23 Apr Hydrocephalus Facts
At ANA, we treat numerous pediatric and adult patients for hydrocephalus. Hydrocephalus may be congenital or acquired. Congenital hydrocephalus is present at birth and possibly acquired during fetal development or due to genetic abnormalities. Acquired hydrocephalus occurs at, or sometime following, birth. This type of hydrocephalus, which may be caused by injury or disease, can affect individuals of all ages.
Speculation is that hydrocephalus may result from inherited genetic abnormalities, such as the genetic defect that causes aqueductal stenosis. One of the most common causes of hydrocephalus is “aqueductal stenosis.” In this case, hydrocephalus results from a narrowing of the aqueduct of Sylvius, a small passage between the third and fourth ventricles in the middle of the brain.
It can also be caused by developmental disorders, such as those associated with neural tube defects including spina bifida and encephalocele (in newborns, a protrusion of some or all of the brain through a defect in the skull). Other possible causes include complications of premature birth such as intraventricular hemorrhage, and diseases such as meningitis, tumors, traumatic head injury, or subarachnoid hemorrhage, which block the exit of cerebrospinal fluid (CSF) from the ventricles to the cisterns or eliminate the passageway for CSF within the cisterns.
Hydrocephalus may also be described as ‘communicating’ or ‘non-communicating.’ Communicating hydrocephalus occurs when the flow of 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. Non-communicating hydrocephalus, also called “obstructive” hydrocephalus, occurs when the flow of CSF is blocked along one or more of the narrow passages connecting the ventricles.
There are two other forms of hydrocephalus, which primarily affect adults and do not fit exactly into the categories mentioned above: hydrocephalus ex-vacuo and normal pressure hydrocephalus (NPH).
Hydrocephalus ex-vacuo follows a stroke or traumatic injury that causes brain damage. In these cases, brain tissue may actually shrink. NPH, which affects an estimated 375,000 older adults, is an abnormal increase of cerebrospinal fluid in the brain’s ventricles that may result from a subarachnoid hemorrhage, head trauma, infection, tumor, or complications of surgery. However, many people develop NPH when none of these factors are present.