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an involuntary trembling of the body or limbs; it may have either a physical or a psychological cause. Early symptoms include trembling of the hands and nodding of the head. Tremors are often associated with parkinson's disease, which affects nerve centers in the brain that control the muscles. They also occur in cerebral palsy, hyperthyroidism, and withdrawal from narcotics or alcohol. They tend to develop as one of the results of aging, and are sometimes symptoms of temporary abnormal conditions such as insulin shock, or of poisoning, especially metallic poisoning. They sometimes appear with a high fever resulting from an infection. Tremors of psychological origin take many forms, some minor and some serious. Violent, uncontrollable trembling is often seen in certain phases of severe mental disorders. If there is no physiological cause, they may be a sign of general tension.
action tremor rhythmic, oscillatory movements of the outstretched upper limb when voluntary movements are attempted, as when writing or lifting a cup; it may also affect the voice and other parts. Called also intention tremor and volitional tremor.
coarse tremor that involving large groups of muscle fibers contracting slowly.
essential tremor a hereditary tremor with onset at varying ages, usually at about 50 years of age, beginning with a fine rapid tremor (as distinct from that of parkinsonism) of the hands, followed by tremor of the head, tongue, limbs, and trunk; it is aggravated by emotional factors, is accentuated by volitional movement, and in some cases is temporarily improved by alcohol.
fine tremor one in which the vibrations are rapid.
flapping tremor asterixis.
intention tremor action tremor.
parkinsonian tremor a type of resting tremor commonly seen with parkinsonism, consisting of slow, regular movements of the hands and sometimes the legs, neck, face, or jaw; it typically stops upon voluntary movement of the part and is intensified by stimuli such as cold, fatigue, and strong emotions.
physiologic tremor a rapid transient tremor of extremely low amplitude found in the limbs and sometimes the neck or face of normal individuals, only subtly detectable on an electromyogram and seldom visible to the naked eye; it may become accentuated and visible under certain conditions.
rest tremor (resting tremor) one occurring in a relaxed and supported limb, such as a parkinsonian tremor.
senile tremor one due to the infirmities of old age.
volitional tremor action tremor.
A resting tremor of the fingers and hands, often called a pill-rolling tremor, that is suppressed briefly during voluntary activity. The tremor disappears during all but the lightest phases of sleep.
See also: tremor