Introduction

Encephalocele is a severe neural tube defect where the skull bones fail to close properly during fetal development. This causes a portion of the brain and its covering membranes to protrude through an opening in the skull. This can appear as a swelling coming out of your child’s skull. These swellings can range in size from quite small to large defects. 

There are two generalised types of encephalocele: anterior (front of the skull) and posterior (back of the skull). These can be detailed further to the specific location on your baby’s head:^1,2

• The lower posterior of your baby’s head (occipital)
• The top of your baby’s head (parietal)
• Near your baby’s forehead (frontoethmoidal or sincipital)
• Front-middle of your baby’s head, behind your baby’s eyes and in front of their ears (sphenoidal)

It is a relatively rare disease, affecting 1.37 births per 10,000 within the UK,³ and it is diagnosed prenatally during your routine ultrasound scans. A magnetic resonance imaging (MRI) scan may be used to confirm the encephalocele diagnosis and explore the extent to which it is affecting the baby. Treatment can begin once you have given birth or within a few months of delivery, depending on the impact encephalocele has on your child, as well as the size and location.⁴

After birth, the encephalocele is confirmed with the presence of several symptoms:

• Visible skin-covered sac protruding from the skull
• Hydrocephalus
• Microcephaly
• Developmental delays
• Seizures
• Visual impairments

Treatment involves the removal of the tissue emerging from the skull (this tissue is non-functioning and can be removed). Before the surgery, computerised Tomography (CT) scans and MRI imaging are used for the assessment of the cranial defect and soft tissue architecture.¹ There may be many parts to this surgery, and your child may need additional support as they grow, such as glasses, seizure medication and special education schooling.⁵

This article will explain the benefits of CT and MRI imaging and will discuss the value of postnatal CT and MRI in surgical planning when treating the encephalocele in your baby.

CT scan of an encephalocele

Computerised Tomography (CT) scans are used to identify the bony defect in the skull and to show the extent of the encephalocele itself. Practically, CT scans are a great tool to use; they can offer low-dose radiation, allowing for longer monitoring of the defect. Furthermore, the scan itself builds an accurate 3D reconstruction of the skull and encephalocele. 

Since CT can create 3D reconstructions, it allows for surgical utility in mapping defect margins.¹⁰ The 3D model provides a detailed view of the bony anomaly from different angles, improving surgical orientation. They are extremely useful in mapping the defect in unstable, wriggling newborns.^6,8

The CT scans generate detailed high-resolution images of the bone structure, emphasising the size, position, and distinctly outlining the bony defect where the brain has herniated. This is crucial when preparing for the removal of the encephalocele, as it allows surgeons to assess the dimensions and shape of the skull opening. This factor significantly influences the amount of skull that must be restored after the encephalocele is excised.⁹

However, CT scans do have some cons. CT scans are limited when creating an image of soft tissue (the brain and the soft material in the encephalocele). This makes it difficult to understand the contents of the encephalocele as well as the encephalocele’s connection to the brain. 

By using CT scans alone, there is an increased risk of misdiagnosis or underestimating the encephalocele defect during surgical planning. Furthermore, CT scans do use radiation to image, and this is not ideal to expose neonates to, as there are links to childhood cancer.¹¹ However, the risk of leaving the encephalocele greatly outweighs the use of CT scans.

MRI scan of encephalocele

Magnetic resonance imaging (MRI) has more benefits compared to CT scans when imaging soft tissue.¹² MRI scans show superior soft tissue contrast, meaning there is a sharp distinction between normal and abnormal tissue.¹³ This is essential for understanding the defect's contents and surrounding structures. This aids surgical planning as MRI precisely outlines the extent of the defect and the relationship between the encephalocele and the surrounding blood vessels and brain structures. 

The accuracy of MRI can usually depict the dural venous sinuses (network of veins in the outermost brain membrane) anatomy, helping surgeons understand their position, which is crucial for surgical planning.¹⁴ 

MRI uses non-ionising radiation (microwaves and magnetic fields), which does not increase the risk of cancer development later in life. They can determine the viability of herniated brain tissue - whether it is healthy or damaged tissue (gliosis). During the planning for encephalocele removal, it is important not to remove any healthy brain tissue to prevent neurodevelopmental diseases or delays.^15,16

There are some limitations with MRI. They take a longer time compared to CT. This raises issues with newborns and infants if they are not sedated because of their constant movement, distortion or blurring is created on the image, reducing the image quality and clarity. 

In examining the bony defect associated with encephalocele, MRI proves to be less precise in evaluating the size of the defect, impacting the success of skull repair after the encephalocele is excised.

Role in surgical planning

Surgical planning is the most crucial step in preparing for encephalocele removal. Postnatal imaging plays a central role in shaping the surgical approach for encephalocele. The key questions for the surgical team are: What does the sac contain? How large is the skull defect, and what associated brain or vascular anomalies need to be considered?^4,18

MRI is particularly useful for evaluating soft tissue such as the contents of the sac, distinguishing between cerebrospinal fluid, meninges, damaged brain tissue, and healthy neural tissue. This information guides whether the herniated tissue can be safely removed or needs to be preserved. MRI also provides important details on associated malformations such as hydrocephalus, Chiari malformations, and corpus callosum agenesis, all of which may influence surgical timing and prognosis.^19,20

CT, on the other hand, offers the best visualisation of the cranial (bone) defect itself.²¹ By clearly mapping the bony margins, it allows surgeons to plan the extent of reconstruction and anticipate technical challenges in closing the defect. 

Preoperative imaging also contributes to safety by identifying vein networks and major vascular structures near the defect, reducing the risk of intraoperative bleeding.²² In some centres, CT and MRI data are combined to generate 3D models, which help surgical teams simulate reconstruction and improve both functional and cosmetic outcomes.

CT and MRI create a complete roadmap. Used together, they enable precise surgical planning, minimise operative risks, and improve long-term outcomes for your affected child.^15,16

Summary

Encephalocele is a serious condition where a part of the brain and its membranes bulge through an opening in the skull due to improper closure of the skull bones during fetal development. It can appear as a swelling and can be classified as anterior (front) or posterior (back) based on its location on the head. After birth, symptoms may include hydrocephalus, microcephaly, developmental delays, seizures, and visual impairments. Treatment usually involves surgery to remove the protruding tissue, with planning assessed by CT and MRI scans. CT scans help highlight the bony defect and provide a 3D view for better surgical planning. They can illustrate the size and shape of the opening in the skull, but are limited in visualising soft tissue. MRI scans offer better soft tissue contrast, showing the contents of the sac and relationships with nearby structures, which aids in surgical planning and protects healthy brain tissue. However, MRIs take longer and may require sedation for infants to obtain clear images. Both imaging methods are essential for surgical planning, helping to identify the defect's size and content and improving safety during surgery. When used together, they enhance surgical outcomes for affected children.