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NeoQuest August 2024: Approach to Ultrasonography-guided Lumbar Puncture

August 1, 2024

A 1-day-old term neonate is admitted to the NICU due to respiratory distress. Upon admission, a blood culture is obtained on admission and has grown gram-negative bacilli. The team decides to perform a lumbar puncture under static ultrasonography guidance. The following view is obtained (Figure 1). 


Figure 1: Longitudinal/sagittal spinal ultrasonography image of an infant with bacteremia. Image from: Will EP, Fraga MV. Ultrasonography-guided lumbar puncture. Neoreviews. 2024;25(8):e527–e529.1

Based on the image above, which of the following statements is true? 

  1. There is a sufficient volume of cerebrospinal fluid to attempt a lumbar puncture.
  2. This view can be used to demarcate where the conus medullaris terminates.
  3. This view can be used to measure the depth of the dura mater.
  4. Both A and C
  5. Both B and C

Answer: D. Both A and C

Explanation:

The ultrasonography image shown is a longitudinal/sagittal view of the infant’s spine. This is the first view needed to perform a lumbar puncture (LP) under static ultrasonography guidance.1 Using a medium to high-frequency linear probe held parallel to the spine, the longitudinal view can help determine if there is normal spinal anatomy and sufficient cerebrospinal fluid present to attempt an LP safely and effectively (Option A). This view can also delineate the approximate depth of the dura mater relative to the skin (Option C), providing guidance on the appropriate depth the needle should be advanced to successfully obtain cerebrospinal fluid.1,2  In Figure 1, there is visible hypoechoic cerebrospinal fluid present (blue dot).1 The depth from the skin to the dura mater (white arrow) can be electronically calculated or gauged using the measurements (in centimeters) in yellow on the right-hand side.1 The cauda equina (green arrow) and conus medullaris (red arrow) are also seen but cannot be demarcated relative to the skin in the longitudinal/sagittal view.1

Once a clear longitudinal view is obtained, the ultrasonography probe is then rotated 90 degrees perpendicular to the spine (Figure 2) to provide a transverse/axial view (Figure 3).1,2 Sliding the probe up and down the infant’s back in the transverse/axial view provides information on key spinal landmarks: 1) Where the conus medullaris terminates and 2) Where the spinal canal narrows.1 The termination point of the conus medullaris can then be marked on the infant’s back, which helps ensure the LP is not attempted through the spinal cord (Figure 2B and 3A) (Option B).1 The point at which the spinal canal narrows (i.e., where an LP is less likely to yield sufficient cerebrospinal fluid) is also marked on the infant’s back (Figure 2).1 These markings serve as important visual landmarks to optimize both the safety and efficacy of performing an LP under static ultrasonography guidance.1 Of the answer choices listed above, Option D is the correct answer.


Figure 2: A: Positioning of an ultrasonography probe in the transverse/axial plane to aid in identifying the vertebral levels where the conus medullaris terminates and where the spinal canal narrows caudally. B: Completed skin marking procedure. Image from: Fraga MV, Stoller JZ, Glau CL, et al. Seeing is believing: ultrasonography in pediatric procedural performance. Pediatrics. 2019;144(5):e20191401.2

Figure 3: A: A transverse/axial view of the spine illustrating the conus medullaris (red arrow).  B: Cauda equina (green arrow) surrounded by cerebrospinal fluid (blue circle). Image from: Will EP, Fraga MV, Ultrasonography-guided lumbar puncture. Neoreviews. 2024;25(8):e527–e529.1

Dynamic ultrasonography guidance can also be used in neonatal LPs.1 Dynamic guidance follows the same method as static ultrasonography guidance to identify key structures as described previously.1 However, after the LP needle is inserted into the skin at an appropriate intervertebral space, the ultrasonography probe is then held next to the needle in the longitudinal/sagittal plane (Figure 4) for the dynamic approach.1 After the needle tip is identified on ultrasonography, the needle is advanced until it can be seen puncturing the dura mater and entering the spinal canal.1 While it is generally beneficial for a patient to remain as still as possible for any LP, it is especially imperative during a dynamic approach to allow for uninterrupted visualization of the needle’s location.1

Figure 4: A: A transverse/axial view of the spine showing the lumbar puncture needle (white arrow).  B: a longitudinal/sagittal view of the spine demonstrating the lumbar puncture needle (white arrows). Image from: Fraga MV, Stoller JZ, Glau CL, et al. Seeing is believing: ultrasonography in pediatric procedural performance. Pediatrics. 2019;144(5):e20191401.2

The current standard of care for neonatal LPs is to palpate for landmarks to identify the L3 to L4 or L4 to L5 intervertebral space.3 A recent study comparing ultrasonography guidance to landmark palpation in neonates and infants found that ultrasonography guidance did not significantly improve LP success rates but did reduce traumatic taps.4 While the use of ultrasonography for LP has not been shown to improve neonatal LP success rates, ultrasonography-guided LPs performed on adults (since the early 2000s) have been shown to reduce the number of attempts and traumatic taps, and can improve LP success rates.5

Check out the ultrasonography-guided lumbar puncture video demonstration: Will EP, Fraga MV, Ultrasonography-guided lumbar puncture. Neoreviews. 2024;25(8):e527–e529.1

Did you know?
The NeoCLEAR trial showed that neonates in a seated position were more likely to have a successful LP on the first attempt compared to neonates in a lateral decubitus position (using standard of care landmark palpation).6

What are current recommendations for performing a lumbar puncture in neonates being evaluated for early-onset and late-onset neonatal sepsis?
To find the answer, please refer to the following article: Aleem S, Greenberg RG. When to include a lumbar puncture in the evaluation for neonatal sepsis. Neoreviews. 2019;20(3):e124-e134.3

NeoQuest August 2024 Authors:

Angelina June MD, FAAP, Fairfax Neonatal Associates, Fairfax, Virginia
Neena Jube-Desai, MD, MBA, FAAP, University of Maryland, Baltimore, Maryland

References

  1. Will EP, Fraga MV, Ultrasonography-guided lumbar puncture. Neoreviews. 2024;25(8):e527–e529 
  2. Fraga MV, Stoller JZ, Glau CL, et al. Seeing is believing: ultrasound in pediatric procedural performance. Pediatrics. 2019;144(5):e20191401
  3. Aleem S, Greenberg RG. When to include a lumbar puncture in the evaluation for neonatal sepsis. Neoreviews. 2019;20(3):e124-e134
  4. Olowoyeye A, Fadahunsi O, Okudo J, et al. Ultrasound imaging versus palpation method for diagnostic lumbar puncture in neonates and infants: a systematic review and meta-analysis. BMJ Paediatr Open. 2019;3(1):e000412
  5. Soni NJ, Franco-Sadud R, Schnobrich D, et al. Ultrasound guidance for lumbar puncture. Neurol Clin Pract. 2016;6(4):358-368
  6. Marshall ASJ, Sadarangani M, Scrivens A, et al. Study protocol: NeoCLEAR: Neonatal champagne lumbar punctures every time - an RCT: a multicentre, randomised controlled 2 × 2 factorial trial to investigate techniques to increase lumbar puncture success. BMC Pediatr. 2020;20(1):165
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