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In the first few weeks of pregnancy, a collection of nerves form a cylindrical structure known as the neural tube, which later becomes an unborn child’s spine, spinal cord, and brain. By the 28th day after conception, the neural tube closes. Spina bifida occurs if the neural tube doesn’t fully close at any point along this structure, preventing the spinal cord, nerves, and meninges—the membrane that covers and protects the spinal cord and brain—from developing completely.
Depending on the extent of nerve or spinal cord damage and the location of the opening in the spinal column, the condition may affect a child’s neurological, physical, and intellectual development. All nerves located below an opening in the spine are affected, so when spina bifida affects the upper spinal column it tends to cause more significant symptoms than it does when it affects the lower spine.
There are three main types of spina bifida: spina bifida occulta, meningocele, and myelomeningocele.
Spina Bifida Occulta
Spina bifida occulta is the most common type of spina bifida and the least likely to cause symptoms that require treatment. In fact, the term “spina bifida occulta” is being used with less frequency as it seldom causes developmental problems, and is rarely diagnosed.
Babies with spina bifida occulta have a gap in the vertebrae, but the meninges and spinal cord are contained within the spinal column and the skin grows normally on the back. Most children experience no symptoms, and if they are diagnosed, it’s often because he or she has an X-ray or other diagnostic test for unrelated reasons. Sometimes a child may have a dimple, dark spot, or tuft of hair on the lower back, but these signs almost never cause physical discomfort.
Rarely, spina bifida occulta may cause complications that can affect a child’s neurological development. In a small number of people, the spinal cord may not grow the right way or may remain attached, or tethered, to the lower part of the spine. The spinal cord may be attached by a single strand of connective tissue, or it may be tethered by a complex grouping of fat and other tissues. How the spinal cord is tethered affects the type of treatment a doctor recommends and may affect the severity of symptoms.
Meningocele occurs when the meninges covering the spinal cord—but not the spinal cord itself—emerges from an opening in a baby’s spine, forming a fluid-filled sac, or cyst. Pediatric surgeons usually close this opening in the first days after birth.
Because this type of spina bifida doesn’t usually damage the spinal cord, a meningocele does not normally cause sensory or motor problems in the legs and feet, nor does it cause significant cognitive problems. However, children with a lesion located in the upper part of the spine are at increased risk of nerve damage and muscle or organ dysfunction.
Myelomeningocele is the most severe type of spina bifida. It occurs when part of the spinal cord and the meninges emerge through an opening in the spine. These tissues are contained within a fluid-filled sac that forms on a baby’s back.
Children with myelomeningocele have some spinal cord damage, which may affect nerve function in muscles and organs throughout parts of the body located below the opening in the spine. Depending on the extent of nerve damage, myelomeningocele can cause a variety of symptoms, such as poor control over leg muscles, a loss of feeling in the legs or feet, tightness or uncontrolled movement in joints, misaligned or irregularly positioned bones, and lack of control over the bladder and bowels.
Less commonly, children with myelomeningocele may also have delayed or impaired cognitive development due to damage in certain parts of the brain. This can lead to learning disorders and intellectual disabilities. Children who have myelomeningocele typically require lifelong medical care.
A neurosurgeon performs surgery to close the opening in the spine in the first few days after a baby’s birth. This procedure minimizes the risk of infection and preserves existing function in the spinal cord. Additional treatments may be required to address common complications.
Hydrocephalus—a buildup of excess fluid in the brain—often occurs in babies with myelomeningocele. Without surgical treatment to drain the fluid, it can cause pressure and swelling that may lead to irreversible brain damage.
Most babies with myelomeningocele are born with a Chiari malformation (Type II), in which brain tissue extends into the spinal canal. If this tissue puts too much pressure on the spinal cord or brainstem, surgery may be required to reduce or eliminate the pressure.
Bladder and Bowel Problems
Myelomeningocele-related nerve damage commonly affects the bladder, bowel, and kidneys. Some children may be incontinent or have frequent urinary tract infections. Our pediatric urologists are part of a multidisciplinary team that cares for your child.
Tethered Spinal Cord
In some children, after the myelomeningocele has been surgically closed, the spinal cord may become stuck, or tethered, to the lining of the spinal canal in the in the area of the surgical repair. As the spine lengthens, the spinal cord stretches out, damaging spinal cord tissue and restricting blood supply to the nerves. Over time, usually months or years, a tethered spinal cord can reduce sensitivity in the legs, bladder, or bowel.
Doctors may recommend surgery to partly or completely detach the spinal cord. Increasing weakness, loss of sensation, new blabber problems, and new orthopedic problem such as scoliosis, in which the spine curves excessively, may suggest a tethered cord.
As a child grows, nerve damage can affect muscle tone, which may lead to changes in the alignment of bones. Weak muscle groups can cause tendons and ligaments in the foot or ankle to tighten, restricting movement.
Muscle weakness or tight tendons may also cause bones in different parts of the body to move out of position. As a result, a child may develop orthopedic conditions such as scoliosis or clubfoot, in which the feet are twisted inward at the ankle.
If a condition is mild and does not cause chronic pain, our physiatrists, doctors who specialize in rehabilitation medicine, and physical therapists may use special exercises to help a child learn how to walk using crutches or a brace. Our doctors may recommend orthopedic surgery if a condition causes chronic pain or increases the risk of other medical problems. For example, if a curved spine presses on the ribcage, it could potentially damage the heart or lungs.
Resources for Spina Bifida in Children
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