Iniencephaly is a rare neural tube defect (incidence 0.1-10:10,000⁴) characterized by an extreme retroflexion of the head which is often combined with CNS malformations like anencephaly, spina bifida and cephalocele. There 2 main types of iniencephaly: "iniencephaly clausus with spinal defect and no cephalocele" and "iniencephaly apertus with spinal defect and cephalocele". The pathogenesis is unknown and the prognosis fatal. Ultrasound diagnostic criteria include extreme retroflexion of the head, cervical and thoracic spine deformities and associated neural tube defects.

Case report

The following images show a case of iniencephaly  apertus, diagnosed at 13 weeks of gestation. This was a pregnancy of 39-year-old woman (G10P2) with non-contributive history. The extreme head retroflexion with upward facing face caused by cervical spine deformities was accompanied by spina bifida with myelomeningocele. Patient opted for the termination of pregnancy due to a fatal prognosis.

Images 1,2: Images show a sagittal view of the fetus with apparent head retroflexion. Arrows on image 1 indicate the cervical spine which is markedly shortened and deformed; image 2 shows a sagittal 3D view of the retroflexed head with face looking upward.

Images 3,4: Images show a view of the head and cervical spine with an incomplete closure of vertebral arches as indicated with arrows.

Images 5,6: Image 5 shows a "lemon sign" shaped head; image 6 shows a "banana sign" of the cerebellum (indicated by arrows) which associated with spina bifida.

Images 7,8: Image 7 shows a transverse view through the abdomen with a myelomeningocele and V-shaped vertebral body; image 8 shows a sagittal and transverse view of the meningomyelocele, apparent retroflexion of the head and lordosis.