Myelomeningocele
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myelo = the nerves of the spinal cord
meningo = the meninges, or coverings around the spinal cord
cele = a swelling or bulging
Myelomeningocele is a condition in which the spinal cord, its meninges (membranes, or coverings), and the bones of the spinal column are not formed correctly.
Very early in an embryo’s development, a sheet of cells called the neural plate folds to form a tube called the neural tube. The top of the neural tube goes on to become the brain, and the rest of the neural tube becomes the spinal cord. Myelomeningocele is caused by an error in the closure of the neural tube.
Myelomeningocele is a form of spina bifida. Spina bifida itself is part of the umbrella category of spinal dysraphism. Other names for myelomeningocele include open spina bifida and spina bifida aperta.
With support, most children and adults with spina bifida lead active and fulfilling lives.
Symptoms
Myelomeningocele is visible at birth as a sac on a newborn’s back, centered over the spine. This sac is formed by the spinal cord and its membranes protruding through the bones of the spinal column. In some cases, the sac is covered with thin transparent skin, while in other cases, the membranes are exposed to the air. This puts the infant’s spinal cord and meninges at high risk for infection.
Other neurological problems often occur along with myelomeningocele. These include leg weakness or paralysis, loss of sensation of the legs and feet, bowel, or bladder incontinence, Chiari II malformation (a protrusion of the back of the brain into the spinal column), and hydrocephalus (an imbalance of cerebrospinal fluid).
Diagnosis
Myelomeningocele is most often diagnosed in utero. The diagnosis can be suggested by the maternal serum alpha-fetoprotein (MSAFP) test. This common test detects alpha-fetoprotein (a protein produced by the fetus) in the mother’s blood. Alpha-fetoprotein normally stays within the developing fetus, so its presence in the mother’s blood sometimes indicates a problem like an open neural tube defect. The MSAFP is not a foolproof test, though. It can return both false positives (results that indicate the condition may be present, when really it is not) and false negatives (results that indicate that the condition is not present, when really it is).
If the MSAFP returns an abnormal result, further testing is usually warranted. At that point, an imaging scan like a high resolution ultrasound can often provide a definitive diagnosis. An ultrasound is a safe procedure, common during prenatal care. It uses high-frequency sound waves to produce images of internal structures. A high resolution ultrasound simply produces more detailed images.
Other times, the condition is not recognized until birth. Myelomeningocele is visible to the naked eye, and can be diagnosed immediately in a newborn.
Risk Factors
There is no single cause of myelomeningocele. Maternal deficiency of folate (a vitamin found in beans, citrus, leafy green vegetables, and fortified grain products) early in development is common in the condition, but cannot cause the condition on its own. Genetic factors seem to play an important role. Elements of the prenatal environment–such as maternal diabetes, obesity or elevated body temperature–may influence the condition’s development.
Treatments
In some cases, surgery to close the spinal cord and back may be performed in utero. It carries risks for both mother and fetus, and cannot be performed in all cases, but in general, results of the procedure have been promising.
Newborns with myelomeningocele are treated quickly to reduce the likelihood of infection or further trauma to the spinal cord. Within the first three days of life, a pediatric neurosurgeon closes the spinal cord and the back. Imaging studies may be performed to look for other possible abnormalities that may be addressed during the surgery.
During surgery, the infant is positioned face-down. Using a surgical microscope and very fine instruments, the pediatric neurosurgeon works delicately, layer by layer. The surgeon protects the spinal cord from further damage, removes as many potentially problematic elements as possible, and restores as much normal structure as possible.
After surgery, the incision will be covered by a gauze dressing for several days. The infant may need to lay face-down or on his or her side in the bassinet, but can be held on his or her stomach for feeding, nursing, therapy, and "skin-to-skin" time with parents.
This operation is necessary to close the defect and to prevent serious complications. Unfortunately, the surgery does not "cure" myelomeningocele. No surgery can restore spinal cord function that did not form normally during development and is not present at birth.
Children with myelomeningocele often have other neurological problems, and some complications will require regular care or monitoring. Consistent follow-up with a team of care providers that may include a pediatric urologist, orthopedist, neurologist, and physical therapist, as well as a pediatric neurosurgeon, will be very helpful for the child with myelomeningocele.
A pediatric neurosurgeon examines each child’s individual case and forms treatment plans with the family. In addition to closing the open spinal defect in newborn, our pediatric neurosurgeons evaluate and treat neurological conditions often found together with myelomeningocele, such as:
- Hydrocephalus, or a buildup of fluid in the brain. Hydrocephalus is present in approximately 80-90% of children with myelomeningocele. It is most often treated with a shunt—a thin tube that a neurosurgeon implants in the body to drain away the excess fluid. More recently, in some cases it can be treated successfully with an endoscopic third ventriculostomy and choroid plexus cauterization in order to prevent the need for a shunt. Hydrocephalus is usually treated before an infant's discharge from the hospital.
- Chiari Malfromation, a condition in which the base of the skull is too small for the base of the brain. (Chiari malformation can have various causes; Type II is the type present at birth, as in spina bifida.) A Chiari malformation causes some portion of the brain tissue to be crowded down out of the skull and into the spinal canal. Chiari malformation does not always cause symptoms. When it causes no symptoms, it needs no treatment. When it causes progressive symptoms (symptoms that get worse over time), surgical treatment is recommended. Symptoms that can occur with Chiari malformations include repeated aspirations (breathing in saliva or food), apnea (pauses in breathing), neck pains, and weakness in the arms. A pediatric neurosurgeon can help families and caregivers be alert for symptoms of Chiari malformation in an infant or child.
- Tethered cord or a restriction on the movement of the spinal cord. This condition is of particular concern in a growing child. When it causes symptoms, surgery to release the tether is often recommended. The surgeon carefully evaluates each child's case and makes a recommendation for surgery or watchful monitoring. The doctor monitors the child's neurological function in office visits, and helps families and caregivers understand how to monitor the child's development at home.
Having a child with myelomeningocele can involve care decisions or challenges that families may feel unprepared for. Our experienced and caring neurosurgeons work as a part of each child's treatment team, supporting the families of his young patients and providing the best possible care for the patients themselves. With the right support, infants, children, and adults with myelomeningocele have the opportunity to lead healthy, productive, fulfilling lives.