Evaluation of Fetal Myelomeningocele

Examination

• Patient physical exam: Although the fetal ultrasound forms the foundation of the fetal myelomeningocele repair workup, a physical exam must be performed on the mother to ensure adequate cardiac, pulmonary, psychiatric, and obstetric form and function for intrauterine surgery.

Laboratory Tests

• Routine prenatal labs: A complete metabolic panel, CBC, and glucose tolerance test should be performed on the mother.
• Fetal karyotype: An amniocentesis should be performed and the fetal karyotype analyzed for exclusionary anomalies. Evidence of aneuploidy or visibly abnormal chromosomal organization is a relative contraindication for fetal myelomeningocele repair.

Radiologic Tests

Ultrasound

• Screening ultrasound: The spinal defect is usually first identified during a routine prenatal ultrasound performed at approximately 20 weeks of gestation. Evaluation by an MFM specialist should be considered at that time.
• Advanced (Level II) ultrasound: This ultrasound, conducted by an MFM specialist, involves a detailed anatomic and physiological evaluation of the fetus. Special attention is given to the assessment of spinal lesion level, cerebral anatomy (including midline structures and ventricular network), limb movement, and any associated anomalies. A fetal echocardiogram is also performed to assess anatomy and motility.
• Sonographic markers for an open NTD: Sonographic markers for suspected open NTD include abnormal cranial shape (“lemon sign”), hindbrain herniation (“banana sign”), ventriculomegaly, or a defect on the spine.

CT Scans

• Not indicated: There is no specific role for computed tomography in the care of a fetus with myelomeningocele. Avoid CT scans to prevent fetal irradiation.

MRI

• Chiari II confirmation: Before confirming eligibility for fetal myelomeningocele repair, a fetal MRI is performed to confirm the presence of the Chiari II malformation.

Fetal MRI demonstrating the Chiari II malformation: MRI of fetus with the Chiari II malformation (white arrow). An open NTD (black arrow) is visualized in the lumbar spine (2).

Nuclear Medicine Tests

• Not indicated: There is no specific role for nuclear medicine evaluations in the care of a fetus with myelomeningocele.

Electrodiagnostic Tests

• Not indicated: There is no specific role for electrodiagnostic testing in the care of a fetus with myelomeningocele.

Neuropsychological Tests

• Useful for tracking development after birth: The use of neuropsychological testing as a child grows can be tailored to their developmental progress, functional goals, and social support.

Correlation of Tests

• Inclusion/exclusion criteria check-off: Results from the prenatal ultrasonography, maternal physical assessment and serum studies, fetal karyotyping, and fetal MRI are compared against the outlined criteria to confirm or refute eligibility for fetal myelomeningocele repair.
• Multidisciplinary assessment and clearance: The mother/family also consults with specialists in pediatric neurosurgery, neonatology, genetic counseling, and perinatal social work to discuss the risks and benefits of the procedure. If no exclusionary factors have been identified, the mother should be informed that all inclusion criteria still must be met. If the mother and family wish to proceed, the surgery is scheduled for between 22 weeks and 25 weeks, 6 days of fetal gestation.
• Alternative, postnatal repair: If at any time during the workup an exclusionary criterion is encountered — or if the patient elects to defer fetal repair — they may choose to deliver in anticipation of postnatal myelomeningocele closure.