1. Definition (ENT Mandatory Statement)

Encephalocoele is a congenital skull-base or cranial defect through which brain tissue + meninges + CSF herniate outside the cranial cavity.
If ONLY meninges herniate → meningocoele.
If meninges + CSF herniate without brain tissue → meningocele.
If functional or dysplastic brain tissue herniates → encephalocoele.
When brain + ventricle + CSF herniate → meningoencephalocele / meningohydroencephalocele.

ENT Relevance:

Basal encephalocoeles may appear as midline nasal masses, often misdiagnosed as nasal polyps, dermoids, or gliomas.
Fatal complications occur if unrecognized (CSF leak, meningitis, catastrophic bleeding).

2. Embryology (Hyper-Detailed ENT + Neuroscience Integration)

Encephalocoele results from failure of neural tube fusion + failure of mesenchymal migration during 3rd–4th week of gestation.

2.1 Primary Embryological Defects

Defective closure of anterior neuropore
Failure of ossification of skull base bones (frontal, ethmoid, sphenoid, occipital)
Deficient mesoderm → persistent bony defect
Herniation of neural tissue due to CSF pressure

2.2 Skull Base Zones Involved

Anterior skull base: cribriform plate, foramen cecum (most ENT-relevant)
Sphenoid bone: transsphenoidal defects
Ethmoidal region: transethmoidal defects

These structural weaknesses explain why basal encephaloceles present as:

Nasal cavity masses
Nasopharyngeal masses
Midline swellings

3. Classification (EXACT ENT Exam Format)

3.1 Based on Location

A. Cranial (Occipital, Parietal, Frontal)

Mostly neurosurgical relevance.

B. Basal Encephalocoele (ENT High-Yield)

Transethmoidal – through cribriform plate → into nasal cavity
Sphenoethmoidal – through junction of ethmoid + sphenoid → into nasal cavity
Transsphenoidal – through sphenoid sinus → into nasopharynx
Frontosphenoidal – between frontal + sphenoid bones
Supraorbital – above orbit

ENT exams LOVE this table — you must memorize all five.

3.2 Based on Contents

Meningocele – CSF + meninges
Meningoencephalocele – CSF + meninges + brain tissue
Hydroencephalocele – CSF + ventricle + brain tissue
Encephalocele – brain tissue only

ENT Key:

Basal encephaloceles are almost always meningoencephaloceles, not just meningoceles.

4. Epidemiology

Incidence: 1 in 5000–10,000 live births
Occipital most common globally
Basal encephalocele = rare (1–10% of all cases)
Higher in:
- Low-folate regions
- Southeast Asia
- Infants born to mothers with hyperthermia in first trimester

5. Etiology (ENT + Fetal Medicine Insights)

5.1 Maternal Factors

Folic acid deficiency
Poor nutrition
Alcohol or drug exposure
Isotretinoin (Retinoic acid)
Anti-epileptic drugs: valproate, carbamazepine
Hyperglycemia (diabetes)
Fever in 1st trimester

5.2 Genetic Factors

Autosomal recessive patterns in some populations
Syndromes: Meckel–Gruber, Walker–Warburg
Abnormalities in neural crest development

5.3 Mechanical Factors

Elevated fetal intracranial pressure
Failure of mesodermal migration
Persistent embryological gaps in skull base

6. Pathogenesis (ENT Super-Expanded Version)

Neural tube fails to close.
Mesenchymal tissue fails to migrate → skull base defect persists.
Brain tissue is displaced by CSF pulsations/herniation forces.
Herniated sac forms:
- lined by meninges
- filled with CSF
- containing viable/dysplastic brain tissue
Intranasal or nasopharyngeal mass forms (in basal cases).

Why ENT must identify this:

A misdiagnosed encephalocele mistaken for a nasal polyp can lead to:

CSF leak
Meningitis
Brain herniation
Death

This is one of the highest-stakes pitfalls in ENT.

7. Clinical Features (ENT Ultra-Expanded)

7.1 External Cranial Encephalocele

Visible mass on scalp (occipital, frontal)
Soft, compressible, sometimes expanding with crying
Overlying skin may be normal or ulcerated
Transillumination positive if CSF-filled

7.2 Basal Encephalocele (ENT GOLD CONTENT)

Presents inside nasal cavity — often misdiagnosed.

