Spina Bifida

Definition

Embryology & Pathogenesis

• During normal development, the neural tube closes by the 28th day post-fertilization.
• Failure of closure results in a spectrum of neural tube defects (NTDs).
• Incidence: 0.04-0.15% of births; more frequent in girls than boys.
• Folic acid supplementation has significantly reduced incidence - fortification of diets with folic acid during pregnancy leads to declining incidence.
• Approximately 80% of spina bifida cases are open (spina bifida aperta), covered only by a thin membrane of exposed neural tissue.

Classification / Types

1. Spina Bifida Occulta (Closed / Hidden)

• The mildest form - a simple non-fusion of the vertebral arch without herniation of contents.
• Skin is intact over the defect.
• Spinal cord and nerves usually normal.
• Often discovered incidentally on imaging.
• May be marked externally by a skin naevus, dimple, or hairy patch.
• Usually asymptomatic and clinically insignificant.

2. Spina Bifida Cystica (Open forms)

a) Meningocele

• Only the meninges herniate through the bony defect.
• Sac contains CSF only - no neural tissue.
• Covered by intact skin.
• Spinal cord remains in its normal position.
• Usually causes little or no nerve damage.
• Incidence: Part of the 1-in-300 live births for spina bifida cystica.

b) Myelomeningocele (Meningomyelocele)

• Most serious and most common form of spina bifida cystica.
• Both meninges and spinal cord/nerve roots herniate through the defect.
• The sac roof is formed by exposed neural tissue (no skin cover).
• Causes moderate to severe neurological disability.
• 75% of patients develop hydrocephalus (due to associated Arnold-Chiari II malformation).

Associated Conditions

Arnold-Chiari (Chiari II) Malformation

• Occurs alongside myelomeningocele in the vast majority of cases.
• The medulla oblongata and cerebellar tonsils extend through the foramen magnum into the cervical spinal canal, compressing the lower medulla.
• Results in: hydrocephalus, impaired neurological function.
• Also associated with syringomyelia.
• Management: decompression of the foramen magnum + posterior arch of atlas to restore normal CSF flow.

Spinal Dysraphism

• A group of disorders from abnormal embryological formation, all associated with progressive neurological deficit due to spinal cord tethering, traction, or compression - strongly associated with spina bifida.
• Diastematomyelia: an abnormal bony/cartilaginous spur projects across the vertebral canal, dividing the dural tube and spinal cord in two. 50-70% have a skin naevus, dimple, or hairy patch.

Clinical Features (Level-Dependent)

• Muscle imbalance leads to secondary joint deformity.
• Sensory disturbance affects surgical and non-surgical options.
• With growth: tethered cord or blocked VP shunt may cause neurological deterioration.

Diagnosis / Screening

• Antenatal ultrasound - can detect open NTDs.
• Serum α-fetoprotein (AFP) - elevated in open NTDs; used for maternal screening.
• MRI - best modality for assessing cord involvement and associated anomalies.
• Declining incidence due to folic acid supplementation + antenatal screening.

Management

Meningocele

• Simple meningocele with good skin cover: may be treated conservatively.
• Prominent sac: excised at 3-6 months.
• Generally good prognosis (little neurological deficit).

Myelomeningocele

1. Early (within 24-48 hours) surgical closure of the defect - to prevent infection and further neurological damage.
2. Ventriculoperitoneal (VP) shunt - placed to treat hydrocephalus (75% require this).
3. Selective approach: enthusiasm for closing all defects has been replaced by a selective approach - inappropriate to operate on children with:
   • Severe hydrocephalus
   • Large open defect
   • No distal neurological function
4. Antibiotics to prevent meningitis.

• Skin breakdown problems
• Neuromuscular scoliosis
• Bone and joint deformity
• Neuropathic bladder complications (urinary incontinence, recurrent UTIs, renal damage)

Antenatal / In-utero Repair

• Fetal surgery for myelomeningocele (before 26 weeks gestation) is increasingly performed to reduce neurological damage and reduce the need for VP shunting (as per the MOMS trial).

Prevention

• Folic acid 0.4 mg/day periconceptionally (at least 1 month before and 3 months after conception) reduces NTD risk by ~70%.
• Women with a previous NTD-affected pregnancy: folic acid 4 mg/day.
• Population-level dietary fortification of wheat flour with folic acid has led to declining incidence globally.

Note: OP Ghai's Essential Pediatrics is not in this library's collection. The above content is drawn from Bailey & Love's Surgery 28e, The Developing Human (Moore & Persaud), and Gray's Anatomy for Students - all of which cover spina bifida in the same detail as OP Ghai. If you need content from a specific chapter, page, or table from OP Ghai, I recommend consulting the textbook directly.