Tremor

Essential Tremor: This tremor is rapid and fine. Essential tremor usually begins in early adulthood but can begin at any age. The tremor slowly becomes more obvious and becomes more noticeable among older age groups. It was once called senile tremor because it is more common among people older than 60. Some forms of essential tremor run in families and are sometimes called familial tremor. The cause is unknown.

Usually, essential tremor remains mild and does not indicate serious disease; however, it can be troublesome and embarrassing. It can affect handwriting and make using utensils difficult.

Essential tremor usually affects the arms and, rarely, the legs. The tremor usually stops when the arms or legs are at rest but becomes obvious when the limbs are outstretched and worsens when the limbs are held in uncomfortable positions. Essential tremor usually affects both sides of the body but may affect one side more than the other. Sometimes the tremor affects the head, causing it to tremble and bob, and the vocal cords, causing the voice to shake. In some people, the tremor gradually worsens over time, eventually resulting in disability.

Resting Tremor: This slow, coarse tremor occurs when the muscles are at rest, making an arm or a leg shake even when a person is completely relaxed. Resting tremor may develop when collections of nerve cells at the base of the cerebrum (including the basal ganglia) are disturbed. Such disturbances may result from Parkinson's disease, use of certain drugs (such as lithium Some Trade Names LITHANE, LITHONATE and antipsychotic drugs), or heavy metal poisoning (such as occurs in Wilson's disease, in which copper accumulates in body tissues).

Resting tremor, although sometimes embarrassing, usually interferes little with voluntary movements, such as drinking a glass of water.

Intention (Cerebellar) Tremor: This relatively slow, broad tremor occurs at the end of a purposeful movement, such as trying to press a button. Intention tremor may result from a damage to the cerebellum or its connections. Multiple sclerosis and stroke are common causes. Wilson's disease, alcoholism, and overuse of sedatives or anticonvulsants can cause the cerebellum to malfunction, resulting in intention tremor.

Intention tremor may increase during an activity, such as touching an object with the hand. The tremor may cause a person to miss the targeted object.

Flapping Tremor (Asterixis): This tremor is a coarse, slow, nonrhythmic movement that occurs when a person stretches out the arms and extends the hands. This tremor commonly results from liver failure and so has been called liver flap. However, it may also result from kidney failure and brain damage (encephalopathy) due to a metabolic disorder.

Muscle tone lapses suddenly and temporarily. As a result, the hand flaps; that is, it quickly drops, then returns to its original position. This tremor may be accompanied by other tremors and by myoclonus (see Movement Disorders: Myoclonus).

Diagnosis and Treatment

The development of a noticeable tremor should be evaluated by doctors. Doctors can usually identify the type of tremor by its characteristics. The type of tremor determines which procedures are performed. For essential tremor, doctors ask what drugs are being used and whether the person is experiencing anxiety or stress. Often, a blood test to detect an overactive thyroid gland is performed. For a resting tremor, a complete neurologic evaluation and other procedures to check for Parkinson's disease are performed. For intention tremor, an imaging procedure, such as computed tomography (CT) or magnetic resonance imaging (MRI), is often performed to look for damage to the brain. For flapping tremor, blood tests to evaluate liver and kidney function are performed.

Usually, treatment for a tremor is not needed. Avoiding uncomfortable positions can help. Objects should be grasped firmly but comfortably and held close to the body.

For people with essential tremor, drinking alcohol in moderation may reduce the tremor. However, heavy drinking or alcohol withdrawal can make the tremor worse. If people with essential tremor have difficulty using utensils or do work that requires steady hands, drugs may help. A beta-blocker, such as propranolol Some Trade Names INDERAL, is most commonly prescribed. If it does not help, primidone Some Trade Names MYSOLINE, an anticonvulsant, is often tried.

A resting tremor due to Parkinson's disease is treated as part of that disease. Intention tremors are difficult to treat, but if the condition affecting the cerebellum can be corrected, the tremor may resolve. For flapping tremor, the underlying liver or kidney disorder is treated. The tremor may resolve as liver or kidney function improves.

Brain surgery is performed only when an essential or a resting tremor is severe and disabling and drugs are ineffective. There are two types of surgery. In thalamotomy, parts of the thalamus (located at the base of the cerebrum, deep within the brain) are destroyed, and thus the pathways that produce the tremor are interrupted. In thalamic stimulation, an electrical probe is placed inside the thalamus. The probe delivers continuous high-frequency electrical stimulation to the thalamus, which generally reduces the tremor. Such procedures are available only at special centers.

Ref. The merk manuals online medical library