eMedicine Specialties > Clinical Procedures > Neurologic Procedures

Lumbar Puncture

Gil Z Shlamovitz, MD, Assistant Professor of Emergency Medicine, University of Connecticut School of Medicine; Attending Physician, Emergency Department, Windham Community Memorial Hospital, Willimantic, CT; Attending Physician, Emergency Department, Hartford Hospital, Hartford, CT
Nirav R Shah, MD, MPH, Assistant Professor and Associate Director for Research, Division of General Internal Medicine, New York University, School of Medicine; Associate Investigator, Center for Health Research, Geisinger Health

Updated: Jul 20, 2009

Introduction

Lumbar puncture is a procedure that is often performed in the emergency department to obtain information about the cerebrospinal fluid (CSF).¹ Although usually used for diagnostic purposes to rule out potential life-threatening conditions such as bacterial meningitis or subarachnoid hemorrhage, lumbar puncture is also sometimes performed for therapeutic reasons, such as the treatment of pseudotumor cerebri. CSF fluid analysis can also aid in the diagnosis of various other conditions, such as demyelinating diseases and carcinomatous meningitis. Lumbar puncture should be performed only after a neurological examination and should never delay potentially lifesaving interventions such as the administration of antibiotics and steroids to patients with suspected bacterial meningitis.²

Indications

Suspicion of meningitis
Suspicion of subarachnoid hemorrhage
Suspicion of central nervous system diseases such as Guillain-Barré syndrome³ and carcinomatous meningitis
Therapeutic relief of pseudotumor cerebri

Contraindications

Absolute contraindications to lumbar puncture are as follows:
- Unequal pressures between the supratentorial and infratentorial compartments, usually inferred by characteristic findings on the brain CT scan:
  - Midline shift
  - Loss of suprachiasmatic and basilar cisterns
  - Posterior fossa mass
  - Loss of the superior cerebellar cistern
  - Loss of the quadrigeminal plate cistern
- Infected skin over the needle entry site
Relative contraindications to lumbar puncture are as follows:
- Increased intracranial pressure (ICP)
- Coagulopathy
- Brain abscess
Indications for brain CT scan prior to lumbar puncture include the following:⁴
- Patients who are older than 60 years
- Patients who are immunocompromised
- Patients with known CNS lesions
- Patients who have had a seizure within 1 week of presentation
- Patients with abnormal level of consciousness
- Patients with focal findings on neurological examination
- Patients with papilledema seen on physical examination with clinical suspicion of elevated ICP

Anesthesia

See the Technique section for details on local anesthesia.
For more information, see Local Anesthetic Agents, Infiltrative Administration.

Equipment

Spinal or lumbar puncture tray (including the items listed below)
Sterile gloves
Antiseptic solution with skin swabs
Sterile drape
Lidocaine 1% without epinephrine
Syringe, 3 mL
Needles, 20 and 25 gauge (ga)
Spinal needles, 20 and 22 ga
Three-way stopcock
Manometer
Four plastic test tubes, numbered 1-4, with caps
Sterile dressing
Optional: Syringe, 10 mL

Lumbar puncture disposable tray. Image courtesy of Gil Z. Shlamovitz, MD.

Positioning

Position the patient in the lateral recumbent position with hips, knees, and chin flexed toward the chest in order to open the interlaminar spaces. A pillow can be used to support the head.

Lumbar puncture lateral recumbent position. Image courtesy of Gil Z. Shlamovitz, MD.

The sitting position may be a helpful alternative position, especially in obese patients (easier to confirm the midline). In order to open the interlaminar spaces, the patient should lean forward and be supported by a Mayo stand with a pillow on it, by hunching over the back of a stool, or by another person.

Lumbar puncture sitting position. Image courtesy of Gil Z. Shlamovitz, MD.

