Ion channel dysfunction causes a range of neurological disorders by alteringtransmembrane ion fluxes, neuronal or muscle excitability, and neurotransmitter release.Genetic neuronal channelopathies affecting peripheral axons provide a unique opportunityto examine the impact of dysfunction of a single channel subtype in detail invivo. Episodic ataxia type 2 is caused by mutations inCACNA1A, which encodes the pore-forming subunit of the neuronalvoltage-gated calcium channel Cav2.1. Here, CACNA1A is linked to episodic ataxia type 2.