Encephalocele: Causes, Symptoms, Diagnosis, Treatment

Encephalocele is a congenital defect of neural tube closure and cranial vault/base bones, in which the meninges (meningocele) and/or brain tissue (encephalomeningocele) along with cerebrospinal fluid protrude through the bone defect. Depending on the location, anterior (frontoethmoid/syncipital and basal) and posterior (occipital, parietal) forms are distinguished; the clinical presentation is determined by the location, size, and composition of the sac. Diagnosis is often made prenatally (ultrasound + fetal magnetic resonance imaging), which allows for planning of delivery and treatment tactics. [1]

The disease is rare: in the United States, it occurs in about 1 in 10,365 newborns (≈350 children per year). Prevalence worldwide varies greatly by region and by access to prevention of neural tube defects (fortification of foods with folic acid, preconception supplements). [2]

The outcome of treatment depends almost entirely on the contents of the sac (whether there is functional brain tissue), associated anomalies (hydrocephalus, Meckel-Gruber syndrome, Chiari malformation) and the timeliness of the surgery (watertight closure of the sac and dura mater, reconstruction of the defect). [3]

ICD-10 and ICD-11 codes

In ICD-10 (section Q01), the following subheadings are used to specify the topography: Q01.0 - frontal, Q01.1 - nasofrontal, Q01.2 - occipital, Q01.80 - parietal, Q01.81 - orbital, Q01.82 - nasal, Q01.9 - unspecified. [4]

In ICD-11, the basic code for the condition is LA01 "Cephalocele", to which anatomy, lateralization, and other dilators are added post-coordination for precise description (e.g., anterior/posterior). [5]

Table 1. Frequently used codes

System	Code	Explanation/When to use
ICD-10	Q01.0	Frontal encephalocele
ICD-10	Q01.1	Nasofrontal (frontonasal)
ICD-10	Q01.2	Occipital
ICD-10	Q01.80/81/82	Parietal/orbital/nasal
ICD-10	Q01.9	Unspecified
ICD-11	LA01	Cephalocele (hereinafter referred to as post-coordination clarifications)

Epidemiology

According to the CDC, the cumulative estimate for the United States is 1:10,365 births (≈354 cases/year), and global reviews show a range in the incidence of neural tube defects of 0.4–215 per 10,000 births (different countries and accounting methods). Encephalocele is the third most common NTD after anencephaly and spina bifida. [6]

The distribution of localization depends on the region: in Europe/USA, occipital forms predominate, while in Southeast Asia and some regions of Africa, anterior frontoethmoidal (syncipital) forms are more common. Women are somewhat more likely to have posterior forms. [7]

Associated anomalies are found in approximately 60% of infants (hydrocephalus, agenesis of the corpus callosum, Dandy-Walker, Chiari III malformation, heart defects, kidney defects; in Meckel-Gruber syndrome - the triad of "occipital encephalocele + polycystic kidneys + postaxial polydactyly"). This determines the prognosis. [8]

Table 2. Epidemiological landmarks

Indicator	Grade
Frequency (USA)	1 in 10,365 births (≈ 350/year)
Localization (in general terms)	The rear ones are more common in the "West", the front ones are more common in Southeast Asia/Africa
Associated anomalies	≈ 60% of cases (nervous system, kidneys/heart)
Risk of hydrocephalus	60-90% for posterior and 10-15% for anterior forms [9]

Reasons

Encephalocele occurs due to disruption of neural tube closure and osteogenesis of the cranial vault/base during early embryogenesis. It is a multifactorial disorder with genetic and environmental contributions. [10]

Some cases are associated with ciliopathies, primarily with Meckel-Gruber syndrome (autosomal recessive, lethal in the perinatal period; dozens of genes: MKS loci, B9D1, etc.). Requires genetic counseling for the family. [11]

Risk factors

Nutritional and maternal factors that increase the risk of NTD (including encephalocele) include folate deficiency, diabetes, obesity, hyperthermia (fever/saunas in the first trimester), valproic acid and some other antiepileptics, and low socioeconomic status. Prevention of NTD with periconceptional folic acid supplementation reduces the risk of primary NTD and recurrence by 70% in women at high risk. [12]

