Neural tube defect is the term used to describe problems with the development of the neural tube in the first few weeks of fetal development. Conditions range from mild (spina bifida occulta) to severe (anencephaly) and may cause death in-utero or immediately after birth.
Increase risk of giving birth to a child with a neural tube defect is associated with maternal history of neural tube defect, maternal history of giving birth to a child with a neural tube defect and being of Hispanic background. Vitamin B9 (folic acid) deficiency increases the risk of all neural tube defects, independent of other risk factors.
Symptoms of neural tube defects are associated with the type of condition. Symptoms also tend to vary within a condition and between patients.
Spina Bifida: The mildest form of spina bifida, occulta, is not associated with symptoms of any kind. Closed neural tube defect may cause partial paralysis in some patients, but other patients show no signs of symptoms of the neural tube defect. Meningocele may cause symptoms in some patients, but other patients have no symptoms. Myelomeningocele is associated with paralysis (partial or complete), hydrocephalus, urinary and bowel problems and learning disabilities. Common symptoms of spina bifida include:
- Leg cramping and weakness
- Problems walking
- Impaired intellectual development
- Impaired physical development
- Numbness in extremities
- Impaired vision
Iniencephaly: A rare neural tube defect, iniencephaly, can cause abnormal, backward bend of the neck, distorted spine, facial skin connected to the neck and scalp connected to the back.
Encephalocele: Failure of the neural tube to close near the brain causes an opening the skull. A bulge or protruding sac may be present at the opening. Other symptoms may include:
- Intellectual and developmental delays
- Ataxia – jerky movements
- Vision problems
Anencephaly: Rare neural tube defect with failure of the neural tube to close at the top leading to fatal symptoms. Infants are typically born with little to no brain mass. At birth infants generally cannot feel pain, see or hear.
Complications of neural tube defects vary widely among patients and conditions. The mildest form of spina bifida causes no complications, while more severe cases can cause early death, severe development delay or paralysis. Chiari II malformation may develop in children with severe spina bifida (myelomeningocele). The malformation blacks cerebrospinal fluid causing hydrocephalus.
Testing and Diagnosis
The majority of neural tube defects are diagnosed via ultrasound, though blood tests and amniotic fluid testing may show high levels of alpha-fetoprotein (AFP) – indicative of a neural tube defect in some cases. The Triple Screen test includes an AFP test. Mild neural tube defects may never be detected if no symptoms develop.
Treatments for neural tube defects vary from removal of a small sac of muscle, tissue and blood vessels to surgery to implant a shunt to drain a buildup of cerebrospinal fluid. Surgical intervention may also include closing the hole in the spine and separating the spinal cord from surrounding tissues in tethering has occurred. Paralysis and/or limited mobility may require the use of a wheelchair, crutches or leg braces. Patients with nerve damage to the urinary or bowel systems may require medication to promote continence and catheter insertion. There are no treatments for iniencephaly or anencephaly.
Prognosis is poor for patients with iniencephaly and patients with anencephaly are unable to live outside the womb. Prognosis for patients with encephalocele and spina bifida depends on the severity of the condition.
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