Evaluation of Tremor

Amy A. Pruitt

Tremor is defined as a regular oscillation of a body part, and it must be distinguished from other rapid, involuntary movements. Many patients assume that the development of “shakiness” is a natural concomitant of aging. The physician must determine the significance of a variety of clinically similar tremors that may have widely dissimilar diagnostic, therapeutic, and prognostic implications. Workup involves differentiating the resting tremor of early parkinsonism from essential tremor and differentiating essential tremor from an exaggerated physiologic tremor. As new specific treatments are developed, accurate clinical distinction becomes increasingly valuable. Unfortunately, it may be difficult to differentiate tremors by clinical observation alone, and evaluation requires a working knowledge of simple electrophysiologic and pharmacologic characteristics.

PATHOPHYSIOLOGY AND CLINICAL PRESENTATION (1, 2 and 3)

The precise neural mechanisms of tremor are unknown despite some clinicopathologic correlations, such as the abolition of the parkinsonian and essential tremors by lesions in the ventrolateral nucleus of the thalamus. Drugs such as L-dopa, which are known to act centrally to increase catecholamines, may worsen essential tremor; this observation has led to the suggestion that β-adrenergic blockers such as propranolol may exert their therapeutic action by central antagonism of β-adrenergic receptors. The patient most frequently reports the insidious onset of “shaking” of a limb. Very likely, the patient will have ignored the symptom initially, assuming that it was a consequence of nervousness or fatigue. However, steady progression impels the patient to see the physician. Tremors can be present during the maintenance of a posture, at rest, or during an action (intention tremor).

Postural (Physiologic) Tremors

Postural or physiologic tremors are fine tremors with a frequency of 8 to 12 Hz; they occur normally in everyone during movement and while a fixed position is held against gravity. A true physiologic tremor is defined as one that does not produce symptoms and is within the given frequency range. The movement is usually invisible to the naked eye, but it may become exaggerated by anxiety, muscular fatigue, ingestion of coffee, use of β-agonists, and hyperthyroidism. Drugs, notably lithium and tricyclic antidepressants, may also accentuate this tremor. Amplitude and frequency vary among different people and in the same person at different times.

Resting Tremors

Unlike physiologic tremors, resting tremors occur when a limb is supported against gravity and no voluntary movement is required.

Parkinson Disease

The most common rest tremor in a relaxed, supported limb is that caused by Parkinson disease. It characteristically begins in the fingers and may later involve the arm and the leg. Flexion and extension of the fingers, abduction and adduction of the thumbs, and pronation and supination of the wrist produce the well-known “pill-rolling” movement. Frequently, this is the symptom that brings parkinsonian patients to the physician and may occur well in advance of the bradykinesia and postural difficulties characteristic of the full-blown syndrome. The tremor is slow (3 to 8 Hz), and its electromyographic (EMG) pattern, quite unlike that of essential tremor, shows alternating discharge in antagonistic muscle groups, which is suppressed with voluntary movement. Most such patients also have some degree of postural tremor. Some parkinsonian patients may have a typical action (essential) tremor, which is worsened by L-dopa therapy. Phenothiazines and haloperidol worsen the rest tremor (see Chapter 174).

Intention (Action) Tremors

These tremors occur with and are worsened by voluntary muscle contraction.

Essential (Familial) Tremor

The major intention tremors are those labeled essential (also referred to as familial). Half of cases are transmitted as an autosomal dominant trait, and half are sporadic. The condition is characterized by an intention tremor of the hands, head, voice, and sometimes legs or trunk. Typically, the tremor is most prominent when the hands or head are held outstretched in a position against gravity and least noticeable at rest (although the tremor of early parkinsonism may also be seen best in an outstretched hand). Tremor may be accentuated by tasks that
require precision, such as writing and carrying full cups of liquid (also seen in some patients with parkinsonism). Many patients report that the ingestion of a small amount of alcohol will temporarily reduce their tremor. Essential tremor may begin at any age, although early and late adult life are the most common periods of onset (which helps to differentiate the condition from parkinsonism, which typically begins in middle age). The tremor increases with age.

Cerebellar Disease

A more dramatic action tremor is displayed by patients with cerebellar diseases and is characterized by progressively increasing amplitude of the tremor as the patient brings the limb toward a target. There is no tremor at rest. In younger patients, this is most frequently caused by multiple sclerosis, but similar clinical states may be produced by cerebellar infarction, degenerative disorders of the spinocerebellar pathways, and chronic, relapsing, steroid-sensitive polyneuropathy. This tremor is multiplanar, with large, irregular, and relatively slow (2 to 4 Hz) oscillations. The tremor often is worsened by alcohol. Propranolol has no effect, and no satisfactory therapy is available.

Other Abnormal Movements

The definition of tremor as a regular oscillation of a body part serves to distinguish it from other rapid, intermittent movements that bespeak a different neurologic state. For diagnostic, therapeutic, and prognostic purposes, several categories of abnormal involuntary movements should be distinguished from tremor. All of the following involuntary movements (and most true tremors) are greatly reduced or disappear altogether with sleep.

Tics

Tics are repetitive, coordinated, usually stereotyped movements that are seen widely in the population and increase in frequency in a given patient in response to stress. They usually involve face or hand muscles, may initially be a conscious mannerism, and usually can be suppressed by voluntary effort. Hemifacial spasm is a kind of oscillating movement usually beginning in a middle-aged or elderly person that is localized to the facial muscles. It is believed to be caused by degenerative lesions of the facial nucleus or peripheral nerve, but the exact mechanism is unknown, and treatment is unsatisfactory.

Asterixis

Asterixis is an irregular contraction of skeletal muscles that results in flapping of the hands; it is electromyographically coincident with brief pauses at irregular intervals. Chorea is an irregular, jerking movement usually involving the fingers and often accompanied by athetosis, in which writhing movements of limbs or trunk may be added. Epilepsia partialis continua refers to a focal seizure in which continuous seizure activity may result in a somewhat rhythmic jerking of one body part. Sudden onset of the illness is the most useful distinguishing feature.

Dyskinesias

These are rhythmic, involuntary movements of the orofacial musculature resulting in tongue protrusion and chewing movements. They are important to recognize because of the frequency with which they occur as early manifestations of the tardive dyskinesia syndrome caused by the use of phenothiazines and other major tranquilizers.

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