Interestingly, chronically speaking, clinical, neuroimaging, and neurophysiological features of PMM2-CDG and CACNA1A related phenotypes are also similar, including, ataxia, ocular motor disturbances (particularly nystagmus and tonic upgaze deviation), and progressive cerebellar atrophy (3, 8, 25). This evidence concerns the gene CACNA1A and Nystagmus.