A myelomeningocele is an open spinal dysraphism resulting from failed primary neurulation, where the neural placode lies on the surface without skin or bone covering. The spinal cord and meninges herniate through a posterior vertebral defect, exposing neural tissue to the external environment. It is the most severe form of spina bifida compatible with life.

 

Q. How is myelomeningocele different from myeloschisis?
 

In myelomeningocele, neural tissue protrudes and forms a placode attached to the skin edge, sometimes elevated above surrounding levels. In myeloschisis, there is no sac, and the open neural plate lies flush with the skin surface, representing the most severe form of non-closure.

 

Q. What is the embryological basis of myelomeningocele?
 

It results from failure of primary neurulation during the 3rd–4th week of gestation, leading to non-fusion of neural folds and continued exposure of neural ectoderm. Subsequent absence of dysjunction prevents mesenchymal migration, leading to failure of vertebral arches, muscle, and skin formation over the neural tube. The exposed placode then protrudes through the defect.

 

Q. What is the epidemiology of myelomeningocele?
 

Incidence ranges 0.5–1 per 1000 live births globally, higher in regions with nutritional deficiencies. Females are slightly more commonly affected. Folic acid deficiency, maternal hyperthermia, diabetes, and valproate exposure significantly increase risk. Recurrence risk in subsequent pregnancies is 2–3%.

 

Q. What anatomical levels are most commonly affected?
 

The lumbar region is most commonly involved, followed by lumbosacral, thoracic, and cervical regions. Higher-level lesions result in more severe neurological deficits.

 

Q. What clinical features are seen at birth?
 

Newborns present with a skinless sac containing neural placode and CSF. Neurological deficits correspond to lesion level: motor weakness or paralysis, sensory impairment, areflexia, neurogenic bladder and bowel dysfunction, and orthopedic deformities. Associated anomalies include Chiari II malformation, hydrocephalus, syringomyelia, and corpus callosum dysgenesis.

 

Q. What skin findings help differentiate an open MMC from closed dysraphism?
 

An open MMC always has no skin covering, exposed placode, and CSF leak. Closed dysraphisms are skin-covered and lack exposed neural tissue.

 

Q. What are the common associated intracranial abnormalities?
 

Chiari II malformation, hydrocephalus, aqueductal stenosis, corpus callosum agenesis/hypoplasia, brainstem kinking, small posterior fossa, ventriculomegaly, and syringomyelia.

 

Q. How do you investigate a newborn with myelomeningocele?
 

MRI spine after closure to assess associated tethered cord; MRI brain to assess Chiari II and hydrocephalus; head ultrasound if unstable; renal ultrasound; urodynamic studies; orthopedic assessment.

 

Q. How is myelomeningocele diagnosed antenatally?
 

Antenatal diagnosis is achieved through elevated maternal serum AFP, targeted obstetric ultrasound showing lemon sign, banana sign, ventriculomegaly, and spinal defect. Fetal MRI further delineates hindbrain herniation and lesion extent. Early diagnosis enables counseling, consideration of in utero repair, and planned delivery at specialized centers.

 

Q. How will you counsel the mother of a child with MMC pre-operatively regarding management and expectations?
 

I will explain that MMC requires early closure within 24–48 hours to prevent infection and protect neural tissue. Neurological deficits present at birth will not reverse and hydrocephalus evaluation and treatment may be required. Long-term risks include tethered cord, orthopedic deformities, and neurogenic bladder. I will outline a multidisciplinary plan involving neurosurgery, urology, orthopedics, and rehabilitation. I will also discuss risks of CSF leak, infection, wound issues, and the need for long-term follow-up.

 

Q. How will you manage a newborn with myelomeningocele at birth?
 

Sterile saline dressings, prone positioning, antibiotics, evaluation for hydrocephalus, and urgent closure within 24–48 hours.

 

Q. When will you operate on myelomeningocele?
 

Within 24–48 hours to prevent infection and neural injury and to allow early hydrocephalus management.

 

In patients with Myelomeningocele (MMC), hydrocephalus is managed through a combination of clinical surveillance, surgical CSF diversion, and careful timing relative to the spinal closure.

 

1. Clinical & Radiological Evaluation

 

Pre- and Post-Closure Surveillance: Monitor head circumference daily, assess fontanelles for fullness/bulging, evaluate the spinal wound for CSF leakage or tension, and observe for signs of raised ICP (irritability, vomiting, poor feeding, sunsetting eyes).

