Disorders of Neural Tube Closure

1. Disorders of Neural Tube Closure Dr Malith Kumarasinghe (MBBS)

2. Review of Neuroembryology • Dorsal induction • Primary neurolation: 3-4 wks gestation Brain and upper spine • Secondary neurolation: 4-5 wks gestation Distal spine

3. Disorders of neural tube closure • Chiari I-IV • Encephaloceles • Anencephaly • Corpus Callosum Agenesis • Spinal Dysraphism (Spina bifida) • - Menigoceles • - Myelomeningoceles • Tethered chord

4. Enephaloceles • Anatomy • Failure of the anterior neural tube to close due to genetic, infection, or toxic reasons. • 1/1000 • Distorted parts of the (covered) brain protruding extracalvarially

5. Encephalocele Anatomy Occipital 90% Parietal 10% Transsphenoidal Frontoethmoidal Nasal

6. Encephaloceles • Parietal encephalocele • Frontoethmoidal encephalocele

7. Encephaloceles • Clinical Depends on involvement • Treatment Surgical excision of sac with water-tight dural closure

8. Anencephaly • 1/1000 • Anencephaly is a defect in the closure of the neural tube during fetal development. • Large defect of the calvarium, meninges, and scalp. • Incompatible with life.

9. Anencephaly

10. Corpus callosum • Location? • Functions?

13. Lateralization of Function • Lateralization of function refers to the idea that each hemisphere of the brain is specialized for different functions. • Each hemispheres controls the contralateral (opposite) side of the body. • Example: skin receptors and muscles mainly on the right side of the body. • Each hemisphere sees the opposite side of the world.

14. Lateralization of Function • The left and right hemisphere exchange information primarily through a set of axons called the corpus callosum. • Other areas that exchange information include: • The anterior commissure. • The hippocampalcommissure. • A few other small commissures. • Information crosses to the other hemisphere with only a brief delay.

15. Fig. 14-2, p. 418

16. Corpus Callosum Agenesis • Expansion of third ventricle • May present with HCP, seizures • May be incidental finding without any clinical significance

17. Spinal Dysraphism (spina bifida) • Spina bifida occulta: 20-30% in North Americans, often incidental, cutaneous manifestations • Spina bifida aperta: • Meningocele • Myelomeningocele

18. Spinal Dysraphism • Spina bifida occulta

19. Spinal Dysraphism • Meningocele

20. Spinal Dysraphism • Myelomeningocele

21. Meningocele • 1-2/1000 • 1/3 have neurological deficits • Surgical repair with water-tight dural closure

22. Meningomyelocele • 1-2/1000 live birth • Failure of complete closure of caudal neural tube • 85% occur in lumbar region

23. Meningomyelocele

24. Meningomyelocele

25. Myelomeningocele • Clinical • Mild to complete paralysis • Ruptured vsunruptured • Urinary incontinence • Skeletal abnormalities

26. Myelomeningocele • Treatment • If open, Gent and Naf IV • Prone, bottom up • Telfa with wet gauze over lesion • Surgical closure within 36hrs • Shunt if overt HCP • Urologic and Orthopaedic consultation

27. Lipomyelomeningocele • Present with back mass, bladder problems, paralysis • Cutaneous stigmata • Treatment is surgical decompression