Technique

Explain the procedure, benefits, risks, complications, and alternative options to the patient or the patient's representative and obtain a signed informed consent.
Wearing nonsterile gloves, locate the L3-L4 interspace by palpating the right and left posterior superior iliac crests and moving the fingers medially toward the spine. Palpate that interspace (L3-L4) as well as one above (L2-L3) and one below (L4-L5) to find the widest space. Mark the entry site with a thumbnail or a marker. To help open the interlaminar spaces, the patient can be asked to practice pushing the entry site area out toward the practitioner.
L3-L4 interspace palpation. Image courtesy of Gil Z. Shlamovitz, MD.
Open the spinal tray, change to sterile gloves, and prepare the equipment. Open the numbered plastic tubes and place them upright, assemble the stopcock on the manometer, and draw the lidocaine into the 10-mL syringe.
CSF collection tubes. Image courtesy of Gil Z. Shlamovitz, MD.
Use the skin swabs and antiseptic solution to clean the skin in a circular fashion starting at the L3-L4 interspace and moving outward to include at least 1 interspace above and below. Just before applying the skin swabs, warn the patient that the solution is very cold, since this can be unnerving to the patient.
Skin preparation. Video courtesy of Gil Z. Shlamovitz, MD.
Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113960.flv.
Place a sterile drape below the patient and a fenestrated drape on the patient. Most spinal trays contain fenestrated drapes with an adhesive tape that keeps the drape in place.
Drape application. Video courtesy of Gil Z. Shlamovitz, MD.
Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113961.flv.
Use the 10-mL syringe to administer local anesthesia. Raise a skin wheal using the 25-ga needle and then switch to the longer 20-ga needle to anesthetize the deeper tissue. Insert the needle all the way to the hub, aspirate to confirm that the needle is not in a blood vessel, and then inject a small amount as the needle is withdrawn a few centimeters. Continue this process above, below, and to the sides very slightly (using the same puncture site).

This process anesthetizes the entire immediate area so that, if redirection of the spinal needle is necessary, the area will still be anesthetized. For this reason, a 10-mL syringe may be more beneficial than the usual 3-mL syringe supplied with the standard lumbar puncture kit. The 20-ga needle can also be used as a guide for the general direction of the spinal needle. In other words, the best direction in which to aim the spinal needle can be confirmed if the 20-ga needle encounters bone in one direction but not in another.
Local anesthesia. Video courtesy of Gil Z. Shlamovitz, MD.
Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113962.flv.
Stabilize the needle (20 or 22 ga) with the index fingers and advance it through the skin wheal using the thumbs. Orient the bevel parallel to the longitudinal dural fibers to increase the chances of the needle separating the fibers rather than cutting them (bevel facing up in the lateral recumbent position and facing to either side in the sitting position). Insert the needle at a slightly cephalad angle toward the umbilicus. Advance the needle slowly but smoothly. Occasionally, the practitioner feels a characteristic "pop" when the needle penetrates the dura. Otherwise, the stylet should be withdrawn after approximately 4-5 cm and observed for fluid return. If no fluid returns, replace the stylet, advance or withdraw the needle a few millimeters, and recheck for fluid return. Continue this process until fluid is successfully returned.
Spinal needle insertion. Video courtesy of Gil Z. Shlamovitz, MD.
Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113963.flv.
To measure the opening pressure, the patient must be in the lateral recumbent position. After fluid returns from the needle, attach the manometer through the stopcock and note the height of the fluid column. The patient's legs should be straightened when measuring open pressure or a falsely elevated pressure will be obtained.
Opening pressure measurement. Video courtesy of Gil Z. Shlamovitz, MD.
Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113965.flv.
Collect at least 10 drops of CSF in each of the 4 plastic tubes, starting with tube #1. The CSF that is in the manometer should be used (if possible) for tube #1.
Replace the stylet and remove the needle. Clean off the skin preparatory solution. Apply a sterile dressing and place the patient in the supine position.
Spinal needle removal. Video courtesy of Gil Z. Shlamovitz, MD.
Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113964.flv.

