Primary orthostatic tremor with prominent muscle hypertrophy.

Abstract

A 33-year-old woman had a 6-year history of progressive postural instability on standing and with walking. There was progressive asymmetric lower limb muscle hypertrophy affecting thigh and calf musculature. Surface EMG recordings showed the rapid development of a synchronized motor unit discharge at a frequency of 17.5 Hz on standing, characteristic of primary orthostatic tremor. These observations suggest that primary orthostatic tremor can be associated with gait disturbance and should be considered in the differential diagnosis of unexplained muscle hypertrophy.