A form of hereditary episodic ataxia (EA) characterized by paroxysmal episodes of ataxia lasting hours, with interictal nystagmus and mildly progressive ataxia. The disease is episodic ataxia type 2 (MONDO_0007163). Also known as: CACNA1A hereditary episodic ataxia, hereditary episodic ataxia caused by mutation in CACNA1A.