Schizencephaly

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WHO-ICD-10 version:2010

Congenital malformations, deformations and chromosomal abnormalities

Congenital malformations of the nervous system

OMIM Number

269160

Gene Map Locus

10q26.1

Description

Schizencephaly is a rare congenital neurological condition characterized by the presence of abnormal clefts in one or both cerebral hemispheres of the brain. The clefts may be open or close lipped, and extend from the surface of the brain down to the ventricles. Bilateral clefts are the more severe form of the condition, and affected individuals present with delays in physical and speech development. Patients with unilateral clefts are less severely affected, and predominantly show paralysis of one side of the body. Other features seen in affected patients include microcephaly, mental retardation, hypotonia, spasticity, seizures, and hydrocephalus.

Imaging studies like CAT and MRI are used to diagnose the condition. There is no cure for schizencephaly; treatment being supportive. Seizures can be controlled with anti-convulsant medications, but may in some cases require surgical removal of some amount of brain tissue. The hydrocephalus can be managed by a surgical shunt that can remove excess fluid from the brain. Prognosis varies for affected individuals. Severely affected patients may require long-term care, and generally have a short life-span.

Molecular Genetics

The physiological basis of schizencephaly is a developmental defect during the embryonal stage, in which the neurons fail to migrate normally from the germinal matrix zone to their final positions in the brain. Although many environmental causes for this defect, such as in utero infections and stroke, are known, the increased incidence of the disease in related individuals has led to the theory of a possible genetic component to the development of the condition.

Recently, a report of mutations in homeobox gene EMX2 associated with cases of schizencephaly indicated that genetic factor might play a key role in the pathogenesis of this brain malformation. The EMX2 gene encodes for a transcriptional regulator which plays an important role in the early development of the brain.

Epidemiology in the Arab World

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Other Reports

Oman

Koul et al. (2006) analyzed data from the pediatric neurology department at Sultan Qaboos University Hospital for children undergoing evaluation for developmental delay and epilepsy. There were 40 cases of neuronal migrational disorders. Corpus callosum agenesis and lissencephaly or pachygyria formed the major group. There were 22 cases of corpus callosum agenesis, 12 of lissencephaly or pachygyria, 2 of schizencephaly, and 1 each of polymicrogyria, holoprosencephaly, hydranecephaly, and hemimegalencephaly. The two cases of schizencephaly included one boy and one girl. One had both open- and closed-lip types, and the second one had the open-lip bilateral type. Only one child (closed lip) had seizures, which were the myoclonic type.

Saudi Arabia

Al-Alawi et al. (2001) reported a Saudi baby girl born to non-consanguineous parents with schizencephaly. She presented at birth with growth retardation and microcephaly, and on the 3rd day of life she developed seizures. Brain computerized tomography (CT) scan and Magnetic resonance imagining (MRI) showed bilateral frontal lobes lissencephaly, numerous nodular and linear calcifications of cerebral parenchyma, basal ganglia and periventricular zones, wide bilateral clefts in the central sulcus zones, and gray matter lining of bilateral open-lip schizencephaly clefts. At the age of 11 months she developed gross psychomotor retardation. She had four healthy siblings, and no mutations were identified in the EMX2 gene, suggesting a sporadic neonatal schizencephaly.

Alorainy (2006) reviewed and analyzed the MRI studies on 808 pediatric patients (aged 3 days to 15 years) over a 3-year period.  A total of 114 congenital cerebral malformations were identified in 86 of these patients via MRI.  One patient was identified with Schizencephaly.

Somalia

Haverkamp et al. (1995) reported on two Somalian siblings, born to non-consanguineous parents, who were diagnosed with schizencephaly. The elder of these siblings was 8-years old when diagnosed. She was born with no obvious abnormalities, but showed developmental retardation starting from the age of 6-months. She presented with severe psychomotor retardation, inability to speak, severe feeding difficulties, contractures of the large joints, and left-sided spasticity. She was found to have no metabolic or infectious disorders, and had a normal karyotype. EEG showed a constant temporal theta rhythm. MRI brain showed bilateral open lipped schizencephalic clefts with heterotopia in the Sylvian fissure, as well as absence of the septum pellucidum. Her younger brother (4-years old) presented with a moderate congenital spastic right sided hemiparesis. His EEG analysis showed mild theta rhythms over the temporo-occipital regions. MRI brain showed similar clefts in the Sylvian fissure. Interestingly, this patient showed an open lipped cleft with heterotopia in the left hemisphere and a close lipped cleft in the right hemisphere. The septum pellucidum was absent. A diagnosis of familial schizencephaly was made. However, both parents and three other siblings were found to be normal. No abnormality could be detected in the extended family history either. In addition, the mother's brain MRI findings were normal. The father was not physically present.

United Arab Emirates

Sztriha et al. (1998) described an infant who had a combination of lobar holoprosencephaly and open-lip schizencephaly. Midline fusion of the basal ganglia was associated with bilateral absence of abundant parts of the brain mantle. Agenesis of the corpus callosum, hypoplasia of the optic nerves and chiasm, absence of the septum pellucidum, posterior pituitary and olfactory bulbs were further components of the malformation. Blindness, intractable seizures, spastic tetraplegia, somatomental retardation and diabetes insipidus were the main clinical features. Sztriha et al. (1998) suggested that defect in the induction of the mediobasal part of the prosencephalon and failure of cell proliferation can be responsible for this complex malformation.

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