2006-05-31-14 Schizencephaly © Cuillier www.thefetus.net/
Cuillier F*, Lemaire P**, Deshayes M**, Fossati P***
* Department of Gynecology, Félix Guyon’Hospital ** Sonographer, Moufia’street *** Department of Radiology, Hôpital Félix Guyon - Ile de la Réunion - France
Definition: An old definition of schizencephaly is “a form of porencephaly characterized by a cyst or cavity in the cerebral hemispheres”. In fact, schizencephaly is a congenital defect due to an abnormal development of the fetal brain. Schizencephaly is certainly an uncommon disorder of neuronal migration, characterized by a cerebrum-spinal fluid-filled cleft, lined by gray matter. The clefts may extend through the entire hemisphere from the ependymal lining of the lateral ventricles to the periphery (pial surface) covering the cortex of some part of the brain. The cleft can be unilateral or bilateral and are commonly located near the pre- or post-central gyri. The gray matter lining can be dysplastic. There are two types of schizencephaly:
Type I: The clefts can be unilateral or bilateral and may be closed (fused lips). In closed-lip (type I), the cleft walls are in apposition, causing obliteration of the CSF space within the cleft.
Type II: The clefts can be unilateral or bilateral and may be separated (open lips). In open-lips (type II), the clefts walls are separated. The CSF fills the cleft from the lateral ventricles to the subarachnoid space that surrounds the hemispheres.
Case report: This is a 30-year-old-woman, G2P1, referred to our antenatal unit due to a hydrocephaly. The triple test and the nuchal translucency were normal. At 21 weeks, a bilateral hydrocephaly was observed. The spine was normal. The cerebellum was visualized. There was no Arnold-Chiari syndrome. The couple was counseled. They refused to perform an MRI or interruption of pregnancy. The serial scans showed a progressive evolution of the brain lesion. The cortical brain seemed present but very thin.
At 36 weeks, a cesarean section was performed due to macrocrania. Few days latter, a CT scan showed a cleft in right temporal-parietal region. A MRI showed a prominent cleft in right temporal-parietal region cleaving the right parietal lobe, extending from cerebral convexity to right lateral ventricle. The two ventricular systems were communicating. Since then, the baby has been hospitalized several times. He does not have any spontaneous movement and he can not swallow.
Brain view at 21 weeks showing the hydrocephaly. The cerebellum seems normal.
Note the cerebral cleft
The drooping choroid plexus in the cerebral cleft
Normal spine and 3D of the brain at 24 weeks
History: Schizencephaly was first described at the end of the XIXth century. The term of schizencephaly was introduced in 1946 by Yakovlev and Waldsworth. They reported a brain lesion due to an abnormal development of the brain and not secondary to the destruction of mature cortex as previously reported in cases of porencephaly.
Synonym: Schizencephaly type I and type II; cerebrum-spinal fluid-filled clef in the brain; abnormal cleft brain; open lip schizencephaly; closed lip schizencephaly; « agenetic porencephaly », « split brain ».
Prevalence: Among neurological cortical malformations, schizencephaly is the most severe restricted disorder. Schizencephaly has an extremely rare prevalence, with an unknown incidence. There is neither sex nor race predilection. In the literature, more than 70 cases of schizencephaly type I have been described, but the exact incidence is still unknown. Schizencephaly type II is more frequent than schizencephaly type I. Schizencephaly is considered as a non-specific risk factor to prematurity. According to Denis et al, 20% of the children born prematurely compared with 10% in the general population.
Etiology: Several theories have been proposed to explain the etiology of schizencephaly. Indeed the exact etiology of schizencephaly remains unclear, some environmental events have been proposed.
Sporadic: is the principal etiology. No specific prenatal events have been identified, but genetic, toxic, metabolic, vascular of infectious etiology can be responsible.
Fetal hypotensive vasculopathy: due to severe bleeding in the first trimester or fetal hemorrhagia by auto-immune thrombocytopenia
Intrauterine infections: early gestational viral infections, viral illness in particular CMV infection
Environmental events do not entirely rule out the possibility of a genetic mechanism. Exceptional familiar cases of schizencephaly have been reported, raising the possibility of an autosomal dominant inheritance with incomplete penetrance and variable expression. There is also evidence suggesting that unilateral schizencephaly can be familiar and probably accounts for previously cases reported as « familial porencephaly ».
Recent studies have linked schizencephaly with a mutated gene called the Homeobox gene EMX2. If the gene EMX-2 is missing or defective, nerve cell growth and migra