Spina = Latin: “spine”
Bifida = Latin: “split”
Spina bifida is one of the most common birth defects in the world. It occurs when an embryo’s developing neural tube, the precursor to the brain and spinal cord, does not close correctly. Spina bifida may affect the spinal cord itself, the coverings of the spinal cord, and/or the bones of the spine. It is one of several forms of spinal dysraphism or malformation of the spinal cord.
There are three kinds of spina bifida. The most severe form is called myelomeningocele, aperta, or open spina bifida. In this form, there is an open channel from the skin to the the spinal cord or its coverings. The defect can usually be seen on fetal ultrasound and is visible to the naked eye in a newborn. Therefore, this form is always diagnosed either in utero or in newborn infants.
Surgery to close the defect is performed within the first days of life. This surgery prevents further damage to the spinal cord, but no surgery can yet repair spinal cord damage that has already occurred. Therefore, as adults, people with open spina bifida generally have some amount of weakness or paralysis. (Note that the condition is called open spina bifida, but that children and adults with the condition do not still have an open channel from the skin to the spinal cord. The surgery performed within the first days of life closes that channel.)
Open spina bifida is often associated with other neurological conditions. Therefore, adults with open spina bifida benefit from regular access to neurosurgical care. Neurosurgeons like those of The Spine Hospital at the Neurological Institute of New York can help monitor conditions like hydrocephalus, Chiari malformation, and tethered cord, all of which are common among people with open spina bifida.
A moderate form of spina bifida, meningocele, is usually discovered in infancy as well. Meningocele causes fewer symptoms than open spina bifida, and is the rarest form of spina bifida.
The mildest form of spina bifida is also the most common. Called spina bifida occulta, or closed spina bifida, it affects only the bones of the spinal column and is not always diagnosed in infancy. Instead, adults may be alarmed when an X-ray or other spinal imaging procedure reveals in passing that they have (and always have had) this birth defect. In fact, up to 10% of people have spina bifida occulta. It is very rare for the condition to cause any symptoms or need any kind of treatment.
Symptoms vary depending on the location and severity of the neural tube defect.
The higher the defect is located in the spinal column, the greater the number of functions it can potentially affect.
The most severe form of spina bifida (myelomeningocele, aperta, or open spina bifida) affects the spinal cord, its coverings, and the bones of the spine. Neurological problems like leg weakness or paralysis, bowel or bladder problems, and hydrocephalus (an imbalance of cerebrospinal fluid) are most common with this form.
The moderate form of spina bifida (meningocele) involves the coverings around the spinal cord, but not the spinal cord itself. Since the spinal cord is spared, people with meningocele do not typically experience neurological symptoms such as paralysis or incontinence.
The mildest form of spina bifida (closed spina bifida, or spina bifida occulta) involves a malformation in the bones of the spine only. It does not involve the coverings or the tissue of the spinal cord. It is very rare for this form to cause symptoms, especially if the defect does not extend beyond one bone. When the defect is larger, a tethered cord sometimes develops.
Spina bifida often occurs in conjunction with other nervous system problems. The more severe the defect, the more likely it is that other nervous system conditions will be present. These conditions include hydrocephalus, syringomyelia, Chiari malformation, and tethered cord. Symptoms of these conditions may include disturbances in bowel and bladder function; respiratory, sp eech, or swallowing difficulties; weakness and pain in the hands, arms, neck, legs, or hips; or scoliosis curvature of the spine).
Causes and Risk Factors
The exact causes of spina bifida are not fully understood.
The spinal cord forms, properly or improperly, during the first few weeks of gestation. This is so early in gestation that most women are not yet aware that they are pregnant. Elements of the early prenatal environment–such as maternal diabetes or elevated body temperature–may influence the development of spina bifida in the fetus, but these environmental factors cannot act alone to cause the condition.
Genetic factors seem to play an important role. People who have spina bifida, or who have a close relative with spina bifida, have a greater chance of having children with spina bifida. Mild cases of closed spina bifida are the exception; these do not seem to carry any increased chance of passing on the condition.
Deficiency of folate (a vitamin found in beans, citrus, leafy green vegetables, and fortified grain products) is common in women whose fetuses develop spina bifida. Folate deficiency alone does not cause spina bifida, but adequate folate levels do seem to protect against it.
Tests and Diagnosis
Open spina bifida is always diagnosed very early in life. It may be diagnosed in utero (by blood test or ultrasound) or at birth (by a visible defect over the spine).
The diagnosis of the moderate form, meningocele, is similar.
Closed spina bifida, however, is not always apparent. Its presence may be suggested by certain skin signs directly over the spine–for instance, a pad of fat, an area of unusual pigmentation, a growth of excess skin, or a patch of thick hair. But in other cases, there is no exterior sign, and the defect in the bone may simply be noted during an X-ray or other scan. This is called an “incidental” finding. In nearly all cases, the condition has no impact and is not a cause for concern.
Adults with spina bifida may seek neurosurgical care for a few reasons. The most common cases are those in which an adult with open spina bifida seeks treatment for a related condition, such as tethered cord, Chiari malformation, syringomyelia or hydrocephalus. These conditions have usually been identified much earlier in life, and the patient and her medical team have been monitoring them. Occasionally, an adult will discover that he has a more severe case of closed spina bifida and a tethered cord.
Some people with tethered cord are diagnosed in childhood or during the growth spurt of adolescence. Other people might not be diagnosed until they are adults. In adults, surgery to release the tether is sometimes recommended. The specific surgical procedure varies depending on the cause and location of an individual’s tether.
Another condition common in people with spina bifida is known as Chiari malformation. In Chiari malformation, some brain tissue extends down into the spinal canal. Most Chiari malformations are either Type I, which develops as an individual grows, or Type II, which is present at birth. (A few are the rare Type III and Type IV.) All people with open spina bifida have some degree of Type II Chiari malformation.
However, while the Chiari malformation is apparent on imaging tests like MRI, it may not cause any symptoms, and therefore does not necessarily need to be treated. Surgical treatment for Chiari malformation is usually reserved for patients with clear evidence of progressive symptoms. Symptoms include repeated aspirations, apnea, neck pains, and weakness or odd sensations in the arms. In a person with spina bifida, any of these symptoms (or a change in previous Chiari symptoms) is reason for evaluation by a neurosurgeon. Surgical treatment is tailored to the individual patient. It usually consists of removing a small amount of bone from the base of the skull or the spinal column in order to provide more room for the brain and spine.
Many people with spina bifida also have hydrocephalus, or a buildup of “fluid on the brain.” Hydrocephalus is treated with a shunt, a thin tube that a neurosurgeon implants in the body to drain away the excess fluid. Shunts sometimes malfunction, and may need to be replaced or repaired by a neurosurgeon more than once throughout a patient’s lifetime.
Over the course of a lifetime, a trusted neurosurgeon can bring great peace of mind to people with spina bifida and to their families.
Preparing For Your Appointment
Drs. Peter D. Angevine, Christopher E. Mandigo, Sheng-fu (Larry) Lo, Richard C.E. Anderson (Pediatric) and Neil A. Feldstein (Pediatric) are experts in treating conditions common among patients with spina bifida. Each can also offer you a second opinion.