HEXB and Cognitive impairment: Overall, we identified 24 rare nucleotide variants in 13 genes (Table S1, supporting information): SACS, KIF1C, ANO10, SPG11, SYNE1, and CACNA1A were related to spastic ataxia (10/19 families, 52.6%); KIF1A, POLG, SETX, and PNKP to ataxia and neuropathy (4/19, 21.1%); PNKP to AOA (2/19, 10.5%); HEXB and ATP1A3 to ataxia and dystonia (2/19, 10.5%); and FA2H to ataxia with cognitive impairment (1/19, 5.3%).