Prenatal diagnosis of iniencephaly.

Iniencephaly is characterized by a variable deficit of the occipital bones, resulting in an enlarged foramen magnum; partial or total absence of cervical and thoracic vertebrae with an irregular fusion of those present, accompanied by incomplete closure of the vertebral arches and/or bodies; significant shortening of the spinal column due to marked lordosis and hyperextension of the malformed cervicothoracic spine; and an upward-turned face and mandibular skin directly continuous with that of the chest due to the lack of neck. This article provides a comprehensive review of the reported cases of prenatally detected iniencephaly, including prenatal diagnosis, associated malformations, associated chromosomal abnormalities, and differential diagnosis. Prenatal diagnosis of a neural tube defect involving a body defect in the occiput and rachischisis of the cervical and thoracic spine with retroflexion of the head should raise the suspicion of iniencephaly. Iniencephaly may be associated with craniorachischisis and other structural anomalies. Prenatal diagnosis of non-isolated iniencephaly and craniorachischisis should alert one to the possibility of chromosomal abnormalities and prompt a cytogenetic investigation.