This makes a 75% positive rate for EWSR1-CREB1 fusion, 79% for EWSR1 rearrangement, and a negative rate of 21% for ESWR1-CREB1 fusion or ESWR1 rearrangement in the 24 cases where genetic study was performed in the reviewed series of PPMS. Here, CREB1 is linked to primary progressive multiple sclerosis.