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Neural tube defects

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general concepts of neural tube defects in pediatrics

general concepts of neural tube defects in pediatrics

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  • 1. NEURAL TUBE DEFECTS C. Ramos Perea, MD. FAAP. Associate Professor Universidad Central del Caribe y Escuela Medicina Ponce
  • 2. INTRODUCTION
    • Deformities involving CNS covering
    • Vary in severity – from the simples Spina Bifida Aperta (incomplete fusion of vertebral arches)
    • Extreme Forms; Anencephaly and Raquischisis where wide openings in cranial and vertebrae bones also absence of brain, nerves and meninges.
  • 3. Vertebral anatomy Vertebral arches(lamina ) Spinous process Vertebral canal Vértebra body TRANSVERSE FORAMEN Articular process Contains arteries & veins
  • 4. Intro - cont.
    • Most malformation especially NTD’S occur
    • early embryogenesis – are likely aberrant
    • expression of yet undefined developmental
    • gene.
    • CNS develops in a precise embriologic sequence; therefore interruption of one area affects remaining development .
  • 5. Intro – cont.
    • NTD’S – mainly embryologic induction disorder failure to properly form mesoderm-neuroectoderm.
    • Primary defect = failure of N. tube to close affecting neural-cutaneus ectodermal structures.
    • Inciting events traced to 17-30 days gestation.
  • 6.  
  • 7. Events in the 3-4 week
  • 8.  
  • 9.  
  • 10.  
  • 11. Intro – cont.
    • Primary defect – failure of neural folds to fuse in midline and form neural tube (Neuroectoderm).
    • Also maldevelopment of mesoderm (forms skeletal and muscular structures that cover neural structures).
    • Defects can be open (communicate-atmosphere) or closed (skin covered).
    • They can be ventral or dorsal
  • 12. Epidemiology
    • Anencephaly major CNS malformation in western world. Neonates=100% mortality
    • 37 times more frequently in females.
    • Recurrence rate in families can be 35%.
    • Incidence highest in: Ireland, Scotland, Wales,
    • Egypt and New Zealand. Lowest in Japan.
  • 13. Anencephaly
  • 14. Neurological lesions cont.
    • Anencefalia – one of the most common – no survival possible. Absence of calvarium, posterior bone elements and deficiency in procencephalus .
  • 15. Epidemiology – cont.
    • People of Celtic origin highest rate.
    • British Isles having highest rate than Asian Countries.
    • In USA and New England drop from
    • 2.3/1000 in 1930’s to .7/1000 births in the 60’s.
    • Reasons: Prenatal screening (AFP) and ultrasound – termination of pregnancy increase 50 fold in Britain & USA probably accounting for that decline in NTD.
  • 16. Epidemiology cont.
    • In Atlanta 1990’s more than 30% of affected pregnancies were terminated based on prenatal test.
    • In Sept. 1992 – US Public Health Service all woman childbearing age, capable of becoming pregnant – should take 0.4 mg Folic Acid per day for purpose of reducing risk of NTD’S.
  • 17. Epidemiology cont.
    • Higher intakes not well known, but can complicate Vit. B 12 deficiency.
    • Ingestion of preconception folate decreases the risk of a child with NTD.
    • In USA highest rates in Boston and Irish descents – lower rates in African and Asians.
    • Recurrence risk of NTB – 10.4% in Belfast -
    • 4.2% in London – USA 1-3%.
    • 50-70% are females.
  • 18. Embryology
    • 2 processes form the C.N.S.
    • 1-Neurulation – formation o neural structures into a tube thereby forming brain – spinal cord.
    • 2-Neurulation – formation lower spinal cord
    • lumbar and sacral elements.
    • First Neural plate at 17 days, then neuronal fold at 21 days and fusion of n. folds at 23 days.
    • Any disruption in this 3 stages = Craniorachischisi (most severe form NTD)
  • 19. Embryology cont .
    • By 23-26 days closure Ant. Neuropore
    • Failure = Anencephaly.
    • By 26-30 days closure of caudal neuropore
    • Failure = Myelomeningocele.
    • Notocord = (precursor of skeletal axis).
    • Somites = Derived from mesoderm
    • (form most of v. column-skeletal muscles and dermis)
  • 20. Embryology cont.
    • Studies on mice embryos – provided some unifying theories for explaining associated anomalies (hydrocephalus, hindbrain(post.) malformations as Chiari II.
