iniencephaly

the observation of a deformed head overriding the shoulder should alert the ultrasonographer to iniencephaly. the presence of the fetal thorax and head in the same scanning plane at the level of the chest indicates severe retroflexion and cervico-thoracic lordosis. if difficulties are experienced trying to locate the fetal spine in a sagittal plane, iniencephaly should also be considered. the principal ultrasound findings in iniencephaly will include: – absence of the normal parietal bones and a deficit of occipital bones resulting in a large foramen magnum – absence of brain tissue – partial or total absence of cervical and thoracic vertebrae with irregular fusion of those present with incomplete closure of the vertebral arches and/or bodies – overriding of the head on the shoulders in fixed retroflexion – craniorachischisis – polyhydramnios is also frequently present associated defects are noted in 80% of cases. other cranial anomalies include cephalocele and hydrocephalus. craniofacial abnormalities such as cyclopia and micrognathia may be observed. related systemic disorders include omphalocele, diaphragmatic hernia, agenesis of the diaphragm, pulmonary hypoplasia or hyperplasia, congenital heart defects, renal malformations (polycystic disease), clubfoot, and gastrointestinal atresia. iniencephaly is a lethal condition, and like other neural tube defects is most probably of multifactoral aetiology. there is a recurrency risk of approximately 5% in each successive pregnancy.