High Yield Overview
Myelomeningocele
Open Neural Tube Defect | Multidisciplinary Lifelong Care
1 in 1000Incidence (Variable)
L3-L4Most Common Level
LatexAllergy MANDATORY
Chiari IIUniversal CNS Finding
Functional Neurological Level
T10-T12 (Thoracic)
PatternFlail lower limbs. No hip/knee control.
TreatmentWheelchair / Standing Frame
L1-L2 (High Lumbar)
PatternHip flexion only (Psoas).
TreatmentWheelchair / KAFO
L3-L4 (Mid Lumbar)
PatternQuads present. No Glutei.
TreatmentKAFO / Crutches
L5 (Low Lumbar)
PatternTibialis Anterior/Tensor Fascia. Hip abductors.
TreatmentAFO / Crutches
S1-S2 (Sacral)
PatternCalf weakness only. Bladder affected.
TreatmentAFO / Independent
Critical Must-Knows
- Definition: Failure of neural tube closure (3-4 weeks gestation). Exposed spinal cord and meninges.
- Latex Allergy: Assume ALL MMC patients are allergic. 50% will develop clinical allergy. Do NOT use latex gloves or catheters.
- Chiari II Malformation: Present in nearly all MMC patients. Cerebellar tonsils herniate into foramen magnum. Causes hydrocephalus.
- Tethered Cord: Progressive neurological deterioration due to scar tethering. Look for new scoliosis, pain, or changing bladder function.
- Folic Acid: Reduces incidence by 70%. Standard public health measure.
Examiner's Pearls
- "The FUNCTIONAL level is often 1-2 segments WORSE than the anatomical level.
- "Sensation is often better preserved than motor (Sacral sparing).
- "Assume shunt malfunction until proven otherwise in any unwell MMC patient.
- "Never use latex! (Tubing, gloves, Foley).
Critical MMC Pitfalls
Latex Allergy
Life Threatening. Anaphylaxis risk. Use non-latex gloves, catheters, IV tubing. Mark charts CLEARLY.
Shunt Failure
Silent Killer. Any headache, vomiting, irritability, or drowsiness = Shunt series + CT Head STAT.
Tethered Cord
Surgical Emergency. New neuro deterioration, scoliosis, or bladder changes = MRI Spine URGENT for tethering.
Pressure Sores
Silent Destroyer. Insensate skin. Brace/Cast breakdown. Ischium/Sacrum ulcers. Prevent with vigilance.
At a Glance: Neural Tube Defects
| Defect | Neural Elements | Prognosis |
|---|---|---|
| Spina Bifida Occulta | None exposed (Covered) | Excellent (Often incidental) |
| Meningocele | Meninges only (CSF sac) | Good (Neurologically normal) |
| Myelomeningocele | Cord + Roots exposed | Variable (Level dependent) |
| Myeloschisis | Open placode (No sac) | Poor (High lesion common) |
Mnemonic
I LOVE Q-TIPSLevel by Muscle
I
Iliopsoas
L1-L2 (Hip Flexion)
L
Liopsoas
L2-L3 (Hip Flexion/Adduction)
O
Obturator
L2-L4 (Adduction)
V
Vastus (Quads)
L3-L4 (Knee Extension)
E
Extensors (Tib Ant)
L4-L5 (Ankle Dorsiflexion)
Q
Quadratus (Gluteus Med)
L4-L5-S1 (Hip Abduction)
T
Triceps Surae
S1-S2 (Plantar Flexion)
Memory Hook:Myotome Map for MMC.
Mnemonic
BEAKSChiari II Features
B
Beaking
Tectal plate beaking
E
Elongation
Brainstem elongation (Medulla herniated)
A
Absence
Absent septum pellucidum / Corpus callosum hypoplasia
K
Kinking
Kinking of brainstem at cervicomedullary junction
S
Syrinx
Syringomyelia (common)
Memory Hook:MRI findings of Arnold-Chiari Type II.
