Lumbar Puncture
Overview
A lumbar puncture (LP), or spinal tap, is a procedure focused on the central nervous system. A healthcare provider places a needle into the lower back, specifically in the space between lumbar vertebrae. During this process, cerebrospinal fluid (CSF)—which cushions the brain and spinal cord—is carefully collected for testing.
Healthcare teams gather information from a lumbar puncture to detect several medical conditions. These include infections like meningitis, as well as other diseases of the central nervous system such as multiple sclerosis and Guillain-Barre syndrome.
Doctors may also use this test to find bleeding around the brain, cancers involving the brain or spinal cord, or to deliver specific medications directly into the CSF.
Main Reasons for a Lumbar Puncture:
- Diagnosing infections
- Checking for neurological diseases
- Detecting bleeding in or around the brain
- Administering certain medicines directly to the nervous system
Reasons for the Procedure
A lumbar puncture helps doctors learn more about problems that might affect the brain or spinal cord. Doctors most often collect cerebrospinal fluid to check for meningitis, encephalitis, or other infections. Sometimes, they also measure the pressure of the fluid around the brain and spine.
Doctors may order a spinal tap to check for bleeding outside the brain, called subarachnoid hemorrhage. They may also use this procedure for certain cancers, like leukemia or tumors in the brain or spine. It helps diagnose nervous system diseases such as multiple sclerosis, autoimmune problems, and cases of sudden fever with an unknown cause.
Doctors can use a lumbar puncture for treatment. They may give medicines, like antibiotics, chemotherapy, or anesthesia, through a lumbar puncture. They also inject special dyes or substances for imaging tests.
Possible Complications
A lumbar puncture, while often considered safe, can still lead to certain complications. One of the most common is a post-lumbar puncture headache. This condition affects up to 1 in 4 people and usually begins several hours to two days after the procedure.
These headaches tend to get worse when standing or sitting and may come with dizziness, nausea, and vomiting. Lying down often helps relieve the pain. The headaches can last anywhere from a few hours to more than a week.
Other possible issues include back pain or tenderness at the site where the healthcare provider inserted the needle. Sometimes, this discomfort can spread down the legs. Bleeding is another risk, though it is not common. Blood may collect near where the needle entered or, in very rare cases, in deeper spaces close to the spinal cord.
A more serious, but rare, complication is brainstem herniation. High pressure in the skull, often from a tumor or similar problem, can push the brainstem downward after spinal fluid is removed. To lower this risk, doctors may use scans, like CT or MRI, before doing the procedure, especially if a person is already at risk for high brain pressure.
| Complication | How Often It Happens | Main Symptoms |
|---|---|---|
| Post-lumbar puncture headache | Up to 25% | Headache, worse when upright, nausea, dizziness |
| Back discomfort | Sometimes | Soreness at site, can extend down the legs |
| Bleeding | Rare | Swelling, pain, or bruising near the puncture site |
| Brainstem herniation | Very rare | Severe symptoms, requires urgent care |
How You Get Ready
Healthcare professionals often give instructions about which foods, drinks, and medicines to take or avoid.
- Tell your healthcare provider about all medicines, especially any blood thinners.
- Mention any allergies to medicines, such as local anesthetics, so the healthcare provider can give safe anesthesia.
- If asked, stop or change certain medicines before the procedure to reduce bleeding risk.
What You Can Expect
Before the lumbar puncture, most people either wear a hospital gown or keep their regular clothes on, depending on instructions. The healthcare team explains the steps and any risks. Patients position themselves to help widen the space between the vertebrae in the lower back.
This might mean lying on one side with knees pulled to the chest or sitting and leaning forward onto a table. Both positions help open up the area between the bones to make it easier for the spinal needle to go into the spinal canal.
The skin over the lower back is cleaned with special soap or iodine, and a clean, sterile cover is placed over the back. Younger children or infants may need help staying in the right position, so another person may hold them still during this part.
What Happens During the Procedure
- The healthcare provider injects a local pain medicine into the skin of the lower back to numb the spot where the spinal needle will go in. There might be a short, stinging feeling when this happens.
- After the area is numb, the health care provider gently pushes a thin, hollow needle between the lower vertebrae, aiming for the space just below the end of the spinal cord. The spinal needle passes through layers called the spinous process and ligamentum flavum before reaching the spinal canal.
- Some pressure may be felt in the back during this step, but sharp pain is unusual. If pain is severe, patients should let the provider know right away.
- Once the needle is in the correct spot, the person may need to change their position slightly. The healthcare provider measures cerebrospinal fluid from around the spinal cord and brain for pressure.
- The healthcare provider collects small amounts of this fluid in test tubes for testing. Afterward, the provider removes the needle carefully and places a bandage over the small wound.
The process may last about 45 minutes. Sometimes, an ultrasound guides the procedure, mostly in infants or young children, making sure the needle goes to the right spot and is not pushed too far.
Steps to Follow Once the Procedure Is Over
Rest is recommended after a lumbar puncture. People should avoid heavy lifting or strenuous activity for the rest of the day. If the job does not include physical work, it’s possible to go back to work the same day. Any activity plans should be discussed with the care team.
The puncture site generally heals quickly, especially with proper rest and aftercare. Use a clean bandage and continue to follow any advice given by healthcare professionals. If there is pain, nonprescription medicine like acetaminophen can help with headaches or back soreness. Severe or long-lasting headaches should be reported to a health care provider.
Findings from Spinal Fluid Analysis
When analyzing cerebrospinal fluid (CSF) collected through a lumbar puncture, healthcare professionals make several important observations to assist with diagnosis.
They first check the physical appearance of the fluid. Healthy CSF is typically clear and lacks color. If it appears orange, yellow, or pink, this can point to bleeding. A greenish tint may be a sign of certain types of infection.
| Test Item | Normal Value | Possible Issues When Abnormal |
|---|---|---|
| General Appearance | Clear, colorless | Orange/yellow/pink: bleeding; Green: infection |
| Total Protein | ≤ 45 mg/dL | High levels: infection, inflammation |
| White Blood Cells (WBC) | 0–5 cells/μL | High count: infection, inflammation |
| Glucose (Sugar) | Two-thirds of blood glucose | Low: infection, tumor, certain diseases |
| Microorganisms | None seen | Presence indicates infection (bacteria, fungi, viruses) |
| Cancer (Tumor) Cells | None seen | Could suggest cancer, tumor spread |
The healthcare team measures protein levels next. Higher-than-normal protein often points to infections or inflammation of the nervous system. They also assess white blood cell counts; an elevated count may be another clue for infection or other disease processes.
CSF glucose is compared to blood glucose levels. If the glucose in the spinal fluid is much lower than expected, it can be associated with infections or tumors. The lab also checks for bacteria, viruses, or fungal organisms using different methods such as Gram stain or culture, helping to pinpoint the type of infection when present.
Detection of cancer cells or abnormal immature blood cells in CSF may suggest the spread of tumors or certain blood diseases. Tumor cells identified in spinal fluid are significant for the diagnosis of some cancers affecting the brain or spinal cord.
All test results are usually reviewed alongside observed CSF pressure and the patient’s symptoms to help healthcare providers make a diagnosis. Results are typically available within a few days, though it may take longer in specific situations.
