What is a "large volume" lumbar puncture for NPH?
A large volume LP is a lumbar puncture done with the specific intention of removing 30-40 ml of cerebro-spinal fluid (CSF). An assessment of gait and balance is often done before and after the large volume lumbar puncture to examine if removal of CSF results in a significant improvement in those parameters. The results from the gait and balance tests help guide treatment decisions.
What tests are needed before a lumbar puncture?
Certain tests are necessary before a lumbar puncture to reduce the risks associated with it. These include:
- A CT Brain or MRI to exclude a brain tumor and to ensure there is no obstruction to CSF flow.
- Blood studies to ensure you don't have a bleeding disorder
- A neurologic examination by your physician regarding the safety of doing a lumbar puncture.
What medicines are not permitted before a lumbar puncture?
Please tell your doctor about all medications you take as some of them, individually or in combination, may affect the performance of the procedure. In particular blood thinners like Clopidogrel (Plavix), Ticlopidine (Ticlid), Prasugrel (Effient), Warfarin (Coumadin), Enoxaparin (Lovenox), Dalteparin (Fragmin), Tinzaparin (Innohep), Dabigatran (Pradaxa), Rivoroxaban (Xarelto), Apixaban (Eliquis), other heparin derivatives may need to be stopped anywhere from 1-7 days before the procedure. Also let your doctor know if you take high doses of garlic, over the counter pain medications like Ibuprofen (Advil), Naproxen (Aleve) or high doses of Aspirin (greater than 325mg). Please discuss alternatives to these medications with your healthcare provider, before stopping them.
How is the test performed?
- Before the procedure, a healthcare provider will administer multiple tests of gait and balance.
- During the procedure the patient must lay on his or her side, with the knees pulled up toward the chest, and the chin tucked downward. Sometimes the test is done with the person sitting up, but bent over.
- After the back is cleaned with an antiseptic solution, the health care provider will inject a local numbing medicine (anesthetic) into the lower spine.
- A spinal needle is inserted, usually into the lower back area.
- Once the needle is properly positioned, spinal fluid pressure is measured, and fluid is collected. In the case of normal pressure hydrocephalus 30 - 40 ml of fluid is drained.
- The needle is removed, the area is cleaned, and a bandage is placed over the needle site. The patient is often asked to lie down for a short time after the test.
How the test will feel?
The position may be uncomfortable, but it is extremely important that the patient stays in the same position to avoid moving the needle.
The anesthetic will sting or burn when first injected. There will be a hard pressure sensation when the needle is inserted, and there is usually some brief pain when the needle goes through the tissue surrounding the spinal cord. This pain should stop in a few seconds.
Overall, discomfort is minimal to moderate. The entire procedure usually takes about 30-60 minutes, but it may take longer.
What if the lumbar puncture is not successful?
In persons who have had back surgery, who have an abnormal back shape such as scoliosis (curvature of the spine), or are very obese, the lumbar puncture may not be successful. In that case the procedure may be done under X-Ray guidance (fluoroscopy).
What are the risks associated with a lumbar puncture?
Risks of lumbar puncture include:
- Headache after the test often transient; 20% will experience one
- Hypersensitivity (allergic) reaction to the anesthetic
- Discomfort during the test
- Infection meningitis < 1%
- Back pain and leg pain
- Hearing loss, dizziness that is often transitory <1%
There is an increased risk of bleeding in persons who take blood thinners.
Brain herniation may occur if this test is done on a person with a mass in the brain (such as a tumor or abscess). This can result in brain damage or death. This test is not done if an exam or test reveals signs of a brain mass.
How long do I need to lie down after the lumbar puncture?
By convention patients are instructed to lie down for 30-60 minutes. However studies have shown no difference in the prevalence of headaches with rest periods after a lumbar puncture.
How can headache associated with a lumbar puncture be treated?
The headache after a lumbar puncture is transitory and resolves in most people in 1-3 days. A typical characteristic that distinguishes a lumbar puncture headache due to a CSF leak is that it goes away after lying down for 5-15 minutes and is worse while standing or sitting. Symptomatic relief may be obtained with acetaminophen or ibuprofen. Some people find drinking caffeinated fluids like tea or coffee helpful. If the headache is severe, persistent, not improving with time you need to contact your physician. In some, the patient's own blood may need to be injected into the spinal area to seal a leak that may be caused during the lumbar puncture. If you have a fever, stiff neck, nausea or vomiting you should contact your physician and go to the emergency room urgently.
What is an epidural blood patch?
About 3 in 10 persons who undergo a lumbar puncture develop a leak of cerebrospinal fluid at the lumbar puncture site inside the body. In most people this seals itself but if cerebrospinal fluid continues to leak and cause debilitating headaches the best treatment is injecting about 10-20 ml of your own blood in that region to seal the leak. We need about 24-48 hours to schedule this procedure. If you cannot tolerate any delay we may need you to come to the emergency room here or go to the nearest one to get it done.
What if there is no improvement in gait and balance after the lumbar puncture? How is the extended CSF drainage procedure different from a large volume LP and why is it necessary?
Some patients with hydrocephalus have a dramatic improvement after a single lumbar puncture. The problem is that many patients who show no significant improvement from a single tap do show a benefit with extended CSF drainage during which 300-400 ml of CSF can be drained over 4-5 days in the hospital. Extended CSF drainage, therefore, is more sensitive - it identifies more patients who will ultimately benefit from a shunt, and it has fewer false-negatives - it doesn't miss the patients who don't respond to a single large volume tap.