Tremor overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Tremor is an unintentional, somewhat rhythmic, muscle movement involving to-and-fro 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. The most common form of tremor, however, occurs in otherwise healthy people.
Historical Perspective
James Parkinson, identified the tremor as "involuntary tremulous motion in parts not in action," in his essay on the shaking palsy, in 1817.
Classification
Tremor may be classified into resting or action tremor. Action tremor includes postural, kinetic (simple or intentional), isometric and task-specific tremor.
Pathophysiology
It is thought that tremor is the result of a combination of different mechanisms that could result in oscillatory/rhythmic movement. These mechanisms are mechanical oscillations, reflex oscillations, central oscillations, and cerebellar oscillation. These mechanisms differ on the basis of their origin. Mechanical oscillations occurs in limbs, could be limited to a particular joint, reflex oscillations originates from afferent muscle spindles, central neuronal pacemaker involves thalamus, basal ganglia, inferior olive, and cerebellar oscillations are due to disturbances in feedforward or feedback loops in cerebellum.
Causes
Common causes of tremor in primary care include enhanced physiologic tremor, essential tremor, and Parkinson’s disease. Other causes are caffeine intake, excessive alcohol, hypoglycemia, stress, anxiety, depression, fatigue, Wilson's disease, hyperthyroidism, multiple sclerosis, normal aging.
Differentiating Tremor from other Diseases
Tremor must be differentiated from diseases that cause involuntary movement: myoclonus, clonus, asterixis, and epilepsia partialis continua. The cause of tremor must also be differentiated from other conditions that cause tremor: essential tremor, physiological tremor, Parkinson's disease, cerebellar tremor, orthostatic tremor.
Epidemiology and Demographics
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History and Symptoms