Neural tube defects (NTDs) are a group of birth defects in which an opening in the spinal cord or brain remains from early in human development. In the 3rd week of pregnancy called gastrulation, specialized cells on the dorsal side of the embryo begin to change shape and form the neural tube. When the neural tube does not close completely, an NTD develops.
There are two types of NTDs: open, which are more common, and closed. Open NTDs occur when the brain and/or spinal cord are exposed at birth through a defect in the skull or vertebrae (back bones).
Anencephaly (without brain) is a neural tube defect that occurs when the head end of the neural tube fails to close, , resulting in an absence of a major portion of the brain and skull. Infants born with this condition are born without the main part of the forebrain—the largest part of the cerebrum—and are usually blind, deaf and unconscious.
Encephaloceles are characterized by protrusions of the brain through the skull that are sac-like and covered with membrane.
Hydranencephaly is a condition in which the cerebral hemispheres are missing and instead filled with sacs of cerebrospinal fluid.
Iniencephaly is a rare neural tube defect that results in extreme bending of the head to the spine.
Causes of NTU is a combination of genetic and environmental risk factors, such as a family history of neural tube defects and folate deficiency.
Spina bifida occulta. Because the spinal nerves usually aren’t involved, typically there are no signs or symptoms. But visible indications can sometimes be seen on the newborn’s skin above the spinal defect, including an abnormal tuft of hair, or a small dimple or birthmark.
Meningocele. The membranes around the spinal cord push out through an opening in the vertebrae, forming a sac filled with fluid, but this sac doesn’t include the spinal cord.
Myelomeningocele. In this severe form of spina bifida:
The spinal canal remains open along several vertebrae in the lower or middle back.
Tissues and nerves usually are exposed, though sometimes skin covers the sac.
Open spina bifida. An infant with myelomeningocele, in which the spinal cord is exposed, can have surgery to close the hole in the back before birth or within the first few days after birth.
Hydrocephalus. If an infant with spina bifida has hydrocephalus (excess fluid surrounding the brain), a surgeon can implant a shunt—a small hollow tube to drain fluid—to relieve pressure on the brain. Treating hydrocephalus can prevent problems such as blindness.
Encephaloceles. People with encephaloceles—sac-like bulges where the brain and surrounding membranes protrude through the skull—are sometimes treated with surgery. During the surgery, the bulge of tissue is placed back into the skull. Surgery also may help to correct abnormalities in the skull and face.
Tethered spinal cord. Surgery can separate the spinal cord from surrounding tissue.1
Paralysis and limitations in mobility. People with spina bifida use different means to get around, including braces, crutches, walkers, and wheelchairs.