Table 3. Risk factors and modifications

Factor	Action
Folate deficiency	Prevention: 400 mcg/day for everyone, 4 mg/day for high risk (before conception and in the first trimester). [13]
Diabetes mellitus, obesity	Glycemic optimization; pre-pregnancy weight management. [14]
Hyperthermia	Avoid saunas/jacuzzis, aggressively treat fever in the first trimester. [15]
Antiepileptics (valproate)	If possible, change to less teratogenic regimens before conception. [16]

Pathogenesis

The key mechanism is a failure of neurulation with defective closure of the neural folds and a disorder of mesenchymal formation of the cranial bones. Through this defect, under the influence of cerebrospinal fluid pulsation, a sac lined by the dura mater forms, containing only meninges and cerebrospinal fluid (meningocele) or meninges and brain tissue (encephalomeningocele). The more viable brain tissue in the sac, the worse the prognosis after reduction. [17]

Posteriorly, the structures of the posterior cranial fossa are often involved; some cases are associated with Chiari III (herniation of the contents of the posterior fossa into the occipital/cervical encephalocele) - this is a rare but prognostically severe combination. [18]

Symptoms

Newborns/infants: soft, elastic tumor-like mass on the head (occiput/forehead/root of the nose), sometimes with thinned skin; signs of cerebrospinal fluid leakage or ulceration; neurological symptoms ranging from mild hypotension to seizures and developmental delay. In basal forms - nasal obstruction, recurrent rhinitis, hypertension of the ocular globe/strabismus due to the orbital component. [19]

In the fetus: ultrasound shows a bone defect and sac; fetal MRI clarifies the composition and connection with the venous sinuses/brain, which is critical for planning delivery and early surgery. [20]

Classification, forms and stages

• By localization:
• Posterior - occipital, parietal;
• Anterior (syncipital/frontoethmoidal) - supraradicular;
• Basal - transethmoidal/sphenoidal/sphenoethmoidal (intranasal/nasopharyngeal).

Anterior syncipital cysts are subdivided into nasofrontal, nasoethmoidal, and nasoorbital subtypes. [21]

By content: meningocele (meninges) vs. encephalomeningocele (meninges + brain). By integrity of the integument: intact vs. torn (high risk of infection). "Giant" encephaloceles are a separate category—a huge sac containing predominantly cerebrospinal fluid; despite their size, their prognosis is sometimes better due to the small proportion of viable brain tissue in the sac. [22]

Table 4. Practical classification

Axis	Options	Clinical value
Localization	Posterior / anterior (syncipital) / basal	Prognosis, associated anomalies, access
Subtype of the front	Nasofront., nasoethmoid., nasoorbit.	Facial skeleton reconstruction plan
Content	Menino- vs. encephalomeningocele	Extent of resection and prognosis
Integrity	Intact / rupture	Urgency of surgery (risk of meningitis)

Complications and consequences

Without surgery, the following are possible: rupture of the sac, cerebrospinal fluid leakage, meningitis/sepsis, ulcerative-necrotic skin changes, hydrocephalus (especially in posterior forms), seizures, and developmental delay. In frontoethmoidal forms, facial deformation, respiratory obstruction, and amblyopia/strabismus are possible. [23]

Postoperative risks include: cerebrospinal fluid fistulas, wound infection/suture dehiscence, the need for shunting or endotracheal ablation in the case of progressive hydrocephalus, and late cosmetic issues. Multidisciplinary monitoring is required (neurosurgeon, ENT/craniofacial surgeon, ophthalmologist, neurologist, and rehabilitation specialist). [24]

When to see a doctor

• During pregnancy: if there is an ultrasound suspicion of a skull defect/sac - referral for fetal MRI and consultation at the perinatal center. [25]
• Newborn: Any mass on head/nose, especially with thinned skin or leakage - urgent evaluation (infection risks).
• In an infant: a growing head, bulging fontanelle, vomiting, drowsiness - exclude hydrocephalus. [26]
• Recurring "rhinitis"/blockage of one side of the nose in an infant - consider basal encephalocele and refer to an ENT/neurosurgeon. [27]

