Tremor is a rhythmic, involuntary muscular contraction characterized by oscillations (to-and-fro movements) of a part of the body. The most common of all involuntary movements, tremor can affect various body parts such as the hands, head, facial structures, vocal cords, trunk, and legs; most tremors, however, occur in the hands. Tremor often accompanies neurological disorders associated with aging. Although the disorder is not life-threatening, it can be responsible for functional disability and social embarrassment.
There are many types of tremor and several ways in which tremor is classified. The most common classification is by behavioral context or position. There are five categories of tremor within this classification: resting, postural, kinetic, task-specific, and psychogenic. Resting or static tremor occurs when the muscle is at rest, for example when the hands are lying on the lap. This type of tremor is often seen in patients with Parkinson's disease. Postural tremor occurs when a patient attempts to maintain posture, such as holding the hands outstretched. Postural tremors include physiological tremor, essential tremor, tremor with basal ganglia disease (also seen in patients with Parkinson's disease), cerebellar postural tremor, tremor with peripheral neuropathy, post-traumatic tremor, and alcoholic tremor. Kinetic or intention (action) tremor occurs during purposeful movement, for example during finger-to-nose testing. Task-specific tremor appears when performing goal-oriented tasks such as handwriting, speaking, or standing. This group consists of primary writing tremor, vocal tremor, and orthostatic tremor. Psychogenic tremor occurs in both older and younger patients. The key feature of this tremor is that it dramatically lessens or disappears when the patient is distracted.
There are some treatment options available for tremor; 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 mental problem may cause the tremor to disappear. Also, patients with tremor due to Parkinson's disease may be treated with Levodopa drug therapy. Symptomatic drug therapy is available for several other tremors as well. For those cases of tremor in which there is no effective drug treatment, physical measures such as teaching the patient to brace the affected limb during the tremor are sometimes useful. Surgical intervention such as thalamotomy or deep brain stimulation may be useful in certain cases.