History: 7-year-old boy with mental retardation and seizures
Findings: An axial CT image at the level of the lateral ventricles shows a large cerebrospinal fluid-filled cleft extending from the inner table of the skull to the lateral ventricle. There is asymmetry of the skull and absence of the septum pellucidum.
Schizencephaly is a rare birth defect that involves slits or clefts in the cerebral hemispheres of the brain. These clefts may appear on either one or both sides of the brain. They may be filled with cerebrospinal fluid.
Cephalic disorders (from the Greek word κεφάλη, meaning “head”) are congenital conditions that stem from damage to, or abnormal development of, the budding nervous system. Cephalic means “head” or “head end of the body.”
Schizencephaly, which is a disorder of sulcation and cellular migration, refers to gray matter-lined cerebrospinal fluid-filled clefts that span from the peripheral surface of the cerebral cortex to the ventricle. The pial covering of the peripheral brain surface therefore extends inward to fuse with the ependyma of the lateral ventricle.
Ependyma is the thin epithelial-like lining of the ventricular system of the brain and the central canal of the spinal cord. Ependyma is one of the four types of neuroglia in the central nervous system (CNS). It is involved in the production of cerebrospinal fluid (CSF), and is shown to serve as a reservoir for neuroregeneration.
The “closed-lip” type of schizencephaly refers to a a cleft that is narrow with apposition of the edges lined with gray matter. A widely separated cleft is referred to as an “open-lip” schizencephaly. The heterotopic gray matter lining the cleft is is usually abnormal, often demonstrating polymicrogyria or pachygyria.
Polymicrogyria (PMG) is a malformation of cortical development characterized by excessive small and prominent convolutions separated by shallow sulci, giving the cortical surface and cortical–white matter junction an irregular appearance.
Associated anomalies include absence of the septum pellucidum (in up to 90% of cases) and septoptic dysplasia.
Septo-optic dysplasia (SOD), (de Morsier syndrome) is a rare congenital malformation syndrome featuring underdevelopment of the optic nerve, pituitary gland dysfunction, and absence of the septum pellucidum (a midline part of the brain). Two of these features need to be present for a clinical diagnosis — only 30% of patients have all three.Neuroradiologically, intracranial malformations associated with septo-optic dysplasia include agenesis of the septum pellucidum, schizencephaly, and lobar holoprosencephaly.
Aunt Minnie’s Pearls:
- A hemispheric cleft lined with gray matter = schizencephaly
- Assocoated anomalies incluse absence of the septum pellucidan and spettptic dysplasia
The septum pellucidum is a thin, triangular, vertical double membrane separating the anterior horns of the left and right lateral ventricles of the brain. It runs as a sheet from the corpus callosum down to the fornix.