Diagnostics

Step 1. Prenatal screening. Standard second-trimester ultrasound; if suspected, detailed neurosonography and fetal MRI to evaluate the contents, venous sinuses, associated posterior fossa and renal anomalies (Meckel-Gruber rule-out). MRI is safe during pregnancy if current recommendations are followed (contrast is contraindicated). [28]

Step 2. Postnatal imaging. MRI of the brain/skull base (composition of the sac, connection with the brain/sinuses/ventricular system) + thin-slice CT for bone window and access/cranioplasty planning. For basal forms - thin-slice CT of the paranasal sinuses; endoscopic ENT evaluation. [29]

Step 3. Laboratory and genetics. For multiple anomalies – chromosomal microarray analysis/panel sequencing (ciliopathies, Meckel-Gruber). In parallel – neurosonography for hydrocephalus, ultrasound of the kidneys/heart. [30]

Step 4. Consultation. Neurosurgeon + ENT/craniofacial surgeon (for anterior/basal) + neonatologist/anesthesiologist + ophthalmologist + geneticist + rehabilitation specialist - select the intervention window, access and extent of reconstruction. [31]

Table 5. Diagnostic minimum "before surgery"

Situation	What you need to have
Any form	MRI of the brain; CT of bones/base; photofixation, neurosonography
Basal	CT scan of the paranasal sinuses + ENT consultation/endoscopic evaluation
Suspected syndrome	Genetic panel (ciliopathies), ultrasound of kidneys/heart
Risk of hydrocephalus	Neurosonography/dynamic MRI

Differential diagnosis

• Dermoid/epidermoid, nasal glioma, meningocele, lymphangioma - in facial/nasal masses.
• Posterior scalp hemangioma, atretic encephalomeningocele vs true (connection with sinuses/brain!).
• TVP cysts/defects of other etiologies. MRI (connection with the cranial cavity), CT (bone defect), and endoscopy are used to determine the diagnosis. [32]

Treatment

The goal of the surgery is to reduce nonviable tissue in the sac, create a watertight closure of the dura mater, eliminate the bone defect (cranioplasty), and correct soft tissue/facial skeletal deformities. Timing varies from person to person: if there is a risk of rupture/cerebrospinal fluid leakage, surgery is performed as soon as possible; if the sac is stable and intact, it is planned for the first few months of life. [33]

For occipital/parietal forms, an arcuate approach is used, opening the sac with preservation and reintegration of the viable cortex (if it is functional), resection of the dysgenetic tissue, tight hermetic suturing of the dura mater with plastic surgery (autodural/fascial flap), and closure of the bone defect (autobone/resorbable plates). Control of cerebrospinal fluid reduces the risk of infection. [34]

Hydrocephalus is common in posterior forms; the strategy is determined based on the dynamics: shunting (VPSh) or endoscopic third ventriculostomy (ETV) - according to standard indications. Sometimes staging is advisable: first a CSF shunt, then radical reconstruction. [35]

Frontoethmoid (syncipital) defects require the combined work of a neurosurgeon and a craniofacial surgeon: a combined intra-/extracranial stage (bicoronial approach, osteotomies, repositioning of nasofrontal structures), closure of the dura mater, and reconstruction of the frontonasal complex. This restores facial contours and prevents recurrence. [36]

Basal (transethmoidal/sphenoidal) encephalomeningoceles are now often closed endoscopically endonasally (ENT + neurosurgeon): layered plastic surgery (fascia/mucoperiosteal flap, "on-on-under"), sometimes using a vascularized septal flap (Hadad). The endonasal route reduces trauma and hospitalization time. [37]

In giant sacs with thin skin, prevention of hypothermia and blood loss, atraumatic mobilization, and preliminary drainage of cerebrospinal fluid to "flatten" the sac (in a controlled manner to avoid hemodynamic shifts) are important. Paradoxically, such patients sometimes have a better prognosis due to the low proportion of viable brain tissue in the sac. [38]

