Large vertex meningoencephalocele with schizencephaly: An interesting case with neurosurgical challenge.

An encephalocele is a developmental disorder of neural tube closure, where as schizencephaly is a developmental disorder of neuronal migration. There are only few case reports suggesting association of schizencephaly with meningoencephalocele. We report a case of 6-year-old child who was brought by her parent with complaints of progressive swelling over her vertex since birth, left sided hemiparesis and intermittent generalized tonic clonic convulsion for last 3 years. Clinical examination, computed tomography (CT) and magnetic resonance imaging (MRI) of brain revealed a large calvarial defect with meningoencephalocele and associated schizencephaly. Initially, ventriculoperitoneal (VP) shunt was carried out, followed by successful repairing of the defect. This case is interesting for late presentation, management difficulties and associated anomalies "schizencephaly", which is a rare developmental disorder.

Introduction

An encephalocele is a developmental disorder in which the bones of the skull do not close completely, creating a gap through which cerebrospinal fluid (CSF), brain tissue and meninges can protrude into a sac-like formation. It occurs due to failure of the neural tube to close completely during fetal development, whereas schizencephaly is a developmental disorder of neuronal migration. Different theories have been described in the etiology of schizencephaly like genetic or a physical insult, such as infection, infarction, hemorrhage, toxin, or mutation.

Case Report

A 6-year-old female child was brought by her parent with complaints of progressive swelling over her vertex since birth, left sided hemiparesis and intermittent generalized tonic clonic convulsion for last 3 years. She was delivered full-term normally at home, and cried immediately after birth. There was no history of consanguineous marriage, intrauterine infection, or teratogenic drug intake by mother. On examination we found a cheerful child with a large fluctuating swelling over vertex of size approximately 12 × 10 × 15 cm. The swelling had impulse on cough and a positive transillumination test. There was microcephaly and talipus equinovarus on the left side. She was having global delay in developmental milestones, left side hemiparesis and left facial palsy of upper motor type. Her visual, auditory, and endocrine assessment was normal. Computed tomography (CT) and magnetic resonance imaging (MRI) of brain revealed a large calvarial defect with meningoencephalocele and associated schizencephaly (Type II) [Figures 1 (a-c) and 2 (a-c)]. Ventriculoperitoneal (VP) shunt was done initially. One month later, the sac was opened at its apex, a large bony dural defect was seen down at the level of the cranium, and the cranial contents were found to be protruding out of it. Redundant dura were dissected free from the internal wall of the sac and used to close the defect in a two layer fashion. Cranioplasty was done with polymethyl methacrylate material. At 1 year follow-up, motor power of left limb had improved and seizure was well-controlled with antiepileptic drug.

Figure 1

(a) MRI of brain-Sagittal T2-weighted image showing a large vertex meningoencephalocele. Note continuity of cerebrospinal fluid between right lateral ventricle and protruding sac (b) CT scan of brain after 3D reconstruction showing a large calvarial defect over vertex with shunt tube inside (c) CT scan of brain after VP shunt showing, protruding parenchyma with a cleft extending from surface to RT lateral ventricle (schizencephaly)

Figure 2

(a) MRI of brain Axial T1-weighted image showing. Blue arrowhead: Heterotropic grey matter. Red arrow: Pachygyria. Blue arrow: Agenesis (b) MRI of brain Axial T1-weighted image in upper cuts showing. Red arrow: Schizencephaly, note gray matter lined clef extending across the entire cerebral hemisphere (Blue arrow). Blue arrowhead: Heterotropic grey matter (c) MRI of brain Axial T2-weighted image showing. Red arrow: Schizencephaly, CSF continuity from ventricular surface to pial surface can be marked

Discussion

Meningoencephalocele cases usually present immediately after birth and surgery is generally performed during infancy.[1] In developing countries, cases may present late, as in our case. If meningoencephalocele is left unrepaired, the growing brain parenchyma will continue to bulge out of it leading to microcephaly. Because of microcephaly, protruding parenchyma may not completely reduce back to cranial cavity, even after pre-operative VP shunt. A delicate judgment is required during dural closure and cranioplasty, as tight closure would increase intracranial tension and fatal complications.

In the case presented, the encephalocele was totally covered with skin; this indicates that neural tube must have closed normally during neurulation. The primary nonseparation of neurectoderm and surface ectoderm has been described as the culprit for such anomalies.[2] This final process of neurulation takes place just after closure of the neural tube in the 4th week of gestation.[123]

This case is even more interesting for its association with schizencephaly; which is a developmental disorder of neuronal migration; occurring around 8th week of gestation.[4] Neuronal migration involves several steps, starting from initial departure of neuroblasts from the ventricular zone to finally arrest of migration at the appropriate layer. Depending upon stage of migration defect, malformation could range from periventricular heterotopias to polymicrogyria and schizencephaly.[45] The latter is characterized by gray matter lined cleft extending across the entire cerebral hemisphere, from the ventricular surface (ependyma) to the periphery (pial surface) of the brain. The clefts may be unilateral or bilateral and may be closed, as in schizencephaly type I, or separated, as in schizencephaly type II. It is frequently associated with other cerebral anomalies like ventriculomegaly, polymicrogyria, heterotopias, agenesis of the corpus callosum, and absence of the septum pellucidum.[67] Patients typically present with seizures, hemiparesis, and developmental deficits. Outcome is variable and depends upon extent of cortex involved in the defect. A clinical presentation and MRI finding of our case fits to a case of schizencephaly. Gray matter lined cleft helped in differentiating schizencephaly from porencephaly; this is best demonstrated on MRI.[7] Management consists of treatment for seizures, physiotherapy, and in cases that are complicated by hydrocephalus, a VP shunt is needed.

Conclusion

Encephalocele should be repaired early. While repairing large vertex encephalocele, few critical points are to be taken care of like slow decompression of cerebrospinal fluid (CSF) from the swelling and preservation of major veins. Initial VP shunt helps in reduction of size and dissection of sac; it further gives a safe feeling during dural closure and cranioplasty. In case of meningoencephalocele it is not only extent of the herniated mass but the presence of additional anomalies of brain which are considered important factors in the prognosis for the patient.