Asymmetric Ventriculomegaly, Interhemispheric Cyst, and Dysgenesis of the Corpus Callosum (AVID)

Abstract

A series of 20 cases from 2 academic institutions is presented with a characteristic imaging triad of asymmetric ventriculomegaly, a large interhemispheric cyst, and partial or complete agenesis of the corpus callosum. Most cases were initially referred as aqueduct stenosis and hydrocephalus or focal porencephaly. We describe the imaging findings that identify an abnormal or absent corpus callosum associated with a type 1 interhemispheric cyst in fetuses initially thought to have hydrocephalus attributable to aqueductal stenosis. We suggest that the acronym AVID (asymmetric ventriculomegaly, interhemispheric cyst, and dysgenesis of the corpus callosum) may be useful in recognition of these cases. All cases presented with markedly asymmetric ventriculomegaly on initial sonography, with progressive hydrocephalus throughout gestation. Fetal magnetic resonance imaging was performed in 15 of 20 cases. Thirteen of 20 cases were identified in male fetuses. Associated fetal and postnatal abnormalities are also reported. Technological improvements in sonography and fetal magnetic resonance imaging allow improved characterization of associated intracranial anomalies in the setting of hydrocephalus. Accurate diagnosis can aid parental counseling, especially because isolated aqueductal stenosis suggests a better prognosis than hydrocephalus with anomalies. Markedly asymmetric ventriculomegaly in this series was the key to excluding isolated aqueductal stenosis and was associated with callosal malformation with a type 1a interhemispheric cyst.

Clinical outcomes following prenatal diagnosis of asymmetric ventriculomegaly, interhemispheric cyst, and callosal dysgenesis (AVID)

“…For children meeting the ultrasound inclusion criteria, DP, KO, and TG reviewed all available fetal MR imaging exams for the presence of (a) interhemispheric cysts or ventricular diverticula and (b) dysgenesis or agenesis of the corpus callosum. After exclusion of all children not meeting these ultrasound and MRI criteria, a total of 15 cases of AVID remained, of which eight were included in our original publication . All available postnatal imaging was reviewed for the 15 cases by DP.…”

“…After exclusion of all children not meeting these ultrasound and MRI criteria, a total of 15 cases of AVID remained, of which eight were included in our original publication. 5 All available postnatal imaging was reviewed for the 15 cases by DP.…”

“…5 In these cases, additional anomalies were identified most reliably using fetal MRI. [5][6][7][8][9] Identification of fetuses with the AVID triad, along with identification of progressive severe fetal macrocephaly, was shown to have important implications for prenatal counseling, delivery planning, and postnatal course. In this follow-up series of 15 fetuses, we present the neurodevelopmental outcomes of a single institution cohort of children diagnosed prenatally with AVID.…”

“…Our previously published case series describes the imaging triad of asymmetric VM, interhemispheric cyst, and dysgenesis of the corpus callosum (AVID). We noted that prenatal sonographic findings of marked asymmetric VM in the setting of severe hydrocephalus and absent cavum septi pellucidi (CSP) can be indicative of an underlying interhemispheric cyst and associated callosal malformation, which are more subtle diagnoses that may be initially missed in the setting of severe ventriculomegaly . In these cases, additional anomalies were identified most reliably using fetal MRI .…”

“…We noted that prenatal sonographic findings of marked asymmetric VM in the setting of severe hydrocephalus and absent cavum septi pellucidi (CSP) can be indicative of an underlying interhemispheric cyst and associated callosal malformation, which are more subtle diagnoses that may be initially missed in the setting of severe ventriculomegaly . In these cases, additional anomalies were identified most reliably using fetal MRI . Identification of fetuses with the AVID triad, along with identification of progressive severe fetal macrocephaly, was shown to have important implications for prenatal counseling, delivery planning, and postnatal course.…”