Role of Botulinum Toxin in Treatment of Secondary Dystonia: A Case Series and Overview of Literature

Introduction: Dystonia can present in primary and secondary forms, depending on co-occurring symptoms and syndromic associations. In contrast to primary dystonia, secondary forms of dystonia are often associated with lesions in the putamen or globus pallidus. Such disorders are commonly neurodegenerative or neurometabolic conditions which produce varied neurologic as well as systemic manifestations other than dystonia. Chemo-denervation with botulinum toxin has been successfully used for focal or segmental dystonia. However, studies evaluating the effect of BoNT therapy on patients with secondary dystonia are sparse, given the heterogeneity in etiology and presentation. Methods: We present a series of patients with secondary dystonia who were managed with botulinum toxin therapy. Patients included in this series had a confirmed neurometabolic cause of dystonia. Results: A total of 14 patients, with ages ranging from 17 to 36 years, with disorders including Wilson's disease, pantothenate kinase-associated neurodegeneration (PKAN), Niemann-Pick disease type C (NPC), glutaric aciduria type 1, Sanfilippo syndrome (Mucopolysaccharidosis Type IIIb), and GM2 gangliosidosis (Sandhoff disease) are presented. Most patients experienced a mild to moderate improvement in treated dystonia with benefits ranging from 6 to 12 weeks, with the median length of the benefits lasting approximately eight weeks, without any significant adverse effects. Conclusion: Although the secondary causes of dystonia are complex and diverse, our presented data and the available reports of the use of botulinum toxin support the conclusion that chemo-denervation plays an important role in symptom alleviation.