "cycles" per second is so fast that it is often not felt as a tremor.

Idiopathic disease: n. a disease that develops without an apparent or known cause. reference

Isolated OT - POT : primary orthostatic tremor with or without upper extremities involvement. reference

OM - Orthostatic Myoclonus - is a rare condition that is similar to primary orthostatic tremor, but myoclonus refers to sudden, involuntary jerking of a muscle or group of muscles caused by muscle contraction or relaxation. Orthostatic myoclonus is characterized by slowly progressive unsteadiness when standing that is relieved by walking or sitting. Some affected individuals experienced bouncing stance and recurrent falls. More research is necessary to determine when orthostatic myoclonus and primary orthostatic tremor are the same disorder or similar, yet distinct, disorders. reference 1 reference 2

The main difference between Orthostatic Myoclonus when compared to Orthostatic Tremor is that the bursts are shorter in duration, nonrhythmic, and irregular. Also, the tremor may not be bilateral and synchronous as seen in OT. In a recent retrospective study "leg jerking" was observed in 4 of the 16 subjects and falling was presented in 2 of the subjects

Orthostasis -Standing, also referred to as orthostasis, is a human position in which the body is held in an upright ("orthostatic") position and supported only by the feet. reference

OT - Orthostatic Tremor : - In definitions of OT you will notice the use of the words such as, “typically”, “most” and other similar terms. Because the initial description of OT was only 30+ years ago, and there is such a small sampling of people with OT, the definition continues to evolve as research advances and more information becomes available. Currently you may find conflicting descriptions of OT, but this will change as our understanding of OT changes. The following are definitions and links to their original reference source. Additional information can be found here , and reading descriptions of life with OT on the forum

a rare syndrome characterized by unsteadiness on standing due to a high-frequency tremor involving the legs. Symptoms usually start in the sixth decade. Typically, the symptoms rapidly improve on sitting or walking, and the need to sit down or to move can be so strong that patients avoid situations where they have to stand still. A polygraphic recording of a fast and synchronous tremor of the legs, between 13 and 18Hz, is mandatory to confirm the diagnosis of OT. Many patients also suffer from tremor, often involving lower frequencies, of the face, hands, or trunk. reference

…a relatively uncommon but distinct disorder, patients find it increasingly difficult to stand still due to sensations variably described as tremor, unsteadiness, and/or pain. Tasks such as waiting in line or doing dishes become troublesome, and patients find themselves needing to walk in place, continuously shift their weight from one leg to the other, or lean against a wall in order to reduce discomfort. OT may also be associated with muscle cramps, and patients will often describe subjective tremor elsewhere in the body, such as the lips, jaws, or hands. Significant disability and depression with substantial curtailing of activities can occur in severe cases. OT is more common in women, with a mean age of onset in the early sixties, and is generally considered to be sporadic, though associations with various other neurologic disorders have been reported, including ET, PD, cerebellar degeneration, progressive supranuclear palsy, and pontine lesions (see OT Plus). Familial occurrence is uncommon, though EMG-confirmed OT in three brothers has been reported. The diagnosis of OT should be suspected in any patient describing pain or other unpleasant sensations shortly after standing that is relieved by sitting or walking. Auscultation (use of stethoscope) of the gastrocnemius muscles can sometimes reveal a characteristic of barely audible noise akin to the sound of a helicopter.
The diagnosis is confirmed by pathognomonic surface EMG recordings revealing rhythmic activation of lower limb muscles at sharply peaked frequencies between 14 and 18 Hz, and sometimes higher....Tremor: Clinical Phenomenology and Assessment Techniques- reference

OT Plus or Orthostatic Tremor Plus : additional neurologic features present with Orthostatic Tremor - reference The following is from the report Natural history and syndromic associations of orthostatic tremor: a review of 41 patients: OT is considered to be a distinct, discrete condition, and little is known about its demographic characteristics, natural history, associated features, and treatment response. We have reviewed these aspects in 41 OT patients fulfilling current diagnostic criteria, seen at our institution between 1986 and 2001. We classified 31 (75%) as having idiopathic "primary OT" either with (n = 24) or without an associated postural arm tremor. We found that 10 of 41 (25%) cases had additional neurological features, and we defined this group as having "OT plus" syndrome. Of these 10, 6 had parkinsonism; 4 of these had typical Parkinson's disease (PD), 1 had vascular and 1 had drug-induced parkinsonism. Among the remaining 4 patients, 2 had restless legs syndrome (RLS), 1 had tardive dyskinesia, and 1 orofacial dyskinesias of uncertain etiology. One patient with PD and the patient with vascular parkinsonism also had RLS. Age at onset was significantly earlier in the "primary OT" (mean +/- SD, 50.4 +/- 15.1) than in the "OT plus" (61.8 +/- 6.4; z = 2.7; P =.006) group. In 7 of the 10 "OT plus" patients, OT leg symptoms preceded the onset of additional neurological features. reference

