Classification

Writing tremor has been variably classified as an independent entity, an ET variant, a focal dystonia, or a bridging entity.

Clinical Features

This is usually characterized by prominent pronation/supination wrist movements, occurs predominantly or exclusively during writing. No other neurological signs are evident except for slight postural and terminal kinetic tremor. Writing tremor can be task-induced or position-sensitive.

Age of onset

Age at onset varies, and cases manifesting during childhood have been reported. The disorder begins slowly, progresses for years, and becomes stabilized. Family history is generally unremarkable.

Distribution

Restricted to one hand.

Differential Diagnosis

Although it resembles ET (because tremor is present on action and on maintenance of a posture, and may affect handwriting), the task specific nature, lack of response to propranolol, and a documented effect of central cholinergic drugs suggest that writing tremor is more closely related to dystonia than to ET. The observation of abnormal co-activation of antagonist muscles also supports this view

Treatment

Propranolol; central cholinergic drugs