Physiology and clinical correlates of hydrocephalus.

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