Intracranial Pressure Monitoring

See all Pictures & Images

How is the Test Performed?

There are three ways of monitoring intracranial pressure:

• Intraventricular catheter (a catheter threaded into one of the lateral ventricles of the brain)
• A subarachnoid screw or bolt (a screw or bolt placed just through the skull in the space between the arachnoid and cerebral cortex)
• Epidural sensor (a sensor placed into the epidural space beneath the skull)

The intraventricular catheter is thought to be the most accurate, but if immediate access is necessary, a subarachnoid bolt will probably be used. If there is not a qualified neurosurgeon to place a bolt, then a epidural sensor will probably be used.

To insert an intraventricular catheter a burr hole is drilled through the skull and the catheter is inserted through the brain matter into the lateral ventricle which normally contains cerebrospinal fluid. Not only can the intracranial pressure (ICP) be monitored, but it can be lowered by draining cerebral spinal fluid (CSF) out through the catheter. This catheter may be difficult to place with increased intracranial pressure, since the ventricles change shape under increased pressure and are often quite small secondary to brain expanding around them from injury and swelling.

A subarachnoid screw or bolt is a hollow screw that is inserted through a hole drilled in the skull and through a hole cut in the dura mater.

The epidural sensor is placed through a burr hole drilled in the skull, just over the epidural covering. Since the epidural lining is not perforated this procedure is less invasive, but it has the disadvantage of not being able to withdraw excess CSF.

Lidocaine or other local anesthetic will be injected at the site where the incision will be made, and you will most likely receive a sedative to help you relax. First the area that is to be incised is shaved and cleansed with Betadine and alcohol.

After drying, an incision is made and the skin is pulled back until the skull is visible. A drill is then used to cut through the bone and expose the epidural tissue.

If an epidural sensor is used, it is then inserted between the skull and epidural tissue. If a bolt is used, an incision is made through the dura and arachnoid tissue exposing the subarachnoid space and the bolt is screwed into the bone. This allows for the sensor to record from the subdural/subarachnoid space.

If an intraventricular catheter is used, it is threaded through the brain matter into one of the lateral ventricles. This type of catheter is most effective and accurate in its ability to sense intracranial pressure measurements.