Long‐term efficacy of bilateral subthalamic deep brain stimulation in the parkinsonism of SCA 3: A rare case report

Abstract Background and purpose Spinocerebellar ataxia type 3 (SCA3) is an autosomal dominant inherited disorder that manifests as a mixture of cerebellar ataxia, parkinsonism, and polyneuropathy; in type IV SCA3, pure parkinsonism is the only symptom. Currently, no disease‐modifying treatment is available, but variable responses to antiparkinsonism agents have been reported. However, the benefits of deep brain stimulation (DBS) for treating parkinsonism in this subtype of SCA3 remain unclear. Methods A 39‐year‐old male patient with a rare disorder of type IV SCA3 presented with pure parkinsonism including unilateral resting tremor, rigidity, and bradykinesia at the age of 30 years. Young‐onset Parkinson disease was diagnosed at the age of 32 years. His family history revealed a mild ataxia in his father since the age of 55 years. Genetic testing confirmed an expanded CAG repeated number, with 66 in this case and 63 in his father for SCA3 mutation. Excellent response to levodopa and dopamine agonists in the first 3 years was noted, but wearing‐off phenomena, levodopa‐induced dyskinesia, and severe impulse control disorders later developed. To alleviate drug‐induced complications, he received bilateral subthalamic nucleus deep brain stimulation (STN‐DBS) in the absence of cerebellar signs, depression, and cognitive impairment. Results As of 2019, no impulsive control disorders, motor fluctuations, or DBS‐related complications were observed during a 4‐year follow‐up, with 66% Unified Parkinson's Disease Rating Scale Part III reduction at medication OFF state noted, whereas levodopa equivalent daily dosage decreased by almost half. Conclusions STN‐DBS may be considered as adjunct treatment for severe dopa‐related motor/nonmotor complications in patients with parkinsonian phenotype of SCA 3.