Essential Tremor: Diagnosis and Treatment

Jack J. Chen, PharmD, David M. Swope, MD


Pharmacotherapy. 2003;23(9) 

In This Article

Tremor Classification by Clinical Phenomenology

In the clinical setting, tremor most commonly is classified by phenomenology (behaviors that activate tremor, such as rest, sustained posture, and movements; Table 2 ) and etiology (Figure 1). Any tremor lower than 4 Hz or greater than 12 Hz can be considered pathologic because these frequencies rarely are encountered in healthy individuals. Classification and definitions of tremor were systematically described, summarized, and disseminated by the tremor investigation group of the International Tremor Foundation and the Movement Disorder Society in 1995 and 1998, respectively.[12,13]

Tremor classifications.

A simple physical examination is all that is required to determine conditions that activate tremor. Resting tremor is present when a body part is fully supported against gravity in a manner not necessitating voluntary activation of skeletal muscles. In the upper extremities, it can be observed with the patient sitting with hands resting in the lap. By definition, resting tremor is suppressed by voluntary movement of the affected body part. Action tremor occurs with voluntary muscle contraction and includes postural, kinetic, and isometric tremors. A postural tremor can be triggered by voluntarily attempting to maintain a position against the force of gravity. For example, it can be detected by having the patient extend the arms forward with fingers extended.

Kinetic tremor occurs during voluntary movement and can be elicited by having patients perform a finger-to-nose test, sign their name, write a sentence, draw freehand spirals, or drink water from a cup. Since kinetic tremor is associated with greater disability than postural tremor, a more detailed assessment of the patient should be performed to determine the presence and severity of functional disability. The examination should include having the patient pour water from one cup to another, drink water from a cup three-quarters full and raised from lap level to mouth, and use a spoon to drink water. These tests should be performed with dominant and nondominant arms.

Intention tremor may be described as a type of kinetic tremor characterized by worsening (increasing tremor amplitude) during the terminal portion of goal-directed actions (as the finger nears the nose). It also can be seen in patients with multiple sclerosis and alcoholic cerebellar degeneration as well as essential tremor. Task-specific tremor is a type of action tremor and occurs only during specific highly skilled tasks (writing, playing the violin). Isometric tremors are present during voluntary muscle contraction against a rigid stationary object (making a fist, flexing the wrist against a flat surface, squeezing the examiner's fingers).

Once tremor is recognized and classified by activation condition, the next step is to investigate its etiology. Information obtained from medical history and neurologic examination are applied to delineate among various possible etiologies. The most common etiologies are essential tremor, parkinsonism, and tremorogenic drugs.