Symptoms:

Persistent nasal obstruction (neonate cannot feed properly)
Respiratory distress
Cyanosis episodes
Snoring/noisy breathing
Recurrent rhinorrhea
Odd nasal shape (wide nasal bridge/hypertelorism)

Signs:

Midline nasal mass
Pink/grey polypoid lesion
Expands with crying or straining (Furstenberg sign)
May show CSF leakage
Pulsatile mass

7.3 Features Suggesting Intracranial Connection

Furstenberg sign positive
Mass is soft, pulsatile
Mass enlarges on jugular compression
Associated hydrocephalus
Clear watery discharge (CSF rhinorrhea)

7.4 Feeding Problems in Neonates

As neonates are obligate nasal breathers, nasal obstruction leads to:
- choking
- failure to thrive
- repeated cyanosis

Same danger seen in choanal atresia — ENT must compare these two conditions.

8. Special ENT Clinical Signs

8.1 Furstenberg Sign

Mass increases in size:
- during crying, coughing
- jugular vein compression
Indicates intracranial communication — a vital ENT viva point.

8.2 Transillumination Test

Positive if sac contains CSF
Negative if brain tissue predominates

8.3 Expansile Pulsation

Pulsation synchronous with heartbeat
Present in encephaloceles
Absent in dermoid cysts and gliomas

9. Differential Diagnosis (Midline Nasal Mass Algorithm)

ENT must NEVER remove a midline mass without imaging.

Differentials include:

Dermoid cyst
Nasal glioma (glial heterotopia)
Hemangioma
Nasal polyp
Meningocele
Encephalocele / meningoencephalocele
Teratoma
Lymphangioma
Rhinosporidiosis (rare in infants)

How ENT differentiates clinically:

Feature	Encephalocoele	Dermoid	Glioma	Polyp
Midline location	Always	Common	Common	Rare
Pulsatile	Yes	No	No	No
Expands on crying	Yes	No	No	No
CSF leak	Possible	No	No	No
MRI/CT	Skull base defect	Sinus tract	No defect	No defect

Written And Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change MBBS 4th Year (Fourth Professional) Otorhinolaryngology (ENT) Free Material

10. Investigations (EXTREMELY HIGH-YIELD ENT SECTION)

10.1 MRI – Investigation of Choice

Provides:

Intracranial continuity
Soft tissue details
Content of sac
Brain tissue involvement
Associated anomalies (hydrocephalus)

MRI T1/T2 sequences differentiate CSF from neural tissue.

10.2 CT Scan (Skull Base Evaluation)

Shows:

Exact bony defect location
Size of defect
Anterior skull base thinning
Sphenoid/ethmoid sinus anatomy

ENT uses CT to plan surgical approach.

10.3 Nasal Endoscopy

Used AFTER imaging, never before.

Findings:

Intranasal mass
Attachment point
CSF leakage
Obstruction level

10.4 β2-Transferrin Test

Confirmatory test for CSF rhinorrhea.

10.5 Ophthalmology + Neurology Evaluation

Needed because frontonasal encephaloceles often present with:

Telecanthus
Hypertelorism
Strabismus
Vision anomalies

10.6 Ultrasound (For Neonatal Cranial Masses)

Sometimes used for external cranial encephaloceles as a non-invasive screening tool.

11. Management of Encephalocoele (ENT + Neurosurgery Integrated Approach)

Management is always surgical, but the timing, approach, and urgency depend on:

Presence of CSF leak
Presence of meningitis
Degree of airway obstruction
Size of skull base defect
Amount of herniated brain tissue
Type of encephalocoele (basal vs cranial)

ENT surgeons are primarily responsible for basal encephaloceles, especially those presenting as midline intranasal masses.

12. Indications for Early / Emergency Surgery

12.1 Absolute Indications

CSF rhinorrhea (risk of meningitis is extremely high)
Recurrent meningitis
Significant airway obstruction in neonates
Rapidly enlarging mass
Ulceration or skin breakdown over external swelling

12.2 Relative Indications

Cosmetic deformity (frontal/occipital)
Feeding difficulties
Snoring/obstructive sleep symptoms

12.3 When Surgery Can Be Delayed

No CSF leak
Small sac
No airway compromise
Medically unstable infant needing optimization

13. Principles of Surgical Treatment (ENT Mandatory Framework)

Complete excision or reduction of herniated sac
Preservation of viable neural tissue
Secure, multilayer skull base reconstruction
Restoration of nasal and craniofacial anatomy
Prevention of CSF leak & meningitis
Protection of olfactory apparatus

14. Surgical Approaches (Ultra-Detailed ENT Operative Anatomy)

The approach depends on the location:

Extracranial (cranial vault) → neurosurgical approach
Basal (nasal cavity or nasopharynx) → ENT endoscopic + neurosurgical team
Craniofacial approach → combined team

15. Endoscopic Endonasal Repair (Gold Standard for Basal Encephalocoele)

Modern ENT practice overwhelmingly favors endoscopic repair.

