Overview

Spina bifida is a neural tube defect and it develops as a result of inadequate closure of the neural tube during the early period of embryonic development. Spina bifida is of two types:

  • Spina bifida occulta- in this abnormality the defect or opening in the spinal cord or backbone is completely covered by skin, though the skin may be abnormal or dysplastic.
  • Spina bifida cystica- it is characterized by the presence of a cystic swelling along the backbone. It is an open type of neural tube defect in which the contents of spinal cord or meninges are protruded through an abnormal opening in the back bone. This type  is further classified into two sub-types mentioned below:
    • i. Meningocele- here the cystic swelling consists of only meninges without spinal cord contents or brain tissue
    • ii. Myelomeningocele- here the cystic swelling contains both meninges and spinal cord contents [1].

spina bifida types

Different Classifications

Myelomeningocele can occur at any site along the back bone. Depending upon the location it can be classified as:

  • Thoracic myelomeningocele
  • Lumber myelomeningocele
  • Sacral myelomeningocele
  • Anterior myelomeningocele
  • Posterior myelomeningocele
  • Lateral myelomeningocele

Though myelomeningocele can be present anywhere along the vertebral column the lumbosacral and sacral areas are the most common location for the development of myelomeningocele [2].

Incidence

Though spina bifida has various types myelomeningocele is the most common type of spina bifida. Myelomeningocele can affect as many as 1 out of every 800 babies. Other conditions may also be associated with myelomeningocele. Such conditions include:

  • Hydrocephalus- this refers to the accumulation of excessive amounts of CSF in the brain. It can affect as many as 90% of children with myelomeningocele. It can raise intracranial pressure (ICP) that may prove fatal if not treated on time.
  • Hip dislocation is another problem associated with myelomeningocele.
  • Syringomyelia may be present along with myelomeningocele, characterized by the presence of cavity/syrinx in the spinal canal. It is also a serious condition [3].

sacral Myelomeningocele

Causes and risk factors

The neural plate is a structure made up of specialized type of cells. It develops in the embryo during early embryogenesis. The neural plate then folds around itself to form the neural tube. The upper end of the neural tube forms the brain and the lower part gives rise to spinal cord. An abnormality in the neural tube results in neural tube defects. In case of it, the two sides of backbone do not fuse adequately, resulting in an abnormal opening in the backbone through which the spinal cord contents along with meninges are herniated out [5]. The exact cause of sacral myelomeningocele is still a mystery. Some scientists believe the following factors to be associated with development of myelomeningocele:

  • Low folic acid level in pregnant women
  • Exposure of women to certain drugs during pregnancy
  • Exposure to radiation
  • A history of spina bifida in a previous child
  • Some type of viral infections [4]

Signs and symptoms

Often babies with it results in cystic swelling in the lower back. Other signs and symptoms may include:

  • Difficulty in walking
  • Poor coordination in walking
  • Paralysis of lower limbs
  • Numbness of lower limbs
  • Pain and heaviness in lower limbs
  • Loss of sensation in peri-anal and genital area
  • Urinary frequency, urgency and incontinence
  • Urinary retention
  • Constipation and diarrhea
  • An allergy to latex
  • Scoliosis
  • Hydrocephalus. It can cause seizures, intellectual disability and sight problems [6].

Diagnosis

Prenatal diagnosis of sacral myelomeningocele can be made by following tests:

  • Serum AFP levels
  • Quadruple or triple screen
  • Ultrasonography
  • Amniocentesis [5,7].

Tests done on the baby in the postnatal period to detect it may include x-rays, ultrasound, CT, or MRI of the spinal area [5].

Treatment

Fetal surgery is a type of surgery that is performed on the fetus before birth. It is of two types:

  • Open fetal surgery- here the uterus of the pregnant lady is opened and the fetus is exposed. A repair for it is carried out and then the fetus is put back into the uterus. The uterus and abdomen are stitched up.  After 5-7 days, a cesarean section is performed to deliver the baby [8].
  • Minimal invasive surgery- here surgery is performed by small needles under the guidance of a fetoscope and sonography [9].

Post natal surgical repair for it is performed just after birth. However, the outcome of prenatal surgery is better than that of post natal.

A ventriculoperitoneal shunt may be placed in case of associated hydrocephalus. If the surgery is delayed after birth, irreversible neurological deficits result. For such cases only conservative medical treatment is carried out [8].

Spina Bifida Fetal Surgery for Myelomeningocele

Conclusion

Sacral myelomeningocele is type of spina bifida that presents as a cystic swelling in the lower back of the baby. Its exact cause is not known and multiple factors are considered to be associated with this defect. It can be detected prenatally by some screening tests. Prenatal fetal surgery to repair this defect has a better outcome than one that is performed after birth.

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References

  1. Copp AJ, Stanier P, Greene ND. Neural tube defects: recent advances, unsolved questions, and controversies. Lancet Neurol 2013;12(8):799-810.
  2. Myelomeningocele [Internet]. [Last updated 15 Mar 2004; Cited on 30 Oct 2013]. Available from: http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002525/.
  3. Persad VL,Hof M, Dube JM,Zimmer P. Incidence of open neural tube defects in Nova Scotia after folic acid fortification. CMAJ 2002; 167(3): 241–5.
  4. Ahrens K, Yazdy MM, Mitchell AA, Wereler MM. Folic acid intake and spina bifida in the era of dietary folic acid fortification. Epidemiology 2011;22(5):731-7.
  5. Greene ND, Coppa AJ. Development of the vertebrate central nervous system: formation of the neural tube. Prenat Diagn 2009;29(4):303-11.
  6. Saboval L,Horn F, Drdulova T, et al.[Clinical condition of patients with neural tube defects]. Rozhl Chir 2010;89(8):471-7.
  7. Birnbacher R, Messerschmidt AM, Pollak AP. Diagnosis and prevention of neural tube defects. Curr Opin Urol 2002;12(6):461-4.
  8. Deprest JA, Devlieger R, Srisupundit K, et al. Fetal surgery is a clinical reality. Semen Fetal Neonatal Med 2010;15(1):58-67.
  9. Bui TH, Deprest JA, Ville Y, Westgren M. Minimally invasive techniques make fetal surgery possible. Disabling abnormalities can be corrected. Lakartidningen 1998;95(44):4848-50,4853-4.