What Is Spina Bifida?

Spina bifida is a congenital birth defect (a condition that is present at birth) that affects a baby’s spine. In order to understand this condition, we must first consider the complicated structure of the spine. The spine is made up of many different layers, and a problem with the development of any one of these layers can result in different health conditions. 

The innermost layer of the spine is the spinal cord, a delicate bundle of nerves that plays a very important role in transmitting signals from the brain to the lower body. Birth defects that damage the spinal cord can cause symptoms like loss of movement or feeling in the baby’s legs and difficulty controlling the bowel and bladder.

The layers around the spinal cord include fluid-filled coverings called meninges, bone, muscle and skin. These layers cushion and protect the spinal cord. Babies with spina bifida have a gap in the bone layer that surrounds the spinal cord. The gap, or defect, in the bone may be small or large. Some cases of spina bifida are completely harmless, while others can be associated with problems in the development of the deeper layers of the spine, including the spinal cord or nerves. Spina bifida refers specifically to a defect in the bone layer of the spine.

Spina Bifida vs. Spinal Dysraphism: What’s the Difference?

The term “spina bifida” can create a lot of confusion among parents. It is often used as a catch-all word for many different types of congenital birth defects involving the spine. For example, spina bifida is commonly used as a synonym for a specific, more involved condition called myelomeningocele. This condition occurs when the spinal cord itself and the layers surrounding it do not form normally when the baby is developing in the womb. This can be associated with more lasting problems with the function of the feet or legs, bowel, and bladder, as well as other problems with circulation of the spinal fluid. Learn more about myelomeningocele.

Spina bifida only refers to abnormalities of the bone that surrounds the spinal cord. These abnormalities can sometimes be very mild and cause no clinical symptoms at all. Many cases of spina bifida are found incidentally or “by accident” on an X-ray done for some other reason. Only a small percentage of patients with spina bifida have other associated problems with the deeper layers of the spine, including the nerves and spinal cord.

There are many factors that determine the health and function of a baby’s spinal cord. The presence or absence of spina bifida does not by itself influence the function of the spinal cord or nerves. It is for this reason that our doctors prefer the term spinal dysraphism rather than spina bifida when referring to problems with a baby’s spinal cord. Spinal dysraphism is a broader term that accounts for spinal problems that occur as a result of a defect in any layer of the spine, which may include the bone, the fluid coverings, the nerves, or the spinal cord.

What Are the Types of Spinal Dysraphism?

Different types of spinal dysraphism are designated as “open” or “closed” depending on whether or not the abnormality is covered with skin.

Types of open spinal dysraphism include:

Types of closed spinal dysraphism include
  • Lipomyelomeningocele
  • Fatty or thickened filum terminale
  • Filum lipoma
  • Meningocele
  • Myelocystocele

In addition to developmental problems with the layers of the spine, some children with these conditions may develop what is called a “tethered” spinal cord. This means that the spinal cord is not able to “float” freely within the spinal fluid the way it normally should.

What Causes Spinal Dysraphism?

Spinal dysraphism is caused by abnormalities that occur during early fetal development. Around the third week of development, the fetus forms a structure called the neural tube, which will eventually extend through the baby’s body and give rise to their nervous system. If the lower section of the neural tube does not close completely, the baby will be born with spinal dysraphism. 

How Is Spinal Dysraphism Treated?

Treatment for spinal dysraphism depends on the type your baby is diagnosed with. Some forms of spinal dysraphism require surgery, while other cases need no intervention at all. At Mass General for Children our doctors will determine if your child is at risk of experience complex medical problems because of their spinal dysraphism. Meet our interdisciplinary team of specialists on our Spina Bifida and Related Disorders Program page.