15.1 Advantages

No external incision
Less morbidity
Excellent visualization
Direct access to skull base
Allows precise removal of sac
Better cosmetic results
Shorter recovery time

15.2 Step-by-Step Procedure

Step 1 – Preparation

General anesthesia
Avoid nasal instrumentation pre-scan
Pediatric endoscopic set
Topical vasoconstriction with caution

Step 2 – Visualization

Introduce 0° or 30° pediatric endoscope
Identify mass origin (ethmoid/sphenoid/cribriform)
Evaluate attachment

Step 3 – Manipulation of the Sac

Sac should NOT be ruptured unless controlled
Enlarge surgical access
Herniated brain tissue evaluated:
- Dysplastic → excised
- Viable → preserved

Step 4 – Skull Base Defect Repair

This is the most crucial step.

The sequence typically includes:

Inlay graft (underlay)
- Fascia lata
- Dura substitute
- Pericranium
Onlay graft (overlay)
- Septal cartilage
- Thin bone graft
Vascularized mucosal flap
- Hadad-Bassagasteguy nasoseptal flap (when anatomy allows)
Biologic glue
- To seal graft layers

Key ENT surgical principle:

A multilayer closure drastically reduces risk of recurrence or persistent CSF leak.

16. External / Open Approaches (Used for Large Fronto-Nasal Lesions)

Sometimes basal encephaloceles are too large or complex for purely endoscopic management.

16.1 Bicoronal (frontal) craniotomy

Provides wide exposure
Used for frontonasal defects
Allows reduction of herniated brain tissue
Excellent for large defects

16.2 External Rhinoplasty Approaches

Useful for minor frontonasal lesions
Cosmetic correction simultaneously

16.3 Transcranial + Transnasal Combined

Best for complex anterior skull base lesions
Neurosurgeon handles intracranial portion
ENT handles intranasal portion

17. Endoscopic Repair of Transsphenoidal Encephalocele (ENT High-Yield)

Key anatomical points

Defect lies in sphenoid sinus
Herniation may extend into nasopharynx
Most often discovered during evaluation for nasal obstruction

Repair steps

Wide sphenoidotomy
Identification of defect
Reduction of sac
Multilayer reconstruction with fascia/cartilage
Optional: lumbar drain

18. Postoperative Care (ENT Ultra-Expanded)

18.1 Nasal Care

No nasal packing if possible
Avoid nose blowing for 2–3 weeks
Saline irrigations after day 7
Avoid nasal suctioning early

18.2 Intracranial Pressure Control

Head elevation 30°
Avoid crying/straining in infants
Stool softeners
Sedation if needed

18.3 Lumbar Drain

Used in high-risk repairs:

Large defects
High CSF pressure
Revision surgery

18.4 Antibiotics

Broad spectrum for meningitis prophylaxis

18.5 Follow-Up

Weekly for 1 month
Endoscopy to evaluate healing
MRI/CT if recurrence suspected

19. Complications of Encephalocele & Surgery

19.1 Complications Before Surgery

Airway obstruction
Feeding difficulty
CSF rhinorrhea
Meningitis
Failure to thrive
Cosmetic disfigurement

19.2 Complications During Surgery

Hemorrhage
Brain injury
Dural tears
Damage to olfactory bulb (anosmia)
Orbital complications (ethmoid/skull base surgeries)

19.3 Postoperative Complications

Persistent CSF leak
Meningitis
Pneumocephalus
Recurrence of encephalocele
Adhesions/synechiae
Anosmia or hyposmia
Hydrocephalus (in some children)

20. Prognosis (ENT Clinical Outcome Section)

20.1 Good Prognosis When:

Small defect
Minimal brain herniation
Early diagnosis
Successful multilayer repair
No postoperative CSF leak

20.2 Poor Prognosis When:

Large encephalocele
Hydrocephalus present
Delayed treatment
Recurrent infections
Associated congenital anomalies (e.g., Meckel–Gruber)

21. High-Yield ENT Revision Tables

21.1 Differences Between Meningocele, Encephalocele, Meningoencephalocele

Feature	Meningocele	Encephalocele	Meningoencephalocele
CSF	Yes	Yes	Yes
Meninges	Yes	Yes	Yes
Brain tissue	No	Yes	Yes
Ventricles	No	No	Possible
Surgery complexity	Low	Moderate-high	High

