Although a lumbar puncture (spinal tap) can measure spinal fluid pressure, continual intracranial pressure monitoring over 24 hours or more may be more appropriate for diagnosis when your doctor wants to detect changes in pressure over time, especially as you move your head and body from one position to another.
Observing changes in the pressure of your cerebrospinal fluid (CSF) pressure can help your care team better understand the cause of your symptoms and recommend appropriate medicine or surgery.
Your doctor can monitor the pressure of the CSF in your brain using a lumbar catheter, a small, flexible tube that is placed in the lumbar spine. It is connected to a measuring device and left in place for a time to track changes in your cerebrospinal fluid pressure. While you have a lumbar catheter in place, your doctor can see how different positions (lying down, sitting or standing) affect your CSF pressure.
Preparing for Intracranial Pressure Monitoring
You will be scheduled for a series of tests 3 to 7 days before your intracranial pressure monitoring. These lab tests, including blood and urine tests, will 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).
If you have been prescribed any equipment or device for sleep apnea, please bring these with you to the hospital unless you are undergoing skull base surgery.
Placing the Lumbar Catheter
- Your practitioner will give you an injection of antibiotic in your arm to reduce the risk of infection.
- You will be asked to sit in a special chair or lie down on one side of the bed.
- The practitioner will mark the area where the spinal needle is to be placed. The surgical team cleans your lower back with a solution and allowed to dry; then covers the area with a sterile drape.
- You will get an injection of medicine to numb the skin on your lower back, which may cause a burning sensation for a few minutes.
- Once your skin is numb, the practitioner will insert the spinal needle into the marked area and direct it toward the spinal canal until it is in the right space. (If you have arthritis in your spine, this part of the procedure may take more time.)
- You will feel pressure as the needle is put in place. If you feel a sharp pain, let the doctor know so he or she can give you more numbing medicine.
- Your surgeon inserts a catheter (flexible tube) through the needle, the removes the needle, leaving the catheter in place.
- The catheter is gently bandaged to the skin on your lower back, then connected to a device that measures the CSF pressure over a 24- to 72-hour period.
Sometimes after the lumbar drain is pulled out, fluid continues to leak from the small hole left by the tube. A simple stitch in the skin can close the wound; this stitch can be removed in one week.
After Your Procedure
- 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 if the headache is still present two days after discharge, let your physician know.
Let a nurse or physician know immediately if any of the following occurs:
- Fever, severe headache, nausea or vomiting
- Dizziness or lightheadedness when you sit or stand
- Disconnection of the lumbar drain tube or monitoring system
- Fluid in the bed or a leak from your lower back
Intracranial Pressure Monitoring Risks
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.
Leg or back pain: Occasionally, as the spinal needle or catheter is entering the lumbar space, it may touch a nerve root, causing a brief pain shooting down the back or leg. Moving the body to a different position usually alleviates the pain, and there is rarely any lasting injury to the nerve root.
Headache: During the procedure, some people develop a headache that gets worse when sitting or standing. You may also experience nausea, dizziness or lightheadedness. Stopping the fluid drain for a few minutes will usually relieve these symptoms. A similar headache can occur after the tube is removed. You should drink plenty of caffeine containing fluids and take ibuprofen or acetaminophen as needed. If this kind of headache persists, a blood patch may be applied to the area to seal the fluid leak.
Bleeding: Bleeding is minimal during the procedure. There is a potential for bleeding around the brain if excess fluid is drained. To decrease the chance of this complication, please notify the nurse when you change positions or have to use the bathroom.
Spinal fluid leak: Rarely, spinal fluid may leak around the catheter and its dressing. If it leaks onto a non-sterile area, the physician may decide to remove the catheter. Depending on how much you have drained, a new one may be put in, or multiple spinal taps may be done to drain more spinal fluid.
Getting Your Results
Your doctor will carefully analyze the information obtained from your intracranial pressure monitoring 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. Experts at the Cerebral Fluid Center discuss complex cases at their weekly case conference to confer on the best course of treatment.