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Neurosurgical Issues in Children with Spina Bifida

Hydrocephalus and shunting

Hydrocephalus is extremely common in children born with myelomeningocele; overall approximately 2/3 will end up needing a shunt, the placement of which is usually performed 5 to 10 days after myelomeningocele closure. Usually, the shunt operation is delayed from the myelomeningocele closure by 5 to 10 days. Although early shunting in the first few weeks of life may improve neurodevelopmental outcome [Sgouros: 2006], many other factors, including the degree of brain malformation, affect ultimate intellectual and functional outcomes. Up to 90% of all children born with myelomeningocele develop hydrocephalus eventually, with about 80% of them requiring a shunt for treatment. Children with myelomeningocele without shunts are followed closely with clinical exam, including neurodevelopmental assessment and imaging. The decision on timing of the first shunt placement must balance the risks of surgery and related complications with potential brain damage from hydrocephalus. Nobody knows if a child with small ventricles and a shunt will do better than a child with stable, large ventricles.

Hydrocephalus and learning problems:
  • Children with myelomeningocele and hydrocephalus do worse neurodevelopmentally than children without hydrocephalus, whether or not they are shunted;
  • They also have more complications, such as seizures; and
  • It is thought that both the underlying brain malformations associated with the hydrocephalus (e.g., neuronal loss and Chiari II malformation) and the continued effects of hydrocephalus on cerebral blood flow are implicated in these problems.


Signs and symptoms
of hydrocephalus:
  • In infants and toddlers, before suture closure:
    • Increasing head circumference
    • Bulging, tense fontanelles
    • Vomiting
    • Sleepiness
    • Irritability
    • Downward eye deviation (sunset sign)
  • In children after suture closure:
    • Acute or slow onset of increased intracranial pressure
    • Headache
    • Nausea/vomiting
    • Blurred or double vision
    • Somnolence
    • Irritability
    • Balance problems
Problems that might occur with shunt surgery:
  • Shunt infection - more likely to occur in younger children and in the first three months after surgery;
  • Mechanical problems - may result from obstruction by biological debris or mechanical failure;
  • Underdrainage - continued increased intracranial pressure, with symptoms of hydrocephalus; and
  • Overdrainage - may lead to subdural hematomas or slit ventricle syndrome, which may cause intermittent symptoms.

Chiari II malformation

  • Refers to displacement of cerebellar tonsils and inferior vermis, and possibly the fourth ventricle, choroid plexus, and medulla, into the spinal canal.
  • Chiari II malformation is present in virtually all patients with myelomeningocele but requires treatment in only a small minority.
  • May be accompanied by decreased gray matter posteriorly and decreased size of the corpus callosum.
  • Infants may present with difficulty breathing, increased high pitched crying, apneic episodes, aspiration, and arching, (the latter is similar to that seen in infants with reflux).
  • Older children present less dramatically, but may have headache, swallowing difficulties, and passing out episodes.
  • It may present with syringomyelia, which occurs in about 1/3 of cases and have accompanying symptoms of spasticity and/or progressive weakness.
  • Symptoms of Chiari II malformation may be difficult to separate from the symptoms of shunt malfunction and/or increasing hydrocephalus in unshunted individuals.
  • Chiari II malformation may contribute to the learning problems observed in this population.

Tethered cord

  • The spinal cord in most children is able to move with the child, but in children with tethered cord, the spinal cord is stretched, eventually leading to damage to nerves that control the bowel, bladder and legs.
  • In some children with myelomeningocele, the cord may become tethered during the initial surgery to close the spine.
  • The cord is also sometimes tethered in children with spina bifida occulta, and in children with other closed neural tube defects such as diastematomyelia. Certain skin findings over the lower part of the back, including fat deposition, a hairy or discolored patch of skin, skin tags and dimples may signal the presence of a tethered cord.
  • Symptoms may include bowel or bladder problems and/or orthopedic problems, including back pain, scoliosis, and weakness and loss of sensation in the legs.
  • If tethered spinal cord is suspected clinically, an MRI of the spine should be performed, and in some cases, if tethered cord is confirmed, surgery is needed to release the spinal cord so that it can move freely within the spinal canal.
  • Controversy exists regarding treatment of tethered cord in children with myelomeningocele; although tethered cord occurs in the majority of patients with myelomeningocele, only approximately 1/3 of those with tethered cord will have symptoms [Liptak: 2003]; the decision to operate is based on clinical symptoms.
  • Symptoms of tethered cord might be subtle, especially in a child who is in a wheelchair where gait problems will not be noted; back and leg pain may be the presenting symptoms; in younger children these might manifest as a decrease in activity, failure of toilet training, or wet diapers between catheterizations in children with neurogenic bladder.
  • Another manifestation of tethered cord might be increased tightness or spasticity in the legs leading to decreased range of motion or new, changing joint contractures or progressive scoliosis.
  • Surgery is helpful in preventing further deterioration and in preventing irreversible damage; however only about half of the patients return to their pre-tethering baseline state with surgery.
  • Tethered cord can recur in about 1/4 of children who have had release surgery; routine follow-up visits with neurosurgery are important .

Syringomyelia

  • Fluid within the spinal cord;
  • Many children with myelomeningocele have syringomyelia yet it causes symptoms in only a small percentage (2-5% [Liptak: 2003]); and
  • It can be difficult to distinguish symptoms of myelomeningocele, tethered cord, Chiari II malformation.

Resources

Services

In general, children with myelomeningocele should be followed periodically

Pediatric Neurosurgery

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Authors

Author: Lynne M Kerr, MD, PhD - 11/2008
Reviewing Author: John Kestle, MD - 11/2008

Page Bibliography

Liptak, G.S.
Evidence-based Practice in Spina Bifida: Developing A Research Agenda.
Evidence-based Practice in Spina Bifida, 2003; Washington D.C.. / http://web.archive.org/web/20040701175406/http://www.sbaa.org/site/Doc...

Sgouros S, Kulkharni AV, Constantini S.
The international infant hydrocephalus study: concept and rational.
Childs Nerv Syst. 2006;22(4):338-345. PubMed abstract