Figure 3.

Entrainment of psychogenic tremor. Electrophysiologic surface recording study. A 28-year-old woman had developed tremor in her legs 3 months previously. The surface EMG recordings shown here were recorded with the patient standing. There is nearly simultaneous and rhythmic activity in both anterior tibial muscles, but the length, amplitude, and shape of the single bursts is less regular than in Figure 2. Simultaneous contractions in both limbs (upper row) often indicate voluntary activation.⁸⁷ There is only a very slight antagonist activity simultaneous with a reflex-like tonic activity in all muscles. When the patient was asked to slowly tap down her right foot (lower row, black bar), the rhythmic activity almost completely abates (entrainment), suggesting a psychogenic cause for this patient’s tremor.