Schizencephaly
Overview
Schizencephaly is a type of cephalic disorder. Schizencephaly is a rare developmental disorder characterized by abnormal slits, or clefts, in the cerebral hemispheres. Schizencephaly can be distinguished from porencephaly by the fact that in schizencephaly the cyst is lined by heterotopic grey matter while a porencephalic cyst is lined by white matter. Individuals with clefts in both hemispheres, or bilateral clefts, are often developmentally delayed and have delayed speech and language skills and corticospinal dysfunction. Individuals with smaller, unilateral clefts (clefts in one hemisphere) may be weak on one side of the body and may have average or near-average intelligence. Patients with schizencephaly may also have varying degrees of microcephaly, mental retardation, hemiparesis (weakness or paralysis affecting one side of the body), or quadriparesis (weakness or paralysis affecting all four extremities), and may have reduced muscle tone (hypotonia). Most patients have seizures and some may have hydrocephalus.
Symptoms
Symptoms can vary widely depending on the extent and the size of the cleft. Patients may show developmental delay that can range from mild to severe. Bilateral and open-lip clefts are associated with more severe delay. Affected individuals may have small heads (microcephaly) or increased pressure due to fluid accumulation inside the brain, known as hydrocephalus. Paralysis of the limbs may be present. The paralysis may be on one or both sides of the body depending on the location of the clefts. Abnormal muscle tone, including decreased tone (hypotonia) and increased tone (spasticity), can be seen. Some patients may have only seizures. Seizures usually present before three years of age, but patients may present with seizures in later life as their only symptom and then be diagnosed with schizencephaly by brain imaging.
Causes
In schizencephaly, the neurons border the edge of the cleft, implying a very early disruption in development. There was once thought to be a genetic association with the EMX2 gene, although this theory has recently been disproved[1]. Causes of this type may include environmental exposures during pregnancy such as medication taken by the mother, sickness during pregnancy, exposure to toxins, or a vascular insult. Often there are associated heterotopias (isolated islands of neurons) which indicate a failure of migration of the neurons to their final position in the brain.
Diagnosis
Diagnosis is made by imaging of the brain. A computed tomography scan (CT) or MRI demonstrates the abnormal clefts, which may be bilateral or unilateral, open or closed lip. The clefts may appear symmetric or asymmetric. MRI may show evidence of polymicrogyria lining the clefts. There is no genetic testing available at this time for schizencephaly.
Prognosis
The prognosis for individuals with schizencephaly varies depending on the size of the clefts and the degree of neurological deficit.
Treatment
Treatment for individuals with schizencephaly generally consists of physical therapy, treatment for seizures, and, in cases that are complicated by hydrocephalus, a shunt.