Encephalocele
An encephalocele is a congenital cranial anomaly in which intracranial contents herniate through a defect in the skull or skull base. The sac may contain meninges and cerebrospinal fluid alone, or meninges with brain tissue. It represents a form of cranium bifidum due to failure of midline neural tube closure and subsequent failure of normal calvarial or skull-base ossification. Clinically, any congenital midline cranial or nasal mass in an infant must be considered an encephalocele until proven otherwise.
Q. How do you distinguish the related terms cranium bifidum, meningocele, and encephalocele?
Cranium bifidum refers to the underlying defect of skull formation, usually in the midline, resulting from failure of bone fusion. When only meninges and cerebrospinal fluid herniate through this defect, the lesion is called a cranial meningocele. When meninges and brain tissue herniate together, the lesion is termed an encephalocele. In practice, many lesions contain some gliotic brain and are described as meningoencephaloceles.
Q. What is the embryological basis of encephalocele?
Encephalocele results from defective closure of the rostral neural tube and failure of subsequent normal ossification of the cranial vault or skull base. When membranous ossification of the calvaria fails, vault defects arise; when endochondral ossification of the anterior or middle cranial base fails, basal defects arise. Through these persistent bony gaps, meninges and, often, brain tissue herniate under the influence of intracranial pressure and pulsation. The same disordered embryogenesis often produces associated malformations such as agenesis of the corpus callosum, Chiari malformations, and Dandy–Walker spectrum abnormalities. Maternal folate deficiency is a primary established etiology (along with hyperthermia and genetic ciliopathies).
Q. How are encephaloceles classified anatomically (Suwanwela and Suwanwela classification)?
Suwanwela and Suwanwela classify encephaloceles based on the anatomic site of the skeletal defect:
1. Occipital (Most common in Western populations, ~75–80%)
2. Frontoethmoidal / Sincipital (Most common in Southeast Asia):
• Nasofrontal
• Nasoethmoidal
• Nasoorbital
3. Cranial Vault:
• Interfrontal, anterior fontanelle, parietal, temporal, and orbital.
4. Basal (Herniate into the nasal cavity, epipharynx, or sphenoid sinus):
• Transethmoidal
• Sphenoethmoidal
• Transsphenoidal
• Sphenoorbital
5. Posterior Fossa (Infratentorial / suboccipital)
Q. What are the key subtypes of frontoethmoidal encephalocele in Suwanwela’s system?
Frontoethmoidal or sincipital encephaloceles are divided into nasofrontal, nasoethmoidal, and nasoorbital types.
In nasofrontal encephalocele, the sac herniates through the fonticulus frontalis and lies above or anterior to the nasal bones.
In nasoethmoidal encephalocele, the herniation passes through the foramen cecum into the prenasal space, between the nasal bones and the upper nasal cartilage.
In nasoorbital encephalocele, the defect involves the medial orbital wall, and the sac protrudes toward or into the medial orbital region.
This anatomical relationship determines the external appearance, the degree of hypertelorism and nasal deformity, and the direction of surgical access.
Q. How will you evaluate a child with encephalocele clinically?
I will begin with a detailed antenatal and perinatal history, including family history of neural tube defects, consanguinity, folate supplementation, and any prenatal ultrasound findings of cranial defects or associated anomalies. I will ask about seizures, feeding difficulty, respiratory distress, recurrent meningitis, and visual or developmental concerns.
On examination, I will inspect the head and face for a midline or paramedian swelling, note its size, position, skin condition, and whether it enlarges with crying or Valsalva. I will palpate to assess consistency, reducibility, and a bony defect at its base, and I will look for transillumination.
I will assess head circumference, fontanelle tension, and cranial sutures to screen for hydrocephalus or craniosynostosis. A full neurological examination will be performed, focusing on tone, power, cranial nerves, visual fixation, and developmental milestones. I will examine the spine for dysraphism and look for other congenital anomalies such as polydactyly, renal or abdominal masses, or ocular abnormalities that may indicate a syndromic encephalocele.
Q. What investigations are needed for a child with encephalocele?
I will obtain MRI of the brain and craniovertebral region as the key study to define the contents of the sac, the presence of functional cortex versus gliotic brain, communication with the ventricles, brainstem involvement, associated anomalies such as corpus callosum agenesis, Chiari malformations, Dandy–Walker malformation, or syringomyelia, and any hydrocephalus.
CT with bone window will be done to delineate the exact size and location of the bony defect, the anatomy of the anterior cranial fossa and paranasal sinuses in frontoethmoidal or basal lesions, and the occipital bone in posterior encephaloceles.
For large occipital encephaloceles, MR venography or CT venography is important to define the relationship of the sac to the torcular Herophili and major dural venous sinuses.
In anterior and basal lesions I will consider CT angiography or MR angiography if there is concern about proximity to anterior cerebral or ophthalmic arteries. In significant craniofacial deformity I will obtain three dimensional CT reconstructions for craniofacial planning.