Pearls

If the patient is dehydrated, a falsely negative dry tap may be obtained as a result of very low CSF volume and pressure. If this is suspected, attempt to rehydrate the patient prior to the procedure.
If the procedure is performed in the sitting position and an opening pressure is required (eg, pseudotumor cerebri), replace the stylet and have an assistant help the patient into the left lateral recumbent position. No data suggest increased risk of spinal headache or transection of the spinal nerves with position change. Take care not to change the orientation of the spinal needle during this maneuver.
The amount of lidocaine provided in most kits is often inadequate. The authors recommend supplementing the kit with a 10-mL syringe and a bottle of 1% lidocaine. Make sure not to exceed the maximal recommend dose of 4.5 mg/kg of lidocaine. A smaller (27 ga, 1 1/4") needle may be used for infiltration. Smaller needles are shown to be associated with less pain during local anesthesia.
If the CSF flow is too slow, ask the patient to cough or bear down as in the Valsalva maneuver, or ask an assistant to intermittently press on the patient’s abdomen to increase the flow. Alternatively, the needle can be rotated 90 degrees such that the bevel faces cephalad.
Never delay intravenous antibiotics for a lumbar puncture or a pre-lumbar puncture CT scan. Meningitis can usually be inferred from the cell count, antigen detection, or both.
The smaller the needle used for the lumbar puncture, the lower the risk of the patient developing a post–lumbar puncture headache. Data suggest a inverse linear relationship to gauge, and the authors recommend using a 22-ga needle, regardless of what size needle is supplied with the kit.⁵
The use of atraumatic needles has been shown to significantly reduce the incidence of post – lumbar puncture headache (3%) when compared to standard spinal needles (approximately 30%).^6,7 Obtaining pressures can be more difficult with these needles.
Prophylactic bed rest following lumbar puncture has not been shown to be of benefit and should not be recommended.^8,9,10

Complications

Post–spinal puncture headache – This is the most common complication of lumbar puncture, observed in 20-70% of patients.^11,12,13 It usually begins 24-48 hours after the procedure and is more common in young adults. The probable etiology is continued CSF leak from the puncture site.¹⁴ The headache is usually fronto-occipital and improves in the supine position. This condition is usually self-limited (up to 7 d) and responds to analgesics and caffeine (300-500 mg q4-6h). Severe cases can be treated with an epidural blood patch that should be performed by an anesthesiologist or a pain specialist. Pencil tip (Whitacre) needles are associated with a significantly lower incidence of post – spinal puncture headaches than are standard bevel-tip (Quincke) needles.¹⁵
Bloody tap – More than 50% of lumbar punctures have falsely present red blood cells in the CSF as a result of microtrauma caused by the spinal needle. This is an uncomplicated occurrence in healthy patients with a normal coagulation system.
Dry tap – Dry tap is usually a result of misplacement of the spinal needle. The most common mistake is a lateral displacement that can be easily corrected by complete withdrawal of the needle, reevaluation of the patient’s anatomy, and reinsertion in the correct place and angle. In obese patients, the regular spinal needle might be too short and a longer one should be used.
Infection – Cellulitis, skin abscesses, epidural abscesses, spinal abscesses, or diskitis can result from a contaminated spinal needle. Adherence to sterile technique, including gloves, gowns, hair covers, and face masks, as well as thorough skin cleansing and disinfecting, should minimize this risk.
Hemorrhage – Epidural, subdural, and subarachnoid hemorrhage are rare complications that might carry significant morbidity and mortality in coagulopathic patients. Lumbar puncture should be deferred in patients with low platelets counts (<50,000) or patients with other coagulopathies (eg, hemophilia, supratherapeutic international normalized ratio [INR]) until the abnormality is corrected.
Dysesthesia – Irritation of nerves or nerve roots by the spinal needle can cause different lower extremity dysesthesias. Withdrawing the needle without replacement of the stylet can cause aspiration of a nerve or arachnoid tissue into the epidural space. Always replace the stylet before moving the needle to prevent this complication.
Postdural puncture cerebral herniation – This is the most serious complication of a lumbar puncture. This is a very rare complication and debate exists in the literature regarding whether the lumbar puncture or the underlying disease process is the cause of the herniation. The body of evidence that a diagnostic lumbar puncture is safe even in patients with increased intracranial pressure (most patients with meningitis) is increasing, but no consensus exists regarding the safety of lumbar puncture in patients with increased intracranial pressure. Until further data are available, a reasonable approach would be to avoid lumbar puncture in patients in whom the disease process has progressed to the neurologic findings associated with impending cerebral herniation (deteriorating level of consciousness, brainstem signs including pupillary changes, posturing, irregular respirations and very recent seizure).^16,17

CSF Analysis

Different institutions have different protocols for the studies sent from the various CSF tubes. Classically, CSF tubes #1-4 are sent for the following studies:

#1 - Cell count and differential
#2 - Glucose and protein levels
#3 - Gram stain, culture and sensitivity (C&S)
#4 - Cell count and differential

In some institutions, only 3 tubes are sent for analysis, with the fourth tube reserved for special studies when indicated. An example is shown below:

#1 - Protein and glucose levels
#2 - Gram stain, C&S
#3 - Cell count and differential
#4 - When indicated, viral titer or cultures, Venereal Disease Research Laboratory (VDRL) test, Cryptococcus antigen, India ink stain, angiotensin-converting enzyme (ACE) level, or other studies.

