Neural tube defects are congenital conditions that occur when the neural tube fails to close fully during early embryonic development. They affect around 1 in 1,500 births in the United States. Neural tube defects can be open, with protrusion of nervous system tissue, or closed without protrusion. Prenatal screening and folic acid supplementation can help reduce neural tube defect risk and aid diagnosis. After birth, treatment depends on the specific defect but may involve surgery to close open defects.

1. TOPIC: NEURAL TUBE
DEFECTS
PREPARED BY: EMMANUEL R. OLA
MEDICAL STUDENT YEAR – 5
NEUROSURGICAL UNIT – JFK MEMORIAL MEDICAL CENTER

2. CONTENTS
•Definition
•Epidemiology
•Classification
•Embryology
•Clinical Presentation
•Diagnosis
•Management

3. DEFINITION
•A neural tube defect, also known as spinal
dysraphism, is a congenital condition where the
covering of the central nervous system does not
fully develop due to a failure of the neural tube
to close during the 3rd or 4th week of embryonic
development.

4. EPIDEMIOLOGY
• 1 in 1,500 births in the United States
• 2nd-most common major congenital anomalies (most
common are cardiac anomalies)
• Incidence
• Has decreased with prenatal folic acid
supplementation and screening
• Varies by ethnicity and geographic region
• Female neonates are affected more commonly.

5. EPIDEMIOLOGY
• Maternal risk factors during pregnancy:
• Folate deficiency
• History of NTD in previous children (5%–10%
recurrence with 1–2 affected siblings)
• Folic acid-depleting medications (valproic acid,
triamterene, trimethoprim, sulfasalazine)
• Poorly controlled maternal diabetes
• Maternal obesity

6. CLASSIFICATION
• Open NTD (80% of cases): a midline defect of the
vertebral bodies with different degrees of protrusion of
the meninges and central nervous system (CNS)
• Defect along the spinal cord:
•Meningocele: Only the meninges protrude.
•Meningomyelocele: Both meninges and spinal
cord protrude (most common NTD).

7. CLASSIFICATION
Defect of the cranium:
•Cranial meningocele: Meninges protrude.
•Cranial encephalocele: Both the meninges
and brainstem/cerebellum/cerebral cortex
protrude.
•Anencephaly: complete failure of the
cephalic neural tube to close resulting in a fully
exposed fetal brain (not compatible with life)

8. CLASSIFICATION
• Closed NTD: a midline defect of the vertebral bodies
without protrusion of the meninges or neural tissue
• Without subcutaneous mass: spina bifida occulta
• With subcutaneous mass:
•Lipomyelomeningocele
•Lipomeningocele

9. EMBRYOLOGY
• Conception to 3rd week of gestation (gastrulation):
• Single cell → single-layered blastula → 3-layer
gastrula: ectoderm, endoderm, and mesoderm
• 3rd–4th week:
• Ectoderm → differentiates into neuroectoderm (creating neural
plate) → cell replication in the neural plate → neural crests +
neural fold
• Mesoderm → differentiates into notochord → signals neural
fold to enlarge/fuse → neural tube (neurulation)
• Neural tube“zips up” from the middle outward → Cranial (head)
and caudal (tail) openings close approximately on days 24 and 28

10. EMBRYOLOGY

11. CLINICAL PRESENTATION
• Most NTDs are discovered during prenatal screening
• Open NTDs are evident at birth, but closed NTDs may have more subtle presentations.
Name: Myelomeningocele
Description: Spinal cord and meningeal herniation
Clinical Features: The higher the lesion in the spine, the more severe the symptoms:
Brainstem: type 2 Chiari malformation (cerebellar tonsillar herniation) with hydrocephalus
• Neck: quadriplegia
• Lumbosacral defect:
• Paraplegia/flaccid paralysis
• Loss of touch and pain sensations in lower limbs
• Anesthesia in perianal area
• Bowel + bladder incontinence

12. CLINICAL PRESENTATION
• Name: Meningocele
• Description: Meningeal herniation without spinal cord
involvement
• Clinical Features: Fluctuant mass, Transilluminates, Covered
by skin
• Name: Encephalocele
• Description: Meninges ± brain tissue protruding from cranial
defect
• Clinical Features: Hydrocephalus, Spasticity, Paralysis,
Seizures, Microcephaly. Developmental delay, Vision
problems, Developmental and growth retardation

13. CLINICAL PRESENTATION
• Name: Anencephaly
• Description: Major component of the brain and skull is absent.
• Clinical Features: Stillbirth/early death, Spastic with
deafness/blindness
• Name: Spina bifida occulta
• Description: Midline vertebral body fusion defect without protruding
dura or neural tissue
• Clinical Features: Usually asymptomatic, If the spinal cord is involved
(tethered cord syndrome), may develop incontinence, constipation, or
ataxia May be accompanied by abnormal overlying skin with a
hemangioma, discoloration, pit, lump, dermal sinus, or hairy patch

14. CLINICAL PRESENTATION

15. DIAGNOSIS
• Prenatal screening
• Serum/amniotic α-fetoprotein (maternal serum α-
fetoprotein; MSAFP): high levels at 15–20 weeks of
gestation suggestive of NTD, but not diagnostic
• Ultrasound: Visualization of defect is 98% specific and
can be used to confirm the diagnosis (closed NTD may
not be detected).

16. DIAGNOSIS
• Postnatal imaging
• Open NTD: ultrasound is commonly used; magnetic resonance
imaging (MRI) can be used if further detail required
• Closed NTD: ultrasound indicated with following cutaneous signs:
• Palpable subcutaneous mass, Hairy patch, overlying spine, Dermal
sinus, Dimples > 5 mm deep or > 25 mm from the anal verge
• Skin tags or tail-like appendages
• Hyperpigmented patches or deviation of the gluteal cleft

17. MANAGEMENT
• Prenatal
• Prevention with folic acid (vitamin B9) supplementation:
• Decreases the incidence of NTD by around 70%
• Preconception dose: 0.4 mg/day of folic acid for at least 1 month
prior to conception and throughout pregnancy
• A higher dose (usually 4 mg/day) is indicated for the following: A
previous pregnancy affected by an NTD, A positive family history
of NTD, Use of folic acid-depleting medications
• Pre-gestational diabetes
• Delivery: cesarean section recommended

18. MANAGEMENT
• Postnatal
• Closed NTD:
• May require no intervention
• Ongoing follow-up for lower neurological symptoms
(incontinence, constipation difficulty ambulating)
• Open NTD:
• Keep warm and in the prone position.
• Cover NTD with a sterile wet dressing.
• Surgical management:
• Neurosurgical intervention for all open NTDs
• Closed NTD typically does not require surgery

19. REFERENCES
1.Boon, R. L. (2010). Textbooks of Paediatrics.
2.Winn, H. R. (2011). Youmans Neurological Surgery E-Book
3.Goetzl, L.M. Folic acid supplementation in pregnancy.
UpToDate. Retrieved Nov 2, 2020
4.Dukhovny, S., Wilkins-Haug, L. Open neural tube defects:
Risk factors, prenatal screening and diagnosis, and pregnancy
management. UpToDate. Retrieved Nov 2, 2020

20. THE END
GALATOMA