Schizencephaly
Incidence
Schizencephaly is believed to occur with comparable frequency in males and females and in all ethnic groups. It is known to be extremely rare, but the exact incidence of the disease is not known.
Clinical Characteristics
Schizencephaly (literally meaning \\\"split brain\\\") is a rare neurologic birth defect characterized by abnormal slits (or clefts) in one or both of the halves of the child\\\'s brain. There are two types of schizencephaly, Type I and Type II. Type I is the less severe type and consists of a small cleft in the brain that is usually filled in with brain matter. Type II is more severe, as the cleft is large and continues all the way from the outer surface of the brain to the innermost portion. This space is filled with cerebrospinal fluid (CSF), the liquid that surrounds and insulates the brain within the skull. In both types, the clefts may be on only one side of the brain (unihemispheric) or on both sides (bihemispheric). Children with bihemispheric schizencephaly generally have more symptoms of the disease than do children with unihemispheric schizencephaly. The symptoms of schizencephaly vary according to the number and severity of brain clefts. Children with the least severe cases usually have seizures (which can usually be treated with medication) but otherwise normal development and functioning. Deeper and wider clefts (as well as multiple clefts) often lead to more symptoms, including muscle weakness and/or paralysis, developmental delay, severe seizures, difficulties with movement, delays in learning to speak and understand speech, visual problems, mental retardation, psychiatric disorders, and hydrocephalus. The symptoms vary from patient to patient, and not all patients with schizencephaly will have all of the symptoms mentioned above. There are several different ideas about what might cause schizencephaly, but none of the ideas have been proven at this point. The disorder is thought to be caused by a defect in brain development that prevents the neurons from becoming organized properly. It is unclear what causes this defect, but it seems likely that various different problems (including a disruption of blood flow, the presence of some type of toxin, or a virus) during pregnancy may lead to schizencephaly. There also have been cases of a genetic form of the disease, but it is unclear. The genetic form is thought to be due to a mutation in the EMX2 gene.
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Schizencephaly is diagnosed after a physician sees evidence of a cleft in the brain on an MRI (magnetic resonance imaging) or CT (computed tomography) scan. MRI is generally considered to be the best tool to aid in the diagnosis of schizencephaly. In theory, this diagnosis can be made at birth, but it is often not done until later. In individuals with Type I schizencephaly, the diagnosis is often not made until later in infancy or early childhood because the symptoms are less severe. It is possible to diagnose schizencephaly before birth with a prenatal ultrasound, but only very rarely does this occur.