Additional tests may be warranted, depending on the clinical situation. All specimens should be taken to the laboratory promptly to prevent hemolysis and specimen misplacement.

Separate specimens should be sent for microscopic study and for centrifugation. The latter must be done promptly, as RBCs hemolyze within a few hours. Normal CSF may contain as many as 5 lymphocytes per cubic mm.

A larger-than-usual number of WBCs suggests infection or, more rarely, leukemic infiltration. While bacterial infections traditionally are associated with a preponderance of polymorphonuclear leukocytes (PMNs), many cases of viral meningitis/encephalitis also have a high percentage of PMNs in the acute phase of the illness (when most lumbar punctures [LPs] are done). In addition, inflammation from any source (eg, CNS vasculitis) can raise the WBC count.

A traumatic tap, of course, introduces both WBCs and RBCs into the CSF. An approximation of 1 WBC per 1000 RBCs can be made, although a repeat tap may be preferable. While no normal value for RBCs in the CSF is known, an occasional RBC may be incident to the tap.

Xanthochromia

The best way to distinguish RBCs related to intracranial bleeding is examination of the centrifuged supernatant CSF for xanthochromia (yellow color). Although xanthochromia can be confirmed visually, it is identified and quantified more accurately in the laboratory.

While xanthochromia can be produced by spillover from a very high serum bilirubin level (ie, >15 mg/dL), patients with severe hyperbilirubinemia usually have been identified prior to the LP (eg, jaundice, known liver disease). With this exception, the presence of xanthochromia in a freshly spun specimen is evidence of preexistent blood in the subarachnoid space. However, note that an extremely high CSF protein level, as seen in LPs below a complete spinal block, also renders the fluid xanthochromic, though without RBCs.

Xanthochromia can persist up to several weeks following a subarachnoid hemorrhage (SAH). Thus, it has greater diagnostic sensitivity than a CT scan of the head without contrast, especially if the SAH occurred more than 3-4 days prior to presentation. Patients with aneurysmal leaks (ie, sentinel hemorrhages) may present days after headache onset, increasing the likelihood of a false-negative head CT scan.

In some cases, the CSF may be another color that strongly suggests a diagnosis. For example, pseudomonal meningitis may be associated with bright green CSF.

Other tests

Assuming the CSF has been collected under sterile conditions, microbiologic studies can be performed. Stains, cultures, and immunoglobulin titers can be obtained. The latter are of special importance in diseases in which peripheral manifestations fade while CNS symptoms persist (eg, syphilis, Lyme disease).

Assessment of CSF protein level, while nonspecific, can be a clue to otherwise unsuspected neurologic disease. The high protein levels in demyelinating polyneuropathies, or postinfectious states, can be informative. A traumatic tap can introduce protein into the CSF. An approximation of 1 mg of protein per 750 RBCs may be used, but a repeat tap is preferable.

CSF glucose level normally approximates 60% of the peripheral blood glucose level at the time of the tap. A simultaneous measurement of blood glucose (especially if the CSF glucose level is likely to be low) is recommended. Low CSF glucose level usually is associated with bacterial infection (probably due to enzymatic inhibition rather that actual bacterial consumption of the glucose). It also is seen in tumor infiltration and may be one of the hallmarks of meningeal carcinomatosis, even with negative cytologic findings. High CSF glucose level has no specific diagnostic significance and is most often spillover from elevated blood glucose level.

Leptomeningeal malignancies: Multiple LP examinations may be required in this situation. At least 3 negative cytologic evaluations (ie, 3 separate samplings) are required to rule out leptomeningeal malignancy (eg, leptomeningeal carcinomatosis).

Multimedia

Media file 1: Lumbar puncture disposable tray. Image courtesy of Gil Z. Shlamovitz, MD.

Media file 2: Lumbar puncture lateral recumbent position. Image courtesy of Gil Z. Shlamovitz, MD.

Media file 3: Lumbar puncture sitting position. Image courtesy of Gil Z. Shlamovitz, MD.

Media file 4: L3-L4 interspace palpation. Image courtesy of Gil Z. Shlamovitz, MD.

Media file 5: CSF collection tubes. Image courtesy of Gil Z. Shlamovitz, MD.