 

Neuroimaging: Baseline cranial ultrasound or rapid-sequence MRI is performed to evaluate ventricular size, brainstem distortion (Chiari II malformation), and aqueductal stenosis. Post-spinal closure imaging is routinely repeated as hydrocephalus often manifests or worsens after MMC repair.

 

2. Timing of Hydrocephalus Treatment - Simultaneous vs. Staged Repair:

 

Staged Repair (Most Common): MMC closure is performed first (within 24–48 hours of birth). The child is then monitored closely, and CSF diversion is performed only if overt signs of hydrocephalus or wound breakdown develop.

 

Simultaneous Repair: Reserved for infants presenting with severe, obvious hydrocephalus (marked ventricular enlargement or high fontanelle tension) at birth to prevent high CSF pressure from causing spinal repair breakdown or CSF leakage.

 

3. Surgical Modalities

Ventriculoperitoneal (VP) Shunt:

 

Gold Standard / Primary Option: Historically and currently the most common treatment (~80% of MMC infants eventually require a VP shunt).

 

Valve Selection: Programmable valves with anti-siphon devices are preferred to minimize complications over time.

 

Endoscopic Third Ventriculostomy with Choroid Plexus Cauterization (ETV/CPC):

 

Alternative to Shunting: Combining ETV with CPC significantly improves success rates in infants under 6 months compared to ETV alone.

 

Indication: Preferred in selected patients to avoid lifelong shunt dependency, particularly when aqueductal stenosis is present and the prepontine cistern is patent on imaging.

 

4. Associated Considerations (Chiari II & Wound Integrity)

Chiari II Malformation: Hydrocephalus exacerbates hindbrain herniation. Decompressing the ventricles often improves Chiari II-related symptoms (stridor, vocal cord paralysis, apnea, or swallowing difficulties).

 

Spinal Repair Protection: Untreated hydrocephalus increases back wound tension, leading to CSF fistula formation and a dramatically higher risk of meningitis. Controlling ventricular pressure directly protects the spinal closure site.

 

Surgical Technique for MMC Closure:

 

I will begin by positioning the newborn prone with the sac well protected on a sterile, moist dressing. I will pad the chest, pelvis, and extremities, ensuring no pressure is placed on the exposed neural placode. After wide antiseptic preparation, I will drape the entire back to allow free mobilization of soft tissues.

 

I will first outline the incision. I will plan a fusiform elliptical incision around the base of the sac, incorporating dysplastic or epithelialized skin while preserving as much healthy skin as possible for closure. I will incise circumferentially through the epithelial–neural junction. As I deepen the incision, I will enter the sac if present and allow CSF to drain in a controlled fashion. Once the sac is opened, I will widely expose the underlying neural placode.

 

At this point, I will use the operating microscope. I will carefully examine the placode to identify the true neural tissue and distinguish it from adherent membranes or epithelium. I will use sharp microsurgical dissection to separate the placode margins from the epithelialized skin. These adhesions may be delicate or fibrous, and I will free the neural edges circumferentially until the placode is completely mobilized from the surrounding tissues. If there is a transitional zone where skin or fibrous tissue blends with the placode, I will sharply define this interface to prevent tethering at closure.

 

Once the placode is circumferentially free, I will begin the neural reconstruction. I will gently lift the lateral margins of the placode and identify the medullary folds. Using microforceps and fine sutures if needed, I will approximate these lateral neural folds toward the midline. My goal will be to re-tubularize the neural plate into a closed neural tube configuration. I will avoid traction, twisting, or compression on the neural tissue. If the placode is wide and cannot be completely tubularized, I will approximate it as much as safely possible to reduce its exposed surface and create a smooth contour under the dura.

 

I will then focus on reconstructing the dura. I will identify the dysplastic dura around the margins of the bony defect. Using meticulous sharp and blunt dissection, I will separate the dura from underlying neural tissue, especially where it may be fused to the placode due to the congenital defect. This step requires careful attention to avoid injuring neural elements. I will extend the dissection laterally and inferiorly to mobilize the dura until I obtain edges that can be approximated without tension. If the dura is insufficient or too thin, I will harvest or place a dural substitute. I will perform a watertight dural closure using fine interrupted sutures, ensuring no gaps are left that could cause postoperative CSF leakage. I will ensure the reconstructed neural tube lies comfortably within the dural sac without compression or angulation.

