Congenital malformations of brain rjj.pptx

overview on congenital malformations of brain

1. C ongenital malformations of brain DR.ROHAN JOHN JACOB

2. • Hindbrain Herniations /Malformations • Disorders of Commissural development • Disorders of Cortical development • Disorders of Diverticulation /Cleavage

3. DEVELOPMENT OF THE CENTRAL NERVOUS SYSTEM 3 rd fetal week: Trilaminar germ disc emerges.neural plate appears at cranial end of embryo 18 days: neural plate invaginates producing neural folds Neural folds fuse to form neural tube.

4. Neural tube proximal 1/3 rd of brain and distal 2/3 rd of spine. Neural crest cells are extruded & migrate laterally to form perineural roots & ganglia of ANS. NT closure (zipper like fashion) begins in hindbrain 4 th week: formation of brain vesicles.NT constricts & bends & forms cerebral hemispheres,cerebellum,brainstem & cavities. Disjunction

5. After closure of NT,surface ectoderm separates from & closes over it. Surface ectoderm future epidermis .

6. Posterior fossa herniation/malformations CHIARI MALFORMATION DANDY WALKER MALFORMATION MEGA CISTERNA MAGNA RHOMBENCEPHALOSYNAPSIS JOUBERT’S SYNDROME

7. CHIARI MALFORMATION- I Herniation of cerebellar tonsils into cervical canal Incidental (50 % asymptomatic) Valsalva -induced suboccipital headache, neck pain

8. IMAGING FEATURES Elongated, peg-shaped cerebellar tonsils Tonsillar descent below basion-opisthion line Diminished/absent CSF flow at posterior FM Crowded foramen magnum

9. Sagittal T1 weighted MR image showing caudal protrusion of the cerebellar tonsils (arrow) below the foramen magnum (spaced lines).

10. Associated conditions Hydrocephalus in up to 30% of cases. In ~35% -associated skeletal anomalies : platybasia /basilar invagination/reduced clival length atlanto -occipital assimilation syndromic associations: Klippel-Feil syndrome, Achondroplasia , Marfans

11. Chiari II Malformation: Complex hindbrain malformation involving skull, dura , brain, spinal cord. Luckenschadel (lacunar skull), concave clivus and petrous ridges Small and shallow posterior fossa with low lying transverse sinuses and Torcular Herophili Hypoplastic tentorium cerebelli with gaping (heart shaped) incisura , Hypoplastic and fenestrated falx cerebri with interdigitating gyri and Gaping foramen magnum.

12. Chiari malformation type III Small posterior fossa Caudally displaced brainstem Low occipital or upper cervical bony defect Cephalocele with herniation of meninges, dysplastic brain, ventricles

13. Chiari IV Malformation: Severe cerebellar hypoplasia or dysplasia, small brain stem and large posterior fossa . - No hydrocephalus and other CNS anomalies

14. Dandy-Walker Spectrum Dandy-Walker malformation (“classic”) Dandy-Walker variant I solated inferior vermian hypoplasia Persistent Blake pouch cyst (BPC) Mega cisterna magna (MCM)

15. CLASSIC DANDY WALKER MALFORMATION ON MRI Large posterior fossa (PF) Cyst extending posteriorly from fourth ventricle Variable vermian , cerebellar hypoplasia High-inserting venous confluence

16. Dandy-Walker variant Hypoplastic Rotated Vermis PF normal size “Keyhole” opening of fourth ventricle Differential : Retro-cerebellar arachnoid cyst: No communication with 4th ventricle

17. Mega Cisterna Magna In this variant, fourth ventricle, vermis , and cerebellar hemispheres are normal. A large cisterna magna is present and may extend above the vermis to the straight sinus.

18. BLAKE POUCH CYST Posterior ballooning of inferior medullary velum into CM, below and posterior to vermis , that communicates with an open 4 th ventricle.

19. Rhombencephalosynapsis Midline brain malformation Absent cerebellar vermis Apparent fusion of the cerebellar hemispheres VACTERL association

20. Joubert’s Syndrome (Congenital Vermian Hypoplasia) AR syndrome Associated ocular, renal ,digital anomalies may be seen

21. Commissural maldevelopment Major Commissures Corpus callosum (13th wk ) Anterior (8th wk ) Posterior (11th wk ) Incidental, Seizure disorder, Developmental disorder

22. Corpus Callosum agenesis Common congenital brain disorder Corpus Callosum agenesis: 1.Complete 2.Partial: splenium and rostrum absent genu and body present.