    • 1992 McLane theories – initial event = failure of neural fold to close completely leaving a dorsal defect (Myeloschisis). This permits CSF to leak into A. Fluid creating collapse of V. System.
    • Failure of ventricular system to increased in size leads to downward herniation of small developing cerebellum.
  • 21. Etiology
    • Teratogens-(hyperthermia, sulfas,antihistaminics, nutr. deficiencies and anticonvulsivants use).
    • Most strongly tied = carbamazepine, valproic acid (folate antagon).
    • Folate deficiency.
    • Woman taking v. acid a risk of 2% (NTD) (important for epileptics undergo prenatal screen (AFP).
  • 22. Etiology cont.
    • 1970’s Smithhells noted erythrocyte folate and low a. acid in WBC in first trimester pregnancies with NTD. This work led to two important randomize studies on the use of periconception folate by British and Hungarians.
    • British study was terminated early due to the protection noted in the folic acid group. Multivitamins has no protective effect. Preconception Folic Acid prevented 72% of recurrent NTD.
    • Hungarian study results were the same.
    • Number of patients more than 2000.
  • 23. Etiology cont.
    • Ingestion of preconception F. Acid is not easy (less than 50% of pregnancies are planned).
    • Folic Acid is not protective unless ingested in periconception period.
    • NTD occurs 26 days post-fertilization – when many woman don’t know they are pregnant.
    • The precise mechanism of F. Acid protection is unclear.
  • 24. Normal Folate Adequate Folate – Healthy Cells Deficient Folate – Unhealthy Cells Perspective on Folate Deficiency Megaloblastic Anemia
  • 25. 50% of U.S. pregnancies are unplanned Folic acid is needed before conception NTDs occur very early in pregnancy Importance of timing in getting folic acid
  • 26. Median serum and red blood cell folate levels, before and after folic acid fortification, U.S. women, aged 15-44 years, NHANES SOURCE: CDC/NCHS, National Health and Nutrition Examination Surveys, 1988-94 and 1999-2000 4.8 0 5 10 15 20 ng/mL Serum folate 13.0 Before After ng/mL 159.9 263.6 0 50 100 150 200 250 300 350 Red blood cell folate Before After
  • 27. Diagnostic Detection and Associated Neurological Lesions.
    • Alpha-Feto-Protein _ Amniotic Fluid or maternal blood stream. *Major serum protein in early embryonic life and is 90% of serum globulin. It’s believe to prevent fetal immune rejection.
    • Can leak from NTD in to a. fluid.
    • Prenatal screen 15-20 weeks (at 20 weeks higher than 1000 ng/ml is indicative of NTD.
    • Ultrasound in 98% reliable in skill hands. (Close defects can be undetected).
  • 28. Conditions Associated with AFP
    • Anencephaly
    • Spina Bifida cystica
    • Encephalocele
    • Conjoined twins
    • Onphalocele + Gastroschisis
    • Polycistic kidneys
    • Oligohydramnios
    • Urinary tract obstructions.
  • 29. Neurological lesions
    • Spina Bifida Occulta – Mildest form, one or more vertebrae (usually L5 and S1) are not closed but no protrusion of spinal cord.
    • Could be associated with Syrinomelia or tethered cord.
    • 17% of population – most asymptomatic – just skin dimple with hair or discoloration over lumbar area.
  • 30. Spina Bifida Occulta
  • 31. Neurological lesions cont.
    • Meningocele – meninges protrude trough a small opening – defect closed.
  • 32. Neurological lesions cont.
    • Myelomeningocele - saccular protrusion containing neural placode and CSF. Surface covered by arachnoid but no dura nor skin. The sac appears yellow with fragile vessels. Nerve roots pass into the sac.
    • Spine tethered by bony defect.
  • 33. Meningomyelocele
  • 34.  
  • 35. Neurological lesions cont.
    • Chiari II malformation – herniation of cerebelar vermis and B. Stem below F. Magnum into C. canal. Paresis of C. nerves (3,6,9 y 10) require decompression of hind brain as an emergency.
  • 36. Neurological lesions cont.
    • Large occipital encephalocele
    • Skin covered sac representing close NTD.
    • Often cranium bifidum – represent a failure of a neuropore.
    • Needed to have V-P shunt to controlled associated hydrocephalus.
    • At 5 years moderate developmental delayed.
  • 37. Large occipital encephalocele
  • 38. Lypomyelomeningocele The left child is a dorsal lipoma – pedunculated. The right child lypomatous mass beneath the skin. Both passed through the dura to the intradural space.