 

After completing the dural layer, I will address the muscle and fascial closure in multiple layers. I will mobilize the paraspinal muscles from their attachments along the defect, elevating them as needed to achieve a midline advancement. I will approximate the muscle and fascia layers over the dural repair in a tension-free manner to create robust, vascularized coverage. I will ensure no dead space remains that could predispose to CSF pooling or infection.

 

I will reassess the remaining skin to ensure it can be closed without tension. If primary closure is possible, I will perform a layered closure with careful attention to preserving skin vascularity. For larger defects or tight margins, I will design rotational or advancement flaps to achieve a tension-free, well-perfused skin closure. I will verify that the final closure sits comfortably over the reconstructed dura and neural tube without tension points.

 

Postoperatively, I will keep the infant prone and monitor closely for CSF leakage, wound breakdown, and hydrocephalus progression. I will initiate early evaluation by urology and orthopedics, and arrange follow-up imaging to assess the repair and guide decisions regarding shunt placement if hydrocephalus develops.

 

Q. How will you close the myelomeningocele defect?
 

I will try closing the defect in at least 5 layers. After re-tubularizing the neural placode, I will first achieve a watertight dural closure, either primarily or with a dural graft. The second layer is reconstruction of the lumbodorsal fascia or thoracolumbar fascia, which I will approximate over the dura when present. The third layer consists of paraspinal muscle advancement, where I will mobilize and bring the muscle bellies to the midline to provide vascularized coverage. The fourth layer is the subcutaneous tissue, which I will gently approximate without tension to eliminate dead space. The fifth and final layer is the skin, which I will close directly or with rotation/advancement flaps to ensure a tension-free, well-perfused final closure. 

 

Q. What are the perioperative complications during repair of myelomeningocele?
 

Perioperative complications include injury to neural tissue during placode dissection, excessive bleeding from dysplastic dura or paraspinal muscles, temperature instability in the neonate, anesthetic difficulties including airway or ventilation issues in prone positioning, inadvertent CSF loss causing hemodynamic instability, difficulty achieving dural mobilization leading to incomplete watertight seal, vascular compromise of skin flaps, and placode torsion or kinking during re-tubularization. 

 

Intraoperative contamination of the exposed neural tissue or sac can increase risk of meningitis. Large defects may also predispose to venous bleeding from epidural plexus, and thoracic lesions may risk respiratory compromise. Some infants develop intraoperative apnea or bradycardia related to Chiari II brainstem dysfunction.

 

Q. What postoperative complications may occur after MMC repair?
 

Postoperative complications include CSF leak, pseudomeningocele, wound dehiscence, superficial or deep wound infection, and meningitis. Hydrocephalus may progress, requiring early VP shunt placement. Tethered cord can develop later due to scarring at the repair site. Skin flap necrosis may occur if closure was under tension. Shunt-related issues include infection, obstruction, or over-drainage. Respiratory dysfunction can worsen in infants with severe Chiari II, and urological deterioration may occur due to neurogenic bladder. Long-term complications include retethering, syringomyelia, and chronic pain.

 

Q. What is the prognosis after MMC repair?
 

Depends on lesion level, early closure, hydrocephalus control. High lumbar/thoracic lesions have poor ambulation; lower lesions may walk. Lifelong tethering risk persists. Renal preservation depends on early urological care. Cognitive outcome relates to hydrocephalus and brain anomalies.

 

Q. What is the MOMS Trial and what were its key findings?
 

The Management of Myelomeningocele Study (MOMS Trial) was a landmark randomized controlled trial comparing prenatal (in utero) repair of myelomeningocele with standard postnatal repair. It demonstrated that prenatal repair significantly reduced the need for ventriculoperitoneal shunting, improved hindbrain herniation associated with Chiari II malformation, and improved motor outcomes at 30 months of age. However, prenatal repair carried increased maternal risks including uterine dehiscence, preterm birth, and complications related to hysterotomy, limiting its applicability to highly selected centers and patients.

 

Q. How will you counsel parents regarding the risk of recurrence in subsequent pregnancies?
 

Recurrence risk is 2–3% after one affected pregnancy and around 10% after two affected pregnancies. High-dose folic acid (4 mg/day) one month pre-conception through the first trimester reduces recurrence by ~70%. Genetic counseling is recommended.

 

Q. What are the recent advancements in management, including in utero surgery?
 

Advancements include fetal surgery (open or fetoscopic) modeled after the MOMS Trial. Benefits include reduced hindbrain herniation and shunt dependence. Risks include maternal morbidity and preterm birth. Minimally invasive fetoscopic approaches are evolving, with improved perioperative fetal monitoring and neonatal support.