Schizencephaly

Schizencephaly is a rare congenital neuronal migration disorder characterized by the presence of a full-thickness cleft, lined with heterotopic gray matter and filled with cerebrospinal fluid (CSF), which connects the pial surface of the cerebral hemisphere with the ependymal surface of the lateral ventricle. Schizencephaly was first described by Wilmarth in 1887. The term was coined from the Greek word "schizen" 'to divide' and introduced by Yakovlev and Wadsworth in 1946, based on their work on cadavers, that classified schizencephaly into two types. These are: Type I (closed-lip): Cleft is fused, preventing CSF passage. Type II (open-lip): A cleft is present, which permits CSF to pass between the ventricular cavity and subarachnoid space. Schizencephaly can be either unilateral or bilateral and has a prevalence of 1.48 per 100,000 live births. Recent literature classifies schizencephaly into three types, as the full-thickness cleft containing CSF is not mandatory for the definition. Type 1 (trans-mantle): No CSF-containing cleft on magnetic resonance imaging (MRI), but contains a trans-mantle column of abnormal gray matter. Type 2 (closed-lip): Presence of cleft containing CSF, but the lining lips of abnormal gray matter are abutting and opposed to each other. Type 3 (open-lip): Presence of cleft containing CSF. The lining lips of abnormal gray matter are not abutting each other.