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Inciteful Med

Your First Steps: Understanding Open Spinal Dysraphism

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Open spinal dysraphism (OSD), such as myelomeningocele, is a congenital condition where the spine fails to close completely. Spinal cord damage happens in two stages: the initial developmental defect, followed by progressive damage from amniotic fluid exposure during pregnancy.

Key Takeaways

  • • Open spinal dysraphism (OSD) is a congenital disorder where the bony arches of the spine fail to close, leaving the spinal cord exposed.
  • • Myelomeningocele is the most common type of OSD, presenting as a visible sac on the baby's back containing spinal cord tissue and nerves.
  • • Spinal cord damage in OSD follows a 'two-hit hypothesis', beginning with the initial spinal defect and worsening through ongoing exposure to amniotic fluid.
  • • Fetal surgery is sometimes offered before birth to close the defect and protect the nerves from further amniotic fluid damage.
  • • Children with OSD achieve the best outcomes through coordinated care from specialized teams of neurosurgeons, urologists, and orthopedic surgeons.

Receiving a diagnosis of open spinal dysraphism (OSD) for your child—whether during pregnancy or shortly after birth—can feel like the world has suddenly shifted. It is completely normal to feel a range of intense emotions, from shock and grief to a “panic spiral” of “what ifs” [1].

While this is a serious, lifelong condition, it is important to know that you are not alone. Advances in medical care and the move toward multidisciplinary care (teams of different specialists working together) have transformed the outlook for children with OSD [1][2]. Many children born with these conditions lead active, fulfilling lives and achieve social independence [1].

What is Open Spinal Dysraphism?

Open spinal dysraphism (also called spina bifida aperta) is a congenital disorder (present from birth) where the bony arches of the spine fail to close completely [3][4].

  • Open vs. Closed: In “open” defects, the spinal cord or nerves are exposed to the outside world, often visible as a cyst or protruding sac on the baby’s back [3][4]. In “closed” defects (spina bifida occulta), the bony defect is fully covered by intact skin [3][4].
  • Common Types: The most common and well-known form of OSD is myelomeningocele (MMC), where a fluid-filled sac containing both the spinal cord tissue and nerves pushes through an opening in the spine [5][6][4].

Understanding the “Two-Hit Hypothesis”

Doctors often use the two-hit hypothesis to explain how the spinal cord is injured in OSD. This framework helps explain why early intervention is so critical:

  1. The First Hit: This occurs very early in pregnancy when the neural tube—the structure that eventually becomes the brain and spinal cord—fails to close properly [7][8].
  2. The Second Hit: Because the spinal cord is left open and unprotected, it is continuously exposed to amniotic fluid (the fluid surrounding the baby in the womb) [8][7]. Over the course of the pregnancy, this exposure causes secondary, progressive damage to the delicate spinal cord tissue [8][7].

Understanding this “second hit” is why some families are offered prenatal surgery (surgery before birth) to close the defect and protect the nerves from further damage while the baby is still in the womb [9][10].

Incidence and the Role of Folic Acid

OSD occurs globally, though the rates vary depending on where you live. The reported incidence ranges from 0.2 to 11 per 1,000 live births [11][12].

Taking folic acid before and during early pregnancy has been a major breakthrough, acting as a critical preventive measure that significantly reduces the probability of a neural tube defect developing [13][14][15]. Public health interventions, like the fortification of flour, have successfully lowered these rates in many regions [16][17].

However, it is vital to understand that OSD can still occur even when parents do everything right, as environmental factors, maternal metabolism, and complex genetics also play a role [18][19]. If you are reading this after a diagnosis, know that this is not your fault.

Moving Forward with Hope

A diagnosis of OSD is not a reason to lose all hope. While your child will likely face challenges with mobility, bladder or bowel control, or brain health (such as hydrocephalus, a buildup of fluid in the brain), there are well-established medical and surgical treatments for all of these [20][21].

Children with OSD now have access to specialized clinics where pediatric neurosurgeons, urologists, and orthopedic surgeons work together to optimize their health and maximize their independence [5][1][22]. Your journey is just beginning, and this guide—along with your care team—is here to help you navigate every step.

