How are fetuses with open spina bifida and myelomeningocele evaluated?
A suspicion for a fetal neural tube defect is often raised by the maternal serum screening for AFP level. An open spinal defect in the fetus results in higher levels of AFP in both the amniotic fluid and maternal serum. Because there are nonfetal causes for elevated AFP levels, US is performed to evaluate the fetal spine. In addition to the elements of the detailed extended examination, evaluation for spina bifida with MMC includes:
- • Detailed evaluation of the brain, particularly the cerebral ventricles as ventriculomegaly often accompanies an MMC
- Determination of whether Chiari II malformation and hindbrain herniation are present
- Evaluation of the cerebral ventricles for evidence of additional complications, including intraventricular hemorrhage and gray matter heterotopia (often better seen with fetal MRI).
- • Determination of the level of the bony defect and the start of the skin defect
- • Evaluation of the spine for any associated bony abnormality such as kyphosis or scoliosis. If present, the Cobb angle is measured.
- • Determination of whether there is an MMC sac or a myeloschisis (there is an open spina bifida but no membrane covering or surrounding the defect).
- • Measurement of the MMC sac
- Evaluation of the spinal cord for associated abnormalities such as syringomyelia
- Real-time examination of the lower extremities for movement and exclusion or confirmation of talipes equinovarus (club foot)