Unlike non-communicating hydrocephalus, which is caused by an obstruction in the flow of CSF within the ventricles, communicating hydrocephalus involves the normal flow of CSF being blocked outside the ventricles.
Communicating hydrocephalus occurs when the flow of cerebrospinal fluid (CSF) is blocked after it exits the ventricles and is entering the subarachnoid space, which is the space between the brain and the skull. This type of hydrocephalus may result from a thickening of the arachnoid around the base of the brain, which blocks the flow of CSF from the spinal to the cortical subarachnoid spaces. CSF normally flows unrestricted through the ventricles and into the subarachnoid space. A thickening of the arachnoid layer around the outside of the brain may prevent the free flow of CSF through this pathway. The word “communicating” refers to the fact that CSF can still flow between the ventricles, which remain open.
Non-communicating hydrocephalus, also known as obstructive hydrocephalus, occurs when the flow of CSF is blocked along one of or more of the narrow passages connecting the ventricles. One of the most common causes is aqueductal stenosis, a narrowing of the aqueduct of Sylvius, a small passage between the third and fourth ventricles of the brain.
The causes of communicating hydrocephalus can include traumatic brain injury, meningitis, subarachnoid hemorrhage, or a tumor.
Signs and symptoms
The symptoms of communicating hydrocephalus are similar to other types of hydrocephalus and may include:
- headaches
- nausea
- vomiting
- visual disturbances
- changes in mental status