there are three ways to monitor pressure in the skull (intracranial pressure).
the intraventricular catheter is thought to be the most accurate method.
to insert an intraventricular catheter, a burr hole is drilled through the skull. the catheter is inserted through the brain into the lateral ventricle. this area usually contains liquid (cerebrospinal fluid or csf) that protects the brain and spinal cord.
the intracranial pressure (icp) can be monitored this way. the icp also can be lowered by draining cerebral spinal fluid (csf) out through the catheter.
the catheter may be hard to get into place when the intracranial pressure is high.
this method is used if the patient needs to be monitored right away. a subdural screw or bolt is a hollow screw that is inserted through a hole drilled in the skull. it is placed through the membrane that protects the brain and spinal cord (dura mater). this allows the sensor to record from inside the subdural space.
if an epidural sensor is used, it is inserted between the skull and dural tissue. the epidural sensor is placed through a burr hole drilled in the skull. this procedure is less [color=#005988]invasive
than other methods, but it cannot remove excess csf.
lidocaine or another local anesthetic will be injected at the site where the cut will be made. you will most likely get a sedative to help you relax.
- first the area is shaved and cleansed with antiseptic.
- after the area is dry, a surgical cut is made. the skin is pulled back until the skull is seen.
- a drill is then used to cut through the bone.
this is usually done to measure intracranial pressure. it is usually done when there is a severe head injury or brain/nervous system disease. it also may be done after surgery to remove a tumor or fix damage to a blood vessel if the surgeon is worried about brain swelling.
high intracranial pressure can be treated by draining csf through the catheter. it can also be treated by changing the ventilator settings for people who are on a respirator, or by giving certain medicines through a vein (intravenously).
normally, the icp ranges from 1 to 20 mm hg.
note: mm hg = millimeters of mercury
note: normal value ranges may vary slightly among different laboratories. talk to your doctor about the meaning of your specific test results.
what abnormal results mean
high intracranial pressure means that both nervous system and blood vessel tissues are under pressure. if not treated, this can lead to permanent damage. in some cases, it can be life threatening.
- brain herniation or injury from the increased pressure
- damage to the brain tissue
- inability to find the ventricle and place catheter
- risks of general anesthesia
a ventriculostomy, also called an external ventricular drain (evd) or ventricular catheter, is a catheter placed into the ventricles, fluid-filled spaces within the brain, and drains cerebrospinal fluid (csf) externally. it is typically connected by tubing to a cerebrospinal fluid collection device which can be elevated or lowered at the bedside to vary the amount of csf that is drained.
a ventriculostomy allows both draining and sampling of the csf and also can be hooked up to a pressure transducer which gives a reading of intracranial pressure. additionally, in some conditions certain medications may also be given directly into the nervous system by injecting them through a ventriculostomy.
a ventriculostomy is typically placed at the bedside but sometimes is placed in the operating room. typically, a small drill hole is made in the skull to allow introduction of the catheter through the brain and into the ventricle.