Mnemonic
SPASMTethered Cord Signs
S
Scoliosis
New or progressive curve
P
Pain
Back or leg pain (often radicular)
A
Asymmetry
Motor or sensory asymmetry
S
Sphincter
Bowel/Bladder dysfunction (new incontinence)
M
Motor
Weakness or spasticity
Memory Hook:Signs of secondary tethering.
Overview and Epidemiology
Definition: Myelomeningocele (MMC) is the most severe form of spina bifida cystica. It is an open neural tube defect (NTD) where the spinal cord and nerve roots are exposed through a defect in the vertebral arches and skin. The neural tissue (placode) lies on the surface of the back, surrounded by meninges and CSF.
Epidemiology:
- Incidence: Approximately 1 in 1000 live births (variable by geography and folic acid fortification).
- Prevention: Periconceptional folic acid supplementation (0.4mg daily) reduces risk by 50-70%.
- Prenatal Diagnosis: Elevated maternal serum AFP (MSAFP), detailed ultrasound (Lemon sign, Banana sign).
- Trends: Incidence decreasing due to folic acid fortification and prenatal diagnosis/termination.
Genetics and Recurrence:
- Recurrence Risk: If one child is affected, the recurrence risk is 2-4%. If two children are affected, risk increases to 10%.
- Folic Acid (Recurrence): High-dose folic acid (4mg daily) is recommended for subsequent pregnancies if there is a history of NTD.
- Genetic Syndromes: MMC is usually sporadic, but can be associated with trisomy 18 or Meckel-Gruber syndrome.
Pathophysiology and Anatomy
Embryology: The neural tube closes between days 21-28 of gestation. Failure of posterior neuropore closure results in MMC. This results in:
- Exposure of Placode: Direct damage and ongoing leakage of CSF.
- Loss of Innervation: Motor and sensory loss below the level.
- Skeletal Deformity: Muscle imbalance drives deformity (hip dislocation, clubfoot, scoliosis).
- Associated CNS Malformations: Chiari II, hydrocephalus.
Chiari Type II Malformation: Present in almost all patients with MMC. The hindbrain (cerebellum, brainstem) herniates through the foramen magnum. This causes:
- Hydrocephalus: 80-90% require shunting.
- Brainstem Dysfunction: Stridor (vocal cord paralysis), apnea, swallowing difficulty.
- Syringomyelia: Cavity formation within the cord.
Tethered Cord: After initial MMC closure, scar formation tethers the neural placode to the dural repair. During growth, differential traction on the cord causes secondary neurological deterioration. This is often insidious.
Classification
Functional Neurological Level
The key to prognosis and treatment planning. Determined by the LOWEST functional myotome.
| Level | Key Muscle | Ambulation Potential |
|---|---|---|
| Thoracic | None | Wheelchair dependent |
| L1-L2 | Iliopsoas (Hip flexion) | Therapeutic walking only (HKAFO) |
| L3 | Quadriceps (Knee extension) | Household ambulation (KAFO) |
| L4 | Tibialis Anterior (Dorsiflexion) | Community ambulation (AFO, Crutches) |
| L5 | Gluteus Medius (Hip abduction) | Community ambulation (AFO, minimal aids) |
| S1-S2 | Gastrocnemius (Plantarflexion) | Independent ambulation (AFO optional) |
The functional level is often 1-2 segments worse than the anatomical (vertebral) level.
Clinical Assessment
Neonatal Assessment:
- Urgent Coverage: The open placode must be surgically covered within 24-48 hours to prevent meningitis.
- Neurological Exam: Document motor level (lowest functioning myotome). Check reflexes. Observe spontaneous movement.
- Head Circumference: Monitor for hydrocephalus (increasing HC, bulging fontanelle, sunsetting eyes).
Orthopedic Assessment:
- Spine: Kyphosis (Gibbus)? Scoliosis?
- Hips: Dislocated (common in L3-L4)? Contractures?
- Feet: Clubfoot? Vertical Talus? Calcaneovalgus?
