This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Which of the following exclusively involve neurouns- 
Select and explain. 
A. Spinocerebellar ataxia, B. Supranuclear palsy, C. Corticobasilar degeneration, D. Multiple system atrophy
A: Spinocerebellar ataxia
Answer: A: Spinocerebellar ataxia 
Explanation: None