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1. What does the neural tube develop from?
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By an infolding of the neural ectoderm.
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2. What do the surrounding meninges and vertebral column develop from?
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Mesodermal tissue.
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3. What is spina bifida occulta?
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Correct answer:
Failure of the vertebral arch fusion only; meninges and nervous tissue are normal.
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4. What is a meningocele?
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A cystic protrusion of the meninges through a posterior vertebral defect without nervous tissue involvement.
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5. What is a myelomeningocele?
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Neural tissue (the cord or spinal roots) protrudes into, and may be adherent to, the meningeal sac.
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7. What is an alternative name for a myelocele?
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Rachischisis.
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8. How can spina bifida be screened for antenatally?
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Antenatal screening (presence of high levels of ∝-fetoprotein in the amniotic fluid and ultrasound) enables a high degree of accuracy in intrauterine diagnosis of neural tube defects, and gives the opportunity for termination of the pregnancy.
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9. What has been the result of antenatal screening for spina bifida?
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The number of infants born with severe spinal abnormalities has, in consequence, greatly declined.
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10. What are the clinical features of spina bifida?
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Correct answer:
These defects are particularly common in the lumbosacral area, although any part of the spine may be involved. There may be an associated overlying lipoma, tuft of hair or skin dimple, which may be an important clue to the astute clinician of the underlying defect. Where nervous tissue is involved there may be paraparesis, paraplegia, sensory disturbance in the limbs and loss of sphincter control. Hydrocephalus nearly always coexists with the myelomeningocele owing to Arnold–Chiari malformation, in which the cerebellar tonsils descend below the foramen magnum with consequent obstruction of the cerebrospinal fluid pathway. As with any other congenital deformity there may be multiple developmental anomalies, e.g. congenital dislocation of the hip, talipes equinovarus, cleft lip or palate, cardiac lesions or supernumerary digits.
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11. Why is does hydrocephalus almost always coexist with a myelomeningocele?
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Correct answer:
This is because of an Arnold–Chiari malformation, in which the cerebellar tonsils descend below the foramen magnum with consequent obstruction of the cerebrospinal fluid pathway.
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12. What should the astute clinician look for in the overlying skin in the case of spina bifida?
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Correct answer:
Tuft of hair; a dimple; an overlying lipoma.
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13. What are the clinical features of spina bifida occulta?
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Correct answer:
This is usually an incidental finding noted on X-ray. When overlying skin changes (dimple, hair tuft, lipoma, sinus) are present, the cord beneath may be tethered to the skin by a fibrous band, and, as the child grows weakness in the legs may occur with sensory loss, pes cavus, or difficulty with bladder and bowel sphincters – ‘the tethered cord syndrome’.
