Define
- Gray matter-lined cleft within the cerebral hemisphere
- often with adjacent polymicrogyria in the lining dysplastic gray matter.
General
- Schiz (schizo) is of Greek origin, meaning “split” or “cleft" in the mantle of the cerebrum
Classification
- Open lip:
- Cleft extends the entire distance to the ventricle
- Most common
- Close lip: cleft stop short of the ventricle within the substance of the cerebrum
- Look for a dimple in the lateral wall of the lateral ventricle immediately under the cortical cleft (the appearance of which may mimic an enlarged sulcus)
Pathophysiology
- disruption of any of the three phases of cortical development (proliferation, migration, and organization),
- but polymicrogyric cortex surrounding the cleft suggests that it is a disorder of cortical organization, probably secondary to hypoperfusion or ischemic cortical injury.
- As such, it may represent a spectrum where mild damage results in polymicrogyria while severe damage may involve the deep radial-glial fibers and result in schizencephaly
- May be unilateral or bilateral;
Pathology
- Macroscopically
- Cleft:
- May extend for part of or the entire distance from the pial lining of the cortical surface --> ependymal lining of the lateral ventricle.
- Lined with cortical gray matter (often abnormal, may have polymicrogyria).
- pia and arachnoid fuse
- may be unilateral or bilateral
- there may be an “abnormal” vein that represents a cortical vein that now looks medullary because it follows the cortex into the cleft)
- absence of septum pellucidum in 80–90%
- Microscopically:
- Clefts comprise cortical neurons that do not exhibit the normal six-layered lamination.
Location
- Pre- or postcentral gyri
- Can be unilateral or bilateral.
- Bilateral clefts are associated with a significantly worse prognosis.
Presentation
- Seizures
- Hemiparesis
- Variable developmental delay, the severity of which is determined by the location, extent, and number of clefts.
Associated with
- Septo-optic dysplasia
- Gray matter heterotopia
- Absent septum
DDx
Feature | Schizencephaly | Porencephaly |
Lining of the cleft | Gray matter | Glial tissue |
Defect | Cleft | Cyst |
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