Purpose or Case Report: Cerebral aqueductal stenosis remains the most common cause of congenital and acquired obstructive hydrocephalus. The objective of this educational exhibit is to interactively illustrate the imaging findings associated with aqueductal stenosis on Fetal and postnatal MRI. Causes of aqueductal stenosis and imaging protocol optimization will also be discussed.

Methods & Materials: Review of the current literature and a retrospective review of cases of aqueductal stenosis imaged with MRI both prenatally and postnatally was performed. The most common and specific fetal imaging findings associated with a postnatally confirmed diagnosis of aqueductal stenosis were identified. Associated pathologies were also documented.

Results: An initial systematic review of the underlying causes of aqueductal stenosis will be provided. Then, we will demonstrate several interactive cases exemplifying the imaging findings of aqueductal stenosis on Fetal and postnatal MRI. Key imaging findings include, but are not limited to, enlargement of the lateral and 3^rd ventricle with a normal sized 4^th ventricle, enlarged inferior 3^rd ventricle recesses, absent or partially absent septum pellucidum and abnormal corpus callosum. Finally, a brief discussion about imaging protocol, followed by an interactive quiz will be available for the viewers to assess themselves about the new acquired knowledge.

Conclusions: Aqueductal stenosis can be diagnosed with high specificity both on Fetal and postnatal MRI. However, some prenatal findings of cerebral aqueductal stenosis can be subtle and challenging. In addition, several underlying causes may account for an increase diagnostic difficulty of this entity. It is extremely important that radiologists become familiar with the imaging findings and underlying causes of aqueductal stenosis in the pediatric population.