Surgery chapters
Spinal dysraphism
Neural tube defects of the spine: spina bifida occulta, meningocele, myelomeningocele, lipomyelomeningocele, diastematomyelia and tethered cord, with their prevention, antenatal screening, newborn care, surgery, and the linked Chiari II malformation and hydrocephalus.
- Spinal dysraphism is failure of the neural tube (posterior neuropore) to close in the 4th week of fetal life; forms range from harmless spina bifida occulta to myelomeningocele, where cord and roots lie in an open sac.
- Folic acid before conception (400 micrograms, 5 mg in high-risk women) prevents many cases; raised maternal AFP and ultrasound detect them antenatally.
- An open myelomeningocele needs a moist sterile cover, closure within about 48 hours, and close watch for hydrocephalus (with Chiari II), which most babies develop and usually needs a VP shunt.
On this page
Overview
Spinal dysraphism is a group of congenital defects in which the neural tube and the bony arches behind it fail to fuse in the midline. It is a major cause of paraplegia from birth and of neuropathic bladder in children, and is closely tied to hydrocephalus.
Neural tube defects remain common in Pakistan, where pre-conception folic acid use is low. They are largely preventable.
Embryology in brief
- The neural plate folds into a tube during the 3rd–4th week after conception. The two ends (neuropores) close last.
- Failure of the anterior (cranial) neuropore → anencephaly (not compatible with life) or encephalocele (brain and meninges through a skull defect, usually occipital).
- Failure of the posterior (caudal) neuropore → spinal dysraphism, most often lumbar or lumbosacral.
Types
| Type | What is in the defect | Skin cover | Neurology |
|---|---|---|---|
| Spina bifida occulta | Missing spinous process/laminae only (often L5 or S1) | Intact; may show a hair tuft, dimple, pit, naevus, haemangioma or lipoma | Usually normal; may hide a tethered cord |
| Meningocele | Sac of meninges and CSF; cord stays in the canal | Usually skin-covered | Usually normal |
| Myelomeningocele | Sac containing spinal cord and/or nerve roots | Often open (neural placode exposed) or thin membrane | Deficit below the level (legs, bladder, bowel) |
| Myelocele (rachischisis) | Flat open plate of neural tissue, no sac | None | Severe deficit |
| Lipomyelomeningocele | Fatty mass joined to the cord passes through the defect into the lumbosacral fat | Skin-covered lump | Tethering → bladder dysfunction, progressive deficit |
| Diastematomyelia (split cord) | Bony or cartilaginous spur splitting the cord and dura in two | Skin marker in about half to two-thirds | Tethering; unilateral foot deformity |
| Dermal sinus | Skin-lined tract from a dimple into the canal | Small pit above the natal cleft | Risk of recurrent meningitis |
Myelomeningocele is the commonest and most serious form of spina bifida cystica; meningocele is much rarer (about 5% of cystic cases) and has a far better outlook.
A midline lumbosacral hairy patch, dimple above the natal cleft, lipoma or naevus is not cosmetic. It may mark an underlying tethered cord or diastematomyelia: image with ultrasound (in infants) or MRI.
"Myelo = marrow": if the word has "myelo", the cord is in the sac and there will be a deficit.
Risk factors and prevention
- Folate deficiency and previous affected pregnancy or family history.
- Antiepileptic drugs, especially valproate and carbamazepine.
- Maternal diabetes and obesity.
- Prevention: folic acid 400 micrograms daily from before conception until 12 weeks of pregnancy. Women at high risk (previous NTD, on antiepileptics, diabetes, obesity) take 5 mg daily. Food fortification also helps; check current national guidance.
Antenatal diagnosis
- Maternal serum alpha-fetoprotein (AFP) is raised with open defects; screening at 15–18 weeks.
- Amniocentesis for amniotic AFP (and acetylcholinesterase) if needed.
- Mid-trimester ultrasound detects about 95% of cases (signs include the "lemon" skull and "banana" cerebellum of Chiari II).
- Allows counselling, delivery planning in a centre with neurosurgery, and in some centres fetal surgery.
Clinical features
At birth (open defects)
- A sac over the lumbar or lumbosacral spine; open lesions show the neural placode in the roof, red and moist, merging into thin skin. A meningocele is covered by normal-looking skin.
- Leg weakness (usually lower motor neurone, flaccid; sometimes mixed with spastic segments), sensory loss, patulous anus, dribbling urine.
- Deformities: talipes equinovarus (club foot), calcaneovalgus, hip dislocation, knee recurvatum, kyphosis.
- Head: big head, tense fontanelle (hydrocephalus may only appear after the back is closed, when the CSF leak stops).
Later presentation (closed defects and tethering)
- Back or leg pain, worsening gait, foot deformity (especially one-sided pes cavus), scoliosis, new bladder symptoms (enuresis, frequency, incontinence) in a growing child.
- These are features of tethered cord syndrome.
Associated conditions
Chiari malformations
| Type | Features |
|---|---|
| Chiari I | Cerebellar tonsils descend more than 5 mm below the foramen magnum; young adults; cough headache, ataxia, lower cranial nerve signs, syringomyelia; treat with foramen magnum decompression |
| Chiari II (Arnold-Chiari) | Descent of the cerebellar vermis, tonsils and brainstem; always with myelomeningocele; causes hydrocephalus, stridor, apnoea, swallowing problems in infancy |
Myelomeningocele is always accompanied by a Chiari II malformation. This is why hydrocephalus is so common in these babies.
Chiari I is the adult form with no spina bifida (tonsils only); Chiari II is the infant form with myelomeningocele (vermis and brainstem too). Do not mix them up.
