CACNA1A and Cerebellar atrophy: The CACNA1A gene encodes the pore-forming α1A subunit of P/Q-type voltage-gate CaV2.1 calcium channels that are dominant calcium channels in Purkinje cells (P-type currents) and are highly present in cerebellar granule cells (P- and Q-type currents), which may be associated with a high incidence of cerebellar atrophy in FHM1 patients.