CACNA1A and cerebellar ataxia: CACNA1A Y1384C carriers presented with mental retardation, progressive deteriorating chronic ataxia, prolonged HM episodes, and early cerebellar atrophy.[9] Functional analysis of Y1384C showed a significant loss of function in current density and changes in gating properties in the neuronal Cav2.1 channel.[10] In this Chinese family, CACNA1A I1379F was identified as the cause of pure FHM without ataxia or mental retardation.