23. COMPLETE AGENESIS Complete absence of corpus callosum (CC) = agenesis Hippocampal commissure (HC) absent Anterior commissure (AC) often present

24. IMAGING Coronal “Viking helmet” or “moose head” appearance “High-riding” third ventricle Probst bundles

25. Malformations of Cortical Development 1.abnormal glial /neuronal proliferation 2.abnormal neuronal migration 3.abnormal post migration

26. Malformations Secondary to Glial/Neuronal Proliferation or Apoptosis Microcephaly Primary- genetic Secondary – Infection,Ischemia , Maternal DM, Trauma Imaging Small cranial vault Closely a pposed sutures Cortex may be normal or show simplified gyration

27. Hemimegaloencephaly Enlarged right hemisphere, hemicranium Enlarged WM in the corona radiata Hyperintense WM

28. Abnormal Neuronal migration Heterotopias: - Characterized by the presence of normal neurons at abnormal sites Nodular type(common) Diffuse(uncommon) Subependymal/ Periventricular Lissencephaly Subcortical Band type

29. Nodular type: Focal subependymal nodules - indent the ventricular wall Diffuse subependymal nodules - border the walls of the lateral ventricle. Do not enhance on administration of intravenous contrast.

30. Subcortical heterotopia focal subcortical mass of heterotopic gray matter Thin overlying cortex

31. Band Heterotopia Double cortex syndrome Affects Females Imaging Band of GM deep to cortex

32. Lissencephaly pachygyria spectrum Refers to “smooth brain” with absent or poor sulcation . Due to neuronal under migration type I (classic) lissencephaly type II (cobblestone complex) lissencephaly

33. Classic Lissencephaly CT APPEARANCE smooth, nearly agyric surface shallow sylvian fissures (Axial)

34. Classic Lissencephaly MRI APPEARANCE Thin cortical ribbon Hyperintense cell-sparse zone Figure of eight configuration of brain with thickened cortex, smooth gray white matter interface, agyria and shallow sylvian fissures

35. Type 2 Lissencephaly Cobblestone appearance Associated with muscular dystrophy syndromes

36. distinctive cobblestone appearance of the thickened frontal gyri

37. Abnormalities of Postmigrational Development Polymicrogyria Irregular cortex with multiple small convolutions Shallow sulci Irregular GWM interface Similar to Lissencephaly type II

38. Axial T2WI in a 2w infant with seizures shows multiple foci of polymicrogyria . The left hemisphere is much more severely affected than the right.

39. Schizencephaly Cleft extending from ventricle to the pial surface lined by gray matter Types Close lipped Open lipped

40. ANOMALIES OF VENTRAL PROSENCEPHALON DEVELOPMENT Holoprosencephaly and variants Septo -optic dysplasia

41. HOLOPROSENCEPHALY Incomplete separation of the two hemispheres ‘ Holo ’ –Single alobar holoprosencephaly semilobar holoprosencephaly lobar Holoprosencephaly Can effect diencephalic structures

42. Alobar Holoprosencephaly single midline monoventricle absent midline structures absent septum pellucidum agenesis or hypoplasia of the corpus callosum absent interhemispheric fissure and falx cerebri

43. Differential - Hydranencephaly occurs in-utero Causes Infarction, Infection, hypoxic ischemic encephalopathy The falx is usually present

44. Semilobar holoprosencephaly absence of septum pellucidum monoventricle with partially developed occipital and temporal horns rudimentary falx cerebri : absent anteriorly incompletely formed interhemispheric fissure

45. Lobar Holoprosencephaly fusion of the frontal horns of the lateral ventricles wide communication of this fused segment with the third ventricle absence of septum pellucidum

46. Axial T2 (A) and coronal T1 (B) weighted images show fusion of the frontal lobes (short arrows), separated thalami (arrowhead) and presence of the falx (long arrows).

47. Syntelencephaly middle interhemispheric variant (MIHV ), is a mild subtype of holoprosencephaly

48. Mid frontal and parietal lobes are fused across the midline

49. Septooptic dysplasia Optic nerve hypoplasia Absence of septum pellucidum Two-thirds of patients show hypothalamic- pituitary dysfunction.

50. Coronal T2 weighted image shows absent septum pellucidum with squared-off appearance of frontal horns with inferior pointing (A). Optic nerves (long arrows) and ocular muscles (short arrows) are hypoplastic (B).