Cerebrospinal fuild (CSF) is always present inside the skull, "bathing" the brain.  CSF gets produced in the lateral and 3rd ventricles.  It then flows through a small area near the brain stem to cover and cushion the brain and the spinal cord.  It is then reabsorbed by the paraneural lymph spaces of the brain and cord.  This is the normal self regulating system.

When the flow of this fluid is blocked, it builds-up and creates intracranial pressure, like in a balloon.  This condition is known as hydrocephalus; it is a cousin of a CSF leak, both related to the flow of the fluid inside the skull. Hydrocephalus can occur after either surgery or radiosurgery, due to post-treatment swelling of the tumor site. It is more likely if the tumor is close to (or touching) the brain stem, where CSF flows through a narrow area. 

The brain is very accommodating, and if the blockage is partial, the brain can adjust for some time.  However, sudden complete blockages that can occur after surgery are life threatening emergencies.  This is because the functioning of the brain stem is affected by the pressure.  Among many things the brain stem is responsible for controlling basic functions such as breathing, heart rate, temperature, blood pressure - basic and very important stuff.  

Hydrocephalus can also occur prior to any treatment if the tumor is large, and can act as the cause of the AN diagnosis.

My husband's symptoms [before AN diagnosis] included unsteady balance, which as time went on became worse, loss of appetite, headaches that became worse and bouts of double vision. He also had some personality changes, some mental confusion and forgetfulness. These problems in his case was directly related to the size of the tumor... is tumor was in the giant size.

Hydrocephalus is more likely for radiosurgery patients, when here are no holes in the scull for the liquid to leak out of; patients with large tumors (over 3.0 cm) are at greatest risk.  On the other hand, CSF leaks are only possible for surgery patients, where there are holes.  

A common symptom is vision problems due to the pressure on the optic nerve; headaches are also common for hydrocephalus, as are balance problems. The pressure of hydrocephalus is very dangerous.  It results in decreased blood flow, which in turn decreases functioning in that area of the brain. The longer the duration of increased pressure, the greater likelihood that this loss of function will be permanent. Continued pressure on the optic nerve is also dangerous -- it can permanently damage the nerve, and destroy vision. Medical attention is necessary.  Because of this possibility, post-treatment patients should keep in touch with their doctor and let them know about their symptoms. 

MRI is used to indicate if there is hydrocephalus -- it is seen as a dilation of the ventricles.  Spinal taps can also be done.  If potential increased intracranial pressure is a concern after surgery, monitoring devices can be placed in surgery to monitor pressure.  Hydrocephalus may be harder to diagnose than a CFL leak, but once diagnosed, both are treatable. Rony Kess-El's story describes a case of hydrocephalus after FSR.

The operation that places a ventriculoperitoneal shunt (or VP shunt) to relieve this pressure is considered relatively simple.  

My husband has had a VP shunt for almost 6 years. In this time period he hasn't any problems with the unit.  It isn't noticeable.

However, in rare cases permanent loss of function can happen as a result of this operation, when the brain is functioning normally before the operation. The shunt tube can injure the brain when it is placed, if it should accidentally pass through critical brain structures. Also, if the resulting draining of the fluids happens too quicky, this rapid decompression can shift the brain, leading to an injury. A postoperative complication known as  "hematoma", or internal bleeding, can also result in permanent injury and subsequent loss of function.   Though these problems are unlikely, the skill of the surgeon is very important for minimizing the chance of it happening.

This page was developed in consultation with Jeffery A Williams, M.D., Director of Stereotactic Radiosurgery, Department of Neurosurgery, The Johns Hopkins Hospital, Baltimore, MD.  The Acoustic Neuroma Archive takes full responsibility for the contents.

Last Edited: Monday, November 17, 2003