Tremors are non-intentional rhythmic movements of a body part, which are the result of alternating or irregular synchronous contractions of muscles that have an opposite effect on a joint. For example, muscles that, when contracted, result in flexion of the wrist are stimulated synchronously with muscles that result in extension of the wrist.


The result is a rhythmic flexion and extension of the wrist. This phenomenon can happen in any part of the body. It is this rhythmic quality that defines and distinguishes tremors from any other abnormal movements.


Tremors Classification


Two main categories can be recognized:

  1. normal (also called physiologic).
  2. abnormal (or pathologic).


The normal or physiological tremor is a fine, almost imperceptible, tremor that is difficult to see by the naked eye and does not interfere with activities. It can be seen in the fingers when the arms are outstretched. The frequency of the contractions is in the area of 8 to 13 cycles per minute. The cause of this tremor is not known, but it is not considered to be associated with any disease process.


The abnormal or pathological tremor it is more obvious and more visible to the naked eye. As such, it does interfere with everyday activities. The frequency of the contractions is in the area of 4 to 7 cycles per minute. In many instances this tremor is associated with defined medical conditions.


Most often the abnormal tremor is observed in the distal parts of the limbs (hands, fingers); however, every part of the body (such as the head, the tongue, the vocal cords, or the trunk) can be affected by the tremor.


The clinical distribution of the tremor might be different depending upon the medical condition associated with it and some individual factors. However, in a particular individual the quality and distribution of the tremor is very constant.


These abnormal tremors can be subclassified into the following categories:


  1. A resting tremor (also call Parkinsonian tremor) is observed in a body part that is not active and is completely supported against gravity. It is a coarse, rhythmic tremor, often localized in the hands and forearms, but less frequently seen in other parts of the body and is observed when the limb is in a position of rest. Intentional movement might decrease the intensity of the tremor. However, the tremor disappears when the limbs are in extreme rest, as it is the case when the patient is sleeping. This phenomenon is common to most of the tremors. In the hands, the tremors result in a peculiar "pill rolling" movement of the fingers, more obvious between the thumb and the index finger. Other parts of the body might also be affected. For example, the eyelids tend to flutter, and the jaw and the lips can flicker. When the legs are impaired it might result in gait (walking) problems. This tremor is most often seen as a manifestation of the Parkinson's syndrome.
  2. Postural, or action tremor, is observed when muscles voluntarily contract. This tremor is exhibited with any attempt to keep the limbs or trunk in a particular position, for example to keep the arms outstretched. This type of tremor becomes worse when the limb is actively moved, for instance, when trying to drink from a cup. However, no tremor is observed when the limb is fully relaxed. This tremor is most often seen as a manifestation of essential tremor.
  3. Intention (ataxic) tremor can be a very disabling type of tremor. It has some of the characteristics of the action tremor in the sense that it is triggered by movement; however, its main feature is that it occurs at the end of an action, when a fine, precise adjustment is needed. For example, when a person is asked to touch the tip of the nose, the early part of the action does not elicit the tremor, but as soon as the finger is near the nose and has to zero in on the tip of the nose, an irregular, rhythmic tremor with a frequency of 2 to 4 oscillations per minute is seen. Unlike action and resting tremor, the oscillations are in different planes and may persist even after the task is achieved. This type of tremor is mostly seen in conditions associated with the cerebellum or its neurological connections. 
  4. Rubral tremor is characterized by intense, violent movement. With this type of tremor, a patient's slight movement of the arms or attempts to maintain a static posture, like trying to keep the arms outstretched, results in an intense rhythmic "wing-beating" movement. It is also associated with some interruptions of the cerebellar connections. This type of tremor is seen most often, among other conditions, in persons with multiple sclerosis.


In general, one particular tremor type is predominant and sometimes the only tremor present in a defined clinical condition, for example, resting tremor in Parkinson's disease or postural tremor in essential tremor.


However, there are several individual variations, and it is not unusual for a patient with a defined clinical condition, for example Parkinson's disease, to have, besides the resting tremor typical of the disease, some degree of postural tremor.


Tremor symptoms may occur with other symptoms, depending on the underlying disease, disorder or condition. Additional symptoms can be characteristic of a variety of different conditions including essential tremor, multiple sclerosis, stroke, hyperthyroidism, or Parkinson’s disease.


Other possible symptoms that may occur with tremor symptoms include:


  • Frequent urination.
  • Impaired balance and coordination.
  • Numbness or tingling in any part of the body.
  • Quavering voice.
  • Shuffling gait (walk).
  • Signs of hyperthyroidism, such as protruding eyes, unexplained weight loss, heat intolerance, perspiration and goiter.
  • Signs of multiple sclerosis, such as weakness, numbness or tingling, vision problems, unsteady walk, fatigue, and depressio.
  • Stooped posture.
  • Tremors that intensify during stress.


