Diagnosis

The history of onset and nature of the symptoms plays a large part in diagnosis of the condition.

Physical examination is usually normal with no specific neurological signs. It is important to observe the patient writing or carrying out the specific task when the typical posture can be observed. In about one third of cases there is also a mild tremor of the limb during the activity.

Investigations to exclude other causes of dystonia are needed and MRI scan of the brain should be undertaken if a central lesion is suspected.

Nerve conduction studies and electromyography (measurement of the electrical activity within a muscle) are useful to exclude specific nerve or muscle damage and may identify simultaneous contraction of agonist and antagonist groups of muscle.