- Overall Posture: Spinal alignment. Pelvic obliquity.
Neurological Monitoring (Lifelong):
- Tethered Cord Surveillance: Annual neuro exam and urodynamics. MRI if any new symptoms (SPASM).
- Shunt Function: Low threshold for shunt series/CT if any change in cognition, headaches, nausea.
Investigations
Clinical Imaging Gallery
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Initial Imaging:
- MRI Brain: Evaluate Chiari II, hydrocephalus, corpus callosum.
- MRI Spine: Assess conus level, syrinx, tethering (if suspected later).
- Hip X-rays: AP Pelvis. Assess hip dysplasia/dislocation.
- Spine X-rays: Evaluate kyphosis, scoliosis, congenital vertebral anomalies.
Urological Workup:
- Urodynamics: Baseline and annual. Assess detrusor function (hyperreflexic vs areflexic), sphincter function.
- Renal Ultrasound: Annual. Monitor for hydronephrosis/reflux.
- VCUG: As indicated.
Functional Assessment:
- Gait Analysis: For ambulatory patients, to plan orthotic needs.
- FIM (Functional Independence Measure): Overall function.
Management Algorithm
📊 Management Algorithm
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Neonatal Management (First 48 Hours)
- Prone Positioning: Protect the sac from rupture or contamination.
- MMC Closure: Urgent surgery within 24-48 hours (Neurosurgery). Goal: Watertight dural closure, skin coverage.
- VP Shunt: Often placed at the same time or shortly after MMC closure (if hydrocephalus develops).
- Latex Precautions: Implement from birth.
- Multidisciplinary Team: Neurosurgery, Orthopaedics, Urology, Physical Therapy, Social Work.
The MOMS trial showed fetal MMC repair (prenatal closure) reduces shunt requirement and improves motor function.
Surgical Technique
Hip in MMC
Dislocation is COMMON (especially L3-L4): Strong hip flexors (Psoas), absent glutei (Gluteus Med/Max).
Management Philosophy:
- Thoracic/High Lumbar (No ambulation potential): Leave the hip dislocated. Reduction surgery does NOT improve function and has high complication rate.
- L3-L4 (Ambulatory potential): Controversial. Some advocate for reduction, others leave alone.
- L5-S1 (Good ambulatory potential): Treat similar to DDH. Reduction may improve gait efficiency.
Procedures (if performed):
- Soft tissue releases (Adductor, Psoas).
- Open Reduction +/- Femoral/Pelvic Osteotomy (for older kids).
- Iliopsoas Transfer (Mustard/Sharrard): Transfer Psoas to Greater Trochanter to create abductor. Very high failure rate and rarely done now.
The key question: Will reducing this hip improve this child's function or quality of life?
Complications
Key Complications
| Complication | Cause | Management |
|---|---|---|
| Shunt Malfunction | Blockage / Infection | Shunt series, CT Head, Urgent Neurosurgery |
| Tethered Cord | Scar tissue from repair | MRI Spine, Urodynamics, Surgical Untethering |
| Pressure Sores | Insensate skin, Brace/Cast | Prevention, Wound Care, Plastic Surgery |
| Latex Anaphylaxis | Protein allergy (sensitization) | Strict latex avoidance, Epi-Pen |
| Pathologic Fracture | Osteopenia, Insensate limb | Often minimally symptomatic. Cast/Splint. |
| Renal Failure | Neurogenic bladder, Reflux | CIC, Anticholinergics, Vesicostomy |
Latex Allergy:
- Affects 30-70% of MMC patients (depending on definition).
- Sensitization occurs from repeated mucosal exposures (surgeries, catheterizations).
- Prevention: Latex-free environment from birth.
- Signs: Urticaria, Angioedema, Bronchospasm, Anaphylaxis.
Postoperative Care
- Wound Care: Paramount due to insensate skin. Padding. Frequent skin checks.
- Latex Free: Non-latex catheters, gloves, IV tubing.
