British Journal of Radiology (2008) 81, e40-e43
© 2008 British Institute of Radiology
doi: 10.1259/bjr/56258419
A case of schizencephaly presenting with unilateral cryptophthalmos
I ÖZTOPRAK, MD
1
H ERDOGAN, MD
2
M GÜRELIK, MD
3
M I TOKER, MD
2 and
B ÖZTOPRAK, MD
1
Departments of 1 Radiology, 2 Ophthalmology and 3 Neurosurgery, Faculty of Medicine, Cumhuriyet University, Sivas, Turkey
Correspondence: Ibrahim Öztoprak, Cumhuriyet Universitesi Tip Fakultesi, Radyoloji AD, Sivas, 58140, Turkey. E-mail: oztoprak{at}cumhuriyet.edu.tr
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Abstract
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We describe an unusual case of schizencephaly associated with unilateral orbital meningoencephalocele, anophthalmos, orbital soft mass, cryptophthalmos and partial agenesis of corpus callosum, along with ectopic kidney and thumb anomaly.
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Introduction
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Schizencephaly is a rare central nervous system (CNS) anomaly which may be associated with other intracranial and facial anomalies. It can be diagnosed easily with sonography or MRI in the prenatal period.
We report a previously undiagnosed patient with unilateral open-lip schizencephaly with a giant cleft occupying almost the whole left hemicranium who presented with cryptophthalmos. Associated multiple anomalies such as orbital meningoencephalocele, anophthalmos and ectopic kidney are also presented.
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Case report
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We present a 4-month-old term-born female infant who did not have any developmental retardation. Her physical examination revealed a normal right eye, but cryptophthalmos and soft mass were present on the left side. The horizontal lid length was 10 mm, but punctums and canalicules did not exist in the left eyelid. No neurological finding was determined.
A large schizencephalic defect occupying nearly the entire left hemispheric area was demonstrated on cranial MRI (Figure 1
). Expansion of the left hemicranium, midline shift, left tentorial and left cerebellar hemispheric compression, and cortical vein distortion were also noted. There was a communication between the cerebrospinal fluid (CSF) area and the third and the right lateral ventricles. The left thalamus was compressed and inferiorly displaced due to both the mass effect and the relationship of the schizencephaly with the third ventricle. The septum pellicidum was absent and the right lateral ventricle was minimally dilated. Partial agenesis of corpus callosum (ACC) with hypoplasia of its corpus and genu, and absence of its rostrum, isthmus and splenium was also determined (Figure 2a). The radial arrangement of the gyri typical of ACC could easily be noticed (Figure 2b).
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Figure 1. (a) Axial T2 weighted MRI reveals a giant schizencephalic cleft and left orbital menigoencephalocele; the optic chiasm and the left internal carotid artery cannot be seen. (b) Expansion of the left hemicranium, the distortion of cortical veins and the midline shift to the right can be seen at a more superior level. Coronal T2 weighted images show the compressed and inferiorly displaced left thalamus (c) and left cerebellar hemisphere and tentorium (d).
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Figure 2. Partial agenesis of corpus callosum(a) and radial arrangement of gyri (b) are demonstrated by sagittal T1 weighted MRI.
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A left orbital meningoencephalocele was seen through a large defect on frontal, sphenoid, ethmoid and nasal bones. The defective orbital space was occupied by dysgenetic brain tissue, and normal orbital elements – bulbus oculi, extraocular muscles and fat, left optic nerve – were absent (Figure 3a,b). The optic chiasm along with the left optic nerve was also absent. It was striking that the neural tissue of the meningoencephalocele was supplied by a branch of the right anterior cerebral artery (Figure 3b). The left internal carotid artery and its branches were not seen above the level of the cavernous sinus (Figure 1
).
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Figure 3. Coronal(a) and axial (b) T2 weighted images reveal a left orbital meningoencephalocele and branches of the right anterior cerebral artery supplying the neural tissue inside the sac (arrow).
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The ectopic left kidney was seen to be located in the pelvis on abdominal ultrasound examination (Figure 4) and this was also confirmed by abdominal MRI. In plain radiography, the left first metacarpal bone was agenetic and phalanges were anomalous (Figure 5). The left first digit was connected to the rest of the hand only by skin tissue. The other systemic examinations, laboratory findings and chromosome analysis were normal.
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Figure 4. On abdominal ultrasound the left kidney cannot be seen in its normal localization(a) whereas the right kidney is normally located (b).
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Discussion
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Schizencephaly was initially described by Yakovlev and Wadsworth [1, 2]. This disorder occurs as hemispheric clefts characterized by grey matter-lined lips in the region of the primary fissures, infolding of grey matter along the clefts. Two types of schizencephaly have been described, type 1 (closed-lip) schizencephaly is characterized by grey matter-lined lips that are in contact with each other. Type 2 (open-lip) schizencephaly has separated lips and a cleft of CSF extending to the underlying ventricle from the pial surface. Schizencephaly may be associated with cerebral malformations, including ventriculomegaly, polymicrogyria, heterotopias, agenesis of the corpus callosum, and absence of the septum pellucidum.