Serious symptoms that might indicate a life-threatening condition


In some cases, tremor symptoms may occur with other symptoms that might indicate a serious or life-threatening condition, such as a stroke, that should be immediately evaluated in an emergency setting.


Seek immediate medical care (call 911) if you, or someone you are with, are exhibiting any of these life-threatening symptoms:

  • Confusion or loss of consciousness for even a brief moment.
  • Difficulty breathing.
  • Difficulty speaking or understanding speech.
  • Difficulty walking.
  • Head injury.
  • Loss of vision or changes in vision.
  • Paralysis.
  • Rapid, involuntary rolling of the eyes (nystagmus).
  • Rigid trunk.
  • Slurred speech.
  • Tremor on one side of the body.
  • Weakness (loss of strength).


Tremor is generally caused by problems in parts of the brain that control muscles throughout the body or in particular areas, such as the hands.


Neurological disorders or conditions that can produce tremor includemultiple sclerosis, stroke, traumatic brain injury, and neurodegenerative diseases that damage or destroy parts of the brainstem or the cerebellum.


Other causes include the use of some drugs (such as amphetamines, corticosteroids, and drugs used for certain psychiatric disorders), alcohol abuse or withdrawal, mercury poisoning, overactive thyroid, or liver failure. Some forms of tremor are inherited and run in families, while others have no known cause.


There is no cure for most tremors. The appropriate treatment depends on accurate diagnosis of the cause.


Some tremors respond to treatment of the underlying condition. For example, in some cases of psychogenic tremor, treating the patient's underlying psychological problem may cause the tremor to disappear.


Symptomatic drug therapy is available for several forms of tremor. Drug treatment for parkinsonian tremor involves levodopa and/or dopamine-like drugs such as pergolide mesylate, bromocriptine mesylate, and ropinirole. Other drugs used to lessen parkinsonian tremor include amantadinehydrochloride and anticholinergic drugs.


Essential tremor may be treated with propranolol or other beta blockers(such as nadolol) and primidone, an anticonvulsant drug.


Cerebellar tremor typically does not respond to medical treatment. Patients with rubral tremor may receive some relief using levodopa or anticholinergic drugs.


Dystonic tremor may respond to clonazepam, anticholinergic drugs, and intramuscular injections of botulinum toxin. Botulinum toxin is also prescribed to treat voice and head tremors and several movement disorders.


Clonazepam and primidone may be prescribed for primary orthostatic tremor.


Enhanced physiologic tremor is usually reversible once the cause is corrected. If symptomatic treatment is needed, beta blockers can be used.


Eliminating tremor "triggers" such as caffeine and other stimulants from the diet is often recommended.


Physical therapy may help to reduce tremor and improve coordination and muscle control for some patients. A physical therapist will evaluate the patient for tremor positioning, muscle control, muscle strength, and functional skills. Teaching the patient to brace the affected limb during the tremor or to hold an affected arm close to the body is sometimes useful in gaining motion control.


Coordination and balancing exercises may help some patients. Some therapists recommend the use of weights, splints, other adaptive equipment, and special plates and utensils for eating.


Surgical intervention such as thalamotomy and deep brain stimulation may ease certain tremors. These surgeries are usually performed only when the tremor is severe and does not respond to drugs.


Thalamotomy, involving the creation of lesions in the brain region called the thalamus, is quite effective in treating patients with essential, cerebellar, or parkinsonian tremor. This in-hospital procedure is performed under local anesthesia, with the patient awake.


After the patient's head is secured in a metal frame, the surgeon maps the patient's brain to locate the thalamus. A small hole is drilled through the skull and a temperature-controlled electrode is inserted into the thalamus.


A low-frequency current is passed through the electrode to activate the tremor and to confirm proper placement. Once the site has been confirmed, the electrode is heated to create a temporary lesion. Testing is done to examine speech, language, coordination, and tremor activation, if any.


If no problems occur, the probe is again heated to create a 3-mm permanent lesion. The probe, when cooled to body temperature, is withdrawn and the skull hole is covered. The lesion causes the tremor to permanently disappear without disrupting sensory or motor control.


Deep brain stimulation (DBS) uses implantable electrodes to send high-frequency electrical signals to the thalamus. The electrodes are implanted as described above. The patient uses a hand-held magnet to turn on and turn off a pulse generator that is surgically implanted under the skin.


The electrical stimulation temporarily disables the tremor and can be "reversed", if necessary, by turning off the implanted electrode. Batteries in the generator last about 5 years and can be replaced surgically. DBS is currently used to treat parkinsonian tremor and essential tremor.


The most common side effects of tremor surgery include dysarthria (problems with motor control of speech), temporary or permanent cognitive impairment (including visual and learning difficulties), and problems with balance.

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