Media file 6: Skin preparation. Video courtesy of Gil Z. Shlamovitz, MD.

Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113960.flv.

Media file 7: Drape application. Video courtesy of Gil Z. Shlamovitz, MD.

Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113961.flv.

Media file 8: Local anesthesia. Video courtesy of Gil Z. Shlamovitz, MD.

Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113962.flv.

Media file 9: Spinal needle insertion. Video courtesy of Gil Z. Shlamovitz, MD.

Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113963.flv.

Media file 10: Spinal needle removal. Video courtesy of Gil Z. Shlamovitz, MD.

Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113964.flv.

Media file 11: Opening pressure measurement. Video courtesy of Gil Z. Shlamovitz, MD.

Video available at http://img.medscape.com/pi/emed/ckb/clinical_procedures/79926-79935-80773-113965.flv.

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Hasbun R, Abrahams J, Jekel J, Quagliarello VJ. Computed tomography of the head before lumbar puncture in adults with suspected meningitis. N Engl J Med. Dec 13 2001;345(24):1727-33. [Medline]. [Full Text].
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[Best Evidence] Lavi R, Yarnitsky D, Yernitzky D, Rowe JM, Weissman A, Segal D. Standard vs atraumatic Whitacre needle for diagnostic lumbar puncture: a randomized trial. Neurology. Oct 24 2006;67(8):1492-4. [Medline].
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Keywords

lumbar puncture, LP, spinal tap, lumbar puncture procedure, lumbar puncture headache, spinal puncture, lumbar puncture pain, cerebrospinal fluid culture, cerebral spinal fluid, CSF, cerebrospinal fluid, bacterial meningitis, subarachnoid hemorrhage, pseudotumor cerebri, CNS diseases, interlaminar spaces, longitudinal dural fibers, opening pressure, post–spinal puncture headache, post–lumbar puncture headache, epidural blood patch, bloody tap, dry tap, dysesthesias, postdural puncture cerebral herniation, increased intracranial pressure

Contributor Information and Disclosures

Author

Gil Z Shlamovitz, MD, Assistant Professor of Emergency Medicine, University of Connecticut School of Medicine; Attending Physician, Emergency Department, Windham Community Memorial Hospital, Willimantic, CT; Attending Physician, Emergency Department, Hartford Hospital, Hartford, CT
Gil Z Shlamovitz, MD is a member of the following medical societies: American Academy of Emergency Medicine and American College of Emergency Physicians
Disclosure: Nothing to disclose.

Coauthor(s)

Nirav R Shah, MD, MPH, Assistant Professor and Associate Director for Research, Division of General Internal Medicine, New York University, School of Medicine; Associate Investigator, Center for Health Research, Geisinger Health
Nirav R Shah, MD, MPH is a member of the following medical societies: American College of Physicians, New York Academy of Medicine, and Society of General Internal Medicine
Disclosure: Nothing to disclose.

Medical Editor

Andrew K Chang, MD, Associate Professor, Department of Emergency Medicine, Albert Einstein College of Medicine, Montefiore Medical Center
Andrew K Chang, MD is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Neurology, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

Luis M Lovato, MD, Associate Clinical Professor, David Geffen School of Medicine at UCLA; Director of Critical Care, Department of Emergency Medicine, Olive View/UCLA Medical Center
Luis M Lovato, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

CME Editor

Rick Kulkarni, MD, Assistant Professor of Surgery, Section of Emergency Medicine, Yale-New Haven Hospital
Rick Kulkarni, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, American Medical Association, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine
Disclosure: WebMD Salary Employment

Chief Editor

Helmi L Lutsep, MD, Professor, Department of Neurology, Oregon Health & Science University; Associate Director, Oregon Stroke Center
Helmi L Lutsep, MD is a member of the following medical societies: American Academy of Neurology and American Stroke Association
Disclosure: Co-Axia Consulting fee Review panel membership; Talecris Consulting fee Review panel membership; AGA Medical Consulting fee Review panel membership; Boehringer Ingelheim Honoraria Speaking and teaching; Concentric Medical Consulting fee Review panel membership; Abbott Consulting fee Consulting; Sanofi Consulting

Acknowledgments

The authors and editors of eMedicine gratefully acknowledge the assistance of Lars Grimm with the literature review and referencing for this article.

Further Reading

MedlinePlus: CSF Collection