CACNA1A and autosomal dominant cerebellar ataxia: Sections “Introduction” to “Familial Hemiplegic Migraine Type 1” are intended to provide sufficient background for the more profound discussion of the more severe neurodevelopmental disorders, which are caused by point mutations in CACNA1A in section “The Expanding Spectrum OF CaV2.1-α1A Channelopathies.” It is important to note that the pathology of this unnamed class of disorders resembles that of spinocerebellar ataxia type 6 (SCA), which is caused by the addition of excess CAG polynucleotide repeats to the CACNA1A transcript (Jodice et al., 1997).