Disorders of Neural Tube Closure

1. Disorders of Neural Tube Closure

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. Neural groove

4. Neural tube

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

6. Chiari I ANATOMY • Peglike cerebellar tonsils displaced into upper cervical canal ( >10mm) • HCP 25% • Syringomyelia 60% • Skeletal anomalies 25%

7. Chiari I: displaced tonsils

8. Chiari I: syringomyelia

9. Chiari I: syringomyelia

10. Chiari I Clinical • Asympotmatic (30%) • Headache • Weakness • Cerebellar signs • Herniation >12mm invariably symptomatic

11. Chiari I Treatment • Observation if asymptomatic • Surgery if symptomatic: p-fossa decompression +- cervical laminectomy

12. Chiari II Anatomy • Calvarial defects • Small p-fossa • Fenestrated falx • HCP in 90% • Myelomeningocele in 100% • Syringohydromyelia in 50%-90%

13. Chiari II: Brain MRI

14. Chiari II: Calvarial defects , falx

15. Chiari II Clinical • Dysphagia • Apneic spells • Stridor • Aspiration • Arm weakness

16. Chiari II Treatment • Shunt • P-fossa decompression • Repair of MM

17. Chiari III and IV Chiari III Most severe form. Chiari II + low occiptial or high cervical encephalocele. Usually incompatible with life Chiar IV Severe cerebellar hypoplasia or absence. No herniation Extremely rare

18. 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

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

20. Encephaloceles • Parietal encephalocele • Frontoethmoidal encephalocele

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

22. 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.

23. Anencephaly

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

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

26. Spinal Dysraphism • Spina bifida occulta

27. Spinal Dysraphism • Meningocele

28. Spinal Dysraphism • Myelomeningocele

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

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

31. Meningomyelocele

32. Meningomyelocele

33. Myelomeningocele • Clinical • Mild to complete LE paralysis • Ruptured vs unruptured • Urinary incontinence • Skeletal abnormalities

34. Myelomeningocele • Treatment • Prone • wet gauze over lesion • Surgical closure within 36hrs • Shunt if overt HCP • Urologic and Orthopaedic consultation

35. Lipomyelomeningocele • Present with back mass, bladder problems, paralysis • Cutaneous stigmata • Symptoms are due to tethered cord and cord compression from fatty mass • Treatment is surgical decompression

36. Tethered Cord Syndrome • Anatomy • Low conus medullaris • Short, thick filum terminale • Intradural lipoma

37. Tethered Cord Syndrome

38. Tethered Cord Syndrome • Clinical • Cutaneous findings • Gait difficulties • Visible muscle atrophy • LE sensory deficits • Bladder dysfunction • Scoliosis

39. Tethered Cord Syndrome • Treatment • Laminectomy with division of filum terminale • Removal of lipoma if present • Followed with MRI