Spina Bifida
Summary
Spina Bifida is the most common disabling birth defect in the US/UK. It is a Neural Tube Defect (NTD) resulting from failure of the embryonic neural tube to close at the caudal end (Day 28). The spectrum ranges from asymptomatic Spina Bifida Occulta to severe Myelomeningocele (Open Spina Bifida), which causes paraplegia, neurogenic bladder, and hydrocephalus. Folic acid supplementation has significantly reduced incidence. [1,2]
Clinical Pearls
Latex Allergy: Up to 70% of Spina Bifida patients have a serious latex allergy (due to early and repeated exposure to latex gloves/catheters during surgeries). ALWAYS treat Spina Bifida patients as Latex Allergic. Use latex-free catheters and gloves.
The VP Shunt: 80-90% of children with Myelomeningocele have Hydrocephalus (associated Arnold-Chiari II Malformation). If a Spina Bifida child presents with vomiting, headache, or lethargy, suspect Blocked Shunt immediately.
Occulta Markers: A hairy patch, deep sacral dimple (above the gluteal crease), or lipoma on the lower back can signify underlying spinal dysraphism.
Stats
- Incidence: 1 in 1000 live births (declining due to screening/folate).
- Risk Factors: Low Folate, Maternal Diabetes/Obesity, Sodium Valproate use, Previous NTD pregnancy.
Prevention
- Folic Acid: 400mcg daily (start before conception until 12 weeks).
- High Dose (5mg): Required if: Previous NTD, Diabetic, Taking Anti-epileptics, BMI > 30.
Embryology
- The neural plate folds to form the neural tube. Closure occurs zipper-like.
- Anencephaly: Failure of cranial closure (Day 25). Fatal.
- Spina Bifida: Failure of caudal closure (Day 27-28).
Types
- Spina Bifida Occulta: Defect in vertebral arch only. Cord/Meninges normal. Covered by skin. Often asymptomatic.
- Meningocele: Sac of meninges protrudes through defect. Cord remains in canal. Neuro function usually preserved.
- Myelomeningocele (Severe): Sac contains meninges AND spinal cord/nerve roots. Exposed neural tissue. Neuro deficit invariably present.
| Condition | Features |
|---|---|
| Myelomeningocele | Neural tissue visible in sac. Transilluminates poorly. |
| Meningocele | Fluid filled sac only. Transilluminates brightly. |
| Sacrococcygeal Teratoma | Solid/Cystic mass. Not usually associated with neuro deficit. |
| Lipomyelomeningocele | Fatty mass under skin connected to cord. |
Neurological
- Motor: Flaccid paralysis of lower limbs (level dependent).
- Sensory: Anaesthesia (risk of pressure sores/burns).
- Reflexes: Absent.
Autonomic (Neurogenic Bladder/Bowel)
- Bladder: Incontinence, Retention (High pressure bladder -> Renal damage).
- Bowel: Constipation / Soiling.
CNS (Chiari II Malformation)
- Hydrocephalus: Enlarging head, "Sunsetting" eyes.
- Hindbrain Herniation: Difficulty swallowing, Apnoea, Stridor.
Musculoskeletal
- Talipes Equinovarus (Club foot): Due to in-utero paralysis.
- Scoliosis.
Antenatal
- Ultrasound: "Lemon sign" (Skull shape) and "Banana sign" (Cerebellum wrapped around brainstem).
- Maternal Serum AFP: Elevated.
- Fetal MRI: To plan repair.
Postnatal
- Examination: Assess lesion level (Lumbosacral most common). Measure OFC (Head circumference).
- Cranial Ultrasound: Assess ventricular size.
- Renal Ultrasound: Check for hydronephrosis (neurogenic bladder).
