Schizencephaly) Aqueductal stenosis Arnold-Chiari malformation type III
A 23-year-old woman, gravida 2, para 1, was referred for fetal ventriculomegaly. Her past medical and family history- unremarkable. She had no prenatal care during this pregnancy until 33 weeks gestation when ventriculomegaly was revealed by her first USG.
US examination showed… Slit like communication between IV ventricle & cisterna magna-Dandy walker variant. Communication between ventricle & subarachnoid space in the parietal region
Fetal MRI showed… Bilateral brain clefts from ventricle to subarachnoid space in both parietal lobes,with lining grey matter filled with CSF. Normal septum pellucidum. No fat or subacute hematoma was visible and the midline was centrally located. Communication between IV th ven & cisterna magna-Key Hole SCHIZENCEPHALY WITH DANDY WALKER VARIANT
At 37weeks gestation, a live female baby was delivered through spontaneous vaginal delivery with a birth weight of 2370 g, Apgar score 8 and 9 at 1 minute and 5 minutes,resp.
Postnatal CT & MRI showed… Bilateral open lip schizencephaly with lining grey matter.
Septum pellucidum & Corpus callosum and B/L optic nerves normal. Mild enlargement of cisterna magna communicating with the IV ventricle-key hole appearance with hypoplasia of vermis-Dandy Walker Variant.
DISCUSSION Incidence -1.54 in 100,000 live births, and most cases are diagnosed only after birth. Antenatal diagnosis is rare. Most cases diagnosed after 28 weeks gestation. Only three antenatally detected cases have been identified at 21 weeks gestation and none before 20 weeks In the present case, schizencephaly was diagnosed at 33 weeks gestation due to absence of prenatal care.
Schizencephaly Split brain is a rare structural malformation of the cerebrum characterized by congenital clefts or defects that are usually symmetrical and involve the parietal or temporal brain. The clefts are lined by cortical gray matter, unlike porencephaly, where white matter lines the clefts Disorder of neuronal migration(2 to 5months of age)
ETIOLOGY Malformation of cortical development-Early perinatal insult affecting germinal zone prior to neuronal migration Destructive: Vascular injury, Teratogen exposure (e.g., cocaine), Infections (especially CMV), Trauma. Developmental Disordered neuronal migration and organization and are considered to be related to polymicrogyria Young parenternal age Genetic Mutations
Open (open lip): allowing CSF communication between the ventricle and subarachnoid space, MC-Bilateral Solid (closed lip): consisting of an abnormal, solid gray matter tract between the ventricle and brain surface-gray matter lined walls are in contact with each other MC -Unilateral
The diagnosis rests on detection of the cerebral clefts or abnormal gray matter traversing from ventricle to cortex. ASSOCIATED ABNORMALITIES: Septo-optic dysplasia, Dysgenesis of the corpus callosum, Absence of the septi pellucidi. Neurodevelopmental delay and seizures are common.
AQUEDUCTAL STENOSIS Location: Stenosis at cerebral aqueduct, either at level of the superior colliculi or at intercollicular sulcus Size: Normal mean cross-sectional area of the aqueduct at birth is 0.2 to 1.8 mm2 "Ballooned" ventricles (lateral, third) and foramina of Monroe proximal to obstruction Normal fourth ventricle and foramina (Luschka, Magendie) distal to obstruction
Arnold-Chiari malformation type III 1.Low occipital meningoencephalocele +intracranial Chiari 2 malformation, 2.Meningomyelocele, 3.Herniated cerebellar tissue and caudal displacement of brainstem 4.Club foot
VENTRICULOMEGALY Measurements of 10 mm or larger suggest VM 10 to 12 mm is mild or borderline. 12 to 15 is moderate. Greater than 15 mm is marked VM.
ABNORMALITIES COMMONLY ASSOCIATED WITH VENTRICULOMEGALY Obstructive hydrocephalus Aqueductal stenosis (idiopathic, infections, bleeding, X-linked, masses) Spina bifida with Chiari III malformation Excess cerebrospinal fluid (CSF) production Choroid plexus cyst Cerebral malformations Agenesis of corpus callosum Vermian dysgenesis and Dandy-Walker malformation Holoprosencephaly Neuronal migration abnormalities Microcephaly Macrocephaly Lissencephaly Schizencephaly Destructive processes (encephaloclasis) Vascular insults, infections, porencephaly Aneuploidy (trisomies 21, 18, 13) Many syndromes
Chiari 1: Herniated CBLL tonsils Chiari 2: Vermis may be impacted, rather than herniated or may "disappear" due to compressive injury Chiari 3: Chiari 2 PLUS encephalocele Chiari 4: Controversial, not just hypoplastic cerebellum Some reserve term for severe hypoplasia of cerebellum in association with Chiari 2