Where along the vertebral column is a needle inserted for a lumbar puncture which landmark can you use to find this level?

In lumbar puncture (LP), a needle is inserted into the lumbar subarachnoid space to collect cerebrospinal fluid (CSF) for laboratory testing, to measure CSF pressure, and sometimes to give intrathecal diagnostic or therapeutic agents.

When it is difficult to palpate landmarks (eg, because of obesity), lumbar puncture can be done by a neuroradiologist using fluoroscopic guidance. Ultrasonography can also be used to identify landmarks and, less commonly, to guide needle placement in real time if equipment and personnel are available. However, ultrasonography is still not commonly used outside of teaching centers.

Diagnostic indications*

• Suspected intracranial hypotension

• To give a radiopaque contrast agent for myelography

* Decide in advance what information you need from the lumbar puncture and what tests you need to order. Confirm requirements for any unusual tests with the clinical laboratory before starting the procedure.

Therapeutic indications

• Reduction of intracranial pressure in idiopathic intracranial hypertension

• Administration of intrathecal drugs (eg, spinal or epidural anesthesia, intrathecal chemotherapy)

Absolute contraindications

• Suspected infection (eg, cellulitis, abscess) at or near the site of needle insertion: If possible, use an alternate, uninfected site. This involves a suboccipital (cisternal) or cervical (C1-C2) approach and is always done under fluoroscopic guidance.

Relative contraindications

• Suspicion of increased intracranial pressure due to an intracranial mass (eg, tumor, brain abscess, or blood) that could precipitate transtentorial or cerebellar herniation Brain Herniation Brain herniation occurs when increased intracranial pressure causes the abnormal protrusion of brain tissue through openings in rigid intracranial barriers (eg, tentorial notch). Because the... read more

  
  * following lumbar puncture. If there are suggestive findings (eg, focal neurologic deficits, altered mental status, papilledema, signs of herniation Symptoms and Signs Brain herniation occurs when increased intracranial pressure causes the abnormal protrusion of brain tissue through openings in rigid intracranial barriers (eg, tentorial notch). Because the... read more
  
  ), do CT or MRI before lumbar puncture. (However, risk of herniation cannot always be predicted by CT or MRI.)

• Cardiopulmonary insufficiency or respiratory distress, which can be exacerbated by recumbent positioning during lumbar puncture

• Anatomic abnormalities at the insertion site (eg, spinal fusion, laminectomy, congenital anomalies)

Bacteremia has not been shown to predispose to meningitis after lumbar puncture and thus is not a contraindication.

† Therapeutic anticoagulation (eg, for pulmonary embolism) increases the risk of bleeding with lumbar puncture, but this must be balanced against the increased risk of thrombosis (eg, stroke) if anticoagulation is reversed. If time permits, discuss any contemplated reversal with the clinician managing the patient's anticoagulation.

• Bleeding into the epidural space (spinal hematoma)

• Lower back discomfort or pain that may radiate to the posterior legs (self-limited)

• Epidermoid tumor, occurs years after lumbar puncture; risk is increased if the spinal needle is inserted or withdrawn with the stylet absent (rare)

• Brain herniation (rare)

• Cortical blindness (rare)

• Cervical spinal cord infarction (rare)

• Transient or permanent deafness (rare)

• Iatrogenic infection (rare)

• Transient nausea and/or tinnitus

Headache develops after lumbar puncture in about 10% of patients, usually hours to a day or two afterward, and can be severe. Younger patients with a small body mass are at greatest risk. Using narrower, noncutting needles reduces risk. Insert these needles with the bevel facing the patient's right or left side (flank). Neither the amount of CSF removed nor a period of recumbency after lumbar puncture affect incidence.

In many centers, prepackaged lumbar puncture kits are available. If not, necessary equipment includes the following:

• Sterile gloves, gown, face mask, and cap

• Sterile drapes and/or towels

• Antiseptic solution (eg, chlorhexidine, povidone-iodine, alcohol wipes)

• Sterile gauze (eg, 10 cm × 10 cm [4" × 4"] squares)

• Local anesthetic (eg, 1% lidocaine without epinephrine, 25- and 20-gauge needles, 10-mL syringe)

• Topical anesthetic (standard for children): Needle-free lidocaine gas-injection device, lidocaine-epinephrine-tetracaine (LET) gel or lidocaine-prilocaine cream

• Spinal needle with stylet: Cutting needle (beveled tip) or noncutting (atraumatic) needle* (pencil-point tip); 20 or 22* gauge; 9-cm-long for adults, 6 cm for children, 4 cm for infants

• 4 CSF collection tubes (labeled 1 through 4) for laboratory studies; additional tubes if large-volume CSF collection is needed (eg, 30 to 40 mL) or additional special tests are needed. Large volumes of 30 to 40 mL of CSF may need to be collected where chronic meningitis Subacute and Chronic Meningitis Subacute meningitis develops over days to a few weeks. Chronic meningitis lasts ≥ 4 weeks. Possible causes include fungi, Mycobacterium tuberculosis, rickettsiae, spirochetes, Toxoplasma... read more

  
  (eg, tuberculous Tuberculous meningitis Subacute meningitis develops over days to a few weeks. Chronic meningitis lasts ≥ 4 weeks. Possible causes include fungi, Mycobacterium tuberculosis, rickettsiae, spirochetes, Toxoplasma... read more
  
  or fungal meningitis Fungal meningitis that develops after epidural methylprednisolone injection Subacute meningitis develops over days to a few weeks. Chronic meningitis lasts ≥ 4 weeks. Possible causes include fungi, Mycobacterium tuberculosis, rickettsiae, spirochetes, Toxoplasma... read more
  
  ) or carcinomatous meningitis are suspected. Additional tubes (enough to contain 30 to 40 mL of CSF) may also be needed if a high-volume LP is planned for diagnosis of normal pressure hydrocephalus.

