Myelomeningocele

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 1, 2016
StartDiseasesMyelomeningocele

Myelomeningocele is the severest type of the birth defect commonly known as spina bifida. This condition occurs when the spine and spinal canal (in which the spinal cord exists) aren’t fully formed during the early weeks of the pregnancy. When the spinal canal fails to close, the result is often an open, bulging area, usually on the lower back

Contents

Definition & Facts 

Myelomeningocele, the most serious form of spina bifida, is categorized as an open neural tube defect. The neural tube forms the brain and spinal cord. When the neural tube develops improperly, the result is an abnormality in which a section of the spinal cord and surrounding nerves are left exposed. This is most commonly seen in the lower back. Muscle and nerve function is often limited or nonexistent below the defect.

Myelomeningocele differs from other types of spina bifida in that the meninges protrude from the defect without the skin covering them, and it involves the malformation of the spinal cord. A less severe as well as the least common form of spina bifida, meningocele, by contrast, involves the skin still covering the protrusion and the spinal cord forming normally. The protrusion in a meningocele doesn't contain spinal nerves and the child typically does not struggle with neurological problems stemming from nerve damage.

Myelomeningoceles may occur in approximately one out of every 4,000 live births in the United States according to the National Institutes of Health. This condition develops during the early weeks of pregnancy. The majority of children with this abnormality survive into adulthood. 

Symptoms & Complaints 

The most noticeable symptoms of spina bifida include loss of bowel control (fecal incontinence) and/or loss of bladder control (urinary incontinence). The result can be kidney problems which are the leading cause of death among these children. A myelomeningocele may be suspected if the newborn has limited movement of the hips, legs, or feet.

The obvious sign of this disorder is an open area or sac protruding from the baby’s back. Another symptom is cerebral edema (brain swelling) from any excess fluid inside the skull (hydrocephalus). The exposed spinal nerves and spinal cord can cause other symptoms including twisted or deformed legs and club foot.

The brain might not form correctly causing a Chiari 2 malformation. As a child reaches their growth spurt during puberty, new issues may arise within the spinal cord. Orthopedic problems such as ankle or foot malformations, dislocation of hip, tightness of the joints, and curvature of the spine (scoliosis) could occur.

Causes 

In a normal pregnancy, the fetus’ spine fuses around the spinal cord, spinal nerves, and the spinal tissues sometime within the first few weeks. The developing brain and spine at this point are called the neural tube. Myelomeningocele is a neural tube defect in which the bones of the spine do not completely form. This results in an incomplete spinal canal allowing the spinal cord, nerves, and tissues to protrude from the infant’s back.

The consensus is that low levels of folate before conception and during the first trimester play a primary role in causing this type of birth abnormality. Proper brain and spinal cord development depend on adequate folic acid in the mother’s body. Family history may play a role in spina bifida as well.

Others theorize that a virus plays a role as the winter months are the time when more cases are seen in obstetrics. Still, others posit that radiation in the environment contributes to this debilitating condition. Those fetuses who have the condition corrected after birth, rather than while they are in the womb, show more ongoing damage to the spinal cord due to the amniotic fluid's on the unprotected spinal cord and spinal nerves. 

Diagnosis & Tests 

The diagnosis of myelomeningocele is often made during prenatal exams. Routine blood tests may reveal elevated levels of the protein called maternal alpha-fetoprotein (AFP). This is one indicator that the fetus has spina bifida.

During the second trimester, the quadruple screen blood test will be administered to screen for developmental abnormalities in the fetus. To confirm the possible diagnosis, an ultrasound or amniocentesis may be performed.

The condition can also be diagnosed once the baby has been born through newborn screening. If the spine appears abnormal, doctors may order X-rays of the spine, an ultrasound, a computed tomography (CT) scan, and/or an magnetic resonance imaging (MRI) to determine the best course of treatment or surgery is necessary to protect the future health of the infant.

A neurologist will likely be involved in testing the baby for the extent of nerve and muscle function below the defect. Often pin pricks are used to monitor the baby’s sensitivity responses. Another indicator of the amount of damage is whether the baby has any range of motion in their legs or any movement at all. Tickling the foot also helps to pinpoint reactions to sensations. If the child does not react to nerve stimulus, this is also a clear indicator of spina bifida.

Treatment & Therapy 

Although not common, some babies qualify for intrauterine surgery at a specialized medical facility. This early intervention appears to reduce the risk of future complications. Antibiotics are administered to prevent infection entering the exposed site, or secondary infections such as neonatal meningitis or urinary tract infections.

To lessen the risk of infection at the exposed site or further damage, neurosurgeons will try to operate within a couple of days of the baby’s birth. While a myelomeningocele can be surgically repaired, full function nerve and motor function usually cannot be restored. The higher up on the back that the defect is, the more damage and loss of function there will be.

Follow-up doctor’s visits are necessary to monitor the child’s physical and mental development as well as to plot a course of action and treatment. New spinal problems can develop during childhood, especially during puberty when most children have a growth spurt. This can lead to further orthopedic conditions such as scoliosis, foot or ankle deformities, dislocated hips, joint tightness, and shortening of muscles and tendons. Physical therapy may be needed to alleviate these.

Many patients with myelomeningocele are fitted with body leg braces and others use a wheelchair for mobility. Assistive devices and mobility aids may be required for the individual with myelomeningocele.

Prevention & Prophylaxis 

The exact cause of spina bifida or myelomeningocele isn’t known, but what is known is that proper preparation to conceive can virtually eliminate the risks of major birth defects. Folic acid is an important part of this preparation because most defects occur in the first few weeks of conception before a woman realizes they are pregnant.

It is important to do everything possible to ensure folic acid levels are not too low before pregnancy occurs. Adequate folic acid is vital to help the brain and spine develop properly from the neural tube.