Table 1

Typical characteristics of tremor types seen in writing and drawing tasks

	Essential tremor	Dystonic tremor	Parkinson’s disease	Functional tremor
Handwriting
Size	Normal or large	Normal	Usually small	Variable
Tremor features	Regular amplitude and frequency	Irregular jerky amplitude and frequency	Regular amplitude and frequency	Variable; often no tremor in writing
Tremor intrusion in letter sections	Vertical letter strokes; unidirectional axis	All sections of letters; multidirectional axis	Vertical letter strokes; unidirectional axis	Variable
Progressive deterioration	No	Yes—shape of letters worsens due to posturing	Sometimes—size of letters may decrement	Not usually
Pen pressure	Normal	Hard pressure	Normal	Normal
Spirals
Size	Normal	Normal	Small	Variable
Spacing of turns	Normal (maybe wider)	Normal (maybe tighter)	Tighter	Variable
Tremor axis	Unidirectional	Multidirectional	Unidirectional	Variable
Tremor frequency	Regular	Irregular/jerky	Regular	Variable
Progressive deterioration	No	Sometimes—more tremor and pressure	No	Variable tremor frequency, axis and amplitude
Straight lines
Tremor axis	Unidirectional Right: 8–2 o’clock Left: 10–4 o’clock	Multidirectional	Unidirectional Right: 8–2 o’clock Left: 10–4 o’clock	Variable
Tremor frequency	Regular	Irregular	Usually regular	Variable
Tremor amplitude	Small, regular	Small, irregular	Small, regular	Large, irregular
Symmetry	Symmetrical	Asymmetrical	Asymmetrical	Variable
Other features		Writing may be worse than drawing tasks	Longer duration to compete task (bradykinesia)	Straight lines usually most impaired task