The aetiology and pathogenesis of schizencephaly are still unknown. It is believed to occur because of abnormal neuronal migration secondary to multiple factors. Mutation in the EMX2 gene [3], and early prenatal injury causing vascular insufficiency [4] are reported to be the possible aetiological factors. One hypothesis is based on vascular compromise during early neuroembryogenesis [5]. The other considered hypothesis is based on a primary dysgenesis of the embryonic pyramidal tracts [6]. Normally, the migration of neuroblasts from the germinal matrix to the cerebral cortex takes place between the fourth and sixteenth weeks of gestation. An ischaemic event in the watershed zone, including the germinal matrix, may lead to an inhibition of neuroblast migration. The severity of ischaemia determines the size of the clefts. The large schizencephalic cleft in our case may be explained by the absence of the left internal carotid artery above its cavernous portion. The dysgenetic brain tissue occupying the left orbit was supplied by the right anterior circulation. We suppose that the left hemicranium was expanded and the development of ipsilateral brain tissue was inhibited by the pulsations of CSF filling the large cleft. The left thalamus, the right cerebral hemisphere, the left tentorium and the left cerebellar hemisphere were displaced for the same reason.
Partial ACC and absence of septum pellicidum, which are present in our case, are well-known intracranial anomalies that are associated with schizencephaly.
Orbital meningoencephalocele is a rare congenital abnormality caused by a developmental defect in the skull with herniation of adjacent meningeal and brain substances. In our case there is dysgenetic brain tissue in the herniated meningeal sac. Anophthalmos, or congenital absence of an eye or both eyes, is a rare anomaly that occurs as a result of insults to the developing eye(s), and usually accompanies other severe head and brain anomalies. Primary anophthalmos is due to an arrest of the development of the optic sac early in the fourth week of gestation. Insults during the second stage of development (4–8 weeks of life) result in degeneration of the elements already formed, which is called "degenerative anophthalmos" [7]. As schizencephaly and meningoencephalocele occur after the fourth week of gestation, the anophthalmos in our case is most likely to be of a degenerative type, and it was the meningoencephalocele which led to the degeneration of already formed orbital tissue. Orbital meningoencephalocele that is associated with anophthalmos and cryptophthalmos in our case might have led to agenesis of normal orbital structures by both of the two possible mechanisms: the neural components of orbital structures are likely to be agenetic since the left brain tissue is maldeveloped; and ectodermal components of orbital content are inhibited by the mass of the dysgenetic brain tissue which occupied the orbit.
As multiple organ anomalies can be seen together with congenital brain anomalies, we suggest that the ectopic left kidney and finger anomaly in our case is not surprising.
Schizencephaly should be distinguished from arachnoid cyst, porencephalic cyst, ventriculomegaly, monoventricle in holoprosencephaly, hydranencephaly and agenesis of the corpus callosum with an interhemispheric cyst. The presence of characteristic grey matter-lined lips in schizencephaly is an important feature in differential diagnosis; however, this finding was not striking in our case as the schizencephalic cleft was occupying almost the entire left hemicranium. Our case can easily be differentiated from mentioned lesions other than hydranencephaly by the demonstration of a large CSF cleft communicated with the ventricle. Hydranencephaly is a rare condition characterized by the complete or almost complete absence of the cerebral hemispheres within a relatively normal-sized cranium. Unlike schizencephaly, it occurs as an isolated defect, not associated with malformations elsewhere. In our case, schizencephaly can be distinguished from hydranencephaly and porencephaly also by its prominent mass effect leading to midline shift and expansion of the ipsilateral hemicranium.
Received for publication July 25, 2006.
Revision received October 16, 2006.
Accepted for publication November 15, 2006.
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References
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- Yakovlev PI, Wadsworth RC. Schizencephalies: a study of the congenital clefts in the cerebral mantle. I. Clefts with fused lips. J Neuropathol Exp Neurol 1946;5:116–30.[CrossRef]
- Yakovlev PI, Wadsworth RC. Schizencephalies: a study of the congenital clefts in the cerebral mantle. II. Clefts with hydrocephalus and lips separated. J Neuropathol Exp Neurol 1946;5:169–20.[CrossRef]
- Brunelli S, Faiella A, Capra V, Nigro V, Simeone A, Cama A, et al. Germline mutations in the homeobox gene EMX2 in patients with severe schizencephaly. Nat Genet 1996;12:94–6.[CrossRef][Medline]
- Montenegro MA, Guerreiro MM, Lopes-Cendes I, Guerreiro CA, Cendes F. Interrelationship of genetics and prenatal injury in the genesis of malformations of cortical development. Arch Neurol 2002;59:1147–53.[Abstract/Free Full Text]
- Komarniski CA, Cyr DR, Mack LA, Weinberger E. Prenatal diagnosis of schizencephaly. J Ultrasound Med 1990;9:304–7.
- Bubis JJ, Landau WM. Agenesis of pyramidal tracts associated with schizencephalic clefts in rolandic cortex. Neurology 1964;14:821–4.[Free Full Text]
- White VA, Rootman J. Eye. In: Dimmick R, editor. Developmental pathology of the embryo and fetus. Philadelphia, PA: Lippincott, 1992: 401–23.
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Abstract
Introduction
