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Myelomeningocele and Related Disorders
The open neural tube defect referred to as "Myelomeningocele" is the most common, serious birth defect. It effects approximately 1 per 1000 children born throughout the world. Complications of this birth defect may include: leg weakness, inability to control bowel and bladder, and learning difficulties. Each affected child, however, will experience a unique spectrum of effects, most will be normal or near-normal. Others will be severely affected with complete paralysis of the lower extremities and impaired mental development. All people with myelomeningocele, however, will require ongoing assistance from doctors and therapists throughout their lives.
What is a
Myelomeningocele?
A myelomeningocele occurs early in the development of the embryo between
the 20th and 28th day, well before most women even realize that they are
pregnant. A piece of tissue, destined to become the spinal cord, must in
that time interval develop a groove and two folds which connect to form a
tube. Failure to form the tube results in a neural tube defect known as "Myelomeningocele"
when it occurs in the region of the spine. Neural tube defects which occur
in the central nervous system will result in a more severe anomaly known
as an anencephaly which is not compatible with prolonged survival. Babies
affected with myelomeningocele, however, do survive and are usually born
with a back defect visible at the time of delivery. Myelomeningocele is
also commonly associated with the development of hydrocephalus 90-95% of
the time as well as with a malformation of the parts of the brain, the
cerebellum and brainstem. This malformation is called the "Chiari II
Malformation".
The Infant
with Myelomeningocele
Shortly after birth, a child with myelomeningocele must have a repair of
the open neural tube. Failure to repair may result in serious infection
which would harm the developing infant brain. After the repair, closure of
the myelomeningocele, many children require the insertion of a device
called a shunt to divert the cerebral spinal fluid to treat the
hydrocephalus. An infant with myelomeningocele develops hydrocephalus
because of failure of the cerebral spinal fluid recycling system. This
system usually fails because the usual pathways are blocked or malformed.
The Chiari malformation in many patients remains asymptomatic, however,
serious and even lethal manifestations of the Chiari malformation may
occur during infancy and may include: respiratory distress, weakness of
the ninth and tenth cranial nerves, resulting in noisy respirations known
as "strider", difficulties with feeding, and episodes of apnea (when the
child does not breathe properly). Urgent surgery to decompress the Chiari
Malformation will help these unfortunate 5% of infants with
myelomeningocele.
The Older
Child with Myelomeningocele
As the child with myelomeningocele grows older, she/he and the family will
need evaluation of urologic function as well as regular evaluations by an
orthopedic surgeon to assess the need for help in correcting deformities
of the spine and lower extremities. Additionally, as the child matures,
issues such as management of incontinence and development of an
independent life can be facilitated by the involvement of a physical
medicine and rehabilitation specialist. Children with myelomeningocele
also benefit from early physical therapy and occupational therapy
intervention and frequently require orthotics (braces) and other devices
to improve the ability to function.
The neurosurgeon follows patients to detect the early signs of post-repair
spinal cord tethering which may include scoliosis; an increasingly crooked
spine, new weakness in the legs and feet and a change in bowel or bladder,
especially a bladder that changes from weak and relaxed to tight and small
capacity. Children with myelomeningocele may also develop late problems
from the Chiari malformation including scoliosis and hand weakness. All of
these problems can be detected by an MRI scan and can be corrected by
surgery.
Prevention and
Detection
A pregnancy effected by myelomeningocele can be both detected and
prevented. The use of prenatal folate, a B vitamin found in green leafy
vegetables, peanut butter, orange juice, and most easily in vitamin
supplements, can result in a 60% decrease in the occurrence of open neural
tube defects. Because the open neural tube defect occurs before most women
even realize that they are pregnant, it is important that all women who
are capable of becoming pregnant are taking in an adequate amount of
folate. The use of preconception vitamin supplementation is encouraged.
Myelomeningocele can also be detected by prenatal screening of maternal
serum alpha feto protein (MSAFP) between weeks 15 and 20 of prenatal
development. MSAFP is extremely sensitive, but not very specific and
usually is elevated for unrelated reasons. However, if an elevated MSAFP
is detected, high resolution ultrasound and possibly amniocentesis can
allow accurate prenatal diagnosis.
Other Spinal
Disorders: Spina Bifida Occulta
Myelomeningocele is occasionally refereed to as "spina bifida aperta" or
open spina bifida. A variation, spina bifida oculta, is much less common.
Spina bifida Occulta is a single term that refers to a range of congenital
anomalies involving
the lumbar and other spinal regions characterized by
normal tissue placed in an abnormal location, resulting in tethering of
the spinal cord into an abnormally low position. Individuals with spina
bifida oculta frequently have skin lesions on the back which appear to be
benign birthmarks, but in reality are the warning of the disordered
embryological development.
Spina bifida oculta includes many different types of problems; from very
simple sinuses lined by skin which can enter the spinal canal and result
in serious infection, to complex combinations of spinal cord, meninges,
and fat tissue which adhere to the spinal cord. Other variations of this
group of disorders include bony spikes which intrude between two halves of
the spinal cord and a spinal cord which end in a trumpet-like or flair of
abnormal tissue rather than in the usual tapering tip called the conus
medullaris. These spinal problems are like myelomeningocele in that they
can result in weakness of the lower extremities and difficulty with
controlling the bowels and bladder, however, they are unlike
myelomeningocele in that they usually do not occur with hydrocephalus and
the other brain malformations which are commonly seen in myelomeningocele.
Another significant difference between the two disorders is that spina
bifida occulta patients can have planned surgery, because spinal fluid is
not draining from an open neural tube defect. Surgery can be delayed for a
period of time to allow the infant to grow. It is recommended that these
congenitally abnormal spinal cords be released within the first three to
six months of life, if possible, and within a few months after detection
in a child who is asymptomatic. Symptomatic children require more urgent
intervention as with any neurosurgical intervention in a person who is
deteriorating.
For further information, contact Pediatric Neurosurgery at (706) 721-5568
For further information on Spina Bifida please visit the Spina Bifida Association of America.