Spina bifida occulta (SBO) is a common malformation of the spine. It occurs during a baby’s development in its mother’s womb, usually in the first month of pregnancy.
In people with this condition, the bones of the spine, called vertebrae, don’t properly close. That leaves small gaps that can expose the sensitive spinal column to injury. The spinal cord, contained within the spinal column, is responsible for the body’s movement.
Some people with SBO experience symptoms, but the vast majority have no symptoms and lead healthy lives. The condition is sometimes called hidden spina bifida because it often displays no outward signs.
According to the Spina Bifida Association, 10 to 20 percent of people have SBO. Many people with this condition don’t know they have it.
While related to SBO, open spina bifida (or myelomeningocele), which is what most people think of when they read about spina bifida, is a more serious birth defect.
In open spina bifida, the spinal canal is open to varying degrees along the back, and a sac with part of the spinal cord extends out through the skin. This kind of defect exposes the spinal cord to injury and infection. It can also severely impact a person’s mobility.
Symptoms and their severity generally depend on how many vertebrae are left open and how big the gaps are. Many cases of SBO are very mild. The gaps in the bones are so small that the spinal cord is still protected and no damage has occurred. About 1 in 1,000 people with SBO will experience symptoms, however.
When symptoms occur, they generally include:
- back pain
- leg weakness
- pain in the back of the legs
- loss of bladder or bowel control
- scoliosis, or a curving of the spine
- numbness in the back or legs
- misshapen legs and feet
Sometimes there are visible signs that a spinal cord abnormality, like SBO, may be present. These signs involve the skin along the lower back. Seeing one of the following signs on your back may prompt your doctor to do more testing:
- hairy patch
- discoloring or birthmark
- dimple or indent
- growth or pad of fat
The most frequent complication of SBO is tethered cord syndrome. This is a condition in which the spinal cord, which runs from the brain down the spinal column, is restricted.
Normally, the spinal cord hangs freely, unattached to any skin or structure. But in tethered cord syndrome, the spinal cord attaches to the spinal column, limiting its movement. In children, it will stretch as they grow. That stretching can cause nerve damage and neurological problems, including:
- back pain
- weakness in the legs and arms
- problems controlling the bladder and bowels
Experts aren’t exactly sure what causes any of the forms of spina bifida, including SBO. One of the biggest risk factors for delivering a baby with spinal cord defects is insufficient intake of folic acid during pregnancy. Folic acid is a B vitamin. Learn more about the importance of B vitamins during pregnancy.
The Centers for Disease Control and Prevention and the U.S. Public Health Service recommend all women who can become pregnant, which means most women 15 to 45 years old, consume 400 micrograms of folic acid daily to prevent spina bifida. Folic acid is found in dark leafy vegetables and fortified foods like cereal.
You may need up to 4,000 micrograms during pregnancy if you have diabetes or already have a child with spina bifida.
Proper folic acid supplementation may reduce the risk of defects like spina bifida by 40 to 100 percent.
SBO is frequently only detected by chance when a doctor is ordering tests or performing an exam for some unrelated condition. That’s because the condition is often asymptomatic. Visual cues such as a dimple, skin discoloration, or tuft of hair can lead a doctor to suspect SBO.
An X-ray can determine if there is a malformation of the spine. If your doctor suspects tethered cord syndrome, they may order an MRI scan.
There is no cure for SBO. Most people never receive treatment because they never have symptoms or even know they have the condition. When symptoms do arise, they are generally treated individually. For example, pain can be managed with medications or physical therapy.
If tethered cord syndrome is diagnosed, surgery may be needed to release the tension in the cord. Tethered cord syndrome usually isn’t diagnosed until adolescence when rapid growth spurts cause the cord to stretch extensively. The surgery is simple and usually successful. The cord can re-tether over time, so repeat surgeries may be necessary.
SBO is a common and mild condition that rarely causes health problems. People with mild SBO usually don’t have a family history of the disease. They also are unlikely to pass the condition on to their children. Even when symptoms do arise, they can be successfully managed with surgery, medications, and therapy.