Iniencephaly clausus: A case report with review of literature.

Iniencephaly is a rare neural tube defect characterized by extreme retroflexion of the head with the absence of neck due to spinal deformities. The important features that help us to diagnose a case of iniencephaly are occipital bone deficit leading to enlarged foramen magnum, fusion of malformed cervical and thoracic vertebrae, and upward turned face with chin continuous with chest because of the absence of neck. The differential diagnoses include anencephaly with spinal retroflexion, Klippel-Fiel syndrome, nuchal tumors such as teratoma, goiter, and lymphangioma and Jarcho-Levin syndrome. Previously many case reports on radiological features of iniencephaly are published, but there are very few articles on necropsy findings and differential diagnosis. In the present case we have discussed in detail the necropsy findings of iniencephaly clausus with special reference to differential diagnosis.

Introduction

Iniencephaly is a rare birth defect having retroflexion of the head combined with severe distortion of the spine. Based on the presence or absence of encephalocele, Lewis[1] has classified iniencephaly into two groups - iniencephaly apertus and iniencephaly clausus. Cardiovascular disorders, diaphragmatic hernias, and gastrointestinal malformations are other additional defects seen in these cases. Most of iniencephalic babies are still born or die soon after birth; however the milder forms of iniencephaly cases are not fatal.[1] Here we present a rare case of iniencephaly clausus with review of literature.

Case Report

A 25-year-old primi visited obstetric out-patient department with complaints of abdomen and back pain. She had neither antenatal check-up nor had taken folic acid supplementation previously. On abdominal ultrasound, a single-live fetus with hyperextension of cervical spine was found. No other abnormalities were detected on USG except for polyhydramnios. She spontaneously delivered a female baby at 29-week gestation who died 10 minutes after delivery.

On autopsy fetus weighed 900 g and showed severe retroflexion of enlarged head (28 cm in circumference, normal is 24.96 cm at 28 weeks and 28.59 cm at 32 weeks of gestation), short spine and neck with mandibular skin touching the chest, micrognathia, low set ears, and bilateral clubfoot [Figure 1a]. Radiograph of the necropsy was done which revealed hyperextension of the neck with occiput touching the cervicodorsal vertebrae with soft tissue continuation on the dorsal aspect of neck. There was a wide gap in the occiput. Cervical and upper thoracic vertebrae showed block vertebrae suggestive of iniencephaly [Figure 1b]. Necropsy of the fetus showed hypoplastic lungs weighing 18 g, small posterior fossa with hypoplastic cerebellum (weight <10 g), widened foramen magnum with anteroposterior (AP) diameter of 3.5 cm, and fusion of cervical and upper four thoracic vertebral bodies anteriorly with crowding of the arches and spinous processes posteriorly [Figures 2a and 2b]. Cerebrum and spinal cord were normal in development. All other organ systems were normal. Umbilical cord showed single artery and microscopic examination of all organs was normal.

Figure 1

(a) External appearance of fetus showing the retroflexed head and bilateral club foot. (b) Radiograph of necropsy showing block vertebrae and occipital bone defect. Inset shows malformed cervical and upper thoracic vertebrae

Figure 2

(a) Sagital section of fetus showing widened foramen magnum (red dotted line), small posterior fossa (black arrow), and malformed cervical and upper thoracic vertebrae in comparison with normal vertebrae (white arrow) (b) Anterior view of malformed and irregularly fused vertebrae (yellow arrow) and normal vertebrae (white arrow)

Discussion

Iniencephaly is an uncommon neural tube defect (NTD). Incidence ranges from 0.1 to 10 in 10,000.[1] It is more common in female babies. The word Inien is derived from the Greek word “Inion” which means nape of the neck. Here inion (posterior most part of occipital bone) fuses with the back leading to the absence of the neck and retroflexion of head.

The exact etiology and pathogenesis is not known, both genetic and environmental causes have been implicated. Chromosomal abnormalities including trisomy 18, trisomy 13, and monosomy X have been associated with this disorder.[2] Environmental causes like poor socioeconomic conditions, low parity, and lack of folic acid supplementation, obesity and drugs including sulphonamide, tetracycline, antihistamines, and antitumor agents are shown to have increased risk.[3] In the present case poor nutrition and lack of folic acid supplementation during pregnancy may be the cause. Previous reports have mentioned about risk of NTDs in mothers having hyperhomocysteinemia. Folic acid lowers the raised homocystein levels and reduces the risk of NTDs.

Antenatally iniencephaly can be diagnosed by USG/MRI or CT. The fetus will show typical star gazing appearance on USG and detailed CNS and spine abnormalities may be known by MRI or CT.[4]

The important features that help us to diagnose a case of iniencephaly are as follows:

Occipital bone deficit leading to enlarged foramen magnum.

Irregular fusion of malformed vertebrae.

Incomplete closure of vertebral arches and bodies.

Retroflexion of the cervical spine.

Upward turned face with chin continuous with chest because of the absence of neck.[1] Our case had all these features and hence was diagnosed as iniencephaly.

Congenital retroflexion of spine is mainly seen in two groups of anomalies, one is anencephaly and other is iniencephaly. Iniencephaly apertus should be differentiated from anencephaly with retroflexion of spine. And iniencephaly clausus should be differentiated from Klippel–Fiel syndrome (KFS) and cervical meningomyelocele.[2] Anencephaly shows a total or partial absence of neurocranium and retroflexed head is not covered with skin. However, in iniencephaly the retroflexed head is completely covered with skin. Cervical vertebrae are abnormal in iniencephaly and they are almost normal in anencephaly. In the present case the retroflexed head was completely covered with skin and there was no encephalocele.

It is important to differentiate between iniencephaly clausus and KFS. KFS is caused by a failure of segmentation of the cervical vertebrae during early fetal development. Although fusion of cervical vertebrae and malformation may be present in both, retroflexion of head is usually not seen in KFS and the presence of retroflexed head should raise suspicion of iniencephaly. At times it is difficult or impossible to differentiate these two; however it is important to separate the two because KFS is not lethal and can be corrected surgically. Other entities that come in differential diagnosis are nuchal tumors such as teratoma, goiter, lymphangioma and Jarcho–Levin syndrome.

Other findings in our case are hypoplastic lungs, cerebellar hypoplasia, bilateral club foot, and single-umbilical artery. Chen in his study has found pulmonary defects and single-umbilical artery in 14.3% of cases.[2] Iniencephaly carries a bad prognosis; there are only six cases of long-term survival of this anomaly in the literature.[56]

In summary, iniencephaly is one of the uncommon NTD which causes obstructed labor and necessitates proper obstetric management.[7] It also carries the risk of recurrence in next pregnancies (1–5%); hence the patient should be counseled and encouraged to take folic acid supplementation at least 3 months prior to conception. We present this case for its rarity and isolated iniencephaly without any other major malformations are not always fatal, and should be diagnosed antenatally because proper postnatal surgical therapy can be planned.