The successful application of botulinum toxin (BTX) injections in the treatment of focal hand dystonia is largely dependent on careful evaluation and selection of muscles to be injected.¹ It has been suggested that patients should be examined for abnormal postures at rest and while carrying out the affected task in question as well as other tasks (such as using a cup or a comb).² Simple techniques such as the localisation of subjective pain and fatigue accompanied by palpation of the area of discomfort can also be used.²

Mirror dystonia consists of dystonic postures and movements of the dominant hand while writing or performing other tasks with the non-dominant hand.³ We present a series of six patients who were successfully injected with BTX using mirror dystonia as an additional tool for muscle evaluation.

We carried out a retrospective review of the case records of consecutive patients with writing dysfunction (writer’s cramp and writing tremor) who had been injected with BTX type A (Botox®, Allergan Pharmaceuticals, Irvine, California, USA) between November 2000 and October 2002 at our movement disorders clinic. Our study was limited to patients with …