Obstructive Hydrocephalus

What Is It?

Obstructive hydrocephalus (also called non-communicating hydrocephalus) is a form of hydrocephalus which is caused by some visible blockage in the flow of cerebrospinal fluid.

Hydrocephalus is a condition caused by abnormal flow and/or re-absorption of the cerebrospinal fluid, the water-like liquid that surrounds the brain and spinal cord and fills the open spaces within the brain, the ventricles. This can lead to increased pressure inside the head which then can lead to dysfunction and/or damage to the nervous system. In most forms of hydrocephalus, the ventricles inside the brain enlarge as the pressure increases.

Hydrocephalus can be caused by a visible (on brain scans) obstruction of the normal flow this fluid. This cause is called obstructive hydrocephalus because it is caused by obstruction of this flow of fluid. Another name for this type of hydrocephalus is non-communicating hydrocephalus. Most commonly, obstructive hydrocephalus is caused either by a mass in the brain which blocks the flow of fluid, such as a brain tumor, or some scarring or malformation which narrows or completely blocks part of the flow of fluid. These are often termed rings or webs. They can occur either due to some prior trauma, bleeding or infection, or can be congenital, present at birth. In some cases they can be idiopathic, meaning that they have no known medical cause.

One of the most common sites in the brain for obstruction is the cerebral aqueduct. This area is a narrowing of the ventricles within the brain and therefore is prone to obstruction. Either rings, webs or tumors in the area can cause obstruction of the aqueduct, termed aqueductal stenosis.

If no obvious point of obstruction is found on neurological testing, it is termed communicating hydrocephalus or non-obstructive hydrocephalus. The fluid spaces in the brain appear to be communicating normally.

What Types of Symptoms Are Typical?

The symptoms of obstructive hydrocephalus are generally indistinguishable from those of any form of hydrocephalus, with a few exceptions. Generally, because of the increased pressure in the brain, the ventricles enlarge and the brain gets compressed. Nervous system tissue does not function well under pressure or compression.

Some of the most common symptoms of hydrocephalus are headache and progressive depression of the level of consciousness. If the pressure gets too severe before treatment is administered, coma and even death can occur.

In young children, hydrocephalus often leads to enlargement of the head since the bones of their skull are not yet fused. The pressure inside pushes the bones apart and enlarges the skull. They can also complain of headache and there can be abnormalities of the movements of the eyes, particularly an inability to look upward. These children, if not treated promptly, can have a delay in their normal neurological development as they get older. Other more subtle symptoms are possible as well.

In older children and adults, the head does not enlarge with hydrocephalus because the skull is fused and cannot expand. As the pressure increases, headache is a common symptom. Progressive deterioration in the level of consciousness and neurological functioning, starting with lethargy and continuing on to coma and death if not treated, can occur. Abnormalities of eye movements are also possible as seen in children. Furthermore, deterioration in vision can occur as the pressure compresses the back of the eye where the nerve exits the back of the eye. This finding is called papilledema and can be found on a careful eye examination.

If obstructive hydrocephalus is caused by a tumor or other mass, the patient may present with other neurological symptoms which are associated with the tumor itself. This varies considerably depending on the type and location of the tumor.

In older adults, some forms of hydrocephalus, such as normal pressure hydrocephalus (NPH), can lead to a trio of symptoms which include difficulty walking (ataxia), confusion and memory loss (dementia) and inability to control their urination (urinary incontinence).

How Is The Diagnosis Typically Made?

When a patient presents with symptoms consistent with obstructive hydrocephalus, a thorough neurological examination is performed, often followed by a CT scan or MRI scan. These imaging studies show the ventricles well and can determine if they are enlarged, consistent with hydrocephalus, or if there is any other physical evidence of an increase in pressure inside the head. The scan can often determine the cause of the hydrocephalus as well, such as a tumor or other structure obstructing the normal flow of cerebrospinal fluid.

If no obvious cause of obstruction to explain the hydrocephalus is found, it is called communicating hydrocephalus. Some special types of MRI scans (such as CISS or FIESTA scans) can help to show more detail of the anatomy of the ventricles and can find subtle obstructions which cannot be seen on a normal MRI. In some cases that were previously thought to be communicating hydrocephalus, these newer forms of MRI are able to demonstrate a subtle obstruction, changing the diagnosis to obstructive hydrocephalus.

In rare cases when a patient has symptoms consistent with some form of hydrocephalus but the scans are not definitive, occasionally a test of the pressure inside the head, the intracranial pressure, can be conducted. This generally requires the patient being admitted to the hospital and a small transducer is placed within the skull through a small hole in the skull. This is hooked up to a computer which records the intracranial pressure to determine if it is elevated. This can help to confirm the diagnosis of hydrocephalus in the cases when the diagnosis is in question.

What Are Some Common Treatments?

Treatment for hydrocephalus is variable depending on the type, the patient's condition and other factors.

In general, one of the most common forms of treatment for hydrocephalus is to place a device, called a shunt, into the ventricles to drain the excess fluid. There are various types of these devices but most are a long, flexible catheter that is connected to a valve and then tunneled under the skin down to the abdomen. This is called a ventriculoperitoneal shunt (VP shunt). It allows the fluid in the head to be diverted to the abdomen where it can be re-absorbed more easily. There are other forms of shunt as well.

In the case of obstructive hydrocephalus, a newer treatment is occasionally used. Particularly in cases of aqueductal stenosis and some other similar forms of obstructive hydrocephalus, a procedure called endoscopic third ventriculostomy (ETV) can occasionally be attempted. This procedure uses an endoscope (a tube with a lens connected to a monitor) to enter the ventricles of the brain. The floor of one of the ventricles, called the 3rd ventricle, is opened to create a communication between the ventricles and the fluid space around the brain. The goal of this operation is to allow the fluid to bypass the obstruction so that the fluid can be absorbed elsewhere. If it works, it can avoid a mechanical shunt. Not all cases of hydrocephalus are suitable for this procedure and each patient should discuss their particular case with their treating physician.

Finally, in some patients, medical treatment with a medication which decreases the production of the cerebrospinal fluid may be tried to improve some of the symptoms of hydrocephalus.

These are just some of the more common treatments for hydrocephalus. As mentioned above, the individualized treatment for any one patient can vary considerably. Each patient should discuss their treatment options with their own personal physician(s).

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Important Note: This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.

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