- Positioning: Avoid pressure on surgical sites and insensate areas.
- Rehabilitation: Intensive physio for gait training post lower limb surgery.
Outcomes
- Survival: Greater than 80% survive to adulthood with modern care.
- Ambulation: Sacral levels walk independently. Thoracic levels are wheelchair-dependent.
- Cognition: Approximately 80% have normal IQ, though learning disabilities are common.
- Quality of Life: Can be excellent with multidisciplinary support.
- Mortality: Primarily from renal failure and shunt complications.
Evidence Base
MOMS Trial
Key Findings:
- RCT comparing prenatal vs postnatal MMC repair.
- Prenatal surgery reduced need for VP shunt (40% vs 82%).
- Improved motor function at 30 months.
- Increased preterm birth risk.
Clinical Implication: Fetal surgery is now an option at specialized centers.
Limitation: Requires highly specialized centers. Maternal risk.
Hip Dislocation Outcome
Key Findings:
- Retrospective review of hip surgery in MMC.
- High complication rate with open reduction.
- No clear functional benefit in non-ambulatory patients.
Clinical Implication: Avoid routine hip reduction in thoracic/high lumbar levels.
Limitation: Retrospective
Tethered Cord Surgery
Key Findings:
- Early untethering can stabilize or improve function.
- Delay in surgery leads to irreversible deficits.
- Urodynamic changes often precede clinical symptoms.
Clinical Implication: Low threshold for MRI and urodynamics if any new symptoms.
Limitation: Case series
Folic Acid Prevention
Key Findings:
- RCT showing folic acid supplementation reduced NTD recurrence by 72%.
- Led to public health policy of food fortification worldwide.
Clinical Implication: Primary prevention is key.
Limitation: Recurrence study (higher risk population)
Latex Allergy
Key Findings:
- Described the high prevalence of latex sensitization in spina bifida.
- Repeated surgical exposure is a major risk factor.
Clinical Implication: Latex-free environment from birth is standard of care.
Limitation: Observational
Viva Scenarios
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
The Newborn with Open Lesion
EXAMINER
"Outline your initial management."
EXCEPTIONAL ANSWER
**Urgent Multidisciplinary Approach.**
1. **Positioning**: Place prone on sterile drape. Cover sac with warm saline-soaked gauze.
2. **Latex Precautions**: Implement immediately.
3. **Neonatology**: Standard neonatal resuscitation/assessment.
4. **Neurosurgery**: Urgent MMC closure within 24-48 hours. Assess for hydrocephalus.
5. **Orthopaedics Consult**: Document neurological level. Assess limbs for deformity, hip dislocation, clubfoot.
6. **Urology Consult**: Baseline urodynamics (later). CIC teaching.
7. **Counsel Parents**: Explain diagnosis, prognosis (based on level), multidisciplinary lifelong care.
KEY POINTS TO SCORE
Urgent closure (less than 48h)
Prone, Saline dressing
Latex-Free from birth
Document neuro level
COMMON TRAPS
✗Delaying closure (Meningitis risk)
✗Forgetting latex precautions
LIKELY FOLLOW-UPS
"What is the most common cause of death?"
"What is Chiari II?"
VIVA SCENARIOStandard
The Dislocated Hip (L3)
EXAMINER
"Discuss your approach to this hip."
EXCEPTIONAL ANSWER
**Conservative Management is likely best.**
1. **Context**: L3 level means Quads present, but no Glutei/lateral hip muscles.
2. **Ambulation**: He is a household ambulator - this may not improve with hip reduction.
3. **Evidence**: Studies (Wright et al) show hip reduction in paraplegic MMC has high failure rate and does NOT necessarily improve function.
4. **My Approach**:
- Acknowledge parental concern.
- Explain that dislocation in MMC is different from DDH. Not painful.
- Focus on optimizing bracing.and gait training.
- Surgery ONLY if the hip is causing pain or functional impairment.