Management Algorithm
NEONATE WITH MYELOMENINGOCELE
↓
PROTECT LESION (Saline gauze)
LATEX FREE ENVIRONMENT
ANTIBIOTICS
↓
SURGICAL CLOSURE (less than 48 Hours)
• Neurosurgery to close dura & skin
• Prevents Meningitis
• Does NOT reverse nerve damage
↓
HYDROCEPHALUS MANAGEMENT
• Monitor Head Circumference / US
• Insertion of VP Shunt usually needed
↓
LONG TERM MDT
• Urology (Catheterisation - CIC)
• Orthopaedics (Hip/Foot surgery)
• Physio (Mobility/Wheelchair)
1. Fetal Surgery (The MOMS Trial)
- In-Utero Repair (at 19-25 weeks) is now an option in specialist centres.
- Benefit: Reduces need for shunting (halved) and improves motor outcome (walking).
- Risk: Maternal uterine rupture, preterm birth.
2. Urology (Crucial)
- Goal: Protect kidneys (prevent reflux/hydronephrosis) and achieve continence.
- CIC: Clean Intermittent Catheterisation (parents/child empty bladder with catheter every 4h).
- Anticholinergics: Oxybutynin (to relax bladder).
- Tethered Cord: As the child grows, the scarred cord gets stuck at the repair site. Symptoms: Deterioration in walking, new bladder issues, pain. Needs surgical de-tethering.
- Shunt Malfunction: Blockage/Infection.
- Obesity: Reduced mobility.
- Learning Difficulty: "Executive function" often impaired, though verbal IQ good ("Cocktail party personality").
- Survival: >90% reach adulthood.
- Mobility: Depends on level. L3 or above usually wheelchair bound. S1 may walk unaided.
- Continence: Most require catheters.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Folic Acid | CDC / NHS | Mandatory fortification of flour (UK 2021 policy). 400mcg/5mg rules. |
| Spina Bifida | Spina Bifida Association | Guidelines for lifetime care. |
Landmark Evidence
1. MOMS Trial (NEJM 2011)
- Management of Myelomeningocele Study.
- Randomized prenatal vs postnatal repair.
- Result: Prenatal in-utero repair reduced shunt rate from 82% to 40% and improved motor scores. Established fetal surgery as standard of care options.
2. MRC Vitamin Study (1991)
- Proved Folic Acid prevented NTDs (72% reduction).
What is Spina Bifida?
It literally means "split spine". While the baby was developing in the womb (very early, first 4 weeks), the spinal column failed to zip up completely. This leaves a gap where the spinal cord (nerves) is exposed.
What does this mean for my baby?
It depends on the type. "Hidden" spina bifida often causes no problems. "Open" spina bifida causes damage to the nerves. This usually results in weakness in the legs (trouble walking) and bladder problems.
Is surgery needed?
Yes. If the back is open, we operate within a day or two of birth to close the skin and protect the nerves from infection. This surgery stops things getting worse, but it cannot fix the nerve damage that has already happened.
What is the "Shunt"?
Most babies with this condition have fluid build-up in the brain (Hydrocephalus). We treat this by placing a small tube (shunt) under the skin to drain the fluid from the head to the tummy.
Primary Sources
- Adzick NS, et al. A randomized trial of prenatal versus postnatal repair of myelomeningocele (MOMS). N Engl J Med. 2011.
- MRC Vitamin Study Research Group. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. Lancet. 1991.
Common Exam Questions
- Prevention: "Dose of Folic acid for epileptic mother?"
- Answer: 5mg.
- Safety: "Allergy in Spina Bifida?"
- Answer: Latex (assume positive).
- Complication: "Spina Bifida child with headache/vomiting?"
- Answer: Blocked VP Shunt (Emergency).
- Assocation: "Brain anomaly?"
- Answer: Arnold Chiari II.
Viva Points
- Lemon Sign: On US, frontal bones collapse inward because the low pressure in the spine pulls the brain down.
- Tethered Cord Syndrome: Why do they get worse? The cord is stuck to the scar. As the child grows in height, the cord is stretched like a rubber band, causing ischaemia.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.