Hydrocephalus
- Develops in most babies with myelomeningocele (Bailey & Love quotes about 75%; Apley's notes about 90% need active treatment).
- Watch head circumference, fontanelle and ultrasound after back closure.
- Treat with a VP shunt. Later headaches, vomiting or a change in neurology should prompt a check for shunt blockage or infection.
Syringomyelia
A fluid cavity in the cord (often with Chiari malformations): "cape" (shawl) loss of pain and temperature with preserved touch, hand weakness and wasting, scoliosis. Treat the Chiari first (posterior fossa decompression).
Investigations
- Ultrasound of the spine in young infants and of the head for hydrocephalus.
- MRI of the whole spine and brain: cord level, tethering, split cord, syrinx, Chiari.
- Plain x-rays/CT: bony defect, vertebral anomalies, a midline bony spur (diastematomyelia).
- Urodynamics and renal ultrasound: neuropathic bladder, reflux, hydronephrosis.
Management
Newborn with an open myelomeningocele
- Nurse prone or on the side; protect the sac.
- Cover with a sterile, moist (saline-soaked) non-adherent dressing to prevent drying and infection.
- No latex gloves or equipment from day one (high risk of latex allergy).
- Antibiotics as per unit policy; full examination, record the neurological level (muscle charting), check for hydrocephalus and other anomalies.
- Neurosurgical closure within about 48 hours: preserve all neural tissue, close the dura watertight, and close skin (undermining or flaps). This lowers the risk of meningitis and ventriculitis. Some centres choose not to operate when the lesion is very high with severe hydrocephalus and no function below.
- VP shunt for hydrocephalus, often a few weeks after back closure.
Meningocele
- With good skin cover: may be managed conservatively, or excised electively at about 3–6 months.
- Thin or leaking cover: early repair.
Closed defects and tethered cord
- Tethered cord syndrome: a thick filum terminale, lipoma, scar after earlier repair or a bony spur pins the cord low; growth stretches it, causing progressive deficits.
- MRI confirms; surgical untethering (cutting the filum, removing the spur or lipoma) is best done before further loss, as recovery of established deficits is limited.
Long-term multidisciplinary care
| Problem | Approach |
|---|---|
| Neuropathic bladder | Clean intermittent catheterisation, anticholinergics, botulinum toxin, bladder augmentation; protect the kidneys |
| Neuropathic bowel | Bowel programme, washouts |
| Orthopaedic | Physiotherapy, splints; correct club foot, hip and spinal deformities; beware pathological fractures in weak, osteoporotic legs |
| Skin | Pressure care; insensate skin ulcerates easily |
| Mobility | Depends on motor level: children with lesions below L4 have active knee extension (quadriceps) and are encouraged to walk; lesions above L1 usually end up in a wheelchair |
| Learning and psychosocial support | Many have normal intelligence; raised ICP and shunt problems can impair learning |
The motor level of the lesion is the best predictor of walking. Quadriceps (L3–L4) working = useful walking potential.
Prognosis
Without closure most babies with open myelomeningocele die in the first year. With early closure, antibiotics and shunting, about half of those who survive the first day reach school age, but long-term problems with bladder, bowel, skin, spine and joints persist. Spina bifida occulta is usually harmless; meningocele generally has an excellent outlook.
Expect: the differences between occulta, meningocele and myelomeningocele (cord in the sac means deficit), skin markers of occult dysraphism, failure of the posterior neuropore in the 4th week, folic acid 400 micrograms (5 mg for high risk), raised maternal AFP and ultrasound at 15–18 weeks, Chiari II always with myelomeningocele and the resulting hydrocephalus needing a VP shunt, newborn care with a moist sterile dressing, prone nursing, latex precautions and closure within 48 hours, tethered cord presenting as progressive gait, foot and bladder problems in a growing child, diastematomyelia, and walking potential set by the motor level (below L4 can walk).
Quick revision
- Occulta: bony gap only (L5/S1), skin markers, usually harmless.
- Meningocele: meninges + CSF, skin-covered, normal neurology.
- Myelomeningocele: cord in sac, deficits, Chiari II, hydrocephalus.
- Prevention: folic acid 400 micrograms (5 mg if high risk) pre-conception to 12 weeks.
- Screening: maternal AFP 15–18 weeks, ultrasound (lemon and banana signs).
- Newborn: prone, moist sterile dressing, no latex, close within 48 h, shunt later.
- Tethered cord: progressive deficit with growth; MRI; untether early.
- Walking likely if lesion below L4.
Written by The House Job from standard references (Bailey & Love; Apley's System of Orthopaedics and Fractures).
FAQ
What is the difference between a meningocele and a myelomeningocele?
A meningocele contains only meninges and CSF with the cord in its normal place, so the child is usually neurologically normal; a myelomeningocele contains cord or nerve roots and causes paralysis and bladder problems below the level.
How much folic acid prevents neural tube defects?
400 micrograms daily from before conception to 12 weeks of pregnancy, and 5 mg daily for women at high risk, such as those with a previous affected baby or on antiepileptic drugs.
Why do children with myelomeningocele get hydrocephalus?
They almost all have a Chiari II malformation, in which the hindbrain is pushed down through the foramen magnum and blocks CSF flow.
What does a tuft of hair over the lower back suggest?
A possible occult spinal dysraphism such as a tethered cord or split cord, which should be imaged.
When is an open myelomeningocele closed?
Within about 48 hours of birth, to stop the exposed neural tissue drying out and to prevent meningitis.