An isolated occipital encephalocele

35 years old 3rd gravida female presented to obstetrics department of G. G. hospital Jamnagar for her routine 2nd-trimester antenatal visit for first time without any active complains/ bad obstetric history/ history of any drug intake, TB, COVID, HTN or DM.

On antenatal USG scan, a well-defined anechoic cystic lesion with internal iso-hyperechoic area was noted arising posterior from the occipital region. There was a defect of size (2.4 x 2.6) cm noted through which intracranial contents (brain parenchyma and meninges) were noted herniating out as seen in figure 2.

With provisional diagnosis of encephalocele on USG, fetal MRI was advised and findings were confirmed. on MRI, a cystic lesion is seen communicating with cranial cavity, filled with CSF and posterior fossa content favouring a diagnosis of occipital meningoencephalocele.(figure 1)

Encephalocele is a defect of the neural tube that refers to congenital malformations in form of skull defect with herniation of intracranial structures. Occipital encephalocele are the most common form of this congenital disorder and are manifested as a swelling of different sizes over the occipital bone in the midline [1]. 

Encephaloceles can be congenital or acquired. Its aetiology could be ethnic, genetic, environmental factors and paternal age. Among environmental factors, fungal and teratogenic agents such as aflatoxin or ochratoxin, found in moldy rice during the wet season, could be involved [2]. Congenital encephalocele is a form of neural tube defect and occur due to a failure of fusion of the cartilaginous neurocranium during embryogenesis, the membranous neurocranium or viscerocranium. 

In adults, acquired encephaloceles are mainly due to traumatic or iatrogenic causes but are also increasingly recognized in idiopathic intracranial hypertension.

Types of encephaloceles include [3]:

• occipital encephalocele: (Most Common)
• Frontoethmoidal Encephalocele
  • Nasoethmoidal
  • Nasofrontal
  • Naso-orbital
  • Interfrontal encephalocele
• parietal encephalocele
• basal encephalocele:
  • intrasphenoidal encephaloceles
  • temporal encephaloceles
  • transsphenoidal or trans ethmoidal or sphenoethmoidal or frontosphenoidal or spheno-orbital, etc.

In 60% of patients, it is associated with other malformations like neural tube defects, microcephaly, Arnold- Chiari malformations Type 2 or 3, craniosynostosis, and syringomyelia [1]. Serum alphafetoprotein and ultrasound establishes the prenatal diagnosis and the prognosis depends on the extent of the herniated neural tissues and associated anomalies. Many times, serum alpha-fetoprotein may remain normal because of intact meninges. The diagnoses were made via ultrasound examinations before cell-free DNA testing for chromosomal abnormality screening at 10 weeks’ gestation, thereby highlighting the importance of performing a routine ultrasound examination before cell-free DNA testing antenatally [4].

Occipital encephalocele can be diagnosed as early as by 9-10 weeks of gestational age on ultrasound. Ossification of cranial bones occurs at 10 weeks and hence defect and herniated sac can be seen.

In our case, provisional diagnosis of encephalocele was made on routine antenatal scan at 20 weeks of gestation in which brain parenchyma and meninges were seen as herniating out through skull defect and for further confirmation of these findings foetal MRI was suggested and final diagnosis of occipital encephalocele was made.

As this is a major congenital anomaly with poor survival, patient was advised to undergo termination of pregnancy by department of obstetrics and gynaecology, G.G. hospital, Jamnagar. 

Targeted imaging for foetal anomalies (TIFFA) is very important for timely diagnosis of neural tube defects like encephalocele which is most severe among spectrum of neural tube defects and has very poor outcome and fetal MRI has its excellent role in evaluation of such anomaly.

Written informed patient consent for publication has been obtained.