Teaching Case

A 2-year-old boy presented with weakness in the right half of the body, diminution of vision and developmental delay. No past history of seizures was elicited.

The MRI revealed a large well-defined extra-axial CSF intensity cystic lesion (hyperintense on T2-weighted sequences and suppressed on FLAIR sequences) in the left fronto-parieto-occipital region. The cystic lesion was lined by grey matter and communicated with the body of left lateral ventricle through a large defect in its wall.

The cystic lesion was compressing the residual posterior temporal and occipital lobes, indenting and displacing left-sided deep grey matter nuclei inferiorly. There was absence of septum pellucidum. Complete agenesis of corpus callosum was also noted.

Schizencephaly is an uncommon structural disorder of cerebral cortical development, which is characterised by congenital clefts spanning the cerebral hemispheres from the pial surface to the lateral ventricles and lined by cortical grey matter. [1]

The prevalence of schizencephaly is 1.5 per 100, 000 live births. It can be associated with septo-optic dysplasia (SOD), optic nerve hypoplasia, absence of the septum pellucidum, pachygyria and polymicrogyria.

The septum pellucidum is absent or nearly absent in about 70-90% of affected patients, and approximately 30-50% of these will have optic nerve hypoplasia on clinical examination. [2]

The aetiology is considered to be due to a neuronal migrational anomaly. It has been classified into type I or closed-lip schizencephaly with grey matter–lined lips that are opposing each other, and type II or open-lip schizencephaly with separated lips and a cleft of CSF extending to the underlying ventricle. [3]

Clinical manifestations of schizencephaly most often include varying degrees of developmental delay, motor impairment, and seizures. [3, 4] When it is associated with septo-optic dysplasia, impairment of vision can be present.

Although ultrasound and CT may aid diagnosis, MRI is the imaging modality of choice due to excellent grey-white matter differentiation.

Identification of grey matter lining the cleft is the pathognomonic finding. [5] MRI of our patient revealed unilateral left fronto-parieto-occipital lobe open-lip schizencephaly along with absent septum pellucidum and optic dysplasia. Agenesis of corpus callosum was identified without poly/pachymicrogyria.

The various imaging differentials include orencephaly, hydranencephaly and holoprosencephaly. Cystic areas of encephalomalacia communicating with the ventricular system but not lined by grey matter is porencephaly. A severe form of porencephaly in which the cerebral hemispheres have transformed into a membranous sac containing cerebrospinal fluid is hydranencephaly. Holoprosencephaly is a brain malformation resulting from incomplete separation of the two hemispheres.

Treatment involves physiotherapy, seizure control, and a ventriculo-peritoneal shunt if complicated by hydrocephalus. In the open-lip variety, failure to thrive, chronic infections and respiratory problems may lead to early death. [5]

Schizencephaly can be diagnosed in the prenatal period as early as 23 weeks. Prenatal ultrasound or particularly prenatal MRI may aid in detection of grey matter lining the defect, communication with the ventricle, and other associated structural abnormalities. [5]

Prenatal diagnosis of schizencephaly is useful when pregnancy termination is not an option and allows counselling of the parents to prepare themselves for the inevitable clinical consequences of the defect. [3]