Antenatal diagnosis of iniencephaly clausus with cystic hygroma

A 22-year-old primigravida visited the antenatal clinic with complaints of 5 months of amenorrhea. The patient was referred to the Department of Radiodiagnosis for a routine antenatal scan. There was no history of consanguinity, fever, or teratogen exposure in the patient. It was an unplanned pregnancy. The patient is not on folic acid supplementation. The patient had not had any previous antenatal scans.

A grayscale image of a gravid uterus at approximately 18 weeks gestational age shows a foetus with an upturned face, short neck, and hyperextended (stargazing) position (Figure 1). An anechoic, well-defined cystic lesion in the cervical region is consistent with cystic hygroma (Figure 2). There is a complete absence of cervical and thoracic vertebrae with fusion of the head to the lumbar region (rachischisis) and irregular and incomplete closure of the vertebral arches and bodies of the upper lumbar vertebra (Figure 3). An abnormal orientation and fusion of the ribs is noticed (Figure 4). The stomach bubble and foetal cardia are at the same level due to complex spinal dysraphism or could be due to diaphragmatic hernia and severe shortening of the spinal column (Figure 5).

The antenatal findings were confirmed in the gross postnatal foetus on examination in the lateral and prone positions (Figures 6a and 6b).

Iniencephaly is a rare and severe neural tube defect that occurs due to improper closure of the neural tube during foetal development [1]. During the development of an embryo, the neural tube closes between the 3rd and 4th weeks of gestation, which begins around day 22 and is typically completed by day 28. Therefore, any neural tube defect could be identified as early as in the first trimester. The overall incidence of iniencephaly is 0.1 to 10 per 10,000 [2]. In India, the incidence of iniencephaly is reported to be 1 in 65,000 births and is more commonly found in female foetuses [3]. The exact aetiology is unknown. Other neural tube defects which could be differentials are anencephaly, craniorachischisis, meningomyelocele and encephalocele [4]. Other associated anomalies include anencephaly, cephalocele, holoprosencephaly, agnathia-microstomia-synmelia, diaphragmatic hernia, clubfoot, and gastrointestinal atresia [5].

The main features of iniencephaly include:

1. Occipital bone defect;
2. Partial or total absence of cervicothoracic vertebrae (rachischisis);
3. Fixed foetal head in retroflexion;
4. Short neck with mandibular skin continuous with that of the chest wall.

There are two subtypes of iniencephaly: one is iniencephaly apertus, and the other is iniencephaly clausus. The apertus subtype is associated with an encephalocele, and the clausus subtype is associated with a spinal defect.

Ultrasound (US) is the modality of choice for prenatal diagnosis because of its cost-effectiveness and real-time foetal imaging. However, diagnostic difficulties can occur due to maternal body habitus, oligohydramnios, or complex foetal anomalies [6]. MR imaging is the next best alternative, as it does not expose the patient to ionising radiation [7].

Differentials

In our case, there is an absence of cervical and thoracic vertebrae with a malformed upper lumbar spine leading to a lordotic deformity and significant shortening of the spinal column, making it a clausus subtype of iniencephaly. There is a fixed foetal head in retroflexion, giving a specific “stargazing position”. There is an associated large cystic swelling encircling the neck and extending to the lower back region, suggestive of cystic hygroma.

Outcome

The ultrasound results for this pregnancy revealed a single live foetus of approximately 18 weeks gestation, displaying features of iniencephaly and cystic hygroma. Considering the poor prognosis, the parents opted for a medical termination of pregnancy (MTP). The prompt and early prenatal diagnosis of this complex neural tube defect allows for informed decision-making regarding the pregnancy. This allows for early counselling of the parents regarding the prognosis and potential outcomes.

All patient data have been completely anonymised throughout the entire manuscript and related files.