LAUSR

In this article, a case of writer ́s cramp in a patient with spinocerebellar ataxia type 3, also known Machado–Joseph disease, is described. To our knowledge, this is the first description of task-specific dystonia in association with ataxia in SCA 3. This case description is very illustrative and may be of great interest for movement disorders community. We included a video as supplementary material. Spinocerebellar ataxia type 3 (SCA3), also known as Machado–Joseph disease (MJD), is the most common autosomal dominant ataxia in Brazil, and is caused by a CAG trinucleotide repeat expansion in exon 10 of ATXN3 gene of chromosome 14, at position 32.12, in a range between 56 and 86 trinucleotides repeats [1]. The clinical onset typically occurs in the second to fourth decades and consists mainly of cerebellar ataxia and a variety of peripheral neuropathies, ophthalmoplegia, pyramidal and extrapyramidal signs [2]. Advances in genetics techniques revealed several atypical cases. Dystonia in SCA3 had an incidence of 28% in a Brazilian series, and can be generalized, focal or segmental [3]. Pure focal dystonia can be the only presenting symptom of SCA3, which may precede cerebellar symptoms for decades [3]. Recently, Méndez-Guerrero and colleagues described the first case of writer’s cramp in a patient with a genetic diagnosis of SCA3 without ataxia [4]. A 50-year-old left-handed man developed progressive gait ataxia for the last 4 years. Two years ago, he observed difficulty in writing, associated with abnormal left hand posture and pain. There was family history of ataxia and one of the cases also had Pisa syndrome. Physical exam revealed mild gait ataxia, nystagmus, mild dysmetria, brisk tendon reflexes without Babinski sign and task-specific dystonia of the left upper limb (Fig. 1). Upper limbs electromyography (video 1) revealed dystonic discharges related to mirror writing movements, confirming the diagnosis of writer’s cramp. Brain MRI showed mild cerebellar atrophy. Genetic test confirmed spinocerebellar ataxia type 3 (SCA3): allele 1: 14 repeats; allele 2: 69 repeats (normal range: 12 to 44 repeats). He was treated with botulinum toxin guided by EMG, with partial improvement. Dystonia in SCA3 usually has an early onset and is associated with greater number of CAG repeats [1]. The presentation is most often severe, may not improve with sensory trick and could be associated with pain [3]. Craniocervical dystonia, blepharospasm and unilateral (or asymmetric) inversion of the foot have been described [2]. To our knowledge, this is the second report of writer’s cramp in SCA3 described in the literature and the first in association with ataxia. Neuroimaging studies have been conducted to uncover the etiopathogenic mechanisms of dystonia in SCA 3. MRI analysis has shown that patients with dystonia have greater thalamic atrophy compared to patients without dystonia [5], suggesting that different phenotypes of SCA could be related to involvement of neuroanatomical sites outside the cerebellum. To date, there is not much evidence of how to handle these patients but in general treatment does not differ from other dystonias such as botulinum toxin [3]. The phenotypes of SCA3 are heterogeneous, even in patients of the same family. Dystonia is a frequent feature in SCA3, however writer’s cramp has only one case described without ataxia. These atypical presentations should lead us to consider that the dystonic spectrum in SCA3 is probably wider than we imagine. Electronic supplementary material The online version of this article (https ://doi.org/10.1007/s1376 0-018-1022-9) contains supplementary material, which is available to authorized users.