What Is Obstructive Hydrocephalus?

ventricular system parts labeled

Obstruction to normal cerebral spinal fluid pathways may involve any portion of the ventricular system. Anatomic anomalies, tumors, cysts, hemorrhage, brain swelling are types of pathology that can obstruct the normal flow. Since cerebral spinal fluid is still being made by the ventricle, fluid backs up from the obstruction. The ventricles enlarge resulting in what is called obstructive hydrocephalus. Next we show the normal CSF flow and how obstructing that pathway leads to obstructive hydrocephalus. Our example will involve the area labeled Foramen of Monroe and III (third) Ventricle. First, review the normal CSF pathway flow below.

Normal Cerebral Spinal Fluid (CSF) Flow

This animation shows how the csf flows. Most of the csf is produced in the body of the lateral ventricle. Normally, it will flow from the lateral ventricle down through the foramen of monro into the III ventricle. From there it proceeds down the aqueduct into the IV ventricle. There are three openings in the IV ventricle: laterally (to the sides) are the foramen of lushka and medially or in the middle is the foramen of magendie.

Obstructive Hydrocephalus

There is a mass (tumor) at the level of the Foramen of Monroe and the III Ventricle. The CSF (Cerebral Spinal Fluid) flow is obstructed and cannot flow down into the III Ventricle to the aqueduct, into the IV ventricle and then out around the brain and down into the spinal cord. The ventricular system is enlarged proximal to (before) the level of the blockage. Since fluid cannot flow past the blockage, both lateral ventricles, especially the frontal horns are dilated. This is an example of obstructive hydrocephalus.

In this web site you will find other examples of Obstructive Hydrocephalus caused by Aqueductal Stenosis, Tumors, Cysts and Hypertensive Hemorrhages. Simply click on the appropriate link on the hydrocephalus home page.