ICP Monitoring: Direct
Knowing your correct fluid pressure will help your care team to better understand your condition and recommend appropriate medicine or surgery.
Intracranial pressure (ICP) monitoring is a diagnostic test that helps your doctors determine if high or low cerebrospinal fluid (CSF) pressure is causing your symptoms. The test measures the pressure in your head directly using a small pressure-sensitive probe that is inserted through the skull.
Why Intracranial CSF Pressure Monitoring?
It is possible to experience intense head pressure even when ICP is in the normal range, and ICP can be significantly elevated only during sleep. This is why it is helpful for your doctors to have pressure recordings over 24 hours or more to detect intermittent abnormalities and determine how well they correlate with your symptoms. Also, your doctor can see how different head and body positions affect ICP. In certain situations, an abnormally low pressure may be detected only after prolonged standing.
Spinal fluid pressure measured during a lumbar puncture (spinal tap) provides an accurate value for intracranial pressure only at the time of the procedure. While this will always be a valuable test to establish a diagnosis and monitor therapy, there are times when a more invasive approach is necessary. Your doctor will discuss with you the pros and cons of the various methods available to measure head pressure, and the basis for his or her recommendation. What follows is some general information to help you make an informed decision about your care and prepare you for your hospital admission.
If you have been prescribed any equipment or device for sleep apnea, it is important to bring this with you to the hospital (unless you are undergoing skull base surgery).
Preparing for the Procedure
You will be scheduled for a series of tests 3 to 7 days before your hospital admission. These lab tests may include blood and urine tests to help ensure you do not have an infection or a tendency to bleed and that it is safe for you to have the procedure. If your results show anything abnormal, your procedure may be postponed. Make sure you have stopped any blood thinners – antiplatelet agents and anticoagulants (Plavix, Coumadin etc.) after discussion with your doctor, and notify him or her if you have an allergy to any local anesthetic (such as lidocaine).
Placing the Intraparenchymal Pressure Microsensor
- This pressure microsensor will be placed by the neurosurgeon in the operating room under general anesthesia
- Your scalp will be prepped with an antiseptic solution and a small hole will be drilled in your skull
- A small pressure microsensor will calibrated and passed through the hole a short distance into the brain.
- When you wake up you may feel the normal side effects of anesthesia and some discomfort at the site of the probe placement in your skull. You will be taken to the intensive care unit for monitoring.
- The pressure probe is then connected to the ICP recording system and intracranial pressure is measured continuously.
- In order to accurately measure CSF pressure, you must notify the nurse whenever you adjust the head of the bed elevation, and always call for assistance when getting up to use the bathroom.
Infection: There is a 2 to 4 percent risk of infection with this procedure despite all safety measures. The infection, meningitis, is serious, but treatable with a 14-day course of intravenous antibiotics.
Bleeding: Bleeding is minimal during the procedure. There is a very small risk of bleeding in the brain during placement of the probe but this is rare.
Report These Symptoms to the Nurse or Doctor
Let a nurse or physician know if you experience:
- Fever, severe headache, neck stiffness, nausea or vomiting
- Dizziness, lightheadedness or hearing changes when you sit or stand
- Disconnection of the monitoring system
- Fluid in the bed or a leak from probe insertion site
When the Recordings Are Completed
Once the monitoring is complete, the surgeon removes the sensor at the bedside and the skin is sutured back into place.
Your doctor will carefully analyze the information obtained from this procedure and consider it along with data from other tests, such as eye examination, shunt studies, MRI or CT scans. This process can take up to a week. Complex cases need to be discussed at the weekly case conference to provide the best course of treatment.
- Avoid straining or lifting heavy weights for 1 week.
- No swimming or bathing for 1 week. Showering is permitted.
- If there are any signs of delayed infection (fever with temperature over 101, stiff neck, nausea and vomiting, excessive sleepiness) your provider should be contacted immediately or report to the nearest emergency room for a lumbar puncture to evaluate for possible meningitis.
- If you have a severe headache that resolves when you lie down, you may have a CSF leak. Increase your fluid intake and avoid straining or heavy lifting.
- If the positional headache is still present two days after discharge, let your physician know.