ABSTRACT
I. Introduction 361
II. Origins of Physiological Tremor 362
A. Historical Note 362
B. Mechanical Factors in Physiological Tremor 363
C. Stretch Reflex in Physiological Tremor 364
D. Central Oscillators in Physiological Tremor 364
III. Enhanced Physiological Tremor 365
A. Description 365
B. Mechanism of Enhanced Physiological Tremor 365
C. Clinical Aspects of Enhanced Physiological Tremor 366
IV. Conclusion 367
References 367
I. INTRODUCTION
Physiological tremor can be broadly defined as an involuntary and continuous
oscillation of any limb segment occurring in otherwise normal subjects (1-3).
This tremor type can be present when the limb segment is at rest, held against
gravity, in motion, or under isometric contraction. The frequency of physiological
tremor varies widely in different body parts, although 8-12 Hz oscillation has
traditionally been evoked as the frequency range (4). The amplitudes of these
oscillations are generally small such that normal finger tremor can barely be
seen with the naked eye. However, by means of either optical magnification or
mechanical-electrical transducers, such as accelerometers, physiological tremor
can be recorded in any joint or muscle that can oscillate (3,4). Another type of
tremor that can occur in normal subjects is enhanced physiological tremor, but
unlike physiological tremor, this tremor type is easily visible to the naked eye,
and can be quite symptomatic.
