Writer's cramp (WC) is a task specific dystonia that occurs from the moment patient starts
writing. It leads to partial or complete inability to use the hand only during the
handwriting gesture. It is characterized by the appearance of cramps or spasms of certain
muscles of the hand and/or forearm.
Clinical scales currently use for the assessment of WC fail to accurately reflect changes in
the characteristics of handwriting in response to treatments (Botulinum Neurotoxin injections
and / or retraining therapy).
The Zigzag Tracking Task (ZZTT), easy to use in current practice provides useful information
in terms of speed and precision of handwriting gesture. This timed handwriting test is to
follow with a pen a zigzag path beset with obstacles to avoid. It permits to evaluate the
time in seconds required to carry out the zigzag path and count the number of errors (output
path and contacts with obstacles). The investigators propose to validate the ZZTT for the
assessment of the handwriting gesture of WC.