Phenotypic spectrum associated with newly identified mutations in episodic ataxia type 1

Episodic ataxia type 1 (EA1) is caused by mutations in KCNA1—the gene encoding potassium channel K_V1.1. A recent study of 15 affected individuals from four families led to identification of three new KCNA1 mutations, which all resulted in loss of K_V1.1 function. Four of the study participants reported impairment of hearing, which expands the clinical phenotype of EA1. The study also included clinical documentation dating back to 1928 in one family, representing the earliest clinical record of EA1.