2. Spina Bifida (Spinal dysmorphism)
Introduction:
→ Spina bifida (literally, “cleft spine”) is a congenital neural tube defect in which
the vertebral arch fails to close completely over the spinal cord.
This results in a cyst-like protrusion of the meninges alone
(meningocele) or of the meninges and the spinal cord
(myelomeningocele) out of the vertebral column.
Incomplete closure of the caudal neural tube during development may
produce various deformities, ranging from the mild and entirely
incidental spina bifida occulta, to the severe, with exposure of neural
tissue to the surface (rachischisis).
In the case of a meningocele, neural tissue is unexposed, and thus neural
deficits are absent or minor.
With a myelomeningocele, the spinal cord, in a cyst-like protrusion with
its nerves, suffers injury, inflammation, and scarring. The result is some
loss of neural function, often including paralysis.
A meningocele can occur in any area of the spine; cranial or upper
cervical meningoceles are frequently associated with hydrocephalus. A
myelomeningocele typically occurs in the lumbar or lumbosacral area.
Another type of spina bifida is one in which minor irregularities in the
vertebral arches exist that are not obvious at birth. This is called spina
bifida occulta (hidden).
→ These defects may be associated with abnormal neurological function of the
lower limbs, with or without sphincter involvement. Associated tethered cord
syndrome may lead to development of neurological problems in later life.
Spina bifida may be a teratogenic consequence of drug therapy (e.g., certain
antiepileptic drugs).
→ This defect can be so subtle that it is found only through incidental radiography
or MRI, or it can be so severe that the spinal canal is open and the baby may
not survive the birth
Demographics:
→ Spina bifida statistics in the United States have recently been declining, but it
still occurs about once in every 1,000 live births, or 1,500 to 2,000 times per
year.
→ It clearly has a genetic component, because having this disorder in the family
raises the risk of having a child with spina bifida, but about 95% of cases occur
in families with no history of the disease.
→ Hispanics and European whites have a higher incidence of spina bifida than
other races.
→ Women who have spina bifida themselves or who have diabetes or seizure
disorders have a higher than normal chance of having a child with this disorder.
3. Etiology:
→ Several types of neural tube defects may occur between day 14 and day 28 after
conception.
→ Although the cause of spina bifida is unknown, a genetic predisposition may
exist. The main risk factor for is a deficiency of folic acid at conception and in
the earliest weeks of fetal development.
→ Folic acid deficiency is common in women; therefore, it is strongly
recommended that all women anticipating pregnancy begin taking folic acid
vitamin supplements at least 3 months before conception.
→ Higher risk factors may include:
o Maternal lack of folic acid and vitamins
o Previous baby & family history of spina bifida
o Maternal obesity
o Diabetes during pregnancy
o Maternal stress
o Woman who has epileptic seizures
o Maternal fever in the first trimester
o Hispanic background
Classification:
Detailed classification includes:
1. Open spinal dysraphism (OSD)
a. Occult
a. Spina bifida occulta
b. Cystic
a. Spina bifida meningocele
b. Spina bifida myelomeningocele
c. Rachischisis
2. Closed spinal dysraphism (CSD)
a. With spinal mass
b. Without spinal mass
i. Simple
ii. Spina bifida occulta
iii. Complex
4. Spina bifida can be classified as:
1. Spina bifida occulta.
→ The vertebral arch, usually in a lumbar vertebra, does not completely fuse,
but no signs or symptoms are obvious.
→ Indeed, a person with spina bifida occulta may never be aware of the
condition unless a low back radiograph is taken for another reason.
→ It is difficult to estimate how common it is; some sources suggest that 5 to
10% of the population may be affected.
→ Some people with spina bifida occulta have a small dimple, birthmark, or
tuft of hair on the spine at the location of the abnormality, but they have no
dysfunction because of it.
→ While spina bifida occulta is usually inconsequential, it can be serious.
→ Two or more vertebrae may be affected, and the person may develop a
tethered spinal cord.
→ This can manifest as problems in the feet (especially pes cavus) and
problems with bladder and bowel control. These often arise during puberty,
when the child goes through a growth spurt that stretches the spinal cord.
2. Spina bifida meningocele.
→ This is the rarest type of cystic spina bifida.
→ Only the dura mater and arachnoid layers of the meninges press through at
the site of the vertebral cleft, forming a cyst that is visible at birth.
→ It is easily reparable with surgery and generally has few or no long-term
consequences for the baby.
3. Spina bifida myelomeningocele.
→ This is the most common and most severe version of cystic spina bifida,
accounting for about 94% of cases.
→ In this case the spinal cord or extensions of the cauda equina protrude along
with the meninges through several incompletely formed vertebral arches.
→ Occasionally the skin doesn’t cover the protrusion, raising a serious risk of
CNS infection if no immediate intervention takes place.