Baseline laboratory tests are obtained for anesthesia; endocrine and ophthalmologic evaluations are considered for basal and syndromic cases. In the presence of multiple anomalies or a suggestive pattern, I will involve genetics and arrange karyotyping or targeted panels.
Q. How will you differentiate encephalocele from a midline growing skull fracture clinically and radiologically?
Encephalocele is a congenital lesion present at or soon after birth, usually with no preceding trauma, and is often midline in the occipital or frontoethmoidal region. The overlying skin may be thinned but is usually intact at birth. The defect margins on imaging are smooth and corticated, representing a primary bone-formation failure, and the sac often communicates with a ventricle or subarachnoid space as a true herniation of intracranial contents.
In contrast, a growing skull fracture is acquired, with a clear history of head trauma in infancy followed by progressive enlargement of a cranial swelling over months. The lesion typically lies over a linear fracture, most often in the parietal or frontal bone, and radiology shows a diastatic fracture line with scalloped and progressively widened bony margins due to pulsatile brain and cerebrospinal fluid through an associated dural tear. In growing skull fracture the initial skin may show signs of previous hematoma, and the age at presentation is later, usually beyond a few months, unlike the immediate neonatal presentation of encephalocele.
Q. What is Furstenberg sign and what is its significance?
Furstenberg sign is the increase in size and pulsation of a nasal or frontonasal mass when the jugular veins are compressed, the child cries, or the Valsalva manoeuvre is performed. It indicates that the mass has an intracranial communication and is typical of a nasal or frontoethmoidal encephalocele. Dermoid cysts and nasal gliomas do not enlarge with jugular compression and therefore have a negative Furstenberg sign. A positive Furstenberg sign should alert you to treat the lesion as an encephalocele and avoid blind biopsy or aspiration.
Q. What syndromes and associated anomalies are commonly seen with encephalocele?
Encephaloceles are associated with a wide range of central nervous system and systemic anomalies. Common intracranial associations include hydrocephalus, agenesis or dysgenesis of the corpus callosum, Chiari malformations, Dandy–Walker malformation, heterotopias, and myelomeningocele.
Systemic and syndromic associations include Meckel–Gruber syndrome, which combines occipital encephalocele with cystic renal dysplasia and polydactyly; Walker–Warburg syndrome with severe lissencephaly, eye anomalies, and muscular dystrophy; Fraser, Knobloch, and Roberts syndromes; as well as ciliopathies such as Joubert syndrome.
Occipital encephaloceles feature prominently in several of these syndromes, and their presence should prompt evaluation for renal, hepatic, ocular, and limb anomalies.
Q. How will you manage a child with encephalocele and what is the role of multimodality care?
I will first stabilize the child, ensure airway and feeding are safe, and treat any active infection or meningitis. If hydrocephalus is present and tense, I will address it either with shunting or endoscopic third ventriculostomy depending on the underlying ventricular anatomy, often before large posterior encephalocele repair to reduce venous congestion and sac tension.
Definitive management is surgical, but it must be planned in a multidisciplinary setting involving neurosurgery, craniofacial or plastic surgery, otolaryngology for basal and frontoethmoidal lesions, anaesthesia, neonatology, and genetics. The aims are to excise non-viable herniated tissue, preserve or reposition functional brain where possible, achieve a watertight dural closure, reconstruct the skull or skull base to restore barrier and support, and correct craniofacial deformities to the extent feasible.
Timing is individualised; life threatening airway compromise, uncontrolled cerebrospinal fluid leak, or recurrent meningitis demand early surgery, whereas otherwise stable anterior vault lesions may be timed to balance neurodevelopmental safety and craniofacial growth. Postoperatively, the child requires long-term follow up for neurodevelopment, vision, seizure control, and shunt function if present.
Q. What general surgical principles do you follow when repairing an encephalocele?
Key Surgical Principles:
1. Management of Hydrocephalus First / Simultaneously:
If hydrocephalus is present, treat it with VP shunting or ETV before or during encephalocele repair. Closing a large sac without controlling hydrocephalus dramatically increases the risk of CSF wound breakdown, pseudomeningocele, and acute intracranial hypertension.
2. Soft Tissue & Venous Preservation:
Open the sac carefully away from major neural structures. Identify and protect major dural venous sinuses (e.g., torcular, transverse sinuses) that may be displaced into or near the neck of an occipital sac using pre-operative MRV/CTV.
3. Handling Herniated Contents:
Non-functional, gliotic, or dysplastic tissue within the sac is safely resected. Functional cortex (more common in sincipital/vault lesions) must be preserved and gently reduced into the cranial vault if space allows.
4. Watertight Dural Closure:
Achieve an absolute watertight duraplasty using autologous pericranium, fascia lata, or synthetic dural substitutes to eliminate CSF leakage.
