Bilateral Globus Pallidus Deep Brain Stimulation for Dystonia and Dystonic Tremor in Spinocerebellar Ataxia 17

Spinocerebellar ataxia 17 (SCA17) is a rare form of autosomal dominant cerebellar ataxia. SCA17 results from trinucleotide repeat expansions and has no effective symptomatic treatments to date. This chapter describes a case of SCA17 with dystonic symptoms that presented during adolescence. Symptoms were generalized in distribution and were accompanied with a dystonic tremor of the arms. Because many medication trials did not alleviate the patient’s symptoms, he underwent bilateral globus pallidus interna (GPi) deep brain stimulation (DBS) surgery. Several DBS programming sessions were performed. Dystonia and dystonic tremor were controlled with the settings adjusted at high pulse widths and low frequencies. Furthermore, the cyclic mode of stimulation was employed to mitigate the capsular side effects. Two years after DBS surgery, the patient presented with cerebellar ataxia that prompted an extensive workup, including genetic testing and revision of his diagnosis from generalized dystonia to a dystonia syndrome. The patient continues to endorse symptomatic benefits with DBS for dystonia and dystonic tremor 11 years after surgery, despite a diagnosis of dystonia syndrome. The current case of SCA17 cerebellar ataxia indicates that bilateral GPi DBS is a potential option for the long-term symptomatic treatment of dystonia and tremor symptoms manifesting as a part of a clinical syndrome.