Schizencephaly

Schizencephaly is a rare birth defect characterized by abnormal clefts lined with grey matter that form the ependyma of the cerebral ventricles to the pia mater. These clefts can occur bilaterally or unilaterally. Common clinical features of this malformation include epilepsy, motor deficits, and psychomotor retardation.

Presentation

Schizencephaly can be distinguished from porencephaly by the fact that in schizencephaly, the fluid-filled component is entirely lined by heterotopic grey matter, while a porencephalic cyst is lined mostly by white matter. Individuals with bilateral clefts often exhibit developmental delays, speech and language difficulties, and corticospinal dysfunction. Unilateral clefts may result in weakness or paralysis on one side of the body with potentially average or near-average intelligence. Other features include:

• Microcephaly
• Cognitive impairment
• Hemiparesis or quadriparesis
• Hypotonia
• Seizures
• Hydrocephalus

Causes

Schizencephaly is thought to result from early disruption of grey matter migration during embryogenesis. The underlying causes may include genetic mutations or environmental insults such as infections, infarctions, hemorrhages, in utero strokes, or exposure to toxins. Normal neuron migration during the second trimester of development is disrupted, leading to the malformation.

Genetic

Some cases have been linked to mutations in genes such as COL4A1, which play a role in brain development and structural integrity.

In utero infections

Environmental exposures during pregnancy, such as maternal infections like Cytomegalovirus, toxin exposure, or vascular events, can also contribute to the condition. Associated heterotopias (misplaced neurons) are often observed, indicating disrupted neuronal migration.

Diagnosis

Diagnosis is typically made using imaging studies, such as:

• Computed tomography (CT)
• Magnetic resonance imaging (MRI)

Genetic testing may confirm mutations associated with susceptibility to the condition.

Treatment

Management focuses on addressing symptoms and may include:

• Physical therapy using neurodevelopmental techniques
• Occupational therapy with specific emphasis on neurological approaches
• Seizure management
• Placement of a shunt in cases of hydrocephalus

Prognosis

The prognosis for schizencephaly varies based on the size of the clefts and the degree of neurological impairment. Individuals with smaller or unilateral clefts generally have better outcomes compared to those with bilateral clefts.

Frequency

Although schizencephaly is rare, having a sibling with the condition increases the risk, suggesting a potential genetic component. Certain gene mutations, including those in SIX3 and COL4A1, may be implicated.

External links

• OMIM entries on Familial Schizencephaly, SIX3-Related

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  Schizencephaly