Introduction
Background
Schizencephaly is an uncommon disorder of neuronal migrational characterized by a cerebrospinal fluid–filled cleft, which is lined by gray matter. The cleft extends 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 (fused lips), as in schizencephaly type I, or separated (open lips), as in schizencephaly type II.
Schizencephaly. Axial T2-weighted MRI in unilateral closed-lip (type I) schizencephaly. The cleft is lined by gray matter and extends from the pial surface to the lateral ventricle.
Schizencephaly. Axial T2-weighted MRI demonstrates a small open-lip schizencephaly. The septum pellucidum is absent.
Presentation and outcome are variable, but patients typically present with seizures, hemiparesis, and developmental deficits. Usually, the severity of symptoms is related to the amount of brain affected by the abnormality.1
Pathophysiology
Several theories have been proposed to explain the etiology of schizencephaly, although none is universally accepted. The leading theory indicates that schizencephaly results from an early, focal destruction of the germinal matrix and surrounding brain before the hemispheres are fully formed.2
Schizencephaly probably occurs as the end result of a variety of insults occurring at a critical time and in a critical location during brain development. No specific inciting or unusual prenatal events have been identified, and reported cases are sporadic.
The lesion is most likely related to multiple etiologies, including genetic, toxic, metabolic, vascular, or infectious causes. Familial cases of schizencephaly have been reported.3,4
Frequency
United States
Schizencephaly is uncommon; to our knowledge, there are no well-documented data on its specific incidence.
International
Schizencephaly is uncommon; to our knowledge, there are no documented geographical differences in its occurrence.
Mortality/Morbidity
Severity of the symptoms depends on the amount of brain involved. Affected patients typically have seizures, hemiparesis, variable developmental delay, and blindness. Patients also have variable degrees of mental retardation.
Patients with open-lip schizencephaly die at an earlier age than patients with the closed-lip form. Usually, death results from failure to thrive, chronic infections, and respiratory problems.
Patients with closed-lip schizencephaly may not present clinically until later in infancy or early childhood and may live to early adulthood.
Age
This condition is present at birth.
Anatomy
Schizencephaly is divided into 2 types, which have prognostic significance. In closed-lip or type I schizencephaly, the cleft walls are in apposition. In open-lip or type II schizencephaly, the cleft walls are separated. Schizencephaly type II occurs more commonly than type I.
The clefts in schizencephaly are lined either totally or in part by gray matter and extend from the pial surface to the ependyma of the lateral ventricle. The clefts can be located anywhere, but they commonly occur in the parasylvian regions. The clefts can be unilateral or bilateral, and can be either symmetric or asymmetric.
The cavity formed in the open-lip type varies in size from small to large and may communicate with the lateral ventricle. The ventricular system may be enlarged, particularly in patients with the open-lip form of schizencephaly.
Gray-matter heterotopia (collections of gray matter in abnormal locations), polymicrogyria, and arachnoid cysts can be associated with schizencephaly. Heterotopias and polymicrogyria typically line the clefts. Microcephaly has been noted in some patients. The septum pellucidum is absent in 80-90% of patients, and schizencephaly may coexist with septo-optic dysplasia.
Presentation
Clinical features of schizencephaly are highly variable. Patients with unilateral clefts with fused lips may have mild hemiparesis and seizures but otherwise have normal development. When the cleft is open, patients present with mild-to-moderate developmental delay and hemiparesis; severity is related to the extent of cortex involved in the defect.5,6
Patients with bilateral clefts present with severe mental deficits and severe motor anomalies including spastic quadriparesis. Frequently, these patients present with blindness, which is often associated with optic nerve hypoplasia. Language development is more likely to be normal in patients with unilateral schizencephaly compared to patients with bilateral clefts.
Intractable seizures frequently are noted in schizencephaly. Several types of seizures have been reported including generalized tonic-clonic, partial motor, and sensory seizures. Infantile spasms have been seen in a few children. Reports have found no correlation between the subtype of schizencephaly and the occurrence or type of seizure disorder.
Preferred Examination
MRI is the imaging modality of choice because of its superior differentiation of gray matter and white matter and its ability to image in more than one plane.
Identification of gray matter lining the cleft is the pathognomonic finding in differentiating schizencephaly from porencephaly; this is best demonstrated on MRIs.
The more complete information obtained by MRI enables a more accurate prediction of neurologic outcome.
Limitations of Techniques
MRIs are degraded by patient motion, and sedation may be required for children. MRI is relatively expensive. The examination cannot be done portably in an ill neonate. The study is relatively lengthy.
