Spina bifida (myelomeningocele, meningocele, occulta) – causes, symptoms, treatment


The term “spina bifida” comes from the
latin “split spine,” which is actually a pretty good description, because spina bifida
is a birth defect where the tissue on the left and right side of the back that normally
come over the spinal cord to protect it, don’t completely meet up to form a nice seal, leaving
behind various degrees of an opening right down the middle of the lower back. Very early on in fetal development, the ectoderm,
which is the outer layer of the fertilized egg, starts to develop a bit of a ridge that
eventually becomes the neural tube. This neural tube goes on to become the spinal
cord, the brain, as well as tissues that enclose and protect them, called the meninges, and
spina bifida occurs when a portion of this neural tube fails to close properly, typically
in the lower back. This constitutes a defect or absence of the
vertebral arches due to failure of mesoderm to organize over the region of the defect,
and it may or may not involve the underlying meninges and neural tissue. Alright so there are three main types of spina
bifida, the first is myelomeningocele, also called meningomyelocele, and this is the most
severe of the three and occurs when the spinal cord and the surrounding meninges protrude
out of an opening in the bony vertebrae and are held together by a sack of skin that pouches
out from the back. In really severe cases, there is no skin at
all, and the nerves of the spinal cord are therefore exposed, a condition called ‘open
spina bifida, and this can cause serious damage to the exposed nerves as well as risk an infection,
resulting in symptoms like loss of sensation or paralysis in the areas of the body below
the damaged site, bladder or bowel movement problems, seizures, as well as leg and foot
deformities. Now a myelomeningocele is typically associated
with a condition called an Arnold Chiari II malformation, which is where cerebellar and
brainstem tissue slip down into the foramen magnum—the opening at the base of the skull. This Arnold Chiari II malformation results
in a variety of symptoms related to the cerebellum and often resulting in hydrocephalus—an
abnormal accumulation of cerebrospinal fluid in the brain. Alright the second type of spina bifida is
meningocele, sometimes called a meningeal cyst. In this condition, the prenatal spinal deformities
result in only the meninges (and not the spinal nerves) slipping into the gaps between the
deformed vertebrae. This one’s the least common form of spina
bifida, and because the spinal cord itself is not damaged, these individuals often do
not experience the severe symptoms that are seen in myelomeningocele. Alright the third type and finaly type is
spina bifida occulta, and this is the most common and most mild form of spina bifida. In fact, ‘occulta’ is latin for hidden,
which is appropriate since many of the normal prenatal tests used to diagnose spina bifida
don’t catch the disorder because the deformities in the tissues of the lower back are tiny. In spina bifida occulta, the spinal cord and
surrounding tissue don’t protrude, nor is any of the tissue forced into the spaces in
between the vertebrae. Since the spinal nerves are undamaged, people
with this form of the disorder are often asymptomatic, and the condition is usually only found accidently
later in life. At most, people might have hair, a dimple,
or birthmark on their back above the site of the lesion. Now, the exact cause of all three types of
spina bifida isn’t known, but there are known risk factors like folate or Vitamin
B9 deficiency during fetal development. Therefore prenatal vitamins include folic
acid, which is the manufactured form of folate. The developmental deformities, though, that
cause spina bifida often take place in the fourth week of pregnancy (which is 21-28 days)
and this could be before a woman might know she’s even pregnant, and therefore she’s
not taking prenatal vitamins yet. To help combat this, enriched grain products
like breakfast cereals made with whole grains have folic acid added to flour as a general
preventative measure. Other risk factors for having a child with
spina bifida include obesity, poorly controlled diabetes, and taking medications that interfere
with folate metabolism like certain anti-seizure medications. Diagnosis for the most severe form of spina
bifida—myelomeningocele—is often done prenatally by looking for an increased level
of alpha fetoprotein (or AFP) in the mother’s serum, which can happen when the skin surrounding
the fetus’s spine is missing and AFP leaks into the amniotic fluid and into the mother’s
bloodstream. AFP, though, can be elevated by other conditions
as well so in order to get a more exact diagnosis, additional blood tests for Human chorionic
gonadotropin (or HCG), inhibin A, and estriol, as well as an ultrasound are usually done. In more serious cases, amniocentesis (where
a sample is taken directly from the amniotic sac surrounding the fetus) can be performed. For treatment, prenatal surgery is done to
close a myelomeningocele, but this surgery can be dangerous to the developing fetus as
well as the mother. In cases where postnatal surgery is chosen,
it is often done within the first few days of an infant’s life in order to minimize the
risk of infection like meningitis. Even if the surgery is successful, people
with this condition typically need additional interventions such as urinary catheterization
to help with urination and crutches or wheelchairs in case of paralysis or low muscle tone, because
the damaged or underdeveloped spinal nerves can’t be repaired. Alright, as a quick recap, the three types
of spina bifida are spina bifida occulta, which is the most common and least severe,
meningocele, which is the least common and also typically not very severe, and myelomeningocele,
which is the most severe form of spina bifida. Thanks for watching, you can help support
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