Communicating Hydrocephalus

What Is It?

Communicating hydrocephalus (also called non-obstructive hydrocephalus) is a form of hydrocephalus which does not arise from a visible blockage in the flow of cerebrospinal fluid.

Hydrocephalus is a condition characterized 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 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 some visible (on brain scans) obstruction of the normal flow this fluid. This obstruction may be a congenital or acquired scarring in some part of the ventricular system or it can be from a mass such as a brain tumor which blocks the normal flow of 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.

In the case of communicating hydrocephalus, neurological testing does not reveal any obvious point of obstruction in the flow of the cerebrospinal fluid. Therefore, the fluid spaces appear to be communicating normally. Communicating hydrocephalus is also know as non-obstructive because no obstruction is seen. It is believed that the hydrocephalus is caused by more subtle changes in the way the fluid is re-absorbed, rather than a frank blockage.

Communicating hydrocephalus can be caused by several things. Prior infection in the space surrounding the brain, called meningitis, can lead to the inability to properly re-absorb the cerebrospinal fluid. Likewise, bleeding into the subarachnoid space where the fluid is, called subarachnoid hemorrhage, can also clog up the normal re-absorption of the fluid. This can be caused by the rupture of a cerebral aneurysm, for example. This form of hydrocephalus can also be congenital or even idiopathic, meaning that no medical cause is known.

What Types of Symptoms Are Typical?

The symptoms of communicating 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.

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?

If a patient presents with symptoms consistent with communicating hydrocephalus, after a neurological exam, often a CT scan or MRI scan will be ordered. These imaging studies can show the ventricles in the brain and determine if they are enlarged 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 flow of 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 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 communicating hydrocephalus, a shunt may be required to treat the increased fluid pressure in the head. Because there is no obvious site of obstruction, no other treatment is generally required. Other forms of hydrocephalus treatment, such as endoscopic third ventriculostomy, are generally not suitable for communicating types of hydrocephalus, although there may be exceptions.

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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