Iniencephaly.

BACKGROUND: Iniencephaly is a severe developmental abnormality of the craniovertebral junction in which the head is retroflexed dramatically. Anatomic studies have identified striking changes in the vertebrae and skull: marked lordosis of the cervical vertebrae, duplicated cervical vertebrae, irregularly fused cervical vertebrae, a widened foramen magnum and a small posterior fossa. The affected infant appears to have no neck, as the skin of the face is continuous with the chest and the skin of the posterior scalp is continuous with the skin of the back. Iniencephaly is considered a rare neural tube defect. The frequency has been higher in geographic areas in which the rates of occurrence of anencephaly and myelomeningocele were high. Most affected fetuses are either stillborn or die soon after birth. However, one affected individual is an adult with normal intelligence.

METHODS: A malformations surveillance program can identify an unselected group of infants with iniencephaly. This approach can determine the prevalence rate, the frequency of associated malformations, and the occurrence of close relatives with other neural tube defects.

RESULTS: Over 41 years, the surveillance of 289,365 births identified eight fetuses and newborn infants with iniencephaly. Five of the eight had either an additional encephalocele or a thoracic myelomeningocele. Two of the eight affected infants had a sibling or a cousin with anencephaly.

CONCLUSION: These findings suggest a relationship between the occurrence of iniencephaly and the most common neural tube defects, anencephaly and myelomeningocele. Recent experience confirms that this complex neural tube defect is not always lethal. Birth Defects Research 110:128-133, 2018. © 2018 Wiley Periodicals, Inc.