The ventricular system can be obstructed anywhere along its path. (See Hydrocephalus: Obstructive Type .)The MRI to the left shows an enlarged III ventricle. There are loculated cysts within the III ventricle. These cyst formed due to scarring from a patient with meningitis. CSF (cerebral spinal fluid) cannot flow past the III ventricle, so the lateral ventricles begin to enlarge. The aqueduct and IV ventricle are normal in size. See the brain model below.

Enlarged III Ventricle With Developement of Early Hydrocephalus

The CSF can flow down its usual pathway, but it is beginning to become obstructed by the enlarged III ventricle. Unless treated, obstructive hydrocephalus will develop.

Porencephalic Cyst and Enlarged Ventricles... is this Hydrocephalus?

When a cyst communicates (is continuous with) one of the ventricles, it is usually congenital (formed during pregnancy). Here we see a large cerebellar cyst communicating with an enlarged IV ventricle. The III ventricle is mildly enlarged as well. Is this early hydrocephalus?

Porencephalic Cyst and Enlarged Ventricles... is this Hydrocephalus?

This patient was in her 60's and did not even know she had a porencephalic cyst. It was found when she had an MRI of the brain after she had some symptoms referable to a possible minor stroke. She always had some mild coordination problems, but never thought much of it.