Rare case of a large congenital parietal meningoencephalocele associated with open lip schizencephaly

Clinical History

A one-year-old male child presented with a midline cranial swelling present since birth. The patient had had occasional convulsions for the past 6 months. He had been provisionally diagnosed with an encephalocele antenatally, and brain MRI was performed for preoperative evaluation.

Imaging Findings

Figure 1 (3D volume-rendered CT image) shows a midline scalp swelling.

MRI findings include a large parietal meningoencephalocele, with herniation of CSF and dysmorphic brain parenchyma through a midline skull vault defect measuring 5.2 x 4.3 cm. The encephalocele itself measures approximately 7.2 x 9.0 x 9.4 cm (AP x TR x CC). (Figures 2, 3, 4, 5 and 7.)

Further associated anomalies were also demonstrated, including partial agenesis of the posterior body and splenium of the corpus callosum (Fig. 2, 6 and 7), underdeveloped frontal horns of both lateral ventricles (Fig. 6), and a dilated third ventricle (Figures 2 and 7).

A unilateral parietal open lip schizencephaly with CSF-filled cleft was also demonstrated, with dysplastic thickened grey matter (Figures 7, 8 and 9) and polymicrogyria complex (Figure 7) adjacent to it.

There is involvement of the superior sagittal sinus within the meningoencephalocele. (Figure 4).

Discussion

Congenital parietal meningoencephalocele is a rare variant of meningoencephalocele, being a protrusion of meninges and brain parenchyma through a congenital midline skull vault defect. Meningoencephaloceles may be congenital or acquired, the latter being traumatic or postsurgical. Congenital meningoencephalocele occurs in 1-3 per 10, 000 live births, out of which parietal meningoencephalocele accounts for 5 to 10% of cases. It occurs due to failure of complete closure of the neural tube during fetal life. Parietal meningoencephalocele arises from a skull defect between lambda and bregma. It is usually associated with other brain anomalies such as corpus callosum agenesis, Dandy-Walker malformation, Chiari II malformation and lobar holoprosencephaly [1, 2]. Here it is associated with schizencephaly, partial agenesis of the posterior body and splenium of the corpus callosum, with underdeveloped frontal horns of both lateral ventricles and third ventricle dilatation. A few published cases suggest an association with meningoencephalocele and schizencephaly [1]. There is a variant called atretic parietal encephalocoele, which are small lesions under the scalp consisting of dysplastic brain tissue, fibrous tissue and dura [3].

Schizencephaly is a different entity, representing a cleft in cerebral parenchyma, lined by grey matter, and extending from ependyma to pia mater. It is a developmental disorder of supra-tentorial neuronal migration. Schizencephaly is a rare disorder that occurs in 1-2 per 1, 000, 000 births. There are two morphological types, called open lip when there is separation of the cleft which is filled with CSF, and closed lip when then cleft walls are opposed. Schizencephaly may be associated with other anomalies such as polymicrogyria, agenesis of the corpus callosum, grey matter heterotopia, and absence of the septum pellucidum. In our case it is associated with meningoencephalocele, polymicrogyria and partial agenesis of corpus callosum [4].

Both meningoencephalocoele and schizencephaly may present with convulsions, motor impairment, hemiparesis and developmental delay [1-6].

Outcome depends upon the type of encephalocele and schizencephaly, whether there is involvement of superior sagittal sinus within the encephalocele, and on associated brain anomalies. Involvement of the superior sagittal sinus means neurosurgical repair is more difficult. Parietal meningoencephalocele is usually associated with structural brain anomalies and therefore has a poorer prognosis.

Management is usually symptomatic treatment for seizures, and surgery and VP shunt for hydrocephalus. Further management may include physiotherapy and occupational therapy [1-6].

Differential Diagnosis List

Final Diagnosis

Congenital parietal meningoencephalocele with unilateral open lip schizencephaly

URL:	https://www.eurorad.org/case/13876
DOI:	10.1594/EURORAD/CASE.13876
ISSN:	1563-4086