Subependymal pseudocysts

Subependymal pseudocysts (SEPC) are benign, cystic lesions located near the lateral ventricles, often detected incidentally in neonatal brain imaging. 

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. The congenital cysts may result from infection, ischemic injury, or hemorrhage.

Subependymal pseudocysts 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. 

The cysts are not epithelium-lined and instead are lined by germinal cells and glial tissue. Their vascular origin is suggested by the presence of macrophage-like cells in the fluid. Brain ultrasound:

Here are the features of SEPC’s that help you differentiate these cystic lesions from other entities:

• Anechoic, well-circumscribed lesions near the lateral ventricular margin, especially the germinal matrix area (caudothalamic groove). 

• May be septated. 

• Usually semicircular in shape (in the parasagittal plane). 

• Post-hemorrhagic vs germinolytic (congenital) cysts are difficult to differentiate sonographically. 

• No blood flow in color Doppler. 

• Best visualized from the anterior fontanelle view in coronal and parasagittal planes. 

• Most subependymal hemorrhages resolve through the subependymal pseudocyst stage. 

• SEPC’s usually resolve in 2-3 months. 

• If the shape of the cyst is rounded, it may be a choroid plexus cyst in the anterior region of the choroid plexus. They may not resolve. 

• Generally, no follow-up is needed (Follow-up is typically not required for isolated SEPCs in otherwise healthy neonates. However, further evaluation may be warranted if cysts are bilateral, multiple, atypical in shape or location, or associated with abnormal clinical or imaging findings.)

Differential Diagnosis:

Consider differential diagnoses such as choroid plexus cysts (often similar in shape and location), connatal cysts (similar in location), and white matter injuries of prematurity, such as cystic periventricular leukomalacia (similar location).