21.2 Basal Encephalocele – ENT Subtypes Table

Subtype	Origin	Presentation	Surgical approach
Transethmoidal	Cribriform plate	Nasal mass	Endoscopic
Sphenoethmoidal	Ethmoid-sphenoid junction	Nasal cavity	Endoscopic
Transsphenoidal	Sphenoid sinus	Nasopharyngeal mass	Endoscopic
Frontosphenoidal	Fronto-sphenoid junction	External deformity	Craniofacial
Supraorbital	Above orbit	Eyelid/forehead swelling	External

22. Radiology Section (ENT + Neurosurgery Integration)

22.1 CT Findings

Bony defect in skull base
Enlargement of foramen cecum
Defect in cribriform plate
Sphenoid sinus defect
Associated sinus anomalies

22.2 MRI Findings

CSF in sac (T2 bright)
Brain tissue continuity with herniated mass
Ventricular extension (if present)
Dural defect visualization

MRI prevents catastrophic mistakes like biopsy of encephalocele misdiagnosed as polyp.

23. Surgical Anatomy Relevant to Encephalocoele (ENT Ultra-High Yield)

Understanding anterior skull-base anatomy is mandatory before attempting surgical repair.

23.1 Cribriform Plate (Ethmoid Bone)

Thinnest part of anterior skull base
Multiple perforations for olfactory nerve filaments
Common site for transethmoidal encephalocoele
Injury risk → anosmia
CT coronal cuts crucial for evaluating thickness

23.2 Foramen Cecum

Midline depression between frontal & ethmoid bones
Persistent patency → pathway for frontonasal encephalocoele
Often associated with hypertelorism

23.3 Sphenoid Bone & Sinus Anatomy

Sphenoid sinus pneumatization varies
Defects → transsphenoidal encephalocele
Close to:
- Internal carotid artery
- Optic nerve
- Cavernous sinus
Surgery must protect these structures

23.4 Ethmoid Roof (Fovea Ethmoidalis)

Lateral lamella of cribriform plate varies in height
Keros classification affects surgical risk:
- Keros I – short (least risk)
- Keros II – medium
- Keros III – long, deep olfactory fossa (highest risk of skull-base injury)

ENT surgeons MUST know Keros to avoid iatrogenic encephalocoele during FESS.

23.5 Nasoseptal Flap Vascular Anatomy

Based on the posterior septal artery (branch of sphenopalatine artery)
Used for reconstruction
Excellent vascularity → superior healing
Not always feasible in neonates due to size

24. Neonatal Considerations (Airway, Feeding, Life-Saving ENT Points)

Encephalocoele presenting intranasally in neonates is a life-threatening airway issue.

24.1 Why neonates struggle more

Neonates are obligate nasal breathers
Nose obstruction = respiratory distress
Feeding requires continuous nasal airflow

24.2 ENT Warning Signs

Cyanosis relieved by crying
Difficulty feeding
Snorting, choking
Apneic episodes
Chest retractions

These symptoms mimic choanal atresia — and both must be differentiated carefully.

24.3 ENT Guidelines for Neonatal Handling

Never attempt to “clear the nose”
Never suction aggressively
Never insert nasal airways
Do NOT compress a midline nasal mass
Keep neonate in upright position
Have intubation equipment ready

24.4 Airway Management Priorities

Gentle mask ventilation
Orotracheal intubation if needed
Avoid pressure on sac
Avoid nasal tubes

Neonatal resuscitation teams must be alerted early.

25. Pathophysiology of CSF Rhinorrhea in Encephalocoele

25.1 Mechanism

Herniation of dura + arachnoid → communication between nasal cavity and subarachnoid space
CSF passes through defect → leaks into nasal cavity

25.2 Clinical Presentation

Clear, watery nasal discharge
Increases on bending forward
Salty taste (older children)
Associated headaches

25.3 ENT Diagnostic Points

Halo sign (not always reliable)
Gold standard: β2-transferrin
Persistent leak increases meningitis risk

26. CSF Leak: Why It’s a Surgical Emergency

26.1 Risks

Meningitis
Pneumocephalus
Brain abscess
Sepsis

26.2 Management Principles

Bed rest + elevation
Start antibiotics
Surgical closure ASAP

27. Detailed Case-Based Viva Scenarios (ENT Exam GOLD)

Scenario 1 — Midline Nasal Mass in a Newborn

A 1-day-old baby presents with severe nasal obstruction and a midline soft mass.

Viva Questions

Q: What is the most dangerous diagnosis?
A: Basal encephalocoele.

Q: What will you NOT do?
A:

No biopsy
No aspiration
No nasal airway insertion
No blind suctioning

Q: Which investigation is FIRST?
A: MRI (for intracranial continuity).

Scenario 2 — Child With Recurrent Meningitis

MRI shows anterior skull-base defect with herniation.

