Neural Tube Defects

Key Features

Essentials of Diagnosis

• Various defects, ranging from anencephaly to open or skin-covered lesions of the spinal cord, may occur in isolation or as part of a syndrome

• Myelomeningocele is usually associated with hydrocephalus, Arnold-Chiari II malformation, neurogenic bladder and bowel, and congenital paralysis in the lower extremities

• Anomalies of the CNS, heart, and kidneys may also be seen

General Considerations

• Neural tube defects comprise a variety of malformations, including anencephaly, encephalocele, spina bifida (myelomeningocele), sacral agenesis, and other spinal dysraphisms

• Evidence suggests that the neural tube develops via closure at multiple closure sites and that each closure site is mediated by different genes and affected by different teratogens

• Hydrocephalus associated with the Arnold-Chiari type II malformation commonly occurs with myelomeningocele

• Sacral agenesis, also called the caudal regression syndrome, occurs more frequently in infants of diabetic mothers

• May occur in isolation (nonsyndromic) or as part of a genetic syndrome

• May result from teratogenic exposure to alcohol or the anticonvulsant valproate

Clinical Findings

• At birth, neural tube defects can present as an obvious open lesion, or as a more subtle skin-covered lesion

• The extent of neurologic deficit depends on the level of the lesion and may include

  • Clubfeet

  • Dislocated hips

  • Total flaccid paralysis below the level of the lesion

• Hydrocephalus may be apparent at birth or may develop after the back has been surgically repaired

• Neurogenic bladder and bowel are commonly seen

Diagnosis

• MRI helps determine the extent of the anatomic defect in skin covered lesions

• Urologic studies are recommended early on to define bladder function and guide management

• Screening includes measurement of maternal serum α-fetoprotein levels at 16–18 weeks' gestation and prenatal ultrasound

• Elevated α-fetoprotein and acetylcholine esterase levels in amniotic fluid can be detected via amniocentesis

• Any infant with dysmorphic features or other major anomalies in addition to a neural tube defect should be evaluated by a geneticist, and a microarray analysis should be performed

Treatment

Neurosurgical Measures

• Infants with an open neural tube defect should be placed in prone position, and the lesion kept moist with sterile dressing

• Neurosurgical closure should occur within 24–48 hours after birth to reduce risk of infection

• Shunts are required in about 85% of cases of myelomeningocele and are associated with complications including malfunction and infection

Orthopedic Measures

• The child's ability to walk varies according to the level of the lesion

• Orthopedic input is necessary to address foot deformities and scoliosis

• Physical therapy services are indicated

Urologic Measures

• Continence can sometimes be achieved by the use of medications, clean intermittent catheterization, and a variety of urologic procedures

• Kidney function should be monitored regularly, and an ultrasound ...