Obstruction to the flow of CSF at the aqueduct of Sylvius will most likely lead to enlargement of

CSF formation - choroid plexuses of the lateral third, and fouh ventricles. Some also originate from the ependymal cells lining the ventricles and from the brain substance CSF Circulation - lateral ventricles - third Ventricle of Sylvius - IV ventricle of magendie and Luschka - subarachnoid space - absorption by arachnoid vill Therefore, obstruction at aqueduct of sylvius will lead to enlargement of both lateral and third ventricles.