Comparing both groups, univariable analysis revealed that a previous diagnosis of epilepsy (OR 6.6, P = .02), QTc of more than 460 ms at first event (OR 6, P = .02), and presence of KCNH2 mutation (OR 4.7, P = .06) were significantly associated with (or showed a tendency towards) SCA or SCD at first presentation. Here, KCNH2 is linked to autosomal dominant cerebellar ataxia.