Into what two types is schizencephaly divided?
Open and closed lip, according to whether or not the cleft has apposing margins (closed) or is gaping, filled with CSF (open).
What cortical abnormality is present? Is this common?
Polymicrogyria is invariably seen lining the cleft, but often bilateral (as in this case).
What structure is absent and what does it suggest?
Septum pellucidum is absent suggesting possible septo-optic dysplasia.
How is open-lipped schizencephaly distinguished from a porencephalic cyst?
In porencephaly a zone of encephalomalacia extends from the cortical surface to the ventricular surface but is lined by gliotic white matter, not grey matter. it is worth noting that some authors would refer to schizencephaly as 'true porencephaly', which only serves to confuse.
A number of congenital developmental abnormalities are demonstrated. Most notably, extending from the left lateral ventricle to the posterior cortex of the left frontal lobe is a grey matter lined CSF cleft. The grey matter lining this defect, and seen quite extensively in the perisylvian grey matter, is abnormal consistent with a finely nodular surface and grey white matter junction. Similar abnormal grey matter is seen involving the posterior frontal lobe on the right, without evidence of an associated cleft. The septum pellucidum is absent. The optic apparatus appears normal. The falx is present, and no abnormal fusion across the midline can be identified. The corpus callosum is normally formed. The posterior fossa is unremarkable.