Navigate This Guide

Frequently Asked Questions

What is the difference between open and closed spinal dysraphism?
In open spinal dysraphism, the spinal cord or nerves are exposed to the outside, often visible as a cyst or sac on the baby's back. In closed spinal dysraphism, also known as spina bifida occulta, the bony defect is completely covered by intact skin.
What is the two-hit hypothesis in OSD?
The two-hit hypothesis explains how the spinal cord is injured during pregnancy. The 'first hit' is the spine failing to close properly. The 'second hit' is the progressive, secondary damage caused by the open spinal cord being continuously exposed to amniotic fluid.
What is a myelomeningocele?
Myelomeningocele is the most common type of open spinal dysraphism. It occurs when a fluid-filled sac containing both the delicate spinal cord tissue and nerves pushes outward through an opening in the baby's spine.
How does folic acid affect the risk of spinal dysraphism?
Taking folic acid before and during early pregnancy acts as a critical preventive measure that significantly lowers the chance of a neural tube defect. However, OSD can still happen even with proper folic acid intake due to complex genetics and environmental factors.
Which doctors will be part of my baby's OSD care team?
Children with OSD require a multidisciplinary medical approach. Your child's core care team will typically include pediatric neurosurgeons, urologists, and orthopedic surgeons working together to maximize their health and independence from birth through adulthood.

Questions for Your Doctor

  • • Is this an 'open' or 'closed' spinal dysraphism, and which specific type (like myelomeningocele) does my baby have?
  • • Based on the imaging, what is the 'anatomical level' of the lesion, and what does that typically mean for future mobility?
  • • Can you explain the 'two-hit hypothesis' in the context of my baby's specific diagnosis and how it relates to our treatment timing?
  • • Do you see signs of a Chiari II malformation or hydrocephalus on the scans, and how would those be managed?
  • • Does our hospital have a dedicated multidisciplinary team (neurosurgery, urology, orthopedics) that will follow my child from birth through adulthood?

Questions for You

  • • What were my first thoughts or feelings when I heard this diagnosis, and have I given myself space to process them without judgment?
  • • Who in my life can I lean on for emotional support or practical help right now?
  • • What information do I feel I need most urgently to feel more prepared for the next few weeks?
  • • How can I best advocate for my child while also taking care of my own mental health during this time?

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References

  1. 1

    Encouraging Results of Bowel and Bladder Management in Spina Bifida Aperta in South India with Quality of Life Scores in a Tertiary Care Institution in South India.

    Kurian JJ, Jacob TJK, Mathai J

    Journal of Indian Association of Pediatric Surgeons 2019; (24(1)):21-26 doi:10.4103/jiaps.JIAPS_195_17.

    PMID: 30686883
  2. 2

    Double jeopardy in early infancy: aperta lipomyelomeningocele with Chiari II malformation complicated by infantile hypertrophic pyloric stenosis.

    Kattamanchi D, Jayaraman K, Kamalakannan SK, Arun A

    BMJ case reports 2025; (18(11)) doi:10.1136/bcr-2025-268860.

    PMID: 41218952
  3. 3

    [Spina bifida].

    Mühl-Benninghaus R

    Der Radiologe 2018; (58(7)):659-663 doi:10.1007/s00117-018-0401-9.

    PMID: 29797041
  4. 4

    Concepts in the neurosurgical care of patients with spinal neural tube defects: An embryologic approach.

    Blount JP, George TM, Koueik J, Iskandar BJ

    Birth defects research 2019; (111(19)):1564-1576 doi:10.1002/bdr2.1588.

    PMID: 31576681
  5. 5

    Myelomeningocele - a single institute analysis of the years 2007 to 2015.

    Januschek E, Röhrig A, Kunze S, et al.

    Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery 2016; (32(7)):1281-7 doi:10.1007/s00381-016-3079-1.

    PMID: 27086130
  6. 6

    Absence of a Hernia Sack in Patients Undergoing Prenatal Repair of Spina Bifida Increases the Risk of Developing Shunt-Dependent Hydrocephalus.

    Pastuszka A, Koszutski T, Horzelska E, et al.

    Diagnostics (Basel, Switzerland) 2023; (13(3)) doi:10.3390/diagnostics13030343.

    PMID: 36766448
  7. 7

    Advances in Fetal Repair of Spina Bifida Integrating Prenatal Surgery, Stem Cells, and Biomaterials.

    Evangelista A, Ruccolo L, Friuli V, et al.

    Biomedicines 2026; (14(1)) doi:10.3390/biomedicines14010136.

    PMID: 41595670
  8. 8

    Spina bifida as a congenital neurodevelopmental condition: Developing a philosophy of health care transition across the lifespan.

    Castillo J, Thibadeau JK, Witt E, et al.

    Journal of pediatric rehabilitation medicine 2025; (18(4)):253-255 doi:10.1177/18758894251394504.

