Iniencephaly is a rare type of cephalic disorder characterised by three common characteristics: a defect to the occipital bone, spina bifida of the cervical vertebrae and retroflexion (backward bending) of the head on the cervical spine. Stillbirth is the most common outcome, with a few rare examples of live birth, after which death invariably occurs within a short time.
The disorder was first described by Étienne Geoffroy Saint-Hilaire in 1836. The name is derived from the Ancient Greek word ἰνίον inion, for the occipital bone/nape of the neck.
Classifications
There are two types of iniencephaly. The more severe group is iniencephaly apertus (open iniencephaly), involving the development of an encephalocele. In the other group, iniencephaly clausus (closed iniencephaly), the encephalocele is absent.
Obesity
Studies have shown that obesity of the mother increases the risk of neural tube disorders such as iniencephaly by 1.7 fold while severe obesity increases the risk by over 3 fold.
History of iniencephaly
Once a mother has given birth to a child with iniencephaly, risk of reoccurrence increases to 1-5%.
Differential diagnosis
Since many of the characteristics of iniencephaly, such as congenital retroflexion of the spine and fusion of the cervical vertebrae, are shared with other disorders, key differences are important to note.
While anencephaly experiences a partial to total lack of the neurocranium, iniencephaly does not. In anencephaly, the retroflexed head is not covered with skin while in iniencephaly, the retroflexed head is covered with skin entirely. Cervical vertebrae are malformed and reduced in iniencephaly while they are almost normal in anencephaly.
Even though KFS does experience malformed cervical vertebra due to failure of segmentation during early fetal development, there is not retroflexion of the head as seen in iniencephaly. While iniencephaly clausus is fatal, KFS is not and can be surgically corrected. Therefore, it is crucial to correctly diagnose KFS and not mistake it for iniencephaly clausus.
Treatment
Since newborns with iniencephaly so rarely survive past childbirth, a standard treatment does not exist.
Prognosis
Iniencephaly of both types carry a lethal prognosis, sometimes even ending in spontaneous abortion or stillborns. Most infants die within hours of childbirth. There are only seven reported cases of relatively long-term survival of those born with iniencephaly. with an incidence rate estimated at 0.1 to 10 in 10,000 deliveries.
For unknown reasons, this disease seems to occur most often in newborn females (about 90%).