Management of Infants with Neural Tube Defects

 

Reviewed by Bobby Tsang (General Paediatrician, Waitemata District Health Board) Andrew Law (Paediatric Neurosurgery, Starship Hospital), Raewyn Gavin (General Paediatrics, Starship Hospital), Clinical Practice Committee
March 2017
Clinical Guidelines Back Newborn Services Home Page
Definition Aetiology Incidence Antenatal Issues
Place and Mode of Delivery Postnatal Management Postoperative Care Prognosis

Antenatal Counselling

This should be multidisciplinary and include:

Place and mode of delivery

Tertiary institution with access to neurosurgical services.

Aim for delivery at term. Mode of delivery should be based on individual assessment by the obstetric team. Current evidence does not show an advantage for improved neurological outcome with elective caesarean delivery.1

Postnatal Management

The goal is for neurosurgical closure within 24 hours. Transfer to Starship is recommended. In the absence of treatment, the mortality of myelomeningocoele is approximately 50%.

Some parents may opt, after discussions with the neurosurgeon, for palliative care or conservative management.

General Cares

  • Avoid latex products (use latex-free gloves for all handling).

Management at birth

  • Attendance is for management of NTD and to admit to NICU.
  • Provided airway, breathing and circulation are normal (they usually are), place baby either prone or on side to protect NTD.
  • Cover the lesion with non-adhesive, sterile, saline-soaked dressing (such as Tefla).
  • Neonates with NTD have increased risk for hypothermia due to immaturity of their thermoregulatory system, lesion related evaporative losses and being nursed bare.

Clinical Assessment

  • Clinical Assessment Careful clinical assessment and structured neurological exam after stabilisation.
  • An additional Major defect or 2 Minor anomalies may indicate a syndrome or chromosomal disorder.
  • Place the infant prone and evaluate the size, location, and appearance of the lesion. Check if lesion is leaking.
  • Measure the head circumference. Palpate fontanelle and sutures for evidence of raised intracranial pressure. Assess facies, alertness and cranial nerve function.
  • Evaluate position at rest and spontaneous movements (note that any stimulation to promote movements should be confined to the upper body, as reflex movements may occur in response to stimulation of paralysed lower limbs and trunk).
  • Evaluate passive range of motion, resistance to stretch, muscle bulk and consistency, any fixed deformities in the hips, knees or feet.
  • Evaluate the sensory level. Use a blunt drawing up needle.
  • Has the baby passed meconium? Assess anal tone. Although a tight sphincter does not indicate normal function and the anal wink is unreliable.
  • Urine output.
    • Is there dribbling of urine?
    • Is the bladder palpable?

Infection Risk

  • Antibiotics should be administered as per the Newborn Services policy.
  • Blood and other cultures are not required unless the baby is clinically unwell.
  • If there will be a delay in closure of the lesion the need for prophylactic antibiotics for risk of ventriculitis should be discussed with neurosurgery.2

Fluids/Electrolytes

  • Remain NBM. 10% dextrose as per Newborn Services Fluids and Electrolytes policy.
  • Infants with urinary retention will require urinary catheterisation.

Neurosurgical Referral

  • Inform the neurosurgical team at the Starship Hospital.
    They will arrange for early transfer and repair of the lesion.

Imaging

  • Cranial ultrasound scan of the brain to evaluate ventricular size and to assess other malformations.
  • A CT scan or MRI is commonly obtained peri-operatively but will be organised by or on the instruction of the neurosurgical team.
  • Renal imaging (renal ultrasound scan +/- MCUG) should be performed in the postoperative period.

Dressings

  • The baby should be nursed in the prone position.
  • The sac must be kept covered and moist prior to closure. Exposure of the tissue to trauma or drying out can lead to a “shock-like” state of the spinal cord.

This needs to be a strictly aseptic latex free technique.

  1. Apply saline soaked Telfa over the sac.
  2. Obtain a Butterfly infusion needle, and remove the needle.
  3. Place the Butterfly tubing on the layer of Telfa then add a second Telfa layer.
  4. Seal the entire dressing with Tegaderm.

