1.schizencephaly 2.holoprosencephaly 3.porencephaly

1.Schizencephaly�
2.Holoprosencephaly
�3.Porencephaly

2. Schizencephaly is a rare cortical malformation
that manifests as a grey matter-lined cleft
extending from the ependyma to the pia matter
The cleft extends across the entire cerebral
hemisphere, from the ventricular surface
(ependyma) to the periphery (pial surface) of the
brain

3. Cause: segmental developmental failure of cell
migration to form cerebral cortex / vascular
ischemia of portion of germinal matrix
Time of injury: 30 to 60 days of gestation

4. Schizencephaly is rare with an estimated
incidence of ~ 1.5 : 100,000 live births.

It is almost always sporadic.
There is no known gender predilection.
Most often the cleft involves the posterior frontal
or parietal lobes (70%).

5. Presentation and outcome are variable
◦Seizures
◦Hemiparesis
◦Developmental deficits
Usually, the severity of symptoms is related to the
amount of brain affected by the abnormality

6. The clefts may be unilateral or bilateral
-CLOSED LIP (Schizencephaly type I)
the cleft walls are in apposition
most common form in unilateral cases
-OPEN LIP (Schizencephaly type II)
the cleft walls are separated and filled with CSF
most common form in bilateral cases

7. Schizencephaly is frequently (50-90%) associated
with :
oPolymicrogyria(66%)
oGrey matter heterotopia
oAbsence/Focal thinning of corpus callosum
oAbsent septum pellucidum

10. Focal cortical dysplasia
Heterotopic grey matter
Porencephaly
Arachnoid cyst
Cystic tumor

11. Focal cortical dysplasia
◦sometimes may have a cleft on the cortical surface that
does not extend completely to the ventricular surface
Heterotopic grey matter
◦closed lip schizencephaly can mimic a band of grey
matter heterotopia.
◦Assessing the ventricular outline will often demonstrate a
slight cleft whereas periventricular grey matter will
usually bulge into the ventricle.

12. Porencephaly
◦A zone of encephalomalacia that extends from the
cortical surface to the ventricular surface but is lined by
gliotic white matter, not grey matter
Arachnoid cyst
oCSF containing intra arachnoid cyst without ventricular
communication

13. MRI is the imaging modality of choice, and
enables identification of the pial-ependymal cleft
visualization of cortical dysplasia and heterotopic
gray matter.

14. Closed lip (type I) : seen as nipple-like
out-pouching at the ependymal surface
Open lip (type II) : heterotopic gray matter lined
CSF cleft seen extending from ventricular to
cortical surface

20. Using computed tomography (CT) scanning, the
diagnosis of schizencephaly is sometimes difficult,
particularly type I, or closed lip schizencephaly.

21. On CT scan Closed lip (type I) may show only a
slight outpouching at the ependymal surface of the
cleft, and a full-thickness cleft may be difficult to
identify on CT scan
The degree of confidence is high when the extent
of the cleft and the gray matter lining its walls can
be identified.

24. may show a unilateral or bilateral defect extending
from the pial surface to the ventricular wall
there may be other features such as
◦absent cavum septum pellucidum
◦occasional fetal hydrocephalus

25. In schizencephaly type I, a hyperechoic line
extends from the parasylvian region to the anterior
portion of the lateral ventricle.
The hyperechoic line represents the cortex lining
the fused cleft.

26. In schizencephaly type II, an anechoic band or
cavity, representing the fluid-filled cleft, extends
from the cortical surface to the lateral ventricle.
The meeting of the closed-lip portion, or apex of
the cleft, with the margin of the ventricle may be
identified as a ventricular diverticulum or dimple.

29. Holoprosencephaly denotes an incomplete or
absent division of the embryonic forebrain
(prosencephalon) into distinct lateral cerebral
hemispheres

30. Although rare in absolute terms,
holoprosencephaly is the most common forebrain
abnormality and is seen in1per 10,000 - 16,000
live births.
The early embryonic occurrence may be even
higher but may not be detected due to most
fetuses aborting in early gestation.

31. Alobar holoprosencephaly
Semilobar holoprosencephaly
Lobar holoprosencephaly

32. Alobar holoprosencephaly: there is a
complete absence of midline forebrain division,
resulting in a monoventricle and fused cerebral
hemispheres.

33. Alobar holoprosencephaly is visible on all
modalities, but in general is identified on antenatal
ultrasound and best characterized by MRI. 

34. The basic structure of the cerebral hemispheres is
lost, with variable amounts of residual cortex.

35. single midline monoventricle (or holosphere)
◦lateral and third ventricles are absent
absent midline structures
◦absent septum pellucidum
◦agenesis or hypoplasia of the corpus callosum
◦absent interhemispheric fissure and falx cerebri
dorsal cyst of holoprosencephaly
thalami fused

39. Associated craniofacial features may also be
present which include
oproboscis
omono-orbit / cyclopia
omono-nostril
ohypotelorism
ocebocephaly

40. The fused cortex can take on three basic shapes :
opancake : cerebral tissue is confined to the
anterior basicranium
ocup : cerebral tissue lines variable amounts of the
anterior cranium with a dorsal cyst present
posteriorly
oball : a complete rim of tissue surrounds the
monoventricle without dorsal cyst

42. Death within 1st year of life / stillborn

43. Semilobar holoprosencephaly
Hydranencephaly
Severe hydrocephalus

44. Semilobar holoprosencephaly: is
characterized by an incomplete forebrain division,
resulting in partial separation of the cerebral
hemispheres, typically posteriorly.

45. The basic structure of the cerebral lobes are
present, but are fused most commonly anteriorly
and at the thalami and there is partial
diverticulation of brain (dorsal cyst).

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

47. partial or complete fusion of the thalami

absent olfactory tracts and bulbs
agenesis or hypoplasia of the corpus callosum
incomplete hippocampal formation

48. Associated craniofacial abnormalities:
omild facial anomalies: midline cleft lip + palate
oHypotelorism
omental retardation

50. infants survive frequently into adulthood

51. lobar holoprosencephaly 
alobar holoprosencephaly
porencephalic cyst
arachnoid cyst
colpocephaly

52. Lobar holoprosencephaly: there is complete
ventricular separation, with focal areas of
incomplete cortical division or anterior falcine
hypoplasia present

53. mildest form with two cerebral hemispheres and
two distinct lateral ventricles

54. fusion of the frontal horns of the lateral ventricles
wide communication of this fused segment with
the third ventricle
fusion of the fornices
absence of septum pellucidum
agenesis or hypoplasia of the corpus callosum

55. Unlike semilobar holoprosencephaly, the falx is
present, the interhemispheric fissure is fully
formed and the thalami are not fused.

59. survival into adulthood

60. semilobar holoprosencephaly
septooptic dysplasia

61. Focal cavity as a result of localized brain
destruction

62. Congenital
Acquired

63. The congenital form is due to localized agenesis
of the cortical mantle resulting in the formation of
a cavity or a lateral slit through which the lateral
ventricle communicates with the convexity of the
brain.

64. The cavity is lined by ependyma and laterally by a
thin pia-ependymal layer which may rupture into
the subarachnoid space.
In less severe forms the cavity may be reduced to
a lateral slit lined by ependyma and partially
fused.

65. The acquired type is secondary to any type of
cerebral destructive process, ranging from trauma
to infarction.
Sometimes called false porencephaly, such cases
are better labeled by their etiological cause if this
is known, e.g. post-traumatic or post infarction
cerebral cavities

66. Porencephalic cavities or clefts can be identified
or suspected by ultrasound in the neonate or
infant.
In children or adults they are demonstrated by CT
or MRI