1. I am posting Eric Adelman’s slides which were much better than mine.
CNS Malformations
Ben Bly
2013
I am posting Eric Adelman’s slides which were much better than mine.

2. Cavum Septum Pellucidum
Normal finding

3. Arachnoid Cysts Pocket of fluid within arachnoid
Walls are arachnoid membrane
Occur close to cisterns, often near sylvian fissure
Do not communicate with CSF spaces
Present in 0.5% at autopsy

4. Arachnoid Cysts Clinical Findings Treatment Asymptomatic
Global disturbances
Headache, signs/symptoms of increased ICP, enlarged HC, seizures, developmental delay
Focal neurologic symptoms related to location
Treatment
If symptomatic: surgical decompression, shunt

5. Arachnoid cyst

6. Porencephaly Porencephalic cysts = cavity within brain parenchyma
Injury during development
Infarct / trauma
Or faulty induction and neuronal migration
Smooth walls, radially oriented gyri
May be in distribution of a cerebral artery
May or may not communicate with ventricle
May require shunting if enlarging or progressive
RITE 2008: question 318

7. Porencephaly

8. Hydranencephaly
Complete or near complete destruction of cerebral hemispheres with extreme dilation of ventricles
Catastrophic injury to brain < 28 weeks gestation
Multiple possible causes: in utero carotid occlusion, CMV or toxoplasma infection
Unlike anencephaly, cranium is intact

9. Mega Cisterna Magna aka Retrocerebellar Arachnoid Pouch, Blake’s Cyst
Enlarged cisterna magna
Communicates with subarachnoid spaces
Posterior fossa = normal size
Unlike arachnoid cysts:
No mass effect on 4th ventricle

10. Mega Cisterna Magna ?Normal Variant Often an incidental finding
?Accuracy of diagnosis of MCM in this study?

11. Dandy Walker Malformation
Core features:
Absence (partial or complete) of the cerebellar vermis
Cyst like dialation of the 4th ventricle
Commonly present:
Cerebellar hemispheres underdeveloped, displaced superiorly
Hydrocephalus
RITE 2008 question 317

12. Dandy Walker Malformation

13. Dandy-Walker Malformation

14. Dandy Walker Malformation
Clinical Findings
Usually evident in infancy
Apnea, hypo/hypertonia, motor delays, nystagmus, titubation, hydrocephalus
Sudden unexpected death, without herniation (vascular compromise from local ICP increases?)
Treatment
Cysto-/Ventriculo- peritoneal shunt
Many associated syndromes

15. Walker-Warburg Syndrome
Dandy-Walker plus ocular Abnormalities
On 9q31, likely AR
Other features:
Hydrocephalus
Lissencephaly

16. Craniorachischisis

17. Neural tube closure defects
Neural plate is converted into a closed neural tube during 3-4th weeks of development

18. Neural tube closure defect
Craniorachischisis:
Most severe type of NTD in which brain and spinal cord are exposed to amniotic fluid and undergo degeneration
May have well developed forebrain and optic nerves

19. Myelomeningocele

20. Neural Tube Closure Defects
Myelomeningocele:
95% associated with Chiari II malformations, hydrocephalus may occur
Malformations in spinal cord above the defect are common

21. Anencephaly Absence of both cerebral hemispheres
Failure of neural tube to close anteriorly
Infants are stillborn or die shortly after birth
RITE 2010 question 319

22. Neural Tube Closure Defects
Anencephaly:
Absent or hypoplastic calvarium, “bat wing” deformity of sphenoid bone, only minimal cranial nerves II-V are present, pons/cerebellum/midbrain are grossly absent, aplasia of descending tracts
May be associated with visceral anomalies including a large thymus and hypoplastic lungs

23. Anencephaly

24. Encephaloceles
Herniation of intracranial contents through a skull defect
Fluctuant balloony mass covered by a membrane or normal skin, may pulsate
Occipital 75%, Frontal 25%
Seen with other malformations and in syndromes

25. Encephalocele

26. Neural tube closure defects
Encephalocele:
In anterior version, herniation occurs through fronto-ethmoidal junction and appears as hypertelorism or bulging tissue
May expand into nasal cavity (30%), pharynx, or orbit
Seen in 90% of patients with Meckel-Gruber syndrome
MG Syndrome –AR, lethal renal dysplasia, CNS malformations, polydactyly, pulmonary hypoplasia, hepatic developmental problems

27. Defective prosencephalization
Forebrain develops between days gestation from a midline vesicle that is generated from the closed anterior neuropore.