5. Osseous & Soft Tissue Reconstruction:
Reconstruct large bony gaps with autologous split calvarial grafts or rigid mesh (in older children) to prevent recurrent herniation and restore structural skull integrity.
Q. Describe the surgical steps for a nasofrontal or frontoethmoidal encephalocele.
I will plan the operation in conjunction with a craniofacial team. I will position the child supine with the head elevated and fixed in a horseshoe or paediatric head holder, taking care to avoid pressure on the sac. I will administer broad spectrum antibiotics and use a bicoronal scalp incision extending from one preauricular region to the other, reflecting the scalp and pericranium anteriorly to expose the frontal bone and the nasal root.
I will fashion a frontal bone flap incorporating the superior orbital rims when needed to expose the anterior cranial fossa floor, the frontal lobes, and the dural attachment of the sac. I will gently dissect the sac from the nasal and orbital soft tissues, controlling small emissary veins, and then open the sac in a controlled manner. I will inspect the contents, preserve any functional frontal cortex that can be safely repositioned intracranially, and excise gliotic or non-viable tissue. I will disconnect the sac at the bony defect, then repair the dural defect with a watertight duraplasty using pericranium.
I will reconstruct the anterior cranial fossa floor with an autologous bone graft, often harvested from the frontal bone, and reposition the frontal bone flap. When indicated, I will perform fronto-orbital advancement or nasal reconstruction to correct hypertelorism and nasal deformity. I will place a subgaleal drain if necessary and close the scalp in layers, ensuring minimal tension over the reconstructed region.
Q. Describe the surgical steps for a basal encephalocele.
The exact approach depends on whether the lesion is transethmoidal, sphenoethmoidal, or transsphenoidal. For a typical midline basal transethmoidal or transsphenoidal encephalocele, I will favour an endoscopic endonasal approach in collaboration with an experienced otolaryngology team. I will position the child supine with the head slightly extended and rotated as needed, and I will prepare and drape the nasal cavity. Using a binostril endoscopic approach, I will identify the nasal septum, turbinates, and sphenoethmoidal recess, then expose the skull-base defect by removing overlying mucosa and carefully drilling or curetting thin bone under endoscopic vision.
I will identify the herniated sac, gently dissect it circumferentially from surrounding mucosa, and then open it in a controlled manner if needed to decompress; otherwise I will coagulate and divide its neck at the level of the skull base. I will repair the dural defect with an underlay graft of fascia or acellular dermis, followed by an onlay graft and a vascularised pedicled nasoseptal flap where anatomy permits. I will secure the reconstruction with fibrin sealant and nasal packing to buttress the flap.
In larger lesions or those with complex anatomy, I may combine a limited transcranial frontobasal exposure to assist with intracranial disconnection and reinforcement of the dural repair. Postoperatively, I will maintain head elevation, avoid nose blowing or Valsalva, and monitor for cerebrospinal fluid leak or meningitis.
Q. Describe the surgical steps for an occipital or posterior fossa encephalocele.
I will position the child prone or in a park-bench position with the head fixed and the sac supported without compression. I will mark a midline occipital incision that encompasses the base of the sac but avoids the thinned dome. After careful dissection of the scalp and suboccipital muscles, I will expose the bony defect and the dural sac. I will identify any major venous sinuses entering the sac with reference to preoperative venography and dissect them gently.
I will open the sac near its base to allow controlled cerebrospinal fluid drainage, inspect the contents, and identify cerebellar or occipital lobe tissue that may be functional. Gliotic and dysplastic tissue is excised, whereas a functional brain that can be repositioned is preserved. I will then excise the redundant sac wall and perform a generous, watertight duraplasty using pericranium or fascia lata.
If the bony defect is large, I will reconstruct it with split calvarial bone grafts or leave a small defect if the dura is well supported and the child is very young. I will ensure meticulous haemostasis, place a subgaleal drain if needed, and close the wound in layers. When hydrocephalus is present, I will have already treated it or will place a shunt at the same sitting, depending on the intraoperative findings and ventricular status.
Q. What factors determine prognosis in a child with encephalocele?
Prognosis depends on the location of the encephalocele, the volume and functional status of the herniated brain, the presence of hydrocephalus, and the burden of associated anomalies or syndromes. Anterior and small vault encephaloceles that contain little or no functional brain and are repaired early with good reconstruction usually have favourable outcomes.
Large occipital encephaloceles containing brainstem or significant cerebellar or occipital lobe tissue, especially in the context of syndromes such as Meckel–Gruber or Walker–Warburg, have a guarded prognosis with high mortality and significant neurodevelopmental impairment in survivors. The presence of severe hydrocephalus, refractory seizures, or major systemic malformations further worsens outcome.
Early multidisciplinary management, careful imaging based planning, and meticulous dural and bony reconstruction can significantly improve survival and quality of life in appropriately selected patients.