Some authors consider that NTD as encephaloceles, meningoceles and iniencephaly most likely not arise directly from a failure in neural tube formation, but more probably from a postneurulation disorder; which is a consistent fact with findings from other causes, for example, encephalocele when these are part of Meckel syndrome.[ 5 ] Iniencephaly is not considered to be an open defect because usually the sac containing CSF contains neural tissue and is covered by an intact dermis.[ 10 ] Lewis[ 11 ] classifies iniencephaly in “iniencephalus apertus” when associated with encephalocele, and “anencephalus clausus”, which is not associated encephalocele.
Source: wiktionary