**If surgery is considered**: Soft tissue release + VDRO + Dega. High revision rate.
KEY POINTS TO SCORE
Function over radiographs
High failure rate if paraplegic
Discussion with family
COMMON TRAPS
✗Operating on asymptomatic dislocated hip in non-ambulator
✗Expecting surgery to make child walk
LIKELY FOLLOW-UPS
"What is the Mustard/Sharrard procedure?"
"When WOULD you operate on an MMC hip?"
VIVA SCENARIOStandard
The Deteriorating Child
EXAMINER
"What is your differential and workup?"
EXCEPTIONAL ANSWER
**High concern for Tethered Cord (vs Shunt Malfunction).**
1. **Differential**:
- *Tethered Cord*: SPASM symptoms. Progressive scoliosis, pain, sphincter change.
- *Shunt Malfunction*: Headache, vomiting, cognitive change. Can cause vague symptoms.
- *Syringomyelia*: Progressive weakness.
2. **Workup**:
- *Shunt Series + CT Head*: Rule out shunt failure first (life-threatening).
- *MRI Spine (Entire)*: Look for tethering at repair site, syrinx.
- *Urodynamics*: Compare to baseline. Change in bladder function is key sign.
3. **If Tethered Cord Confirmed**:
- *Neurosurgery referral*: Surgical untethering.
- Early surgery prevents irreversible deficits.
KEY POINTS TO SCORE
Tethered cord until proven otherwise
Rule out shunt failure first
MRI + Urodynamics
COMMON TRAPS
✗Blaming growth for all changes
✗Delaying investigation (leads to irreversible deficit)
LIKELY FOLLOW-UPS
"What is the risk of re-tethering?"
"What urodynamic findings suggest tethered cord?"
MCQ Practice Points
Chiari II vs Chiari I
Q: What is the key difference between Chiari I and Chiari II malformation? A: Chiari I is tonsillar herniation only (often acquired). Chiari II is seen with MMC and includes brainstem herniation, tectal beaking, and hydrocephalus.
Latex Allergy Prevention
Q: What is the single most important measure to prevent latex allergy in MMC? A: Latex-free environment from birth. Avoid all latex exposure (gloves, catheters, balloons).
Ambulatory Prognosis
Q: What is the main determinant of ambulatory potential in MMC? A: The Functional Neurological Level. Patients with L5 or lower levels have the best ambulatory potential. Thoracic levels are wheelchair dependent.
Folic Acid
Q: By how much does folic acid supplementation reduce the risk of neural tube defects? A: Approximately 50-70% reduction.
Hip Surgery Indication
Q: In a child with thoracic-level MMC and bilateral hip dislocation, should you reduce the hips? A: No. Hip reduction in non-ambulatory patients has high failure rates and does not improve function. Leave them alone unless painful.
Australian Context
- Folic Acid Fortification: Mandatory in bread flour in Australia since 2009. Has reduced NTD incidence.
- Prenatal Diagnosis: Widely available. Counseling for fetal surgery (MOMS) offered at specialized centers.
- Spina Bifida Australia: National support organization for patients and families.
- Multidisciplinary Clinics: Major pediatric hospitals run dedicated MMC clinics (e.g., RCH, Westmead, LCCH).
High-Yield Exam Summary
Levels
- •L1-L2: Hip Flexion Only
- •L3: Quads (Knee Ext)
- •L4: Tib Ant (Dorsiflex)
- •L5: Glut Med (Abduct)
- •S1: Gastroc (Plantar)
Chiari II
- •Brainstem Herniation
- •Tectal Beaking
- •Hydrocephalus (80%)
- •Syringomyelia
- •Universal in MMC
Tethered Cord
- •S: Scoliosis (New)
- •P: Pain
- •A: Asymmetry
- •S: Sphincter (Bladder)
- •M: Motor Loss
Latex Rules
- •Assume ALL MMC allergic
- •Latex-Free from Birth
- •No latex gloves/catheters
- •Mark charts CLEARLY