Clinical and neurophysiologic spectrum of orthostatic tremor: case series of 26 subjects.

Orthostatic tremor (OT) is a condition described as high-frequency tremors predominantly in the legs and trunk, which are present not only in the standing position but also during isometric contraction of the limb muscles. This report is one of the largest OT series describing clinical and neurophysiologic findings in 26 subjects with OT. The main findings included 13.0 to 18.6 Hz leg tremors while standing with varied patterns of phase relationships between the antagonists of the ipsilateral leg and between the homologous muscles of the contralateral leg, short latency tremor onset upon standing with abrupt cessation after sitting, coexistence of tremors in the cranial structures and the arms, and sense of unsteadiness without actual falls. Although the oscillator of OT is most likely located in the brainstem, cerebral cortex, basal ganglia, and cerebellum may also be involved in its pathogenesis.