ATXN3 and autosomal dominant cerebellar ataxia: While IMC30-40 − IMC15-25 could not differentiate between the two SCA subtypes (AUC = 0.57; Supplemental Table 4), it had fair diagnostic ability differentiating SCA6 from neurotypical controls (AUC = 0.72) and good ability in differentiating SCA3 from neurotypical controls (AUC = 0.82; Fig. 3B).