POT : Primary Orthostatic Tremor, see term “Primary” - generally Orthostatic Tremor without the associated disorders or symptoms of OT Plus

POTS : Postural Orthostatic Tachycardia Syndrome ( not Orthostatic Tremor ) - Postural orthostatic tachycardia syndrome (POTS) is one of a group of disorders that have orthostatic intolerance (OI) as their primary symptom. In POTS, the lightheadedness or fainting is also accompanied by a rapid increase in heartbeat of more than 30 beats per minute, or a heart rate that exceeds 120 beats per minute, within 10 minutes of rising. The faintness or lightheadedness of POTS are relieved by lying down again. Anyone at any age can develop POTS, but the majority of individuals affected (between 75 and 80 percent) are women between the ages of 15 to 50 years of age. Some women report an increase in episodes of POTS right before their menstrual periods. POTS often begins after a pregnancy, major surgery, trauma, or a viral illness. It may make individuals unable to exercise because the activity brings on fainting spells or dizziness. reference

Proprioception : Everyone learns in school about the five senses: vision (sight), audition (sound), olfaction (smell), taction (touch), and gustation (taste). These senses are responsible for our interaction with the external world. Additionally, we have several senses that are responsible for our internal functioning. One of the most important internal senses is called proprioception, or position sense. reference

Primary disease: n. A disease arising spontaneously and not associated with or caused by a previous disease or injury. - reference

Pseudo-Orthostatic Tremor : dominant frequency 6.2 to 6.9 sporadic subharmonics at 8 to 18 Hz... all patients had dopamine transporter abnormalities. reference

Restless Legs Syndrome : - RLS (not Primary Orthostatic Tremor) : People with restless legs syndrome have uncomfortable sensations in their legs (and sometimes arms or other parts of the body) and an irresistible urge to move their legs to relieve the sensations. reference

Romberg's test : A patient who has a problem with proprioception can still maintain balance by using vestibular function and vision. In the Romberg test, the standing patient is asked to close his or her eyes. A loss of balance is interpreted as a positive Romberg's test. reference

Shaky-Leg Syndrome or Shaky Legs Syndrome : less common and older name of Orthostatic Tremor, but often confused with Restless Leg Syndrome - RLS

Slow Orthostatic Tremor : An idiopathic orthostatic tremor on standing generally in the range of 4-8Hz. This study also aligns dystonia with slow OT reference

Surface EMG - sEMB : A technique in which electrodes are placed on (not into) the skin overlying a muscle to detect the electrical activity of the muscle. reference

Tardive Orthostatic Tremor : This report describes a drug induced OT (tardive), as a result of Dopamine blocking agents - "Tremor disappeared completely in 3 patients and improved markedly in the other one after gradual withdrawal of the offending drugs (metoclopramide in case 1, sulpiride and thyethylperazine in case 2, and sulpiride in cases 3 and 4)." reference

Vestibular system : The body senses whether it is upright or lying down or whether it is moving or standing still through the vestibular system, which is in the upper portion of the inner ear.. reference

White Rabbit Syndrome : A term that has been used to characterize OT because of the inclination to sit down or keep moving. reference


Disclaimer: This list/glossary is not perfect and we will attempt to update and correct as new information becomes available. This website does not offer medical advice and nothing contained in this website is intended to constitute professional advice for medical diagnosis or treatment. Information you receive through this website should not be relied upon for medical, legal, or financial decisions and you should consult with an appropriate professional for advice tailored to your specific situation. Although this website may be updated from time to time, please note that medical information changes rapidly. Therefore, some of the information may be out of date and/or may contain inaccuracies or typographical errors.

This website is intended to be an informal guide, and is not a substitute for medical advice.

The purpose of this site is to share information about Primary Orthostatic Tremor (OT). Since my diagnosis, my quest to learn more about this disorder has been frustrating and difficult to track. Hopefully, for all persons interested in this disorder, this website will become a coordinating link for collecting information, contacting other people with OT, and spreading awareness of this problem. Here you will find an active forum, my story / blog, and many other people that have shared their stories, advice and tips on coping with Orthostatic Tremor. If you have any information, suggestions, stories or services that you would like to share please email me.
This website is intended to be an informal guide. Any information relating to a therapy, treatment or diagnosis must be received with caution. Only a physician is authorized to confirm its validity. It must not, under any circumstances, delay or replace the advice of the treating physician. And is not a substitute for medical advice.

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