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.