Subependymal cysts may either be postnatally acquired post-hemorrhagic cysts or may be congenital (germinolytic). The congenital cysts may result from infection, ischemic injury, or hemorrhage.
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Epidemiology
Subependymal cysts are most frequently seen in preterm infants, likely related to their persistent germinal matrix at the caudothalamic groove and propensity for hemorrhage in this location.
Congenital cysts may often be an isolated incidental finding in healthy newborns. However, they also have associations with congenital viral infections (mainly cytomegalovirus and rubella), metabolic disorders (predominantly Zellweger syndrome), chromosomal abnormalities, and maternal cocaine use.
Pathology
The cysts are not epithelium-lined and rather are lined by germinal cells and glial tissue. Their vascular origin is suggested by macrophage-like cells in the fluid.
Radiographic features
Can be differentiated from other cystic lesions (such as periventricular leukomalacia and connatal cysts) by location. Subependymal cysts should be located below the external angle of the lateral ventricles (superior/lateral margin of the frontal horn) and posterior to the foramen of Monro.
Post-hemorrhagic vs germinolytic (congenital) cysts are difficult to differentiate sonographically.
Differential diagnosis
See article: intracranial cystic lesions in the perinatal period.