Tremor

Tremor
ICD-10 R25.1
ICD-9 781.0
DiseasesDB 27742
MeSH D014202

Tremor is an unintentional, somewhat rhythmic, muscle movement involving to-and-from movements (oscillations) of one or more parts of the body. It is the most common of all involuntary movements and can affect the hands, arms, head, face, vocal cords, trunk, and legs. Most tremors occur in the hands. In some people, tremor is a symptom of another neurological disorder. A very common kind of tremor is the chattering of teeth, usually induced by cold temperatures or by fear.

Contents

Causes

Tremor is generally caused by problems in parts of the brain that control muscles throught the body or in particular areas, such as the hands. Neurological disorders or conditions that can produce tremor include multiple 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, caffeine, corticosteroids, and drugs used for certain psychiatric disorders), alcohol abuse or withdrawal, mercury poisoning, overactive thyroid or liver failure. Tremors can be an indication of hypoglycemia, along with palpitations, sweating and anxiety. Tremor can also be caused from lack of sleep or vitamins, or stress. Deficiencies of magnesium and vitamin B1 have also been known to cause tremor or shaking which resolves when the deficiency is corrected. See magnesium in biology. Some forms of tremor are inherited and run in families, while others have no known cause. Tremors can also be caused by some spider bites i.e. the redback spider of Australia.

Characteristics may include a rhythmic shaking in the hands, arms, head, legs, or trunk; shaky voice; difficulty writing or drawing; or problems holding and controlling utensils, such as a fork. Some tremors may be triggered by or become exaggerated during times of stress or strong emotion, when the individual is physically exhausted, or during certain postures or movements.

Tremor may occur at any age but is most common in middle-aged and older persons. It may be occasional, temporary, or occur intermittently. Tremor affects men and women equally.

Etiologies

Tremor is most commonly classified by clinical features and cause or origin. Some of the better known forms of tremor, with their symptoms, include the following:

Tremor can result from other conditions as well. Alcoholism, excessive alcohol consumption, or alcohol withdrawal can kill certain nerve cells, resulting a tremor known as asterixis. Conversely, small amounts of alcohol may help to decrease familial and essential tremor, but the mechanism behind this is unknown. Tremor in peripheral neuropathy may occur when the nerves that supply the body’s muscles are traumatized by injury, disease, abnormality in the central nervous system, or as the result of systemic illnesses. Peripheral neuropathy can affect the whole body or certain areas, such as the hands, and may be progressive. Resulting sensory loss may be seen as a tremor or ataxia (inability to coordinate voluntary muscle movement) of the affected limbs and problems with gait and balance. Clinical characteristics may be similar to those seen in patients with essential tremor. Tobacco withdrawal symptoms also include tremor.

Diagnosis

During a physical exam a doctor can determine whether the tremor occurs primarily during action or at rest. The doctor will also check for tremor symmetry, any sensory loss, weakness or muscle atrophy, or decreased reflexes. A detailed family history may indicate if the tremor is inherited. Blood or urine tests can detect thyroid malfunction, other metabolic causes, and abnormal levels of certain chemicals that can cause tremor. These tests may also help to identify contributing causes, such as drug interaction, chronic alcoholism, or another condition or disease. Diagnostic imaging using CT or MRI imaging may help determine if the tremor is the result of a structural defect or degeneration of the brain.

The doctor will perform a neurological exam to assess nerve function and motor and sensory skills. The tests are designed to determine any functional limitations, such as difficulty with handwriting or the ability to hold a utensil or cup. The patient may be asked to place a finger on the tip of her or his nose, draw a spiral, or perform other tasks or exercises.

The doctor may order an electromyogram to diagnose muscle or nerve problems. This test measures involuntary muscle activity and muscle response to nerve stimulation.

Categories

The degree of tremor should be assessed in four positions. The tremor can then be classified by which position most accentuates the tremor: [1]

Position Name Description
At rest Resting tremors Tremors that are worse at rest include Parkinsonian syndromes and essential tremor if severe. This includes drug-induced tremors from blockers of dopamine receptors such as haloperidol and other antipsychotic drugs.
During contraction (eg a tight fist while the arm is resting and supported) Contraction tremors Tremors that are worse during supported contraction include essential tremor and also cerebellar and exaggerated physiologic tremors such as a hyperadrenergic state or hyperthyroidism[1]. Drugs such as adrenergics, anti-cholinergics, and xanthines can exaggerate physiologic tremor.
During posture (eg with the arms elevated against gravity such as in a 'bird-wing' position) Posture tremors Tremors that are worse with posture against gravity include essential tremor and exaggerated physiologic tremors[1].
During intention (eg finger to nose test) Intention tremors Intention tremors are tremors that are worse during intention, e.g. as the patient's finger approaches a target, including cerebellar disorders.

Treatment

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.

Medications

Symptomatic drug therapy is available for several forms of tremor:

Lifestyle

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.

Surgery

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.

Biomechanical loading

As well as medication, rehabilitation programmes and surgical interventions, the application of biomechanical loading on tremor movement has been shown to be a technique that is able to suppress the effects of tremor on the human body. It has been established in the literature that most of the different types of tremor respond to biomechanical loading. In particular, it has been clinically tested that the increase of damping and/or inertia in the upper limb leads to a reduction of the tremorous motion. Biomechanical loading relies on an external device that either passively or actively acts mechanically in parallel to the upper limb. This phenomenon gives rise to the possibility of an orthotic management of tremor.

Starting from this principle, the development of upper-limb non-invasive ambulatory robotic exoskeletons is presented as a promising solution for patients who cannot benefit from the use of medication to suppress the tremor. In this area robotic exoskeletons have emerged, in the form of ortheses, to provide motor assistance and functional compensation to disabled people. An orthosis is a wearable device that acts in parallel to the affected limb. In the case of tremor management, the orthosis must apply a damping or inertial load to a selected set of limb articulations.

Recently, some studies demonstrated that exoskeletons could achieve a consistent 40% of tremor power reduction for all users, being able to attain a reduction ratio in the order of 80% tremor power in specific joints of users with severe tremor [2]. In addition, the users reported that the exoskeleton did not affect their voluntary motion. These results indicate the feasibility of tremor suppression through biomechanical loading.

The main drawback of this mechanical management of tremor is: (1) the resulting bulky solutions, (2) the inefficiency in transmitting loads from the exoskeleton to the human musculo-skeletal system and (3) technological limitations in terms of actuator technologies. In this regard, current trends in this field are focused on the evaluation of the concept of biomechanical loading of tremor through selective Functional Electrical Stimulation (FES) based on a (Brain-to-Computer Interaction) BCI-driven detection of involuntary (tremor) motor activity. [3]

See also

References

  1. 1.0 1.1 1.2 Jankovic J, Fahn S. Physiologic and pathologic tremors. Diagnosis, mechanism, and management. Ann Intern Med. 1980;93:460-5. PMID 7001967
  2. Rocon E, Belda-Lois JM, Ruiz AF, Manto M, Moreno JC, Pons JL. Design and Validation of a Rehabilitation Robotic Exoskeleton for Tremor Assessment and Suppression. IEEE Transactions on Neural Systems and Rehabilitation Engineering. 2007;15(3):367-378
  3. Tremor project - ICT-2007-224051