• Manometer and stopcock; optionally, short extension tubing

• Adhesive bandage

* Use of noncutting needles and smaller caliber (ie, 22-gauge) needle reduces risk of post-lumbar puncture headache.

For ultrasonographic guidance:

• Bedside ultrasound device with a high-frequency linear array probe

• If needed, draw blood for blood glucose to compare with CSF glucose; blood for oligoclonal bands can be collected at the same time.

• Short-term sedation (eg, with propofol or fentanyl and/or midazolam) may be needed for children and anxious adults.

• The desired insertion point of the needle is the L3-L4 or L4-L5 interspace; thus, the needle is inserted below the level of the spinal cord.

• The spinous process of L4 lies along an imaginary line between the top of the posterior superior iliac crests.

• In a midline insertion (most common approach), the spinal needle first traverses the supraspinous and interspinous ligaments between the vertebral spinous processes, before reaching the ligamentum flavum.

  A lateral insertion (eg, 1 cm both lateral and caudad to the midline skin insertion point) bypasses the midline ligaments and may facilitate lumbar puncture in older patients whose ligaments are calcified and sclerotic.

• The ligamentum flavum is thick connective tissue, and a distinct pop may (or may not) be palpable when the needle traverses it.

• The needle then passes through epidural space (fat tissue and internal vertebral venous plexus) and then may palpably pop—again—through the dura mater (and simultaneously through the adjacent subarachnoid membrane) to enter the subarachnoid space (CSF space). Note that in many cases, no "pop" can be appreciated.

  In children or infants, whose fibrous tissue offers little resistance to penetration, a pop may not be palpable as the needle passes the ligamentum flavum or dura.

The goal is to flex the lumbar spine to expand the intervertebral spaces. The patient may either lie in the lateral decubitus position or be seated. The lateral decubitus position is generally preferred and should be used if CSF manometry is desired. The sitting position may be helpful for obese patients and is preferred for infants.

• Lateral decubitus position: The patient lies on the side in a fetal position, with the hips flexed as much as is tolerable. Ensure the pelvis, back, and shoulders are perpendicular to the bed. Place a pillow under the head to align the head with the spine and between the knees for comfort if needed. An assistant can help the patient curl up as much as possible. Before beginning, assume a comfortable position close to the patient.

• Sitting position: The patient sits at the edge of the bed with their feet on a stool or chair to flex the hips, and leans forward with the head and shoulders resting on a bedside table.

  For an infant, an assistant holds the arms and legs from the front, maintaining the infant in a sitting fetal position on the bed. The head is also supported to prevent asphyxiation due to neck flexion.

• Bedrest after lumbar puncture is unnecessary and does not reduce the incidence of post-lumbar puncture headache; however, recumbency remains helpful in treating post-lumbar puncture headache.

• Increased oral intake of fluids has been suggested to treat post-procedural headache but has not been effective in controlled trials. Caffeine may help prevent post-procedural headache.

• Instruct the patient to be vigilant for persistent or worsening back pain (may occur up to several days after the lumbar puncture), which requires prompt evaluation to exclude or hematoma.

• Be sure to keep the patient's hips, back, and shoulders precisely perpendicular to the bed.

• When using the lateral decubitus position, maintain the patient's tightly curled fetal position.

• Be sure to direct the needle toward the midline (not angled to one side) and slightly cephalad.

These errors make it difficult to enter the spinal canal.

• Do not withdraw the needle without reinserting the stylet.

• If the spinal canal is not entered, do not try to reposition the needle by moving the tip to one side or another; this can damage tissue. Instead, withdraw the needle nearly to the skin surface (ie, outside of the spinal ligament) before changing the angle and direction of insertion.

• Seat yourself comfortably close to the patient before doing the procedure in the lateral decubitus position.

• Consider holding the needle with both hands to obtain better control.

• Avoid inserting the lumbar puncture needle through tattooed skin because of a theoretical possibility that tattoo ink could be introduced into the CSF and cause irritation or toxicity. If necessary, either use an adjacent interspace or make a small stab incision through the tattooed epidermis with a scalpel and then introduce the needle through the incision.

• After the needle is through the skin and into the spinous ligament, recheck the patient's alignment (hips perpendicular to bed) and direction of the needle (perpendicular to spine) before inserting further.

• Draw blood to measure glucose level before (eg, by up to 30 minutes) lumbar puncture so that level can be accurately compared with the CSF glucose level. With this timing, serum and CSF oligoclonal bands can be compared also.

• If lumbar puncture is unsuccessful in the decubitus position, try the sitting position, which may be successful because of increased spinal flexion and intervertebral space opening.

Click here for Patient Education

What are the landmarks for a lumbar puncture?

Where is the location of needle insertion in lumbar puncture?

What bone landmarks help located the level where the lumbar puncture needle is inserted?

Why is the needle inserted between L3 and L4 for a lumbar puncture?