non-syndromic central nervous system malformation neural tube defect A congenital defect characterized by failure of the neural tube to close completely; this results in the presence of openings in the brain or spinal cord. Examples of neural tube defects include encephalocele and spina bifida. DOID:0080074 ICD9:742.8 MESH:D009436 MONDO:0018075 NCIT:C84923 NTD Orphanet:3388 SCTID:253098009 spinal dysraphism genetic nervous system disorder central nervous system malformation