Clinical Menifestations:
Open spinal dysraphism (OSD)
All OSD are associated with Chiari malformation type II.
Learning disabilities and seizures are more common in children with spina
bifida
5. 1) Spina bifida occulta may be asymptomatic or associated with:
→ Not obvious at birth
→ May present as:
o Patch of hair growth along the spine
o Midline dimple, usually in the lumbosacral area
→ Gait or foot abnormalities
→ Poor bladder control
2) Cystic spina bifida
→ Obvious with a sac containing meninges and/or spinal cord material protrudes
on the back of the newborn infant.
→ It usually occurs in the lumbar spine, and the sac is often red and raw looking.
→ The severity of cystic spina bifida is determined by the location and size of the
cyst. The higher the defect, the more paralysis tends to be present.
→ Fortunately, most cases present in the thoracic or lumbar spine.
a) Spinal meningocele may be asymptomatic or associated with:
→ A sac-like protrusion of meninges (dura and arachnoid only) and CSF from the
back
→ Clubbed foot
→ Gait disturbance
→ Bladder incontinence
→ Seldom neurological consequences
b) Spinal myelomeningocele is associated with:
→ Protrusion of meninges (dura, arachnoid and neural tissue) , CSF, and spinal
cord
→ Evident at birth
→ Neurologic deficits at and below the site of exposure
→ Severe disability
c) Rachischisis
→ Exposure of neural tissue to surface
→ Evident at birth
→ Severe disability
Closed spinal dysraphism (CSD) = skin-covered
1) With spinal mass:
→ Lipoma,
→ Dural defect
→ Meningocele
6. 2) Without spinal mass:
a) Simple:
o Tight filum terminale
o Intradural lipoma.
b) Spina bifida occulta:
o Incomplete closure of the vertebral laminae;
o May be evident only as dimpling of the skin or a hairy patch over the
lumbar spine, or only seen radiologically.
o May be asymptomatic or may present with progressive lower limb
sensorimotor and sphincter dysfunction in later life due to cord
tethering.
c) Complex:
o Split cord malformation (diastematomyelia)
o Caudal regression.
Diagnosis:
→ Spina bifida is detectable prenatally.
→ Testing begins with a blood sample; it shows elevated levels of a fetal protein
called alfa-fetoprotein.
→ A follow-up ultrasound may diagnose the condition in utero and/or
amniocentesis may be scheduled.
→ Some research indicates that a cesarean section is safer than vaginal birth for a
baby with spina bifida; this can be planned.
→ Furthermore, a few facilities have begun to try in utero corrective surgery. This
approach is very new, but early reports suggest a lower risk of hydrocephalus
for these children. This procedure carries very high risks, however, to both the
mother and the child.
Differential Diagnosis:
→ Severe degrees of dysraphism are unlikely to be mistaken, but the progressive
paraparesis of cord tethering has a broad differential, including structural and
inflammatory spinal cord disease.
7. Treatment:
→ No treatment may be required for spina bifida occulta or meningocele.
→ Surgical repair of the myelomeningocele, and sometimes the meningocele, is
required.
→ If surgical repair is performed, placement of a shunt to allow for CSF drainage
is necessary to prevent hydrocephalus and a subsequent increase in intracranial
pressure.
→ Planned cesarean section before the initiation of labor can be important in
reducing the neurologic damage seen in an infant with a spinal cord defect.
→ Afterward, even tiny babies are supported with rigorous physical therapy and
exercises to maintain function in the leg muscles as much as possible.
→ As children mature and their functional level becomes clear, they may be
taught to use crutches, braces, wheelchairs, or other equipment as necessary.
→ Many spina bifida patients undergo multiple surgeries, not only to reduce the
protruding cyst but also to correct a tethered cord, in which the spinal cord
doesn’t slide freely within the spinal canal; to deal with the complications of
hydrocephalus as discussed earlier; and to address whatever complications may
be brought about by severe scoliosis.
Complications:
→ Hydrocephalus, or water on the brain, affects about 85% of children with
cystic spina bifida which may occur with a meningocele or myelomeningocele.
o The insertion of a shunt that drains cerebrospinal fluid from the brain
down the neck and into the abdominal cavity prevents hydrocephalus
from damaging the brain.
→ Many have mild to severe learning disabilities that may make it difficult to
function in a mainstream classroom.
→ Many spina bifida patients develop very severe latex hypersensitivity, possibly
from having multiple intrusive surgeries and other medical procedures early in
life which may create a dangerous anaphylactic reaction later in life.
→ Other common complications include:
o Decubitus ulcers
o Digestive tract problems
o Urinary tract problems
o Obesity
o Severe muscle imbalances that can lead to flaccidity on one side,
contractures on the other
o Severe scoliosis.