The wound can be irrigated hourly using the fine Butterfly tubing, with small amounts of warmed saline.

Parental Support

  •  Ensure adequate time is taken to provide parents accurate explanations relating to the lesion, treatments, pending surgery and complications. Encourage parent involvement in care.
  • Referral to Paediatric Neurosurgical Social Worker will be arranged following surgery.
  • A Child Disability Allowance form should be filled out.

Useful information for parents can be accessed from the Spina Bifida Association New Zealand http://spinabifida.org.nz/


Postoperative Care

Will usually be undertaken on the Neurosurgical and Neurology Ward (26A) at Starship Hospital.

There is a high incidence of neurogenic bladder. A urinary catheter usually remains in situ postoperatively (preferably until renal imaging has been undertaken).

Prognosis

Hydrocephalus is a common occurrence after surgery but may not develop for some weeks. However most become evident in the first 10 days post closure.

Children require multidisciplinary follow-up including the neurosurgical team, a developmental or general paediatrician, urologists, orthopaedic surgeons, and physiotherapists. There should be a supervising “overviewing” paediatrician.

Children with spina bifida from West and North are seen by Dr Bobby Tsang, Paediatrician at Wilson Centre.

Those from Central and South are seen by Dr Raewyn Gavin, Paediatrician at Greenlane Clinical Centre.

Normal intellect should be assumed in the absence of significant hydrocephalus or dysmorphism.

Children with myelomeningocoele have a lifetime increased risk of latex sensitivity and therefore need to be cared for in a latex-free environment at hospital and at home.

Urological and orthopaedic referral will be organised by the neurology/neurosurgery services.

Definitions3,4

In the embryo, the neural tube forms the brain and spinal cord. Failure of normal closure results in a neural tube defect (NTD). A midline defect can occur from cribiform plate to sacral spine. Spinal dysraphism and spina bifida are terms for congenital maldevelopment of the neural tube known as myelodysplasia.

Anencephaly - defective closure of anterior portion of the neural groove results in an unfused, partially developed forebrain and calvarium. This condition is always lethal.

Encephalocele – protrusion of brain and meninges through a skull defect. Craniomeningocoele – protrusion of meninges and CSF only through skull defect. Craniorachischisis – open NTD of entire spine and incompatible with life.

Myelomeningocoele aka Meningomyelocoele - the most common type of spina bifida, is a sac like structure which protrudes through a defect in the vertebral arches, containing meninges, CSF and spinal cord and /or nerve roots. Meningocoele - structure contains meninges and CSF only. Lipomeningomyelocoele – closed NTD with lipomatous malformation or tethering of the spinal cord. Diastomatomyelia – split spinal cord with intervening fibrous, cartilaginous or boney spur (may be occulta).

Spina bifida occulta - is a common midline defect of the vertebral bodies without protrusion of spinal cord or meninges. An asymptomatic isolated radiological boney defect is common, 5% - 40%. However, a widened spinal canal on Xray or overlying neurocutaneous stigmata may be associated with underlying cord anomaly.

Meningomyelocoeles and meningocoeles may occur anywhere along the spinal cord but are most common in the lumbar and sacral region.
The degree of neurological impairment depends on the position and extent of the lesion.

Myelomeningocoeles cause variable paralysis and sensory loss caudal to the lesion, with secondary deformity, neurogenic bladder and bowel dysfunction.

Most patients with myelomeningocoele have Chiari II (Arnold-Chiari) malformation with small posterior fossa, caudal displacement of medulla, lower pons and cerebellar vermis and elongated 4th ventricle through the foramen magnum. Caudal displacement of cervical spine and kinking of medulla also occurs. Obliteration of the cisterna magna and obstructive hydrocephalus may ensue.

Coexisting CNS malformations may include polymicrogyria, heterotopia, encephalocoele, callosal agenesis, brainstem abnormalities, and syrinxes in the cord above the lesion.

Orthopaedic abnormalities secondary to disrupted muscle innervation (i.e. dislocated hips and club feet) are common. There may be an associated spinal deformity – scoliosis or kyphosis.

