Clinical features

The condition is essentially task-specific. Onset tends to be insidious with aching, stiffness or incoordination of the hand occurring while carrying out the repetitive task or shortly afterwards. As the condition develops, attempts to perform the task result in an exaggerated response where the hand ‘cramps’ into a semi-flexed position with the fingers extended and drawn together into a typical dystonic posture. It becomes difficult to hold the pen and attempts to write may be accompanied by darting movements across the page. The spasm is usually short lived and relaxes shortly after ending the attempt to carry out the specific task.

The condition rarely spreads to affect other parts of the limb but in some cases use of the opposite hand will result in spasm despite that limb having not been subjected to prolonged repetitive activity.

Other tasks using the hand, such as picking up a cup or using cutlery, do not seem to be affected and there is usually no dystonic posturing as seen in other dystonic conditions.

In some cases the condition presents as Primary Writing Tremor when attempts to perform the specific task result in a significant course tremor of the hand without spasm or cramping. This also is task specific and unlike other forms of tremor is not likely to affect the hand in performing other functions.