Antibiotic prophylaxis is performed according to neurosurgical standards; in case of rupture/fistula, immediate closure and anti-infective measures are required. Early soft tissue reconstruction (Z-plasty, local flaps) improves the cosmetic outcome and reduces the risk of skin necrosis. [39]

Ophthalmological care is needed for frontoethmoid/orbital forms: monitoring of intraocular pressure, treatment of amblyopia/strabismus, and, if indicated, subsequent steps (botulinum therapy/strabismus surgery). The goal is to preserve visual function while reconstructing craniofacial structures. [40]

Anesthesia/neonatology: prevention of hypothermia, gentle intubation (in basal cases - difficult airway), correction of electrolytes in case of large cerebrospinal fluid losses, thromboprophylaxis in mothers after cesarean section. The delivery plan (cesarean section in case of giant sacs) is determined by the perinatal center. [41]

What definitely NOT to do: “observe” ruptured sacs; puncture the sac outside the operating room; postpone the consultation if there are signs of meningitis/hydrocephalus; consider fetal surgery - for encephalocele it is not standard (unlike myelomeningocele). [42]

Table 6. Selecting an approach based on the clinical situation

Situation	Basic tactics
Intact small sac, no hydrocephalus	Planned reconstruction in the first months of life
Rupture/CSF leak/infection	Urgent closure of the dura mater + antibiotics
Posterior + hydrocephalus	Shunt/ETV → definitive reconstruction
Basal/syncipital	Combined neurosurgery-ENT/craniofacial; endonasal techniques as indicated

Prevention

Prevention of NTD is effective: daily intake of 400 mcg of folic acid for all those planning a pregnancy, and 4 mg/day in cases of high risk (previous NTD in the fetus/child, use of valproate, diabetes, etc.), starting 1-3 months before conception and in the first trimester. In a number of countries, flour is fortified with folic acid. [43]

Glycemic control in diabetes, weight loss before pregnancy, avoidance of hyperthermia, and review of teratogenic drugs before conception reduce the risk of NTD. [44]

Forecast

The prognosis is determined by the "rule of three": location, volume of viable brain tissue in the sac, and associated anomalies. In the presence of significant viable tissue and in the presence of a Chiari III malformation, the outcome is worse; in "giant" sacs with a predominance of cerebrospinal fluid, the outcome is often better than expected based on size. Early radical reconstruction and treatment of hydrocephalus improve neurodevelopment. [45]

According to clinical series, about half of the children have satisfactory neurodevelopment after timely closure, but a significant proportion will require long-term rehabilitation and observation (neurologist, speech therapist, occupational and physical therapy). [46]

Table 7. Unfavorable prognostic factors

Factor	Why is it important?
Viable brain tissue in a sac	Risk of loss of function during reduction, seizures
Posterior location + hydrocephalus	High risk of re-intervention/bypass
Chiari III / severe syndromes	High mortality/disability
Infection/fistula before surgery	Increased neurological deficit and mortality

FAQ

Can this be "cured"?
Yes. The goal is to reliably close the dura mater and cranial defect, remove non-viable tissue, and restore shape. With early surgery and the absence of severe anomalies, development is often acceptable. [47]

Is surgery necessary immediately?
Urgently – in case of a rupture/cerebrospinal fluid leak/infection. If the skin is intact and the child is stable, surgery is planned for the first weeks to months of life after full planning. [48]

Does folic acid really help?
Yes. 400 mcg/day for everyone (before conception and in the first trimester) reduces the risk of NTD; for those with a high risk, 4 mg/day prevents recurrence (reduction of ≈ 70%). [49]

Can treatment be performed in utero, as with spina bifida?
No, fetal surgery is not the standard for encephalocele; treatment is postnatal. [50]

What is a "frontoethmoidal" encephalocele?
This is an anterior form, divided into nasofrontal, nasoethmoidal, and nasoorbital; treatment is combined (neurosurgery + ENT/craniofacial), sometimes endonasal. [51]