Major congenital anomalies of organ systems outside the nervous system are unusual and should lead to a search for an associated chromosomal disorder or syndrome. Eg cleft palate, radial hypoplasia or renal anomalies.

Incidence

The rate of neural tube defects per live births is declining worldwide at approximately 1 per 1,000 total births and terminations. New Zealand rates based on 2003 data: 0.34 per 1,000 live births; 0.57 per 1,000 early terminations and; 0.21 per 1,000 fetal deaths.5
Greater risk in lower socio-economic status, and Celtic, German or Hispanic ancestry.

Aetiology

Genetic factors

All first degree relatives of people with spina bifida require genetic counselling. There is a 4% recurrence risk after one affected child, 10% risk after two affected children and 2% risk in offspring of adults or parent sibling with NTD.

Chromosomal disorders / syndromes

Teratogens

Other

Antenatal Issues

Periconceptional folate supplementation reduces the incidence of first NTD by >50%.

Fifty percent of pregnancies are not recognised until 4 weeks at the earliest when neural tube development is almost complete. Therefore, the CDC recommends 0.4mg folic acid in all women of child bearing age.7

Current New Zealand recommendations: http://www.health.govt.nz/our-work/preventative-health-wellness/nutrition/folate-folic-acid

Low risk – 0.8mg folic acid daily, 4 weeks prior to and 12 weeks after conception.

High risk – 5mg folic acid daily 4 weeks prior to and 12 weeks after conception.

High risk: Women with NTD or had a child with NTD, or close family member who has had an NTD, or whose partner is affected or had a family history of NTD; Women on insulin for diabetes; Women on medications known to increase risk for NTD.

Screening and Detection

  • Maternal Serum Alpha Feto Protein (MSAFP) is often done at 15-20wk to screen for trisomies. An elevated MSAFP 2 – 2.5 median value detects 80% open NTD and 90% anencephaly. Uncertain gestational age results in a 5% false positive rate.
  • Amniotic Alpha Feto Protein (AFP) and Acetylcholinesterase are raised with open NTDs. The latter is specific for NTD while AFP is raised in other open defects eg. Gastroschisis.
  • USS: Diagnosis often made at 16-18 week USS. Often seen as lateral displacement of the spinal pedicles, but the sac may also be visualised.
    • An axial cross section through the fetal skull may demonstrate a “lemon head” shape, with a depression of the metopic suture in the frontal region.
    • Visualisation of the posterior fossa may demonstrate a “banana sign”, observed at the level of the cerebellum and cistern magna. It is caused by herniation of the cerebellar vermis through the foramen magnum, giving the cerebellum the appearance of a banana.
    • USS should evaluate for other structural abnormalities of limbs, brain, kidneys, and other organs.
CoronalSpine.jpg (17363 bytes)  Coronal view of spine

SagittalSpine.jpg (19227 bytes)  Sagittal view of spine

LemonHead.jpg (15065 bytes)  "Lemon" shaped skull

References

1

Greene S., Lee P.S., Deibert C.P., et al. The impact of mode of delivery on infant neurologic outcomes in myelomeningocele. Am J Obstet Gynecol 2016;Oct;215(4):495.e1-11
2 Ventriculitis in Newborns with Myelomeningocoele. Charney E.B., Melchionni J.B., Antonucci D.L. Am J Dis Child 1991; 145(3):287-290.
3 Volpe JJ. Neurology of the newborn 4th ed. WB Saunders Co, Philadelphia 2001
4 Levene MI, Chervanek FA, Whittle MJ (eds). Fetal and neonatal neurology and neurosurgery, 3rd Ed. Churchill Livingstone, London 2001.
5 Improving folate intake in New Zealand: Policy Implications: http://www.health.govt.nz/our-work/preventative-health-wellness/nutrition/folate-folic-acid
6 Wu Y.W., Croen L.A., Henning L., Najjar D.V., Schembri M., and Croughan M.S. A Potential Association Between Infertility and Spinal Neural Tube Defects in Offspring. Birth Defects Res A Clin Mol Teratol. 2006 Oct;76(10) 718-722.
7 Folic acid and neural tube defects: the current evidence and implications for prevention. Ciba foundation Symposium 181:192-208