Our group has shown previously that, compared to controls, patients with EPM1 due to biallelic pathogenic repeat expansion have a prolonged cortical silent period (CSP), implying enhanced GABABergic inhibition8; the degree of CSP prolongation correlated with the size of the repeat expansion in the more affected allele (henceforth referred to as greater repeat number [GRN]), and independently predicted the severity of myoclonus.2 Here, CSTB is linked to Myoclonus.