In addition, the median index of intrathecal synthesis of GAD65-ab in available paired serum/CSF was higher in 14 patients with cerebellar ataxia (median: 9.7 [IQR: 3.6–16.6]) compared to that of 11 with SPS (5.3 [2.3–17.4]); p = 0.38. Here, GAD2 is linked to cerebellar ataxia.