Viva Points:

This is encephalocele until proven otherwise.
Repair defect to prevent future episodes.
Endoscopic approach preferred for basal lesions.

Scenario 3 — Mass Misdiagnosed as Polyp

Resident removed “polyp” → sudden clear fluid gushes.

Diagnosis: Encephalocoele

What went wrong?

No imaging before biopsy
Catastrophic CSF leak

Management:

Stop bleeding
Keep patient upright
Immediate neurosurgery consultation

Scenario 4 — Fronto-Nasal Swelling in Infant

Visible midline swelling between eyes.

Features pointing to encephalocoele:

Expands on crying
Positive transillumination
Pulsatile

28. OSCE Station Notes (Scoring Format)

Station: Evaluate Neonatal Nasal Obstruction

Examiner expects:

Consider encephalocoele
Consider choanal atresia
Look for respiratory distress
Ask for MRI BEFORE touching lesion
Identify Furstenberg sign

Station: Interpret CT + MRI

CT coronal: defect in cribriform plate
MRI sagittal: continuity of brain tissue with sac
T2 hyperintense CSF component

Scoring points:

Identify defect
Identify herniated tissue
Identify approach needed
Mention bilateral nasal cavity involvement?

29. Complications — ENT Expanded Explanation

29.1 Before Surgery

Recurrent meningitis
Feeding difficulty
Airway obstruction
Craniofacial deformity

29.2 After Surgery

CSF leak
Pneumocephalus
Recurrence
Adhesions / synechiae
Damage to olfactory nerve → anosmia
Infection / meningitis

30. Prognosis — Detailed Considerations

Good Prognosis When:

Early detection
Small defect
Minimal brain tissue involvement
Effective multilayer reconstruction
No postoperative CSF leak

Poor Prognosis When:

Large herniation
Hydrocephalus
Delayed intervention
Recurrent meningitis
Associated syndromes (Meckel–Gruber)

31. MCQs (15 ENT-Level High-Yield Questions)

MCQ 1

A midline nasal mass that increases on crying is most likely:
A. Dermoid
B. Glioma
C. Encephalocoele
D. Nasal polyp
Correct Answer: C

MCQ 2

Best investigation for intracranial connection:
A. Ultrasound
B. CT scan
C. MRI
D. X-ray skull
Correct Answer: C

MCQ 3

Most dangerous complication of encephalocele:
A. Epistaxis
B. Sinusitis
C. Meningitis
D. Allergic rhinitis
Correct Answer: C

MCQ 4

Which is contraindicated in evaluation of a midline nasal mass?
A. MRI
B. CT
C. Nasal endoscopy (after imaging)
D. Biopsy
Correct Answer: D

MCQ 5

Furstenberg sign indicates:
A. Vascular lesion
B. Intracranial connection
C. Allergic swelling
D. Dermoid
Correct Answer: B

MCQ 6

Gold standard treatment:
A. Steroids
B. Endoscopic repair
C. Radiotherapy
D. Observation
Correct Answer: B

MCQ 7

Which defect leads to transsphenoidal encephalocele?
A. Ethmoid roof
B. Cribriform plate
C. Sphenoid sinus
D. Orbital floor
Correct Answer: C

MCQ 8

What is contained in encephalocele sac?
A. Meninges only
B. CSF only
C. Brain tissue + meninges + CSF
D. Bone fragments
Correct Answer: C

MCQ 9

Complication of removing encephalocele thinking it’s a polyp:
A. Allergic reaction
B. Severe bleeding
C. CSF leak
D. Synechiae
Correct Answer: C

MCQ 10

Which graft is best for skull base repair?
A. Skin graft
B. Fascia lata
C. Muscle graft
D. Fat graft
Correct Answer: B

MCQ 11

Basal encephalocele most commonly arises from:
A. Frontal bone
B. Ethmoid region
C. Occipital bone
D. Temporal bone
Correct Answer: B

MCQ 12

Which sign differentiates encephalocele from nasal glioma?
A. Midline location
B. Firm consistency
C. Increase on crying
D. No discharge
Correct Answer: C

MCQ 13

Most common complication after endoscopic repair:
A. CSF leak
B. Epistaxis
C. Hypertrophy of turbinates
D. Rhinitis
Correct Answer: A

MCQ 14

Which factor worsens prognosis?
A. Early surgery
B. Small defect
C. Hydrocephalus
D. Minimal herniation
Correct Answer: C

MCQ 15

Which is part of multilayer skull-base reconstruction?
A. Overlay graft
B. Underlay graft
C. Nasoseptal flap
D. All of the above
Correct Answer: D