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The Importance Of A Lumbar Puncture

Information obtained from a lumbar puncture is essential to make the diagnosis of IIH and in ruling out another cause that can be treated in another manner.

A lumbar puncture (LP)  is an invasive procedure. It is part of an extensive workup when a neurological disorder is suspected. Also known as a spinal tap, an LP can detect if an infection, bleeding, or an abnormal process (ie: cancer) is occurring in the central nervous system. As part of the Dandy Criteria, the information obtained from an LP is essential to make the diagnosis of IIH and in ruling out another cause that can be treated in another manner. Throughout the course of IIH, it may be necessary to repeat an LP several times to alleviate the high pressure in the brain.

Reasons to perform (indications) or not perform (contraindications) a lumbar puncture:

Image courtesy of REV MED, an online medical education platform for learners in healthcare.

A lumbar puncture is an invasive procedure used for diagnostic and therapeutic purposes. It is diagnostic because it can measure pressure in the brain (opening pressure) and the cerebrospinal fluid obtained can be analyzed for appearance, and red blood cells, white blood cells, protein, and glucose can be quantified. The results of the CSF fluid can detect if there is a viral or bacterial infection and diagnose some autoimmune disorders.

CSF Fluid Normal Viral Bacterial
Opening Pressure 5-20 cm H₂0 Normal or elevated Elevated
Appearance Clear Clear Turbid
WBC < 5 and no PMNs* 10-1000 > 100 and > 80% PMNs*
RBC < 10 Normal (< 10) Normal (< 10)
Protein 15-45 mg/dL Elevated >50 mg/dL Elevated > 50 mg/dL
Glucose > 60% serum glucose < 40% serum glucose > 60% serum glucose

A lumbar puncture is also therapeutic as it helps decrease the pressure in the brain. This is a critical intervention used for idiopathic intracranial hypertension (IIH), if increased pressure from CSF fluid is causing papilledema leading to vision loss, debilitating headaches, and a wide range of chronic symptoms. Having CSF removed can help bring the pressure in the brain back to normal and can reverse some of the known signs and symptoms of IIH. It can be performed in an emergent or non-emergent setting depending on symptoms and physical exam findings.

Caution should be used in people with known extremely high pressure in the brain as this procedure can cause a herniation.

An LP or spinal tap is performed by a trained medical professional such as an emergency medicine physician, a neurologist, interventional radiologist, or a neurosurgeon. As with any other invasive procedure, there are risks of a lumbar puncture. Some of these risks can be minimized with proper positioning, the choice of needle, and use of imaging guidance such as ultrasound or fluoroscopy.1

Images courtesy of REV MED, an online medical education platform for learners in healthcare.

Caution should be used in people with known extremely high pressure in the brain as this procedure can cause a herniation. An LP should be avoided if a spinal epidural abscess is suspected and in those at risk for bleeding (such as if one has thrombocytopenia or are on blood thinner medications).1 There are interventions that can be done in those at-risk for bleeding prior to the procedure.

The most common risks of an LP are:

    • Back pain (17%)
    • Headache (19%)
    • Postdural Puncture Headache (PDHP) (9%)2

*Rare risks of an LP are:

    • Post-LP infection
    • Spinal and subdural cerebral hematoma
    • Cerebral Venous Thrombosis2

*Seen in less than 0.01% of a review of 3868 adult patients2

A postdural puncture headache (PDHP) is a challenging complication of a lumbar puncture. It is seen in about 9-11 out of every 100 lumbar punctures performed.3 The symptoms that typically occur are: headache that worsens when sitting upright, photophobia, neck stiffness, and nausea. The exact reason why these symptoms occur after a lumbar puncture is unknown but it is theorized that a CSF leak is occurring into the dural space from that hole that was made from the needle. When there is a CSF leak is greater than the rate of production of CSF, that causes a low pressure in the central nervous system; however, not all patients with a CSF leak have these symptoms.3 Some risk factors that may lead to a PDHP are: female gender, pregnancy, removal of large amounts of CSF, needle size and type, and orientation of bevel of needle.3 Depending on the severity of the symptoms, it will guide the management to treat PDHP that can range from bedrest to an epidural blood patch. PDHP will be discussed in detail in a future article.

By educating yourself with accurate information, you are serving as your own healthcare advocate. This will allow you to actively participate in your medical care and give yourself a sense of control. You do not have to travel on your medical journey alone. Involving family, friends, and others in the IIH community can help empower you to make the difficult medical decisions to come.

Thank you REV MED for allowing us to use their images. You can follow them on Instagram @REV.MED.

For a detailed step-by-step explanation of how a lumbar puncture is performed, please visit Merck Manual’s Professional Version under “How to do lumbar puncture” that contains illustrations and a complete video.

  1. Johnson K, Sexton, D. Lumbar puncture: Technique, indications, contraindications, and complications in adults. In: UpToDate. Aminoff M (Ed.). Updated: October 7, 2021. Accessed March 1, 2023.
  2. Engelborghs S, Niemantsverdriet E, Struyfs H, et al. Consensus guidelines for lumbar puncture in patients with neurological diseases. Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring. 2017;8:111-126.
  3. Bateman B, Naida C, Sun-Edelstein C. Post dural puncture headache. In: UpToDate. Crowley M, Goddeau R (eds.). Updated: November 3, 2022. Accessed March 5th, 2023.

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