What is a lumbar puncture (LP)?
A lumbar puncture (LP) is the insertion of a needle into the spinal canal to collect and examine the fluid that surrounds the brain and spinal cord (cerebral spinal fluid). It is termed a "lumbar puncture" because the needle is placed in the lumbar portion of the back and used to puncture through tissues to enter the spinal canal.
Other names for a lumbar puncture (an LP) include spinal tap, spinal puncture, thecal puncture, and rachiocentesis.
Why is a lumbar puncture done?
An LP is most commonly performed to obtain a sample of the fluid that surrounds the brain and spinal cord. Examination of the fluid can be crucial in diagnosing diseases such as meningitis, neurologic diseases, or effects of systemic disease on the brain and spinal fluid. An LP can also be done to treat diseases, and as a way of administering antibiotics, cancer drugs, or anesthetic agents into the spinal canal. Spinal fluid is sometimes removed by LP for the purpose of decreasing spinal fluid pressure in patients with uncommon conditions (such as, normal-pressure hydrocephalus and benign intracranial hypertension, for example).
Sometimes a lumbar puncture is performed in patients with migraines to assure that no other underlying pathology exists.
How is the LP procedure performed?
Patients typically lie on their side for the procedure. Less often, the procedure is performed while the patient is sitting up and leaning slightly forward.
After local anesthesia is injected into the lumbar area of the back, a long needle is inserted in between the bones of the spine (vertebrae) into the spinal canal. (The needle is most commonly placed between the third and fourth lumbar vertebrae.)
Spinal fluid pressure can then be measured and cerebrospinal fluid (CSF) removed for testing.
What is the cerebrospinal fluid (CSF)?
The CSF circulates around the brain and spinal cord (central nervous system). This "water bath" acts as a support of buoyancy for the brain and spinal cord. The support of the CSF helps to protect the brain from injury.
The normal CSF appears clear and contains various substances, such as protein and sugar (glucose), and few if any cells. The spinal fluid also has a normal pressure when first removed.
What is normal CSF?
Normal values for spinal fluid examination are as follows:
- Protein (15-60 mg/dl)
- Glucose (50-80 mg/dl)
- Cell count (0-5 mononuclear cells)
- Initial pressure (70-180 mm)
These normal values can be altered by injury or disease of the brain, spinal cord, or adjacent tissues. The values are routinely evaluated during examination of the spinal fluid obtained from the lumbar puncture. Additionally, spinal fluid is tested for infection in the microbiology laboratory.
A health care professional will usually review and interpret the test results with the patient. These results often will need to be evaluated in relation to other blood and radiologic test results.
What diseases are diagnosed by examination of the CSF?
Spinal fluid obtained from the lumbar puncture can be used to diagnose many important diseases such as bleeding around the brain; increased pressure from hydrocephalus; inflammation of the brain, spinal cord, or adjacent tissues (encephalitis, meningitis); tumors of the brain or spinal cord, etc. Sometimes spinal fluid can indicate diseases of the immune system, such as multiple sclerosis.
What are possible risks, complications, or side effects of a lumbar puncture?
When spinal fluid is removed during an LP, the risks include headache from a persistent spinal fluid leak, brain herniation, bleeding, and infection. Each of these complications are uncommon with the exception of headache, which can appear from hours to up to a day after a lumbar puncture. Up to 25% of patients will get headaches after the procedure. Headaches occur less frequently when the patient remains lying flat several hours after the procedure.
What are the benefits of a lumbar puncture?
The benefits of the LP depend upon the exact situation for which it is performed, but a lumbar puncture can provide lifesaving information.
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Brain Hemorrhage
A brain hemorrhage is a type of stroke caused when an artery bursts in the brain, causing localized bleeding in the surrounding tissue. Causes of brain hemorrhage include aneurysm, liver disease, brain tumor, head trauma, high blood pressure, and blood vessel abnormalities. Symptoms and signs include sudden severe headache, nausea, vomiting, loss of balance, tingling, numbness, vision changes, loss of consciousness, and loss of fine motor skills. Treatment depends upon the cause, location, and size of the brain hemorrhage.
Brain Lesions (Lesions on the Brain)
A brain lesion is defined as an area of damaged brain. Brain lesions (lesions on the brain) are caused by trauma, inflammation, autoimmune diseases, cancers, other diseases, stroke, bleeding, pituitary adenomas, and cerebral palsy. Symptoms of brain lesions include headache, nausea, fever, neck pain and stiffness, affected vision and speech, and weakness or paralysis to one side of the body. Diagnosis of brain lesions is generally accomplished with imaging studies like CT or MRI scans. Treatment and prognosis of brain lesions depends on the cause of the lesion.
CT Scan (Computerized Tomography)
A CT scan is an X-ray procedure that combines many X-ray images with the aid of a computer to generate cross-sectional and three-dimensional images of internal organs and structures of the body. A CT scan is a low-risk procedure. Contrast material may be injected into a vein or the spinal fluid to enhance the scan.
Dementia
Dementia is defined as a significant loss of intellectual abilities such as memory capacity, severe enough to interfere with social or occupational functioning. There are several different types of dementia, including cortical, subcortical, progressive, primary, and secondary dementias. Other conditions and medication reactions can also cause dementia. Dementia is diagnosed based on a certain set of criteria. Treatment for dementia is generally focused on the symptoms of the disease.
Headache
Headaches can be divided into two categories: primary headaches and secondary headaches. Migraine headaches, tension headaches, and cluster headaches are considered primary headaches. Secondary headaches are caused by disease. Headache symptoms vary with the headache type. Over-the-counter pain relievers provide short-term relief for most headaches.
Meningitis
Meningitis is inflammation of the membranes that cover the spinal cord and brain. Symptoms include fever, headache, and a stiff neck. Treatment of meningitis depends upon the cause of the infection and may include antibiotics or antiviral medications.
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Spinal Fusion
A minimally invasive surgical procedure, the spinal fusion is used to treat lumbar (lower back) pain if the pain hasn't resolved on its own after six to 12 weeks. A spinal fusion operation causes the vertebrae (bones of the spine) in the lower back to grow together, reduce pressure on the nerves, and reduce pain.
MRI (Magnetic Resonance Imaging Scan)
MRI (or magnetic resonance imaging) scan is a radiology technique which uses magnetism, radio waves, and a computer to produce images of body structures. MRI scanning is painless and does not involve X-ray radiation. Patients with heart pacemakers, metal implants, or metal chips or clips in or around the eyes cannot be scanned with MRI because of the effect of the magnet.
Multiple Sclerosis (MS)
Multiple sclerosis or MS is an autoimmune disorder in which brain and spinal cord nerve cells become demyelinated. This damage results in symptoms that may include numbness, weakness, vertigo, paralysis, and involuntary muscle contractions. Different forms of MS can follow variable courses from relatively benign to life-threatening. MS is treated with disease-modifying therapies. Some MS symptoms can be treated with medications.
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What Is a Lumbar Discography Procedure?
A discography, or discogram, is an imaging test of the spine to determine which particular disc is causing a patient’s back pain. The doctor injects a dye into a specific disc to reveal damage on an X-ray image.