    PMID: 41213895
  9. 9

    Fetal myelomeningocele repair: a narrative review of the history, current controversies and future directions.

    Yamashiro KJ, Farmer DL

    Translational pediatrics 2021; (10(5)):1497-1505 doi:10.21037/tp-20-87.

    PMID: 34189108
  10. 10

    Fetal surgery for spina bifida.

    Dewan MC, Wellons JC

    Journal of neurosurgery. Pediatrics 2019; (24(2)):105-114.

    PMID: 31370010
  11. 11

    Neural tube defects: Different types and brief review of neurulation process and its clinical implication.

    Ravi KS, Divasha , Hassan SB, et al.

    Journal of family medicine and primary care 2021; (10(12)):4383-4390 doi:10.4103/jfmpc.jfmpc_904_21.

    PMID: 35280642
  12. 12

    Research: Prevalence of neural tube defects Khartoum, Sudan August 2014-July 2015.

    Omer IM, Abdullah OM, Mohammed IN, Abbasher LA

    BMC research notes 2016; (9(1)):495 doi:10.1186/s13104-016-2298-6.

    PMID: 27881182
  13. 13

    Severe myelomeningocele in the fourth pregnancy of a 29-year-old woman: a case report.

    Anghelina L, Şerbănescu MS, Gheonea C, et al.

    Romanian journal of morphology and embryology = Revue roumaine de morphologie et embryologie 2025; (66(3)):587-592 doi:10.47162/RJME.66.3.16.

    PMID: 41382955
  14. 14

    Epidemiology of congenital anomalies of the central nervous system in children in Enugu, Nigeria: A retrospective study.

    Eke CB, Uche EO, Chinawa JM, et al.

    Annals of African medicine 2016; (15(3)):126-32 doi:10.4103/1596-3519.188892.

    PMID: 27549417
  15. 15

    Folic Acid Exposure Rescues Spina Bifida Aperta Phenotypes in Human Induced Pluripotent Stem Cell Model.

    Sahakyan V, Duelen R, Tam WL, et al.

    Scientific reports 2018; (8(1)):2942 doi:10.1038/s41598-018-21103-8.

    PMID: 29440666
  16. 16

    Prevention of neural tube defects by the fortification of flour with folic acid: a population-based retrospective study in Brazil.

    Santos LM, Lecca RC, Cortez-Escalante JJ, et al.

    Bulletin of the World Health Organization 2016; (94(1)):22-9 doi:10.2471/BLT.14.151365.

    PMID: 26769993
  17. 17

    Real prevalence of neural tube defects in Japan: How many of such pregnancies have been terminated?

    Kondo A, Akada S, Akiyama K, et al.

    Congenital anomalies 2019; (59(4)):118-124 doi:10.1111/cga.12333.

    PMID: 30883906
  18. 18

    Novel Mode of Defective Neural Tube Closure in the Non-Obese Diabetic (NOD) Mouse Strain.

    Salbaum JM, Kruger C, MacGowan J, et al.

    Scientific reports 2015; (5()):16917 doi:10.1038/srep16917.

    PMID: 26593875
  19. 19

    Association between rare variants in specific functional pathways and human neural tube defects multiple subphenotypes.

    Zou J, Wang F, Yang X, et al.

    Neural development 2020; (15(1)):8 doi:10.1186/s13064-020-00145-7.

    PMID: 32650820
  20. 20

    Myelomeningocele: Long-Term Neurosurgical Management.

    Marcati E, Meccariello G, Mastino L, et al.

    Advances and technical standards in neurosurgery 2024; (49()):95-122 doi:10.1007/978-3-031-42398-7_6.

    PMID: 38700682
  21. 21

    Foundations of Myelomeningocele Management: History, Embryology, Diagnosis, and Treatment of Myelomeningoceles Through the Sheffield Study.

    Adapa AR, Teasley DE, Fogel H, Feldstein N

    World neurosurgery 2025; (199()):123984 doi:10.1016/j.wneu.2025.123984.

    PMID: 40685174
  22. 22

    Fetal surgical intervention for myelomeningocele: lessons learned, outcomes, and future implications.

    Danzer E, Joyeux L, Flake AW, Deprest J

    Developmental medicine and child neurology 2020; (62(4)):417-425 doi:10.1111/dmcn.14429.

    PMID: 31840814

This page provides educational information about open spinal dysraphism and fetal development. Always consult your pediatric neurosurgeon or maternal-fetal medicine specialist for advice regarding your baby's specific diagnosis and care plan.

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