Subependymal cysts may either be postnatally acquired posthemorrhagic cysts or may be congenital (germinolytic). The congenital cysts may result from infection, ischemic injury, or hemorrhage.
Subependymal pseudocysts, or subependymal germinolytic cysts, were described by Banker and Larroche in 1962
When apparently isolated SEPC are observed at prenatal US, further investigations should be performed under the following circumstances: (1) SEPC great axis ≥ 9 mm; (2) SEPC adjacent to the occipital and temporal horns; (3) SEPC located posterior to the caudothalamic notch; (4) SEPC with atypical morphology 1).
Differentiation of non-haemorrhagic from post-haemorrhagic germinolysis is necessary to clarify the aetiology and pathogenesis of non-haemorrhagic pseudocysts. Caudothalamic germinolysis possibly is the result of infection with stenotic intima proliferation following vasculitis. The results are thalamostriatal vasculopathy and germinal necrosis. Anterior plexus cysts might be the result of folding faults of the ependyma in the growth period of the choroid plexus. Pseudocysts lateral of the frontal horns should not be mistaken for ventricular ligaments 2).