What Is Communicating Hydrocephalus?

Communicating hydrocephalus develops when there is more fluid being produced than can be absorbed. The ventricular system enlarges to hold the excess fluid. This can compress the surrounding brain tissue. It is like having a partially clogged drain --- the faucet is delivering water faster than the drain can remove the water. For example, sometimes due to scarring from infection or bleeding the cerebral spinal fluid absorption pathways are no longer able to absorb as much fluid as they had prior to the scarring. Fluid accumulates and the ventricular system expands. Communicating Hydrocephalus may result from various types of hemorrhages (bleeding). The blood can be very irritating to the brain resulting in scarring along the absorptive pathways of the cerebral spinal fluid. With less fluid being absorbed, the result is the brain is producing more fluid than it is absorbing.

This animation shows how normal 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 Monroe into the III ventricle. From there it proceeds down the aqueduct into the IV ventricle. There are three openings in the IV ventricle: laterally are the foramen of lushka and medially or in the middle is the foramen of magendie. Communicating hydrocephalus develops when there is more fluid being produced than can be absorbed. The ventricular system enlarges to hold the excess fluid which is animated next.

Communicating Hydrocephalus

One can see that although CSF is flowing, the ventricular system has enlarged to hold the excess fluid. This compresses the surrounding brain tissue. Think of having a partially clogged drain --- the faucet is delivering water faster than the drain can remove the water. Some causes: scarring from infection or bleeding may scar over the aborption pathways for the cerebral spinal fluid and the ventricular system is no longer able to absorb as much fluid as it had prior to the scarring. Fluid accumulates and the ventricular system expands.

As stated above, Communicating Hydrocephalus may result from various types of hemorrhages such as Subarachnoid Hemorrhage. This is discussed later under Hydrocephalus: Some Types and Causes on the hydrocephalus home page. There is a special case of Communicating Hydrocephalus called Normal Pressure Hydrocephalus. There is a link to that as well on the home page.

CAT Scans showing Communicating Hydrocephalus vs Normal, No Hydrocephalus

CT Showing Communicating Hydrocephalus
Communicating Hydrocephalus
Normal CT, No Hydrocephalus
Normal CT, No Hydrocephalus
Normal CT, No Hydrocephalus
Normal CT, No Hydrocephalus