Also known as non-obstructive hydrocephalus, communicating hydrocephalus occurs when the flow of cerebrospinal fluid (CSF) is blocked after it exits the ventricles. This form is called communicating because the CSF can still flow between the ventricles, which remain open.
Normal Pressure Hydrocephalus (NPH)
This type only affects people ages 50 years or older. It may develop after a stroke or injury. As opposed to other types of hydrocephalus, NPH develops slowly due to the gradual blocking of CSF drainage, which subsequently causes slow fluid buildup over time. The enlarged ventricles then press on the brain and cause symptoms. These include dementia-like signs similar to Alzheimer’s disease, and walking difficulties that resemble Parkinson’s disease. That’s why the diagnosis is often problematic. The good news, however, is that unlike those conditions, NPH can be resolved.
In most cases, the cause of NPH is undetermined. However, NPH can occur due to bleeding in the brain following a head injury, stroke, brain tumor, meningitis (an infection of the tissue surrounding the brain), or even following brain surgery.
Since diagnosis is complicated by the fact that many people assume the symptoms of NPH (difficulty walking/gait disturbances, cognitive challenges/mild dementia, urinary urgency or incontinence) are related to aging, it is important to recognize that those symptoms may be part of NPH, which is a treatable condition.
Hydrocephalus ex-vacuo occurs from brain damage caused by stroke or injury. In this condition, there may be an actual shrinkage of brain substance. Although there is more cerebrospinal fluid (CSF) than usual, and the ventricles are enlarged, the CSF pressure may or may not be elevated in hydrocephalus ex-vacuo.
This dilation of the cerebral ventricles, which is due to loss of brain tissue, is a common result of brain diseases such as luekoystrophies (a group of rare genetic disorders that affect the central nervous system), multiple sclerosis, multiple strokes, Alzheimer’s disease, Huntington’s disease and other related diseases.