Topic 2
Neural Tube Defects & Hydrocephalus
Neural Tube Defects
Etiology
o Neural tube defects occur when there is a failure of the neural tube to close
during the embryo’s first 3-5 weeks
o The etiology of NTDs is multifactorial. The cause is thought to be a combination
of the following:
• Medications – for example, valproic acid (an epileptic drug)
• Radiation – for example, x-rays during pregnancy
• Maternal malnutrition – low maternal Vitamin B12 and maternal obesity,
maternal diabetes
• Chemicals
• Genetic mutations in the folate pathways – recommended that women of
childbearing age take 0.4mg of folic acid daily to prevent risk
o Prenatal diagnosis is possible through maternal serum alpha feto-protein
(MSAFP) and through ultrasound
Types
o Anencephaly is the first type of neural tube defects
• Anencephaly occurs when minimal brain tissue is developed
• Babies are usually born live with this condition, but die within the first few
hours of life
o Spina bifida is the second type of neural tube defect, which can be broken down
into two further types: • Spina bifida occulta – occurs when babies do not have complete closure of
the spinal cord by vertebrae. The baby may have a back dimple or tuft of hair
on back. There usually are no deficits/risks associated with spina bifida
occulta.
• Spina bifida cystica – refers to a visible defect with an external saclike
protrusion. Spina bifida cystica refers to two types of defects; meningocele
and myelomeningocele
▪ Meningocele – sac-like protrusion that encases meninges and spinal
fluid. This defect usually does not cause neurological deficits.
▪ Myelomeningocele – sac-like protrusion that encases meninges, spinal
fluid and nerves. This defect is the most common, accounting for 90% of
spinal cord lesions. This defect usually causes neurological deficits of
varying severities.
o These babies are born via C-section, if diagnosed prenatally.
o If the sac ruptures, then the babies are at extreme risk for infection.
Clinical Manifestations
o The degree of neurological dysfunction is dependent on the anatomical level of
the defect and the amount of nerve tissue involved
o Sensory disturbances are parallel to motor dysfunction (motor/sensory function
is impaired below the defect)
o Almost all babies will have bladder and bowel dysfunction, and most babies will
have joint deformities
• For example, kyphosis, scoliosis, hip dislocation or subluxation
o Is associated with hydrocephalus and Chiari II malformation in about 80% of
spina bifida babies • Hydrocephalus is a condition in which there is an abnormal build up of CSF in
the ventricles of the brain
• Chiari malformations are structural defects in the cerebellum (part of the
brain that controls balance). Normally, the cerebellum and parts of the brain
stem sit in an indented space at the lower real of the skull, above the foramen
magnum. When part of the cerebellum is located below the foramen
magnum, it is called a Chiari malformation.
• Type II involves the extension of both cerebellar and brain stem tissue into
the foramen magnum.
Management
Fetal surgery would be ideal for this condition, however it is still in early stages
of development and is high risk to the mother and for premature birth. This is
not commonly practiced today.
o Support is multidisciplinary for care of babies with this condition, and thus
requires intensive nursing skills
o As for family support and newborn care…
• Proper care of the sac should be maintained and taught to parents. Dressing
should be applied and changed q2-4 hrs (dependent on the doctor’s orders),
and always moistened with normal saline. During dressing changes, the sac
should be inspected for leaks, abrasion, irritations or any signs of infection.
• Babies should lay in prone positioning. The baby should never lay supine as
this puts the child at risk for sac rupture.
• Proper skin care should also be performed to reduce risks of infection and
skin breakdown
o Neurosurgery usually takes place within 24 hours – the surgeon will return the
spinal cord and nerves to normal positioning and close the hole. • If the baby suffers from hydrocephalus, the surgeon may perform a shunt
procedure. VP shunts are most commonly used in this procedure.
• Post-surgery vital signs, I&O and pain management should be monitored.
Neuro signs should also be monitored, including whether the baby cries,
pupil response, and lethargy.
• Babies should also be monitored for signs of increased intracranial pressure
• Post-surgery, the babies should remain in prone positioning until directed by
the surgeon. Surgeons might allow side-lying for feeds, unless there are other
contraindications such as hip issues. Babies may be held as long as pressure
is not placed on site of the defect.
o Orthopaedic considerations involve prevention of joint contractures, correction
of existing deformities, prevention/minimization of effects of motor and sensory
deficits, and prevention of skin breakdown.
• To prevent joint contractures, parents should be taught to perform range of
motions on their children
• Common deformities that exist in spina bifida are club foot, or deformities of
the hip (subluxation), knee, and spine.
• Because children with spina bifida usually have sensory deficits in the lower
extremities, skin care is extremely important. It is important to take proper
precautions to reduce risk for skin breakdown and to perform thorough
assessments.
o Myelomeningocele commonly causes neurogenic bladder dysfunction and
varying degrees of fecal incontinence.
o Bladder considerations include the following:
• The characteristics of bladder dysfunction in children vary according to the
level of the neurological lesion and the influence of bony growth and
development on the spine. Thus, ongoing urological monitoring is essential.
• Clean, intermittent catheterization is taught to the children and parents to
regularly empty the child’s bladders. This may
More
Less
