Video 1. Phenomenology of Primary Writing Tremor in a 48-year-old Left-handed Male. Segment 1. There is a moderate-amplitude kinetic tremor of the left hand while writing. The tremor mainly involves the wrist. While writing with the right hand, tremor is barely discernable. Segment 2. No postural tremor is seen. However, there is mild dystonic posturing (i.e., flexion) of the left wrist in the wing-beat position (reproducibly seen three times). Even when asked to “keep your arms in a single plane, like airplane wings,” the abnormal (i.e., dystonic) flexed wrist posture is seen. There is no tremor while the arms are at rest in his lap, and only mild kinetic tremor during finger-to-nose maneuver and when drinking from a cup. Tremor is very apparent in a handwriting sample (“There are earthquakes in California”) and Archimedes spiral, drawn with the left hand.

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