Objective: We describe the response to Deep Brain Stimulation (DBS) in a patient with Parkinsonism having significant motor fluctuations and heterozygous Spino Cerebellar Ataxia type 2 (SCA2) mutation. 

Background: Homozygous and heterozygous SCA2 mutations have been described in patients with Parkinsonism. DBS has been described as being beneficial in improving tremor in a patient with SCA2 mutation. (1) Studies have explored correlation between patterns in neuro-degeneration and clinical manifestations of parkinsonism in patients with Spino-cerebellar ataxia. (2)

Methods: We describe 51 year old man with levodopa responsive asymmetrical Parkinsonism who had been symptomatic for 10 years. He  was admitted six years after initial presentation with  delusional psychosis while on levodopa and Ropinirole. Due to suspicion of having precipitated psychosis, Ropinirole was gradually withdrawn. Entacapone was added. He developed severe motor fluctuations and dyskinesias two years later. His quality of life  was significantly impaired, and was referred for DBS. There was no significant autonomic dysfunction. He had mild tandem gait abnormality with slow horizontal saccades and gaze evoked nystagmus. This prompted investigations including genetic testing.

Results: Formal neuropsyhcometry showed executive dysfunction. MRI showed cerebellar volume loss.  Patient had heterozygous, intermediate (32+/-1) CAG repeat length for SCA2.  He successfully underwent STN DBS and had no post-operative complications. His stimulation was gradually optimised in view of previous neuro-psychiatric symptoms. At one-year follow up patient reported significant improvement in quality of life. UPDRS III motor score improved by 65% with stimulation alone and by 85% with both stimulation and medication.  Improvement was also seen in Non Motor Scale, PDQ39 and SF36. Subsequently, his father noted similar clinical features and has heterozygous SCA2 mutation with similar repeat length. 

Conclusions: Our case highlights the complexity of decision-making process regarding DBS in a patient with Parkinsonism who also had a SCA2 mutation. STN DBS could be considered in this group as demonstrated by the improvement in quality of life in our patient. Long term follow up for DBS efficacy will help understand its influence on the course of illness. 

References:  

1. Freund, Hans-Joachim; Barnikol, Utako B; Nolte, Dagmar; et al. Subthalamic-thalamic DBS in a case with spinocerebellar ataxia type 2 and severe tremor-A unusual clinical benefit. Movement disorders; Apr 2007; vol. 22 (no. 5); p. 732-735

 2. Schöls, Ludger; Reimold, Matthias; Seidel, Kay et al. No parkinsonism in SCA2 and SCA3 despite severe neurodegeneration of the dopaminergic substantia nigra. Brain; Nov 2015; vol. 138 ; p. 3316-3326

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MDS Abstracts - https://www.mdsabstracts.org/abstract/deep-brain-stimulation-in-a-case-with-parkinsonism-and-sca2-mutation-case-report-highlighting-challenges-and-outcome/