What is Hydrocephalus

What are the Signs and Symptoms of Hydrocephalus?

What is the Treatment for Hydrocephalus?

What is Hydrocephalus?

Hydrocephalus is a neurological condition in which too much cerebrospinal fluid (hydro = water) builds up within the brain (cephal us = head). Cerebrospinal fluid (CSF) is normally produced within the brain and fills a system of internal chambers called cerebral ventricles. CSF is produced continuously in large amounts - about 1 pint per day - and must be reabsorbed as fast as it is produced.

Reabsorption occurs because CSF flow s from within the cerebral ventricl es to a thin space overlying the surface of the brain, the subarachnoid space. From the subarachnoid space CSF enters the venous system of the brain and is absorbed into the blood stream. Hydrocephalus occurs if there is any blockage of the normal flow of CSF. When this happens the ventricles expand in front of the blockage site. As the ventricles enlarge the pressure in the brain usually increases. Compression and stretch of the surrounding brain can cause damage, and the increased intracranial pressure (ICP) can be life-threatening.

Above: An MRI scan showing the ventricles from a side view. The arrows point to the ventricles. images taken from About Hydrocephalus. A Book for Parents, The Hydrocephalus Association and The University of California San Francisco, 1986

Above: CT scans showing the ventricles as viewed from the top of the head. The dark areas are the fluid-filled ventricles. The gray area is the brain. The white slit is the shunt. images taken from About Hydrocephalus. A Book for Parents, The Hydrocephalus Association and The University of California San Francisco, 1986

Click for full sized image

What Causes Hydrocephalus?

Hydrocephalus can occur from many causes at any age. In children, it can be caused by a congenital (hereditary) defect, as a complication of premature birth, or as the result of a head injury, brain tumor, bleeding into the brain (hemorrhage, stroke, aneurysm), or an infection such as meningitis. In adults, hydrocephalus can be caused by head injury, brain tumor, hemorrhage, or infection, as well as the wasting of brain tissue that may occur with Alzheimer's disease and dementia. This last condition is often referred to as normal pressure hydrocephalus (NPH), because ICP is not elevated consistently.

What are the Signs and Symptoms of Hydrocephalus?

The most obvious and consistent findings in a patient with hydrocephalus are head enlargement, lethargy, irritability, vomiting, fever, impaired memory and learning, and movement deficits. In infants, the scalp veins may also be prominent and the "soft spot" on the forehead (fontanelle) may bulge outward. Patients at any age may experience seizures and developmental delays. Elderly patients with NPH often have loss of leg coordination and an unsteady gait, along with uncontrolled urination (incontinence).

What is the Treatment for Hydrocephalus?

Although a few

image taken from About Hydrocephalus. A Book for Parents, The Hydrocephalus Association and The University of California San Francisco, 1986

patients with hydrocephalus can experience a natural resolution of their condition, nearly all patients require drainage of the excess CSF to other resorption sites in the body. This treatment involves a surgical procedure in which a catheter (shunt) is inserted into the cerebral ventricle through a small hole in the skull. The remaining tubing is "tunneled" under the skin and usually inserted into the abdominal cavity through a small slit in the muscles of the belly. In this case, the excess CSF that drains into the abdominal cavity is absorbed by the tissue lining the body wall (the peritoneum). The entire system is referred to as a "ventriculo-peritoneal shunt". Sometimes the catheter is placed into the internal jugular vein and passed to the first chamber of the heart. In this case, CSF drains through a "v entriculo-atrial shunt" to be absorbed in the blood. Many shunt systems are very sophisticated, with valves to control CSF flow and prevent over-drainage ("siphoning") when the patient stands up. Recently, shunts have been developed that can be adjusted electronically through the skin, and thus set to the precise specifications required for each patient.

In the past 10 years, an alternative to shunting has been developed that involves making a small hole in the bottom of the brain through which CSF can escape from the ventricles. This treatment for hydrocephalus is called third ventriculoscopy, because the opening is made in the floor of the third ventricle by a surgical instrument called an endoscope. The endoscope allows the surgeon to see into the brain, visualize the ventricular system, and watch the opening being made. This procedure cannot be used on all forms of hydrocephalus, depending on where the CSF block is located, but it has eliminated the need for a shunt in some patients.

Some patient's symptoms improve immediately after shunting, while others may take several days or even weeks to improve. It is not unusual to have temporary headaches for a few days after surgery. These headaches are usually caused by the changes in pressure within the brain and cranial cavity. Most patients remain in the hospital for 1-2 days. An individual with a shunt can participate in most physical activities, but not contact sports.