What Is It?
Adult hydrocephalus is hydrocephalus which occurs in an adult patient. While in some cases it may represent a patient with prior congenital hydrocephalus, it can also be caused by the new onset of hydrocephalus later in life. On this page we will discuss the later. Hydrocephalus which occurs in children at or around the time of birth is covered elsewhere on the congenital hydrocephalus
Adult hydrocephalus can be caused by many different pathologies. Below, we will cover some of the more common etiologies of acquired hydrocephalus:
- Aqueductal Stenosis: The cerebral aqueduct is a tube connecting parts of the fluid-filled ventricles within the brain. Because it represents a narrowing of the flow of cerebrospinal fluid, it can be prone to obstruction. Hydrocephalus which results from blockage of the aqueduct is termed aqueductal stenosis. While this obstruction can be caused by a tumor which compresses the aqueduct (see below), it can also be due to other causes. Occasionally this can be congenital but not detected until adulthood. In other cases aqueductal stenosis may occur from unknown causes or secondary to infection (see below). There is often web or adhesion across the narrow aqueduct which prevents the normal flow of fluid through the ventricular system.
- Meningitis and other infections: Infection within the cerebrospinal fluid spaces surrounding the brain can lead to scarring which interrupts the normal flow of fluid and causes adult hydrocephalus. The most common cause of this form of acquired hydrocephalus is bacterial meningitis, infection of the surroundings of the brain by a bacteria. Not all patients who suffer from meningitis will develop hydrocephalus. Other rare infections, including parasitic infections such as neurocystercercosis can also lead to hydrocephalus.
- Subarachnoid Hemorrhage: Subarachnoid hemorrhage is bleeding into the cerebrospinal fluid space around the brain. It can be caused by trauma to the head but the largest hemorrhages are most commonly associated with the rupture of a cerebral aneurysm. The blood in this area can basically clog up the normal flow and/or absorption of the fluid, leading to adult hydrocephalus. This can occur acutely shortly after the hemorrhage or chronically after the hemorrhage.
- Brain Tumor: If a tumor in or near the brain causes compression or obstruction of the normal flow of cerebrospinal fluid, it can cause hydrocephalus. For example, a tumor near the cerebral aqueduct can compress the flow of fluid through the aqueduct and block it, termed aqueductal stenosis. Likewise, tumors within the ventricles themselves, if big enough, can block the flow of fluid at some point.
- Normal Pressure Hydrocephalus: One particular form of hydrocephalus in adults has been termed normal pressure hydrocephalus because the patients do not experience the prolonged high pressures that is typical of many forms of hydrocephalus. Nonetheless, there is an abnormality in the dynamics of the fluid flow, leading to symptoms. This particular form of adult hydrocephalus typically occurs in older adults and often leads to symptoms of dementia (memory loss, decline in cognitive function, etc.), instability of gait and urinary incontinence (inability to normally control urination). The cause is generally not known although some patients labeled with normal pressure hydrocephalus may have another cause to explain it, such as aqueductal stenosis.
What Types of Symptoms Are Typical of Adult Hydrocephalus?
Symptoms of hydrocephalus in adults vary somewhat depending on the underlying cause. However, in general, common symptoms, regardless of cause, can include headaches, nausea and vomiting, lethargy and somnolence and eventually decline in visual function. Other neurological symptoms that can occur in some patients include abnormalities of the movement of the eyes.
In the specific case of normal pressure hydrocephalus, and in some other forms of hydrocephalus which occur in elderly patients, typical symptoms can include dementia (memory loss, decline in cognitive function, etc.), instability of gait and urinary incontinence (inability to normally control urination). Because of the similarity in symptoms, some of these patients may be initially diagnosed with other forms of dementia such as Alzheimer's disease.
How Is The Diagnosis Typically Made?
While each adult hydrocephalus patient's presentation varies somewhat, their symptoms may eventually bring them to medical attention. After a thorough neurological evaluation, most patients undergo a CT scan
or MRI scan
. Both of these imaging studies can show the fluid spaces within the brain, the ventricles. Typically, the ventricles are enlarged in most forms of hydrocephalus. In addition, the scans can sometimes show the underlying cause of the hydrocephalus such as a web causing aqueductal stenosis or a tumor blocking the flow of fluid.
What Are Some Common Treatments?
Hydrocephalus is a complex disorder with different treatments which may be best for different patients. In general however, most patients with symptomatic hydrocephalus will require some form of shunting procedure
. These are surgeries that introduce a catheter into the cerebrospinal fluid space, typically in the ventricles, which is connected to a valve and a long catheter which diverts the fluid to elsewhere where it can be reabsorbed. The most common type of shunt is a ventriculoperitoneal shunt, which shunts the fluid from the ventricles to the abdominal cavity. In some cases of hydrocephalus, depending on the cause, the fluid can be shunted completely internally without a shunt catheter or valve. This procedure is called a third ventriculostomy
and is usually done with an endoscope which is introduced into the ventricles to create an opening to drain the fluid into the space surrounding the brain.
As with most disorders, these treatments are highly individualized depending on the specifics of each case and the underlying pathology which causes the hydrocephalus. Each patient should discuss their treatment options with their treating physician(s).