The schizencephalies (Yakovlev and Wadsworth 1946a,b; Gabriel 1980) comprise a number of developmental defects in which there are unilateral or bilateral congenital clefts in the cerebral mantle, which extend from the cortical surface to the underlying ventricular cavities; the brain proximal to or below its clefts may be relatively normal, while that above is hypoplastic or rudimentary, so that the upper part of the cerebrum on both sides may be represented by a cyst covered with a paper-thin layer of nervous parenchyma.
The differential diagnosis from acquired porencephaly (which is usually unilateral and due to focal infarction or other injury in fetal life or early infancy) may then arise, but that from congenital porencephaly (with absence of the corpus collosum and septum pellucidum and large ventricles) may be much more difficult.
MRI will show the extent of clefting and associated heterotopic grey matter, and other abnormalities in which the lips of the cleft may be open or closed.
Fig.1 Closed lips schizencephalies
Fig.2 Open lips schizencephalies
Severely affected individuals show spastic tetraplegia, severe mental retardation, and seizures. Modern imaging has demonstrated that there are more mildly affected children with limited, and sometimes unilateral, deficits, with partial seizures, milder learning problems, and focal motor deficits. Eighty per cent have epilepsy (Granata et al. 1996).