by Connie Deline, MD
Lumbar punctures play an important role in diagnostics and treatments in medicine but can result in a persistent spinal CSF leak after the procedure, often termed a post-dural puncture headache (PDPH). This is the most common iatrogenic cause of spinal CSF leaking. There are procedural aspects that can reduce but not eliminate this risk.
What happens during a lumbar dural puncture?
The brain and spinal cord is bathed in cerebrospinal fluid (CSF) and that fluid is held in place by the meninges, a connective tissue with several layers. The outmost layer of the meninges, the dura, is the toughest layer. The dura is pierced with a needle to access this space around the spinal cord where cerebrospinal fluid flows. CSF can be removed or fluids, drugs or contrast can be injected.
Lumbar punctures, which puncture the dura, are used commonly diagnostically to:
1) Sample the CSF to test the CSF pressure or to perform lab tests on the fluid. When meningitis is a possibility, the fluid should be tested for cells, chemistry, bacteria and so on. In some neurological diseases, the analysis of CSF can be helpful.
2) Perform diagnostic imaging such as myelography. The radiologist injects contrast into the intrathecal space (the space where CSF flows) in order to image the spine or brain with CT, MRI or nuclear medicine imaging.
Lumbar punctures are also used in treatment. Fluids and/or medications can be infused into the intrathecal space. Spinal anesthesia is a fairly common therapeutic use of lumbar puncture.
In most cases, the puncture hole in the dura will seal over spontaneously. A percentage of lumbar dural punctures will persist for days and more rarely for months or years. The most common clinical manifestation of this is a positional headache that is worse when upright following the procedure as a result of loss of CSF volume by leakage through the hole. This is termed “Post Dural Puncture Headache”, abbreviated to PDPH. This is almost always recognized by physicians promptly. There are a number of factors that influence the risk of the dural puncture to persist:
• The skill, technique and experience of the physician performing the procedure
• The size of the LP needle
• The type of LP needle
• Patient factors such as gender, age, body habitus
• Inadvertent movement of the patient during the procedure
Physicians performing diagnostic lumbar punctures commonly include ER physicians, anesthesiologists and neurologists. Anesthesiologists also perform spinal anesthesia and other procedures which include lumbar puncture. Radiologists and neuroradiologists perform lumbar punctures with imaging guidance for diagnostic imaging such as myelography as well as for other procedures. Physicians that do these more frequently usually employ a technique that can reduce the incidence of post-dural puncture headache.
The size of the needle used for a lumbar puncture is an obvious factor that influences risk of PDPH or persistent dural hole which leaks CSF. Needles come in various sizes, measured by gauge. Lower gauge numbers are larger needles. For sampling of CSF, a smaller needle is adequate. For injection of contrast, the specific needs of the procedure influence the adequacy of the needle gauge and type elaborated on below.
There are two main types or styles of needles for dural punctures.
1) Sharp beveled “cutting” needles with hole at tip of needle
2) Atraumatic pencil-point needles with a blunt tip and opening on side of needle
These two needle styles are seen in the photo below. Examples of atraumatic pencil-point needles include Gertie Marx, Sprotte and Whitacre needles.
Re-produced with permission by International Medical Development, Inc.
Numerous studies and meta-analyses have shown that the pencil-point needle is less traumatic to the dura and has a lower risk of post dural puncture headache or persistent dural defect. For regular diagnostic lumbar punctures, the literature is clear that the smaller gauge atraumatic pencil-point needles would usually be the preferred type of needle. While many anesthesia departments have adopted the use of the atraumatic type of needles, the routine use in emergency departments, outpatient and inpatient settings is not yet standard of care across the country. “We have used atraumatic pencil-point needles in inpatient and outpatient settings for lumbar punctures for several years in our institution” says Wouter Schievink, MD, neurosurgeon at Cedars-Sinai Medical Center in Los Angeles, a center that treats many iatrogenic and spontaneous spinal CSF leaks.
Marcel Maya, MD, interventional neuroradiologist of Cedars-Sinai Medical Center offered his perspective regarding needle use for the various types of myelography done at a high frequency at their institution. For injection of contrast for conventional myelography (with subsequent imaging), contrast need not be injected rapidly, so a smaller gauge pencil-point needle can be used. They currently have atraumatic pencil-point needles available for conventional myelography. In some other types of myelography, such as dynamic CT myelography and digital subtraction myelography (DSM), the contrast must be injected rapidly under pressure to achieve a higher diagnostic yield, so they have found that smaller gauge pencil-point needles are less suitable. The sharp beveled needles are used for these cases. It is important to keep in mind that this center does a very high volume of myelography and the physicians performing these procedures are highly skilled.
The interventional neuroradiologists at Duke University also treat a large volume of patients with known or suspected spinal CSF leaks. Linda Gray Leithe, MD, reports that small gauge atraumatic pencil-point needles are routinely used for CT myelography in their department.
We anticipate surveying a number of other institutions across the country to determine the current adoption rates of atraumatic pencil-point needle use for lumbar punctures and myelography.
Beyond physician experience and needle size and type, patient factors, such as an undiagnosed heritable disorder of connective tissue, gender, spinal anatomy and body weight can influence the risk of post dural puncture CSF leak, but these are not modifiable factors.
When a post-dural puncture headache (CSF leak) occurs and does not resolve spontaneously, an epidural blood patch (EBP) is usually performed. This involves the injection of the patient’s blood outside the dura in the epidural space. Occasionally, this must be repeated and more rarely an open surgical repair is necessary.
The benefit of a diagnostic procedure that includes a lumbar puncture usually outweighs the risk of post dural puncture CSF leak. However, the risk of this complication, along with the associated suffering, morbidity and health care costs, can be reduced with the use of atraumatic pencil-point needles for regular diagnostic lumbar punctures and conventional myelography. More widespread adoption of the routine use of these atraumatic needles should be encouraged where appropriate.
Links to PubMed for publications on atraumatic LP needles.