28. Holoprosencephaly

29. Holoprosencephalic children
Hypoteloric
Proboscis
RITE 2010: question 310

30. Holoprosencephalic cat

31. Holoprosencephaly Defective clevage
No division of prosencephalon (forebrain)
No interhemispheric fissure
Telencephalon = single lobe
No olfactory bulbs or tracts
Absence of midline structures

32. Holoprosencephaly Craniofacial dysplasia Cyclopia (single median eye)
Ethmocephaly: nose replaced by a proboscis located above hypoteloric eyes
Cebocephaly: hypotelorism and a nose with a single nostril
Premaxillary agenesis: hypotelorism, flat nose, midline cleft lip

33. Holoprosencephaly
Failure of prosencephalon to cleave into symmetric cerebral hemispheres
Variable severity
Alobar
Semilobar
Lobar

34. Semilobar Holoprosencephaly
Some differentiation of hemispheres, posteriorly
Diencephalon/Forebrain still fused in midline

35. Semilobar Holoprosencephaly

36. Lobar Holoprosencephaly
Hemispheres separated (interhemispheric fissure present)
Absent septum pellucidum
Fused thalami
Diffuse pachygyria
Interdigitation of frontal gyri

37. Lobar Holoprosencephaly

38. Agenesis of the Corpus Callosum

39. Agenesis of the Corpus Callosum
Corpus Callosum forms front to back; myelinates back to front
If CC is partially absent, most likely posterior portion
Anterior part alone can be absent in holoprosencephaly, frontal schizencephaly, frontal porencephalic cysts
Thin CC: insult after completely formed (like PVL)

40. Agenesis of the Corpus Callosum

41. Agenesis of the Corpus Callosum

42. RITE 2008: question 254; RITE 2009 question 269

43. Schizencephaly Clefts in the cerebral hemispheres
Flawed development of cortical mantle during cell migration in first trimester
Genetic vs. acquired

44. Schizencephaly Most clefts near sylvian fissures
Clefts extend from surface of cortex into a ventricle
Neighboring gyral pattern abnormal
Lips are formed by dysplastic gray matter
(Porencephalic cyst lined by white matter)

45. Schizencephaly Open Lip: Lips of cleft are separated by CSF
Closed Lip: Lips of cleft are in contact

46. Closed Lip Schizencephaly

47. Closed Lip Schizencephaly

48. Open Lip Schizencephaly

49. Schizencephaly Clinical Findings Often presents with seizures
Can be focal or generalized; infantile spasms
Hemiplegia

51. Hemimegalencephaly
Brain volume increased from errors in neuroepithelial proliferation
Histology: increase in number of cells (neurons and glia) and cell size
Association of hemimegalencephaly with neuro-cutaneous disorders
Linear sebaceous nevus syndrome and hypomelanosis of Ito

52. Hemimegalencephaly Macrocephaly at birth
May have accelerated head growth in first few months of life
Present with seizures, developmental delay, hemiparesis, hemihypertrophy
Seizures sometimes require hemispherectomy or callosotomy

53. Hemimegalencephaly

54. Joubert Syndrome Molar Tooth Sign
Complete agenesis of cerebellar vermis
4th ventricle enlarged (batwing shape)
Other cerebral malformations, especially occipital encephaloceles

55. Joubert Syndrome

56. Chiari Malformation

57. Chiari Malformations Chiari I
Extension of cerebellar tonsils (sometimes posterior vermis) into upper cervical canal
Associated with syrinx
Chiari II
Displacement of cerebellar vermis (? medulla) in upper cervical canal
Associated with lumbar myelomeningocele
Chiari III
Occipital encephalocele
Chiari IV
Absence of cerebellum

58. Chiari I with Syrinx

59. Chiari III

61. Lissencephaly Disorder of neuronal migration
Abnormal migration of post-mitotic neurons from the ventricular zone to form the cortical plate
Smooth cerebral surface: absence of gyri, abnormally thick cortex, abnormal lamination

62. Lissencephaly

63. Defects of cellular migration
Miller-Dieker syndrome
Lissencephaly
Microcephaly
Characteristic facies
Upturned nares, micrognathia, high forehead, thin upper lip, low set ears
Deletion on chromosome 17

64. X-linked defects of cellular migration (DCX mutation)
Boys
Lissencephaly
Girls
Subcortical band heterotopia
Gray matter in the wrong places

65. RITE 2009: question 257

66. Polymicrogyria Too many small abnormal gyri
Convolutions may not have sulci, or sulci might be bridged by fusion of overlying molecular layer which may give smooth appearance on surface
Gray-white interface not distinct

67. Polymicrogyria Clinical findings depend on extent of abnormality
Diffuse: severe developmental delay and hypertonia
Focal deficits if focal
Seizures common

69. Heterotopias
Collections of normal-appearing neurons in an abnormal location
Proposed mechanisms
Damage to radial glial fibers
Premature transformation of radial glia into astrocytes
Radial glial surface molecule deficiency
Isolated/multiple/diffuse
Usually no cause apparent

70. Heterotopias Periventricular Nodular Heterotopias
X-linked dominant (females only, lethal in males)
Filamin A, aka Filamin 1
Failure of neuronal migration at an early stage from ventricular zone
Filamin A anchors membrane proteins to actin cytoskeleton

71. Mobius syndrome
Facial diplegia, bilateral abducens palsy, often involvement of other lower cranial nerves
Pathogenesis: selective ischemia of midline and paramedian zones of developing brainstem