KCNC3 and spinocerebellar ataxia type 13: Our observation that extracellular potassium increases the Kv3.3 outward currents and that it reduces cumulative Kv3.3 inactivation by destabilizing the inactivated state of the channel provides a promising therapeutic approach to treat the patient, but also other SCA13 cases with Kv3.3 loss-of-function mutations.