[Orthostatic tremor - a disregarded diagnosis].

Orthostatic tremor is a rare and often neglected diagnosis with a synchronised bilateral high frequency tremor of 13-18 Hz, affecting primarily the legs and trunk muscles while standing. The patient is troubled by an intense feeling of unsteadiness. Tremor and unsteadiness diminish significantly by sitting down or starting to walk. The exact pathophysiology is yet unknown but is considered to involve a disruption in the cerebello-thalamo-cortical network supporting balance and adjustements of standing position. The feeling of unsteadiness is probably increased by a proprioceptive disturbance caused by the high frequency tremor.