Delayed CNS myelination HP:0006974 HP:0005770 HP:0007300 Delayed myelination in the central nervous system. Delay in central nervous system myelination A delay in the process of myelination, which normally begins in the fifth fetal month and is about 90 percent complete at the age of two years. Myelination continues into early adulthood. UMLS:C4021758 HP:0002188 Abnormal CNS myelination Delayed myelination