  • 39.                                                     Spinal cord (close up)  location of spina bifida Occulta Outer part of vertebrae not completely joined. Spinal cord and covering (meninges) usually undamaged. Hair often at site of defect. Meningocele Outer part of vertebrae split. Spinal cord usually normal. Meninges damaged and displaced through opening. Myelomeningocele Outer part of vertebrae split. Spinal cord and meninges damaged and displaced through opening. Usually hydrocephalus.
  • 40. Anomalies Associated with Myelomeningocele Approximate Percent of Patients Chiari II malformation 90%+ Hydrocephalus 90%+ Syringomyelia 88% Brainstem malformations (cranial nerve) 75% Cerebral ventricle abnormalities 90%+ Cerebellar heterotopias 40% Cerebral heterotopias 40% Agenesis of the corpus callosum 12% Polymicrogyria 15-30%
  • 41.  
  • 42. Signs and Symptoms
    • Radiologic Signs:
    • Lamina Defects
    • Hemivertebrae
    • Scoliosis
    • Widening of interpedicular Distance
    • Butterfly Vertebrae
    • Cutaneous Stigmata:
    • Capillary Hemangioma
    • Caudal appendage
    • Dermal Sinus
    • Hypertrichosis
    • Orthopedic finding:
    • Extremely asymmetry
    • Foot deformities
    • Neurological Problems:
    • Weakness of leg- radiculopathy
    • Leg atrophy or asymmetry
    • Loss of sensation, Abnormal gait
    • Urologic Problems:
    • Neurogenic bladder
    • Incotinence
    • Anal wink
  • 43. Spina Bifida Occulta The child has long hairy tail with underline spina bifida occulta.
  • 44. Treatment and option s
    • If parents decide not to terminate pregnancy:
    • Extensive counseling and expectations once the child is born.
    • If diagnosed early enough fetal surgery promising??
    • Two major sequelae: Hydrocephalus shunt dependent + CMII malf.
  • 45. Initial Exam + Treatment
    • Neonate born with NTD – Exam focus on N. Sequelae.
    • a) Site and level of lesion b) Motor and sensory level c) presence of hydrocephalus or CMII d) ortho deformities.
    • Covered with saline sponge (drying of neural placode).
    • Prone position
    • NPO + IVF’s + Antibiotics (meningitis due to leaking lesion – ventriculitis.
  • 46. Treatment cont.
    • Ultrasound of the head for early detection of hydrocephalus – MRI for CMII and migrational problems.
    • Ortho evaluation – 10–20% NTD – hip disloc.
    • Scoliosis – Kyphosis (no skin flaps possible).
    • Once repair 95% need V-P shunt.
    • Repair within 72 hrs. after birth.
    • Any signs of CMII (stridor, apnea, dysphagia, quadriparesis) urgent posterior fossa decompression.
  • 47. Innovative Fetal Surgery
    • Vanderbilt Univ. researchers (Tulipan & Brunner) published their experience in JAMA-99 29 patients underwent intrauterine NTD repair between 24-30 wks. gestation and compare with control group.
    • Intrauterine fixed patients experience a lower incidence of hydrocephalus (59% vs. 91%) and a lower incidence of hindbrain herniation (38% vs. 95%).
  • 48. HAND OF HOPE
  • 49. Innovative Fetal Surgery cont.
    • Only one death occurred due to oligohydramnios, reason why amniotic fluid was returned to the uterus once repair was finished.
    • Extremely encouraging results but several questions remain unanswered.
    • Long term intellect?? Risk for the mother and the fetus?? Decreased shunt dependency hold for how long??
  • 50. Hydranencephaly
  • 51. Sirenomelia-mermaid
  • 52. Onphalocele
  • 53. Exencephaly
  • 54. Gastroschisis
  • 55. Encephalocele; Rachischisis; Iniencephaly
  • 56. Holoprocencephaly sequence
  • 57. Mid line anomalies “ El bosque seria muy triste si solo cantaran los pájaros que lo hacen mejor”rabindranath tagore
  • 58.  
  • 59.
    • “ Y los humanos deberían saber que de
    • solo el encéfalo y nada mas provino el gozo, la alegría, la risa,la broma,la tristeza, la aflicción, el desaliento y el lamento por esto en forma especial adquirimos sabiduría y conocimiento,vemos,oimos,conocemos lo nefasto ,lo justo, lo dulce y lo desabridos.”
    • Escritos hipocráticos