Differential Diagnoses
Other Problems to Be Considered
Porencephaly
Porencephalic cyst
More on Schizencephaly |
 Overview: Schizencephaly |
| Imaging: Schizencephaly |
| Follow-up: Schizencephaly |
| Multimedia: Schizencephaly |
| References |
| Further Reading |
| Next Page » |
References
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Blümcke I. Neuropathology of focal epilepsies: a critical review. Epilepsy Behav. Feb 24 2009;[Medline].
Shinder R, Wolansky L, Turbin RE. Congenital homonymous hemianopia and cortical migration abnormalities in a young adult. J Pediatr Ophthalmol Strabismus. Jan-Feb 2009;46(1):38-41. [Medline].
Goez H, Zelnik N. Schizencephaly in Infants With Thrombophilia. J Child Neurol. Jan 23 2009;[Medline].
Spalice A, Parisi P, Nicita F, Pizzardi G, Del Balzo F, Iannetti P. Neuronal migration disorders: clinical, neuroradiologic and genetics aspects. Acta Paediatr. Mar 2009;98(3):421-33. [Medline].
Maeda T, Akaishi M, Shimizu M, Sekiguchi K, Anan A, Takano T, et al. The subclassification of schizencephaly and its clinical characterization. Brain Dev. Nov 25 2008;[Medline].
Steinbok P, Gan PY, Connolly MB, Carmant L, Barry Sinclair D, Rutka J, et al. Epilepsy surgery in the first 3 years of life: A Canadian survey. Epilepsia. Jan 19 2009;[Medline].
Barkovich AJ. Schizencephaly. In: Pediatric Neuroimaging. 2nd ed. Philadelphia: Lippincott-Raven;. 1996:219-25.
Barkovich AJ, Norman D. MR imaging of schizencephaly. AJR Am J Roentgenol. Jun 1988;150(6):1391-6. [Medline].
Barth PG. Schizencephaly and nonlissencephalic cortical dysplasias. AJNR Am J Neuroradiol. Jan-Feb 1992;13(1):104-6. [Medline].
Bird CR, Gilles FH. Type I schizencephaly: CT and neuropathologic findings. AJNR Am J Neuroradiol. May-Jun 1987;8(3):451-4. [Medline].
Byrd SE, Osborn RE, Bohan TP, Naidich TP. The CT and MR evaluation of migrational disorders of the brain. Part II. Schizencephaly, heterotopia and polymicrogyria. Pediatr Radiol. 1989;19(4):219-22. [Medline].
Chamberlain MC, Press GA, Bejar RF. Neonatal schizencephaly: comparison of brain imaging. Pediatr Neurol. Nov-Dec 1990;6(6):382-7. [Medline].
Denis D, Chateil JF, Brun M, et al. Schizencephaly: clinical and imaging features in 30 infantile cases. Brain Dev. Dec 2000;22(8):475-83. [Medline].
DiPietro MA, Brody BA, Kuban K, Cole FS. Schizencephaly: rare cerebral malformation demonstrated by sonography. AJNR Am J Neuroradiol. Mar-Apr 1984;5(2):196-8. [Medline].
Komarniski CA, Cyr DR, Mack LA, Weinberger E. Prenatal diagnosis of schizencephaly. J Ultrasound Med. May 1990;9(5):305-7. [Medline].
Lee SH, Rao K, Zimmerman RA. Schizencephaly. In: Cranial MRI and CT. 4th ed. New York: McGraw-Hill;. 1999: 163-5.
Miller GM, Stears JC, Guggenheim MA, Wilkening GN. Schizencephaly: a clinical and CT study. Neurology. Aug 1984;34(8):997-1001. [Medline].
Osborne AG. Schizencephaly. In: Diagnostic Neuroradiology. St Louis: Mosby-Year Book;. 1994:52-6.
Packard AM, Miller VS, Delgado MR. Schizencephaly: correlations of clinical and radiologic features. Neurology. May 1997;48(5):1427-34. [Medline].
Further Reading
Clinical guidelines
Guidelines on routine cerebrospinal fluid analysis. Report from an EFNS task force.
European Federation of Neurological Societies - Medical Specialty Society. 2006 Sep. 10 pages. NGC:005489
Clinical trials
Human Epilepsy Genetics--Neuronal Migration Disorders Study
Related eMedicine topics
Corpus Collosum, Agenesis
Identification of Potential Epilepsy Surgery Candidates
Neuroimaging in Epilepsy Surgery
Infantile Spasm
Keywords
schizencephaly, cerebrospinal fluid–filled cleft in the brain, abnormal cleft of the brain, type I schizencephaly, type II schizencephaly, open-lip schizencephaly, closed-lip schizencephaly
